Merge branch 'throwables' into develop

Sources/BaseDataTransaction+Importing.swift

@@ -151,7 +151,7 @@ public extension BaseDataTransaction {
                     return nil
                 }
                 
-                if let object = self.fetchOne(From(entityType), Where<D>(uniqueIDKeyPath, isEqualTo: uniqueIDValue)) {
+                if let object = try self.fetchOne(From(entityType), Where<D>(uniqueIDKeyPath, isEqualTo: uniqueIDValue)) {
                     
                     guard entityType.shouldUpdate(from: source, in: self) else {
                         
@@ -215,7 +215,8 @@ public extension BaseDataTransaction {
                 importSourceByID = try autoreleasepool { try preProcess(importSourceByID) }
 
                 var existingObjectsByID = Dictionary<D.UniqueIDType, D>()
-                self.fetchAll(From(entityType), Where<D>(entityType.uniqueIDKeyPath, isMemberOf: sortedIDs))?
+                try self
+                    .fetchAll(From(entityType), Where<D>(entityType.uniqueIDKeyPath, isMemberOf: sortedIDs))
                     .forEach { existingObjectsByID[$0.uniqueIDValue] = $0 }
               
                 var processedObjectIDs = Set<D.UniqueIDType>()

Sources/BaseDataTransaction+Querying.swift

@@ -39,13 +39,13 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      - returns: the number of `DynamicObject`s deleted
      */
     @discardableResult
-    public func deleteAll<D>(_ from: From<D>, _ deleteClauses: DeleteClause...) -> Int? {
+    public func deleteAll<D>(_ from: From<D>, _ deleteClauses: DeleteClause...) throws -> Int {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to delete from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.deleteAll(from, deleteClauses)
+        return try self.context.deleteAll(from, deleteClauses)
     }
     
     /**
@@ -56,13 +56,13 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      - returns: the number of `DynamicObject`s deleted
      */
     @discardableResult
-    public func deleteAll<D>(_ from: From<D>, _ deleteClauses: [DeleteClause]) -> Int? {
+    public func deleteAll<D>(_ from: From<D>, _ deleteClauses: [DeleteClause]) throws -> Int {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to delete from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.deleteAll(from, deleteClauses)
+        return try self.context.deleteAll(from, deleteClauses)
     }
     
     /**
@@ -74,14 +74,14 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      - returns: the number of `DynamicObject`s deleted
      */
     @discardableResult
-    public func deleteAll<B: FetchChainableBuilderType>(_ clauseChain: B) -> Int? {
+    public func deleteAll<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> Int {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to delete from a \(cs_typeName(self)) outside its designated queue."
         )
         
-        return self.context.deleteAll(clauseChain.from, clauseChain.fetchClauses)
+        return try self.context.deleteAll(clauseChain.from, clauseChain.fetchClauses)
     }
     
     
@@ -136,15 +136,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the first `DynamicObject` instance that satisfies the specified `FetchClause`s
+     - returns: the first `DynamicObject` instance that satisfies the specified `FetchClause`s, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchOne<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> D? {
+    public func fetchOne<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> D? {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.fetchOne(from, fetchClauses)
+        return try self.context.fetchOne(from, fetchClauses)
     }
     
     /**
@@ -152,15 +153,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the first `DynamicObject` instance that satisfies the specified `FetchClause`s
+     - returns: the first `DynamicObject` instance that satisfies the specified `FetchClause`s, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchOne<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> D? {
+    public func fetchOne<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> D? {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.fetchOne(from, fetchClauses)
+        return try self.context.fetchOne(from, fetchClauses)
     }
     
     /**
@@ -173,15 +175,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: the first `DynamicObject` instance that satisfies the specified `FetchChainableBuilderType`
+     - returns: the first `DynamicObject` instance that satisfies the specified `FetchChainableBuilderType`, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchOne<B: FetchChainableBuilderType>(_ clauseChain: B) -> B.ObjectType? {
+    public func fetchOne<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> B.ObjectType? {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.fetchOne(clauseChain)
+        return try self.context.fetchOne(clauseChain)
     }
     
     /**
@@ -189,15 +192,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: all `DynamicObject` instances that satisfy the specified `FetchClause`s
+     - returns: all `DynamicObject` instances that satisfy the specified `FetchClause`s, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchAll<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> [D]? {
+    public func fetchAll<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> [D] {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.fetchAll(from, fetchClauses)
+        return try self.context.fetchAll(from, fetchClauses)
     }
     
     /**
@@ -205,15 +209,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: all `DynamicObject` instances that satisfy the specified `FetchClause`s
+     - returns: all `DynamicObject` instances that satisfy the specified `FetchClause`s, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchAll<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> [D]? {
+    public func fetchAll<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> [D] {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.fetchAll(from, fetchClauses)
+        return try self.context.fetchAll(from, fetchClauses)
     }
     
     /**
@@ -226,15 +231,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: all `DynamicObject` instances that satisfy the specified `FetchChainableBuilderType`
+     - returns: all `DynamicObject` instances that satisfy the specified `FetchChainableBuilderType`, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchAll<B: FetchChainableBuilderType>(_ clauseChain: B) -> [B.ObjectType]? {
+    public func fetchAll<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> [B.ObjectType] {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.fetchAll(clauseChain)
+        return try self.context.fetchAll(clauseChain)
     }
     
     /**
@@ -242,15 +248,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the number `DynamicObject`s that satisfy the specified `FetchClause`s
+     - returns: the number of `DynamicObject`s that satisfy the specified `FetchClause`s
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchCount<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> Int? {
+    public func fetchCount<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> Int {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.fetchCount(from, fetchClauses)
+        return try self.context.fetchCount(from, fetchClauses)
     }
     
     /**
@@ -258,15 +265,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the number `DynamicObject`s that satisfy the specified `FetchClause`s
+     - returns: the number of `DynamicObject`s that satisfy the specified `FetchClause`s
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchCount<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> Int? {
+    public func fetchCount<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> Int {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.fetchCount(from, fetchClauses)
+        return try self.context.fetchCount(from, fetchClauses)
     }
     
     /**
@@ -279,15 +287,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: the number `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`
+     - returns: the number of `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchCount<B: FetchChainableBuilderType>(_ clauseChain: B) -> Int? {
+    public func fetchCount<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> Int {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.fetchCount(clauseChain)
+        return try self.context.fetchCount(clauseChain)
     }
     
     /**
@@ -295,15 +304,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s
+     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> NSManagedObjectID? {
+    public func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> NSManagedObjectID? {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.fetchObjectID(from, fetchClauses)
+        return try self.context.fetchObjectID(from, fetchClauses)
     }
     
     /**
@@ -311,15 +321,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s
+     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> NSManagedObjectID? {
+    public func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> NSManagedObjectID? {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.fetchObjectID(from, fetchClauses)
+        return try self.context.fetchObjectID(from, fetchClauses)
     }
     
     /**
@@ -332,15 +343,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchChainableBuilderType`
+     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchChainableBuilderType`, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchObjectID<B: FetchChainableBuilderType>(_ clauseChain: B) -> NSManagedObjectID? {
+    public func fetchObjectID<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> NSManagedObjectID? {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.fetchObjectID(clauseChain)
+        return try self.context.fetchObjectID(clauseChain)
     }
     
     /**
@@ -348,15 +360,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s
+     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> [NSManagedObjectID]? {
+    public func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> [NSManagedObjectID] {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.fetchObjectIDs(from, fetchClauses)
+        return try self.context.fetchObjectIDs(from, fetchClauses)
     }
     
     /**
@@ -364,15 +377,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s
+     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> [NSManagedObjectID]? {
+    public func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> [NSManagedObjectID] {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.fetchObjectIDs(from, fetchClauses)
+        return try self.context.fetchObjectIDs(from, fetchClauses)
     }
     
     /**
@@ -385,15 +399,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`
+     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchObjectIDs<B: FetchChainableBuilderType>(_ clauseChain: B) -> [NSManagedObjectID]? {
+    public func fetchObjectIDs<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> [NSManagedObjectID] {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.fetchObjectIDs(clauseChain)
+        return try self.context.fetchObjectIDs(clauseChain)
     }
     
     
@@ -407,15 +422,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      - parameter from: a `From` clause indicating the entity type
      - parameter selectClause: a `Select<U>` clause indicating the properties to fetch, and with the generic type indicating the return type.
      - parameter queryClauses: a series of `QueryClause` instances for the query request. Accepts `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
-     - returns: the result of the the query. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - returns: the result of the the query, or `nil` if no match was found. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: QueryClause...) -> U? {
+    public func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: QueryClause...) throws -> U? {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to query from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.queryValue(from, selectClause, queryClauses)
+        return try self.context.queryValue(from, selectClause, queryClauses)
     }
     
     /**
@@ -426,15 +442,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      - parameter from: a `From` clause indicating the entity type
      - parameter selectClause: a `Select<U>` clause indicating the properties to fetch, and with the generic type indicating the return type.
      - parameter queryClauses: a series of `QueryClause` instances for the query request. Accepts `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
-     - returns: the result of the the query. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - returns: the result of the the query, or `nil` if no match was found. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: [QueryClause]) -> U? {
+    public func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: [QueryClause]) throws -> U? {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to query from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.queryValue(from, selectClause, queryClauses)
+        return try self.context.queryValue(from, selectClause, queryClauses)
     }
     
     /**
@@ -449,15 +466,16 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      )
      ```
      - parameter clauseChain: a `QueryChainableBuilderType` indicating the property/aggregate to fetch and the series of queries for the request.
-     - returns: the result of the the query as specified by the `QueryChainableBuilderType`
+     - returns: the result of the the query as specified by the `QueryChainableBuilderType`, or `nil` if no match was found.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func queryValue<B: QueryChainableBuilderType>(_ clauseChain: B) -> B.ResultType? where B.ResultType: QueryableAttributeType {
+    public func queryValue<B: QueryChainableBuilderType>(_ clauseChain: B) throws -> B.ResultType? where B.ResultType: QueryableAttributeType {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to query from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.queryValue(clauseChain.from, clauseChain.select, clauseChain.queryClauses)
+        return try self.context.queryValue(clauseChain.from, clauseChain.select, clauseChain.queryClauses)
     }
     
     /**
@@ -469,14 +487,15 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      - parameter selectClause: a `Select<U>` clause indicating the properties to fetch, and with the generic type indicating the return type.
      - parameter queryClauses: a series of `QueryClause` instances for the query request. Accepts `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
      - returns: the result of the the query. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: QueryClause...) -> [[String: Any]]? {
+    public func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: QueryClause...) throws -> [[String: Any]] {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to query from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.queryAttributes(from, selectClause, queryClauses)
+        return try self.context.queryAttributes(from, selectClause, queryClauses)
     }
     
     /**
@@ -488,14 +507,15 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      - parameter selectClause: a `Select<U>` clause indicating the properties to fetch, and with the generic type indicating the return type.
      - parameter queryClauses: a series of `QueryClause` instances for the query request. Accepts `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
      - returns: the result of the the query. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: [QueryClause]) -> [[String: Any]]? {
+    public func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: [QueryClause]) throws -> [[String: Any]] {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to query from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.queryAttributes(from, selectClause, queryClauses)
+        return try self.context.queryAttributes(from, selectClause, queryClauses)
     }
     
     /**
@@ -520,14 +540,15 @@ extension BaseDataTransaction: FetchableSource, QueryableSource {
      ```
      - parameter clauseChain: a `QueryChainableBuilderType` indicating the properties to fetch and the series of queries for the request.
      - returns: the result of the the query as specified by the `QueryChainableBuilderType`
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func queryAttributes<B: QueryChainableBuilderType>(_ clauseChain: B) -> [[String: Any]]? where B.ResultType == NSDictionary {
+    public func queryAttributes<B: QueryChainableBuilderType>(_ clauseChain: B) throws -> [[String: Any]] where B.ResultType == NSDictionary {
         
         CoreStore.assert(
             self.isRunningInAllowedQueue(),
             "Attempted to query from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.context.queryAttributes(clauseChain.from, clauseChain.select, clauseChain.queryClauses)
+        return try self.context.queryAttributes(clauseChain.from, clauseChain.select, clauseChain.queryClauses)
     }
     
     

Sources/CSBaseDataTransaction+Querying.swift

@@ -93,7 +93,8 @@ public extension CSBaseDataTransaction {
             self.swiftTransaction.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.swiftTransaction.context.fetchOne(from, fetchClauses)
+        return (try? self.swiftTransaction.context.fetchOne(from, fetchClauses))?
+            .flatMap({ $0 })
     }
     
     /**
@@ -110,7 +111,8 @@ public extension CSBaseDataTransaction {
             self.swiftTransaction.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.swiftTransaction.context.fetchAll(from, fetchClauses)
+        return (try? self.swiftTransaction.context.fetchAll(from, fetchClauses))
+            .flatMap({ $0 })
     }
     
     /**
@@ -127,9 +129,8 @@ public extension CSBaseDataTransaction {
             self.swiftTransaction.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.swiftTransaction.context
-            .fetchCount(from, fetchClauses)
-            .flatMap { NSNumber(value: $0) }
+        return (try? self.swiftTransaction.context.fetchCount(from, fetchClauses))
+            .flatMap({ NSNumber(value: $0) })
     }
     
     /**
@@ -146,7 +147,8 @@ public extension CSBaseDataTransaction {
             self.swiftTransaction.isRunningInAllowedQueue(),
             "Attempted to fetch from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.swiftTransaction.context.fetchObjectID(from, fetchClauses)
+        return (try? self.swiftTransaction.context.fetchObjectID(from, fetchClauses))
+            .flatMap({ $0 })
     }
     
     /**
@@ -166,7 +168,8 @@ public extension CSBaseDataTransaction {
             self.swiftTransaction.isRunningInAllowedQueue(),
             "Attempted to query from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.swiftTransaction.context.queryValue(from, selectClause, queryClauses)
+        return (try? self.swiftTransaction.context.queryValue(from, selectClause, queryClauses))
+            .flatMap({ $0 })
     }
     
     /**
@@ -186,6 +189,7 @@ public extension CSBaseDataTransaction {
             self.swiftTransaction.isRunningInAllowedQueue(),
             "Attempted to query from a \(cs_typeName(self)) outside its designated queue."
         )
-        return self.swiftTransaction.context.queryAttributes(from, selectClause, queryClauses)
+        return (try? self.swiftTransaction.context.queryAttributes(from, selectClause, queryClauses))
+            .flatMap({ $0 })
     }
 }

Sources/CSDataStack+Querying.swift

@@ -93,7 +93,8 @@ public extension CSDataStack {
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.bridgeToSwift.mainContext.fetchOne(from, fetchClauses)
+        return (try? self.bridgeToSwift.mainContext.fetchOne(from, fetchClauses))?
+            .flatMap({ $0 })
     }
     
     /**
@@ -110,7 +111,8 @@ public extension CSDataStack {
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.bridgeToSwift.mainContext.fetchAll(from, fetchClauses)
+        return (try? self.bridgeToSwift.mainContext.fetchAll(from, fetchClauses))
+            .flatMap({ $0 })
     }
     
     /**
@@ -127,9 +129,8 @@ public extension CSDataStack {
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.bridgeToSwift.mainContext
-            .fetchCount(from, fetchClauses)
-            .flatMap { NSNumber(value: $0) }
+        return (try? self.bridgeToSwift.mainContext.fetchCount(from, fetchClauses))
+            .flatMap({ NSNumber(value: $0) })
     }
     
     /**
@@ -146,7 +147,8 @@ public extension CSDataStack {
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.bridgeToSwift.mainContext.fetchObjectID(from, fetchClauses)
+        return (try? self.bridgeToSwift.mainContext.fetchObjectID(from, fetchClauses))?
+            .flatMap({ $0 })
     }
     
     /**
@@ -163,7 +165,8 @@ public extension CSDataStack {
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.bridgeToSwift.mainContext.fetchObjectIDs(from, fetchClauses)
+        return (try? self.bridgeToSwift.mainContext.fetchObjectIDs(from, fetchClauses))
+            .flatMap({ $0 })
     }
     
     /**
@@ -183,7 +186,8 @@ public extension CSDataStack {
             Thread.isMainThread,
             "Attempted to query from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.bridgeToSwift.mainContext.queryValue(from, selectClause, queryClauses)
+        return (try? self.bridgeToSwift.mainContext.queryValue(from, selectClause, queryClauses))
+            .flatMap({ $0 })
     }
     
     /**
@@ -203,6 +207,7 @@ public extension CSDataStack {
             Thread.isMainThread,
             "Attempted to query from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.bridgeToSwift.mainContext.queryAttributes(from, selectClause, queryClauses)
+        return (try? self.bridgeToSwift.mainContext.queryAttributes(from, selectClause, queryClauses))
+            .flatMap({ $0 })
     }
 }

Sources/CSError.swift

@@ -247,6 +247,14 @@ extension CoreStoreError: CoreStoreSwiftType, _ObjectiveCBridgeableError {
             
         case .userCancelled:
             self = .userCancelled
+
+        case .persistentStoreNotFound:
+            guard let entity = info["entity"] as? DynamicObject.Type else {
+
+                self = .unknown
+                return
+            }
+            self = .persistentStoreNotFound(entity: entity)
         }
     }
 }

Sources/CSListMonitor.swift

@@ -132,7 +132,7 @@ public final class CSListMonitor: NSObject {
     @objc
     public func hasObjectsInSection(_ section: Int) -> Bool {
         
-        return self.bridgeToSwift.hasObjectsInSection(section)
+        return self.bridgeToSwift.hasObjects(in: section)
     }
     
     /**
@@ -155,7 +155,7 @@ public final class CSListMonitor: NSObject {
     @objc
     public func objectsInSection(_ section: Int) -> [NSManagedObject] {
         
-        return self.bridgeToSwift.objectsInSection(section)
+        return self.bridgeToSwift.objects(in: section)
     }
     
     /**
@@ -167,7 +167,7 @@ public final class CSListMonitor: NSObject {
     @objc
     public func objectsInSafeSection(safeSectionIndex section: Int) -> [NSManagedObject]? {
         
-        return self.bridgeToSwift.objectsInSection(safeSectionIndex: section)
+        return self.bridgeToSwift.objects(safelyIn: section)
     }
 
     /**
@@ -201,7 +201,7 @@ public final class CSListMonitor: NSObject {
     @objc
     public func numberOfObjectsInSection(_ section: Int) -> Int {
         
-        return self.bridgeToSwift.numberOfObjectsInSection(section)
+        return self.bridgeToSwift.numberOfObjects(in: section)
     }
     
     /**
@@ -214,7 +214,7 @@ public final class CSListMonitor: NSObject {
     public func numberOfObjectsInSafeSection(safeSectionIndex section: Int) -> NSNumber? {
         
         return self.bridgeToSwift
-            .numberOfObjectsInSection(safeSectionIndex: section)
+            .numberOfObjects(safelyIn: section)
             .flatMap { NSNumber(value: $0) }
     }
     
@@ -227,7 +227,7 @@ public final class CSListMonitor: NSObject {
     @objc
     public func sectionInfoAtIndex(_ section: Int) -> NSFetchedResultsSectionInfo {
         
-        return self.bridgeToSwift.sectionInfoAtIndex(section)
+        return self.bridgeToSwift.sectionInfo(at: section)
     }
     
     /**
@@ -239,7 +239,7 @@ public final class CSListMonitor: NSObject {
     @objc
     public func sectionInfoAtSafeSectionIndex(safeSectionIndex section: Int) -> NSFetchedResultsSectionInfo? {
         
-        return self.bridgeToSwift.sectionInfoAtIndex(safeSectionIndex: section)
+        return self.bridgeToSwift.sectionInfo(safelyAt: section)
     }
     
     /**
@@ -263,7 +263,7 @@ public final class CSListMonitor: NSObject {
     @objc
     public func targetSectionForSectionIndexTitle(title: String, index: Int) -> Int {
         
-        return self.bridgeToSwift.targetSectionForSectionIndex(title: title, index: index)
+        return self.bridgeToSwift.targetSection(forSectionIndexTitle: title, at: index)
     }
     
     /**
@@ -287,7 +287,7 @@ public final class CSListMonitor: NSObject {
     public func indexOf(_ object: NSManagedObject) -> NSNumber? {
         
         return self.bridgeToSwift
-            .indexOf(object)
+            .index(of: object)
             .flatMap { NSNumber(value: $0) }
     }
     
@@ -300,7 +300,7 @@ public final class CSListMonitor: NSObject {
     @objc
     public func indexPathOf(_ object: NSManagedObject) -> IndexPath? {
         
-        return self.bridgeToSwift.indexPathOf(object)
+        return self.bridgeToSwift.indexPath(of: object)
     }
     
     

Sources/CoreStore+CustomDebugStringConvertible.swift

@@ -152,6 +152,10 @@ extension CoreStoreError: CustomDebugStringConvertible, CoreStoreDebugStringConv
             
         case .userCancelled:
             firstLine = ".userCancelled"
+
+        case .persistentStoreNotFound(let entity):
+            firstLine = ".persistentStoreNotFound"
+            info.append(("entity", entity))
         }
         
         return createFormattedString(

Sources/CoreStore+Observing.swift

@@ -113,7 +113,7 @@ public extension CoreStore {
      
      ```
      CoreStore.monitorList(
-         { (monitor) in
+         createAsynchronously: { (monitor) in
              self.monitor = monitor
          },
          From<MyPersonEntity>()
@@ -123,7 +123,6 @@ public extension CoreStore {
      ```
      - parameter createAsynchronously: the closure that receives the created `ListMonitor` instance
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: a `ListMonitor` for a list of `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`
      */
     public static func monitorList<B: FetchChainableBuilderType>(createAsynchronously: @escaping (ListMonitor<B.ObjectType>) -> Void, _ clauseChain: B) {
         
@@ -212,7 +211,7 @@ public extension CoreStore {
      Asynchronously creates a `ListMonitor` for a sectioned list of `DynamicObject`s that satisfy the specified `SectionMonitorBuilderType` built from a chain of clauses.
      ```
      CoreStore.monitorSectionedList(
-         { (monitor) in
+         createAsynchronously: { (monitor) in
              self.monitor = monitor
          },
          From<MyPersonEntity>()
@@ -221,8 +220,8 @@ public extension CoreStore {
              .orderBy(.ascending(\.age))
      )
      ```
+     - parameter createAsynchronously: the closure that receives the created `ListMonitor` instance
      - parameter clauseChain: a `SectionMonitorBuilderType` built from a chain of clauses
-     - returns: a `ListMonitor` for a list of `DynamicObject`s that satisfy the specified `SectionMonitorBuilderType`
      */
     public static func monitorSectionedList<B: SectionMonitorBuilderType>(createAsynchronously: @escaping (ListMonitor<B.ObjectType>) -> Void, _ clauseChain: B) {
         

Sources/CoreStore+Querying.swift

@@ -80,11 +80,12 @@ public extension CoreStore {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the first `DynamicObject` instance that satisfies the specified `FetchClause`s
+     - returns: the first `DynamicObject` instance that satisfies the specified `FetchClause`s, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func fetchOne<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> D? {
+    public static func fetchOne<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> D? {
         
-        return self.defaultStack.fetchOne(from, fetchClauses)
+        return try self.defaultStack.fetchOne(from, fetchClauses)
     }
     
     /**
@@ -92,11 +93,12 @@ public extension CoreStore {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the first `DynamicObject` instance that satisfies the specified `FetchClause`s
+     - returns: the first `DynamicObject` instance that satisfies the specified `FetchClause`s, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func fetchOne<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> D? {
+    public static func fetchOne<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> D? {
         
-        return self.defaultStack.fetchOne(from, fetchClauses)
+        return try self.defaultStack.fetchOne(from, fetchClauses)
     }
     
     /**
@@ -109,11 +111,12 @@ public extension CoreStore {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: the first `DynamicObject` instance that satisfies the specified `FetchChainableBuilderType`
+     - returns: the first `DynamicObject` instance that satisfies the specified `FetchChainableBuilderType`, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func fetchOne<B: FetchChainableBuilderType>(_ clauseChain: B) -> B.ObjectType? {
+    public static func fetchOne<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> B.ObjectType? {
         
-        return self.defaultStack.fetchOne(clauseChain)
+        return try self.defaultStack.fetchOne(clauseChain)
     }
     
     /**
@@ -121,11 +124,12 @@ public extension CoreStore {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: all `DynamicObject` instances that satisfy the specified `FetchClause`s
+     - returns: all `DynamicObject` instances that satisfy the specified `FetchClause`s, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func fetchAll<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> [D]? {
+    public static func fetchAll<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> [D] {
         
-        return self.defaultStack.fetchAll(from, fetchClauses)
+        return try self.defaultStack.fetchAll(from, fetchClauses)
     }
     
     /**
@@ -133,11 +137,12 @@ public extension CoreStore {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: all `DynamicObject` instances that satisfy the specified `FetchClause`s
+     - returns: all `DynamicObject` instances that satisfy the specified `FetchClause`s, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func fetchAll<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> [D]? {
+    public static func fetchAll<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> [D] {
         
-        return self.defaultStack.fetchAll(from, fetchClauses)
+        return try self.defaultStack.fetchAll(from, fetchClauses)
     }
     
     /**
@@ -150,11 +155,12 @@ public extension CoreStore {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: all `DynamicObject` instances that satisfy the specified `FetchChainableBuilderType`
+     - returns: all `DynamicObject` instances that satisfy the specified `FetchChainableBuilderType`, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func fetchAll<B: FetchChainableBuilderType>(_ clauseChain: B) -> [B.ObjectType]? {
+    public static func fetchAll<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> [B.ObjectType] {
         
-        return self.defaultStack.fetchAll(clauseChain)
+        return try self.defaultStack.fetchAll(clauseChain)
     }
     
     /**
@@ -162,11 +168,12 @@ public extension CoreStore {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the number `DynamicObject`s that satisfy the specified `FetchClause`s
+     - returns: the number of `DynamicObject`s that satisfy the specified `FetchClause`s
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func fetchCount<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> Int? {
+    public static func fetchCount<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> Int {
         
-        return self.defaultStack.fetchCount(from, fetchClauses)
+        return try self.defaultStack.fetchCount(from, fetchClauses)
     }
     
     /**
@@ -174,11 +181,12 @@ public extension CoreStore {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the number `DynamicObject`s that satisfy the specified `FetchClause`s
+     - returns: the number of `DynamicObject`s that satisfy the specified `FetchClause`s
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func fetchCount<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> Int? {
+    public static func fetchCount<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> Int {
         
-        return self.defaultStack.fetchCount(from, fetchClauses)
+        return try self.defaultStack.fetchCount(from, fetchClauses)
     }
     
     /**
@@ -191,11 +199,12 @@ public extension CoreStore {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: the number `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`
+     - returns: the number of `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func fetchCount<B: FetchChainableBuilderType>(_ clauseChain: B) -> Int? {
+    public static func fetchCount<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> Int {
         
-        return self.defaultStack.fetchCount(clauseChain)
+        return try self.defaultStack.fetchCount(clauseChain)
     }
     
     /**
@@ -203,11 +212,12 @@ public extension CoreStore {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s
+     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> NSManagedObjectID? {
+    public static func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> NSManagedObjectID? {
         
-        return self.defaultStack.fetchObjectID(from, fetchClauses)
+        return try self.defaultStack.fetchObjectID(from, fetchClauses)
     }
     
     /**
@@ -215,11 +225,12 @@ public extension CoreStore {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s
+     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> NSManagedObjectID? {
+    public static func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> NSManagedObjectID? {
         
-        return self.defaultStack.fetchObjectID(from, fetchClauses)
+        return try self.defaultStack.fetchObjectID(from, fetchClauses)
     }
     
     /**
@@ -232,11 +243,12 @@ public extension CoreStore {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchChainableBuilderType`
+     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchChainableBuilderType`, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func fetchObjectID<B: FetchChainableBuilderType>(_ clauseChain: B) -> NSManagedObjectID? {
+    public static func fetchObjectID<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> NSManagedObjectID? {
         
-        return self.defaultStack.fetchObjectID(clauseChain)
+        return try self.defaultStack.fetchObjectID(clauseChain)
     }
     
     /**
@@ -244,11 +256,12 @@ public extension CoreStore {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s
+     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> [NSManagedObjectID]? {
+    public static func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> [NSManagedObjectID] {
         
-        return self.defaultStack.fetchObjectIDs(from, fetchClauses)
+        return try self.defaultStack.fetchObjectIDs(from, fetchClauses)
     }
     
     /**
@@ -256,11 +269,12 @@ public extension CoreStore {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s
+     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> [NSManagedObjectID]? {
+    public static func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> [NSManagedObjectID] {
         
-        return self.defaultStack.fetchObjectIDs(from, fetchClauses)
+        return try self.defaultStack.fetchObjectIDs(from, fetchClauses)
     }
     
     /**
@@ -273,11 +287,12 @@ public extension CoreStore {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`
+     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func fetchObjectIDs<B: FetchChainableBuilderType>(_ clauseChain: B) -> [NSManagedObjectID]? {
+    public static func fetchObjectIDs<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> [NSManagedObjectID] {
         
-        return self.defaultStack.fetchObjectIDs(clauseChain)
+        return try self.defaultStack.fetchObjectIDs(clauseChain)
     }
     
     /**
@@ -288,11 +303,12 @@ public extension CoreStore {
      - parameter from: a `From` clause indicating the entity type
      - parameter selectClause: a `Select<U>` clause indicating the properties to fetch, and with the generic type indicating the return type.
      - parameter queryClauses: a series of `QueryClause` instances for the query request. Accepts `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
-     - returns: the result of the the query. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - returns: the result of the the query, or `nil` if no match was found. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: QueryClause...) -> U? {
+    public static func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: QueryClause...) throws -> U? {
         
-        return self.defaultStack.queryValue(from, selectClause, queryClauses)
+        return try self.defaultStack.queryValue(from, selectClause, queryClauses)
     }
     
     /**
@@ -303,11 +319,12 @@ public extension CoreStore {
      - parameter from: a `From` clause indicating the entity type
      - parameter selectClause: a `Select<U>` clause indicating the properties to fetch, and with the generic type indicating the return type.
      - parameter queryClauses: a series of `QueryClause` instances for the query request. Accepts `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
-     - returns: the result of the the query. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - returns: the result of the the query, or `nil` if no match was found. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: [QueryClause]) -> U? {
+    public static func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: [QueryClause]) throws -> U? {
         
-        return self.defaultStack.queryValue(from, selectClause, queryClauses)
+        return try self.defaultStack.queryValue(from, selectClause, queryClauses)
     }
     
     /**
@@ -322,11 +339,12 @@ public extension CoreStore {
      )
      ```
      - parameter clauseChain: a `QueryChainableBuilderType` indicating the property/aggregate to fetch and the series of queries for the request.
-     - returns: the result of the the query as specified by the `QueryChainableBuilderType`
+     - returns: the result of the the query as specified by the `QueryChainableBuilderType`, or `nil` if no match was found.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func queryValue<B: QueryChainableBuilderType>(_ clauseChain: B) -> B.ResultType? where B.ResultType: QueryableAttributeType {
+    public static func queryValue<B: QueryChainableBuilderType>(_ clauseChain: B) throws -> B.ResultType? where B.ResultType: QueryableAttributeType {
         
-        return self.defaultStack.queryValue(clauseChain)
+        return try self.defaultStack.queryValue(clauseChain)
     }
     
     /**
@@ -338,10 +356,11 @@ public extension CoreStore {
      - parameter selectClause: a `Select<U>` clause indicating the properties to fetch, and with the generic type indicating the return type.
      - parameter queryClauses: a series of `QueryClause` instances for the query request. Accepts `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
      - returns: the result of the the query. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: QueryClause...) -> [[String: Any]]? {
+    public static func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: QueryClause...) throws -> [[String: Any]] {
         
-        return self.defaultStack.queryAttributes(from, selectClause, queryClauses)
+        return try self.defaultStack.queryAttributes(from, selectClause, queryClauses)
     }
     
     /**
@@ -353,10 +372,11 @@ public extension CoreStore {
      - parameter selectClause: a `Select<U>` clause indicating the properties to fetch, and with the generic type indicating the return type.
      - parameter queryClauses: a series of `QueryClause` instances for the query request. Accepts `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
      - returns: the result of the the query. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: [QueryClause]) -> [[String: Any]]? {
+    public static func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: [QueryClause]) throws -> [[String: Any]] {
         
-        return self.defaultStack.queryAttributes(from, selectClause, queryClauses)
+        return try self.defaultStack.queryAttributes(from, selectClause, queryClauses)
     }
     
     /**
@@ -381,9 +401,10 @@ public extension CoreStore {
      ```
      - parameter clauseChain: a `QueryChainableBuilderType` indicating the properties to fetch and the series of queries for the request.
      - returns: the result of the the query as specified by the `QueryChainableBuilderType`
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public static func queryAttributes<B: QueryChainableBuilderType>(_ clauseChain: B) -> [[String: Any]]? where B.ResultType == NSDictionary {
+    public static func queryAttributes<B: QueryChainableBuilderType>(_ clauseChain: B) throws -> [[String: Any]] where B.ResultType == NSDictionary {
         
-        return self.defaultStack.queryAttributes(clauseChain)
+        return try self.defaultStack.queryAttributes(clauseChain)
     }
 }

Sources/CoreStoreError.swift

@@ -73,6 +73,11 @@ public enum CoreStoreError: Error, CustomNSError, Hashable {
      The transaction was cancelled by the user.
      */
     case userCancelled
+
+    /**
+     Attempted to perform a fetch but could not find any related persistent store.
+     */
+    case persistentStoreNotFound(entity: DynamicObject.Type)
     
     
     // MARK: CustomNSError
@@ -109,6 +114,9 @@ public enum CoreStoreError: Error, CustomNSError, Hashable {
             
         case .userCancelled:
             return CoreStoreErrorCode.userCancelled.rawValue
+
+        case .persistentStoreNotFound:
+            return CoreStoreErrorCode.persistentStoreNotFound.rawValue
         }
     }
     
@@ -154,6 +162,11 @@ public enum CoreStoreError: Error, CustomNSError, Hashable {
             
         case .userCancelled:
             return [:]
+
+        case .persistentStoreNotFound(let entity):
+            return [
+                "entity": entity
+            ]
         }
     }
     
@@ -195,6 +208,9 @@ public enum CoreStoreError: Error, CustomNSError, Hashable {
             
         case (.userCancelled, .userCancelled):
             return true
+
+        case (.persistentStoreNotFound(let entity1), .persistentStoreNotFound(let entity2)):
+            return entity1 == entity2
             
         default:
             return false
@@ -233,6 +249,9 @@ public enum CoreStoreError: Error, CustomNSError, Hashable {
         case .userError(let error):
             hasher.combine(error as NSError)
 
+        case .persistentStoreNotFound(let entity):
+            hasher.combine(ObjectIdentifier(entity))
+
         case .userCancelled:
             break
         }
@@ -303,6 +322,11 @@ public enum CoreStoreErrorCode: Int {
      The transaction was cancelled by the user.
      */
     case userCancelled
+
+    /**
+     Attempted to perform a fetch but could not find any related persistent store.
+     */
+    case persistentStoreNotFound
 }
 
 

Sources/CoreStoreFetchedResultsController.swift

@@ -49,7 +49,7 @@ internal final class CoreStoreFetchedResultsController: NSFetchedResultsControll
     @nonobjc
     internal init<D>(context: NSManagedObjectContext, fetchRequest: NSFetchRequest<NSManagedObject>, from: From<D>, sectionBy: SectionBy<D>? = nil, applyFetchClauses: @escaping (_ fetchRequest: NSFetchRequest<NSManagedObject>) -> Void) {
         
-        _ = from.applyToFetchRequest(
+        _ = try? from.applyToFetchRequest(
             fetchRequest,
             context: context,
             applyAffectedStores: false
@@ -58,7 +58,7 @@ internal final class CoreStoreFetchedResultsController: NSFetchedResultsControll
         
         self.reapplyAffectedStores = { fetchRequest, context in
             
-            return from.applyAffectedStoresForFetchedRequest(fetchRequest, context: context)
+            try from.applyAffectedStoresForFetchedRequest(fetchRequest, context: context)
         }
         
         super.init(
@@ -71,14 +71,8 @@ internal final class CoreStoreFetchedResultsController: NSFetchedResultsControll
     
     @nonobjc
     internal func performFetchFromSpecifiedStores() throws {
-        
-        if !self.reapplyAffectedStores(self.fetchRequest, self.managedObjectContext) {
-            
-            CoreStore.log(
-                .warning,
-                message: "Attempted to perform a fetch on an \(cs_typeName(self)) but could not find any persistent store for the entity \(cs_typeName(self.fetchRequest.entityName))"
-            )
-        }
+
+        try self.reapplyAffectedStores(self.fetchRequest, self.managedObjectContext)
         try self.performFetch()
     }
     
@@ -97,5 +91,5 @@ internal final class CoreStoreFetchedResultsController: NSFetchedResultsControll
     // MARK: Private
     
     @nonobjc
-    private let reapplyAffectedStores: (_ fetchRequest: NSFetchRequest<NSManagedObject>, _ context: NSManagedObjectContext) -> Bool
+    private let reapplyAffectedStores: (_ fetchRequest: NSFetchRequest<NSManagedObject>, _ context: NSManagedObjectContext) throws -> Void
 }

Sources/DataStack+Observing.swift

@@ -152,7 +152,7 @@ public extension DataStack {
      
      ```
      dataStack.monitorList(
-         { (monitor) in
+         createAsynchronously: { (monitor) in
              self.monitor = monitor
          },
          From<MyPersonEntity>()
@@ -162,7 +162,6 @@ public extension DataStack {
      ```
      - parameter createAsynchronously: the closure that receives the created `ListMonitor` instance
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: a `ListMonitor` for a list of `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`
      */
     public func monitorList<B: FetchChainableBuilderType>(createAsynchronously: @escaping (ListMonitor<B.ObjectType>) -> Void, _ clauseChain: B) {
         
@@ -288,7 +287,7 @@ public extension DataStack {
      Asynchronously creates a `ListMonitor` for a sectioned list of `DynamicObject`s that satisfy the specified `SectionMonitorBuilderType` built from a chain of clauses.
      ```
      dataStack.monitorSectionedList(
-         { (monitor) in
+         createAsynchronously: { (monitor) in
              self.monitor = monitor
          },
          From<MyPersonEntity>()
@@ -297,8 +296,8 @@ public extension DataStack {
              .orderBy(.ascending(\.age))
      )
      ```
+     - parameter createAsynchronously: the closure that receives the created `ListMonitor` instance
      - parameter clauseChain: a `SectionMonitorBuilderType` built from a chain of clauses
-     - returns: a `ListMonitor` for a list of `DynamicObject`s that satisfy the specified `SectionMonitorBuilderType`
      */
     public func monitorSectionedList<B: SectionMonitorBuilderType>(createAsynchronously: @escaping (ListMonitor<B.ObjectType>) -> Void, _ clauseChain: B) {
         

Sources/DataStack+Querying.swift

@@ -82,15 +82,16 @@ extension DataStack: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the first `DynamicObject` instance that satisfies the specified `FetchClause`s
+     - returns: the first `DynamicObject` instance that satisfies the specified `FetchClause`s, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchOne<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> D? {
+    public func fetchOne<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> D? {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.fetchOne(from, fetchClauses)
+        return try self.mainContext.fetchOne(from, fetchClauses)
     }
     
     /**
@@ -98,15 +99,16 @@ extension DataStack: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the first `DynamicObject` instance that satisfies the specified `FetchClause`s
+     - returns: the first `DynamicObject` instance that satisfies the specified `FetchClause`s, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchOne<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> D? {
+    public func fetchOne<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> D? {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.fetchOne(from, fetchClauses)
+        return try self.mainContext.fetchOne(from, fetchClauses)
     }
     
     /**
@@ -119,15 +121,16 @@ extension DataStack: FetchableSource, QueryableSource {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: the first `DynamicObject` instance that satisfies the specified `FetchChainableBuilderType`
+     - returns: the first `DynamicObject` instance that satisfies the specified `FetchChainableBuilderType`, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchOne<B: FetchChainableBuilderType>(_ clauseChain: B) -> B.ObjectType? {
+    public func fetchOne<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> B.ObjectType? {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.fetchOne(clauseChain)
+        return try self.mainContext.fetchOne(clauseChain)
     }
     
     /**
@@ -135,15 +138,16 @@ extension DataStack: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: all `DynamicObject` instances that satisfy the specified `FetchClause`s
+     - returns: all `DynamicObject` instances that satisfy the specified `FetchClause`s, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchAll<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> [D]? {
+    public func fetchAll<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> [D] {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.fetchAll(from, fetchClauses)
+        return try self.mainContext.fetchAll(from, fetchClauses)
     }
     
     /**
@@ -151,15 +155,16 @@ extension DataStack: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: all `DynamicObject` instances that satisfy the specified `FetchClause`s
+     - returns: all `DynamicObject` instances that satisfy the specified `FetchClause`s, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchAll<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> [D]? {
+    public func fetchAll<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> [D] {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.fetchAll(from, fetchClauses)
+        return try self.mainContext.fetchAll(from, fetchClauses)
     }
     
     /**
@@ -172,15 +177,16 @@ extension DataStack: FetchableSource, QueryableSource {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: all `DynamicObject` instances that satisfy the specified `FetchChainableBuilderType`
+     - returns: all `DynamicObject` instances that satisfy the specified `FetchChainableBuilderType`, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchAll<B: FetchChainableBuilderType>(_ clauseChain: B) -> [B.ObjectType]? {
+    public func fetchAll<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> [B.ObjectType] {
 
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.fetchAll(clauseChain)
+        return try self.mainContext.fetchAll(clauseChain)
     }
     
     /**
@@ -188,15 +194,16 @@ extension DataStack: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the number `DynamicObject`s that satisfy the specified `FetchClause`s
+     - returns: the number of `DynamicObject`s that satisfy the specified `FetchClause`s
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchCount<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> Int? {
+    public func fetchCount<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> Int {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.fetchCount(from, fetchClauses)
+        return try self.mainContext.fetchCount(from, fetchClauses)
     }
     
     /**
@@ -204,15 +211,16 @@ extension DataStack: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the number `DynamicObject`s that satisfy the specified `FetchClause`s
+     - returns: the number of `DynamicObject`s that satisfy the specified `FetchClause`s
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchCount<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> Int? {
+    public func fetchCount<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> Int {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.fetchCount(from, fetchClauses)
+        return try self.mainContext.fetchCount(from, fetchClauses)
     }
     
     /**
@@ -225,15 +233,16 @@ extension DataStack: FetchableSource, QueryableSource {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: the number `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`
+     - returns: the number of `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchCount<B: FetchChainableBuilderType>(_ clauseChain: B) -> Int? {
+    public func fetchCount<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> Int {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.fetchCount(clauseChain)
+        return try self.mainContext.fetchCount(clauseChain)
     }
     
     /**
@@ -241,15 +250,16 @@ extension DataStack: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s
+     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> NSManagedObjectID? {
+    public func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> NSManagedObjectID? {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.fetchObjectID(from, fetchClauses)
+        return try self.mainContext.fetchObjectID(from, fetchClauses)
     }
     
     /**
@@ -257,15 +267,16 @@ extension DataStack: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s
+     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> NSManagedObjectID? {
+    public func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> NSManagedObjectID? {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.fetchObjectID(from, fetchClauses)
+        return try self.mainContext.fetchObjectID(from, fetchClauses)
     }
     
     /**
@@ -278,15 +289,16 @@ extension DataStack: FetchableSource, QueryableSource {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchChainableBuilderType`
+     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchChainableBuilderType`, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchObjectID<B: FetchChainableBuilderType>(_ clauseChain: B) -> NSManagedObjectID? {
+    public func fetchObjectID<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> NSManagedObjectID? {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.fetchObjectID(clauseChain)
+        return try self.mainContext.fetchObjectID(clauseChain)
     }
     
     /**
@@ -294,15 +306,16 @@ extension DataStack: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s
+     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> [NSManagedObjectID]? {
+    public func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> [NSManagedObjectID] {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.fetchObjectIDs(from, fetchClauses)
+        return try self.mainContext.fetchObjectIDs(from, fetchClauses)
     }
     
     /**
@@ -310,15 +323,16 @@ extension DataStack: FetchableSource, QueryableSource {
      
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s
+     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> [NSManagedObjectID]? {
+    public func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> [NSManagedObjectID] {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.fetchObjectIDs(from, fetchClauses)
+        return try self.mainContext.fetchObjectIDs(from, fetchClauses)
     }
     
     /**
@@ -331,15 +345,16 @@ extension DataStack: FetchableSource, QueryableSource {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`
+     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func fetchObjectIDs<B: FetchChainableBuilderType>(_ clauseChain: B) -> [NSManagedObjectID]? {
+    public func fetchObjectIDs<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> [NSManagedObjectID] {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to fetch from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.fetchObjectIDs(clauseChain)
+        return try self.mainContext.fetchObjectIDs(clauseChain)
     }
     
     
@@ -353,15 +368,16 @@ extension DataStack: FetchableSource, QueryableSource {
      - parameter from: a `From` clause indicating the entity type
      - parameter selectClause: a `Select<U>` clause indicating the properties to fetch, and with the generic type indicating the return type.
      - parameter queryClauses: a series of `QueryClause` instances for the query request. Accepts `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
-     - returns: the result of the the query. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - returns: the result of the the query, or `nil` if no match was found. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: QueryClause...) -> U? {
+    public func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: QueryClause...) throws -> U? {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to query from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.queryValue(from, selectClause, queryClauses)
+        return try self.mainContext.queryValue(from, selectClause, queryClauses)
     }
     
     /**
@@ -372,15 +388,16 @@ extension DataStack: FetchableSource, QueryableSource {
      - parameter from: a `From` clause indicating the entity type
      - parameter selectClause: a `Select<U>` clause indicating the properties to fetch, and with the generic type indicating the return type.
      - parameter queryClauses: a series of `QueryClause` instances for the query request. Accepts `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
-     - returns: the result of the the query. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - returns: the result of the the query, or `nil` if no match was found. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: [QueryClause]) -> U? {
+    public func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: [QueryClause]) throws -> U? {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to query from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.queryValue(from, selectClause, queryClauses)
+        return try self.mainContext.queryValue(from, selectClause, queryClauses)
     }
     
     /**
@@ -395,15 +412,16 @@ extension DataStack: FetchableSource, QueryableSource {
      )
      ```
      - parameter clauseChain: a `QueryChainableBuilderType` indicating the property/aggregate to fetch and the series of queries for the request.
-     - returns: the result of the the query as specified by the `QueryChainableBuilderType`
+     - returns: the result of the the query as specified by the `QueryChainableBuilderType`, or `nil` if no match was found.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func queryValue<B: QueryChainableBuilderType>(_ clauseChain: B) -> B.ResultType? where B.ResultType: QueryableAttributeType {
+    public func queryValue<B: QueryChainableBuilderType>(_ clauseChain: B) throws -> B.ResultType? where B.ResultType: QueryableAttributeType {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to query from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.queryValue(clauseChain.from, clauseChain.select, clauseChain.queryClauses)
+        return try self.mainContext.queryValue(clauseChain.from, clauseChain.select, clauseChain.queryClauses)
     }
     
     /**
@@ -415,14 +433,15 @@ extension DataStack: FetchableSource, QueryableSource {
      - parameter selectClause: a `Select<U>` clause indicating the properties to fetch, and with the generic type indicating the return type.
      - parameter queryClauses: a series of `QueryClause` instances for the query request. Accepts `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
      - returns: the result of the the query. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: QueryClause...) -> [[String: Any]]? {
+    public func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: QueryClause...) throws -> [[String: Any]] {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to query from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.queryAttributes(from, selectClause, queryClauses)
+        return try self.mainContext.queryAttributes(from, selectClause, queryClauses)
     }
     
     /**
@@ -434,14 +453,15 @@ extension DataStack: FetchableSource, QueryableSource {
      - parameter selectClause: a `Select<U>` clause indicating the properties to fetch, and with the generic type indicating the return type.
      - parameter queryClauses: a series of `QueryClause` instances for the query request. Accepts `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
      - returns: the result of the the query. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: [QueryClause]) -> [[String: Any]]? {
+    public func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: [QueryClause]) throws -> [[String: Any]] {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to query from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.queryAttributes(from, selectClause, queryClauses)
+        return try self.mainContext.queryAttributes(from, selectClause, queryClauses)
     }
     
     /**
@@ -466,14 +486,15 @@ extension DataStack: FetchableSource, QueryableSource {
      ```
      - parameter clauseChain: a `QueryChainableBuilderType` indicating the properties to fetch and the series of queries for the request.
      - returns: the result of the the query as specified by the `QueryChainableBuilderType`
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    public func queryAttributes<B: QueryChainableBuilderType>(_ clauseChain: B) -> [[String: Any]]? where B.ResultType == NSDictionary {
+    public func queryAttributes<B: QueryChainableBuilderType>(_ clauseChain: B) throws -> [[String: Any]] where B.ResultType == NSDictionary {
         
         CoreStore.assert(
             Thread.isMainThread,
             "Attempted to query from a \(cs_typeName(self)) outside the main thread."
         )
-        return self.mainContext.queryAttributes(clauseChain.from, clauseChain.select, clauseChain.queryClauses)
+        return try self.mainContext.queryAttributes(clauseChain.from, clauseChain.select, clauseChain.queryClauses)
     }
     
     

Sources/FetchableSource.swift

@@ -71,18 +71,20 @@ public protocol FetchableSource: class {
 
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the first `DynamicObject` instance that satisfies the specified `FetchClause`s
+     - returns: the first `DynamicObject` instance that satisfies the specified `FetchClause`s, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func fetchOne<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> D?
+    func fetchOne<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> D?
 
     /**
      Fetches the first `DynamicObject` instance that satisfies the specified `FetchClause`s. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
 
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the first `DynamicObject` instance that satisfies the specified `FetchClause`s
+     - returns: the first `DynamicObject` instance that satisfies the specified `FetchClause`s, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func fetchOne<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> D?
+    func fetchOne<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> D?
     
     /**
      Fetches the first `DynamicObject` instance that satisfies the specified `FetchChainableBuilderType` built from a chain of clauses.
@@ -94,27 +96,30 @@ public protocol FetchableSource: class {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: the first `DynamicObject` instance that satisfies the specified `FetchChainableBuilderType`
+     - returns: the first `DynamicObject` instance that satisfies the specified `FetchChainableBuilderType`, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func fetchOne<B: FetchChainableBuilderType>(_ clauseChain: B) -> B.ObjectType?
+    func fetchOne<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> B.ObjectType?
 
     /**
      Fetches all `DynamicObject` instances that satisfy the specified `FetchClause`s. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
 
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: all `DynamicObject` instances that satisfy the specified `FetchClause`s
+     - returns: all `DynamicObject` instances that satisfy the specified `FetchClause`s, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func fetchAll<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> [D]?
+    func fetchAll<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> [D]
 
     /**
      Fetches all `DynamicObject` instances that satisfy the specified `FetchClause`s. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
 
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: all `DynamicObject` instances that satisfy the specified `FetchClause`s
+     - returns: all `DynamicObject` instances that satisfy the specified `FetchClause`s, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func fetchAll<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> [D]?
+    func fetchAll<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> [D]
     
     /**
      Fetches all `DynamicObject` instances that satisfy the specified `FetchChainableBuilderType` built from a chain of clauses.
@@ -126,27 +131,30 @@ public protocol FetchableSource: class {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: all `DynamicObject` instances that satisfy the specified `FetchChainableBuilderType`
+     - returns: all `DynamicObject` instances that satisfy the specified `FetchChainableBuilderType`, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func fetchAll<B: FetchChainableBuilderType>(_ clauseChain: B) -> [B.ObjectType]?
+    func fetchAll<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> [B.ObjectType]
 
     /**
      Fetches the number of `DynamicObject`s that satisfy the specified `FetchClause`s. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
 
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the number `DynamicObject`s that satisfy the specified `FetchClause`s
+     - returns: the number of `DynamicObject`s that satisfy the specified `FetchClause`s
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func fetchCount<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> Int?
+    func fetchCount<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> Int
 
     /**
      Fetches the number of `DynamicObject`s that satisfy the specified `FetchClause`s. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
 
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the number `DynamicObject`s that satisfy the specified `FetchClause`s
+     - returns: the number of `DynamicObject`s that satisfy the specified `FetchClause`s
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func fetchCount<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> Int?
+    func fetchCount<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> Int
     
     /**
      Fetches the number of `DynamicObject`s that satisfy the specified `FetchChainableBuilderType` built from a chain of clauses.
@@ -158,27 +166,30 @@ public protocol FetchableSource: class {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: the number `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`
+     - returns: the number of `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func fetchCount<B: FetchChainableBuilderType>(_ clauseChain: B) -> Int?
+    func fetchCount<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> Int
 
     /**
      Fetches the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
 
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s
+     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> NSManagedObjectID?
+    func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> NSManagedObjectID?
 
     /**
      Fetches the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
 
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s
+     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchClause`s, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> NSManagedObjectID?
+    func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> NSManagedObjectID?
     
     /**
      Fetches the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchChainableBuilderType` built from a chain of clauses.
@@ -190,27 +201,30 @@ public protocol FetchableSource: class {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchChainableBuilderType`
+     - returns: the `NSManagedObjectID` for the first `DynamicObject` that satisfies the specified `FetchChainableBuilderType`, or `nil` if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func fetchObjectID<B: FetchChainableBuilderType>(_ clauseChain: B) -> NSManagedObjectID?
+    func fetchObjectID<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> NSManagedObjectID?
 
     /**
      Fetches the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
 
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s
+     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> [NSManagedObjectID]?
+    func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> [NSManagedObjectID]
 
     /**
      Fetches the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
 
      - parameter from: a `From` clause indicating the entity type
      - parameter fetchClauses: a series of `FetchClause` instances for the fetch request. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
-     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s
+     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchClause`s, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> [NSManagedObjectID]?
+    func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> [NSManagedObjectID]
     
     /**
      Fetches the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchChainableBuilderType` built from a chain of clauses.
@@ -222,9 +236,10 @@ public protocol FetchableSource: class {
      )
      ```
      - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
-     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`
+     - returns: the `NSManagedObjectID` for all `DynamicObject`s that satisfy the specified `FetchChainableBuilderType`, or an empty array if no match was found
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func fetchObjectIDs<B: FetchChainableBuilderType>(_ clauseChain: B) -> [NSManagedObjectID]?
+    func fetchObjectIDs<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> [NSManagedObjectID]
     
     /**
      The internal `NSManagedObjectContext` managed by this `FetchableSource`. Using this context directly should typically be avoided, and is provided by CoreStore only for extremely specialized cases.

Sources/From.swift

@@ -139,29 +139,40 @@ public struct From<D: DynamicObject> {
         self.findPersistentStores = findPersistentStores
     }
     
-    internal func applyToFetchRequest<ResultType>(_ fetchRequest: NSFetchRequest<ResultType>, context: NSManagedObjectContext, applyAffectedStores: Bool = true) -> Bool {
+    internal func applyToFetchRequest<U>(_ fetchRequest: NSFetchRequest<U>, context: NSManagedObjectContext, applyAffectedStores: Bool = true) throws {
         
         fetchRequest.entity = context.parentStack!.entityDescription(for: EntityIdentifier(self.entityClass))!
         guard applyAffectedStores else {
             
-            return true
+            return
         }
-        if self.applyAffectedStoresForFetchedRequest(fetchRequest, context: context) {
-            
-            return true
+        do {
+
+            try self.applyAffectedStoresForFetchedRequest(fetchRequest, context: context)
+        }
+        catch let error as CoreStoreError {
+
+            CoreStore.log(
+                error,
+                "Attempted to perform a fetch but could not find any persistent store for the entity \(cs_typeName(fetchRequest.entityName))"
+            )
+            throw error
+        }
+        catch {
+
+            throw error
         }
-        CoreStore.log(
-            .warning,
-            message: "Attempted to perform a fetch but could not find any persistent store for the entity \(cs_typeName(fetchRequest.entityName))"
-        )
-        return false
     }
     
-    internal func applyAffectedStoresForFetchedRequest<U>(_ fetchRequest: NSFetchRequest<U>, context: NSManagedObjectContext) -> Bool {
+    internal func applyAffectedStoresForFetchedRequest<U>(_ fetchRequest: NSFetchRequest<U>, context: NSManagedObjectContext) throws {
         
         let stores = self.findPersistentStores(context)
         fetchRequest.affectedStores = stores
-        return stores?.isEmpty == false
+        if stores?.isEmpty == false {
+
+            return
+        }
+        throw CoreStoreError.persistentStoreNotFound(entity: self.entityClass)
     }
     
     

Sources/ListMonitor.swift

@@ -136,7 +136,7 @@ public final class ListMonitor<D: DynamicObject>: Hashable {
      */
     public subscript(safeSectionIndex sectionIndex: Int, safeItemIndex itemIndex: Int) -> ObjectType? {
         
-        guard let section = self.sectionInfoAtIndex(safeSectionIndex: sectionIndex) else {
+        guard let section = self.sectionInfo(safelyAt: sectionIndex) else {
             
             return nil
         }
@@ -202,9 +202,9 @@ public final class ListMonitor<D: DynamicObject>: Hashable {
      - parameter section: the section index. Using an index outside the valid range will return `false`.
      - returns: `true` if at least one object in the specified section exists, `false` otherwise
      */
-    public func hasObjectsInSection(_ section: Int) -> Bool {
+    public func hasObjects(in section: Int) -> Bool {
         
-        return self.numberOfObjectsInSection(safeSectionIndex: section)! > 0
+        return self.numberOfObjects(safelyIn: section)! > 0
     }
     
     /**
@@ -241,9 +241,9 @@ public final class ListMonitor<D: DynamicObject>: Hashable {
      - parameter section: the section index. Using an index outside the valid range will raise an exception.
      - returns: the number of objects in the specified section
      */
-    public func numberOfObjectsInSection(_ section: Int) -> Int {
+    public func numberOfObjects(in section: Int) -> Int {
         
-        return self.sectionInfoAtIndex(section).numberOfObjects
+        return self.sectionInfo(at: section).numberOfObjects
     }
     
     /**
@@ -252,9 +252,9 @@ public final class ListMonitor<D: DynamicObject>: Hashable {
      - parameter section: the section index. Using an index outside the valid range will return `nil`.
      - returns: the number of objects in the specified section
      */
-    public func numberOfObjectsInSection(safeSectionIndex section: Int) -> Int? {
+    public func numberOfObjects(safelyIn section: Int) -> Int? {
         
-        return self.sectionInfoAtIndex(safeSectionIndex: section)?.numberOfObjects
+        return self.sectionInfo(safelyAt: section)?.numberOfObjects
     }
     
     /**
@@ -263,7 +263,7 @@ public final class ListMonitor<D: DynamicObject>: Hashable {
      - parameter section: the section index. Using an index outside the valid range will raise an exception.
      - returns: the `NSFetchedResultsSectionInfo` for the specified section
      */
-    public func sectionInfoAtIndex(_ section: Int) -> NSFetchedResultsSectionInfo {
+    public func sectionInfo(at section: Int) -> NSFetchedResultsSectionInfo {
         
         CoreStore.assert(
             !self.isPendingRefetch || Thread.isMainThread,
@@ -278,7 +278,7 @@ public final class ListMonitor<D: DynamicObject>: Hashable {
      - parameter section: the section index. Using an index outside the valid range will return `nil`.
      - returns: the `NSFetchedResultsSectionInfo` for the specified section, or `nil` if the section index is out of bounds.
      */
-    public func sectionInfoAtIndex(safeSectionIndex section: Int) -> NSFetchedResultsSectionInfo? {
+    public func sectionInfo(safelyAt section: Int) -> NSFetchedResultsSectionInfo? {
         
         CoreStore.assert(
             !self.isPendingRefetch || Thread.isMainThread,
@@ -312,17 +312,17 @@ public final class ListMonitor<D: DynamicObject>: Hashable {
     /**
      Returns the target section for a specified "Section Index" title and index.
      
-     - parameter title: the title of the Section Index
-     - parameter index: the index of the Section Index
+     - parameter sectionIndexTitle: the title of the Section Index
+     - parameter sectionIndex: the index of the Section Index
      - returns: the target section for the specified "Section Index" title and index.
      */
-    public func targetSectionForSectionIndex(title: String, index: Int) -> Int {
+    public func targetSection(forSectionIndexTitle sectionIndexTitle: String, at sectionIndex: Int) -> Int {
         
         CoreStore.assert(
             !self.isPendingRefetch || Thread.isMainThread,
             "Attempted to access a \(cs_typeName(self)) outside the main thread while a refetch is in progress."
         )
-        return self.fetchedResultsController.section(forSectionIndexTitle: title, at: index)
+        return self.fetchedResultsController.section(forSectionIndexTitle: sectionIndexTitle, at: sectionIndex)
     }
     
     /**
@@ -345,7 +345,7 @@ public final class ListMonitor<D: DynamicObject>: Hashable {
      - parameter object: the `DynamicObject` to search the index of
      - returns: the index of the `DynamicObject` if it exists in the `ListMonitor`'s fetched objects, or `nil` if not found.
      */
-    public func indexOf(_ object: ObjectType) -> Int? {
+    public func index(of object: ObjectType) -> Int? {
         
         CoreStore.assert(
             !self.isPendingRefetch || Thread.isMainThread,
@@ -364,7 +364,7 @@ public final class ListMonitor<D: DynamicObject>: Hashable {
      - parameter object: the `DynamicObject` to search the index of
      - returns: the `IndexPath` of the `DynamicObject` if it exists in the `ListMonitor`'s fetched objects, or `nil` if not found.
      */
-    public func indexPathOf(_ object: ObjectType) -> IndexPath? {
+    public func indexPath(of object: ObjectType) -> IndexPath? {
         
         CoreStore.assert(
             !self.isPendingRefetch || Thread.isMainThread,
@@ -1164,6 +1164,57 @@ public final class ListMonitor<D: DynamicObject>: Hashable {
             try! self.fetchedResultsController.performFetchFromSpecifiedStores()
         }
     }
+
+
+    // MARK: Deprecated
+
+    @available(*, deprecated, renamed: "hasObjects(in:)")
+    public func hasObjectsInSection(_ section: Int) -> Bool {
+
+        return self.hasObjects(in: section)
+    }
+
+    @available(*, deprecated, renamed: "numberOfObjects(in:)")
+    public func numberOfObjectsInSection(_ section: Int) -> Int {
+
+        return self.numberOfObjects(in: section)
+    }
+
+    @available(*, deprecated, renamed: "numberOfObjects(safelyIn:)")
+    public func numberOfObjectsInSection(safeSectionIndex section: Int) -> Int? {
+
+        return self.numberOfObjects(safelyIn: section)
+    }
+
+    @available(*, deprecated, renamed: "sectionInfo(at:)")
+    public func sectionInfoAtIndex(_ section: Int) -> NSFetchedResultsSectionInfo {
+
+        return self.sectionInfo(at: section)
+    }
+
+    @available(*, deprecated, renamed: "sectionInfo(safelyAt:)")
+    public func sectionInfoAtIndex(safeSectionIndex section: Int) -> NSFetchedResultsSectionInfo? {
+
+        return self.sectionInfo(safelyAt: section)
+    }
+
+    @available(*, deprecated, renamed: "targetSection(forSectionIndexTitle:at:)")
+    public func targetSectionForSectionIndex(title: String, index: Int) -> Int {
+
+        return self.targetSection(forSectionIndexTitle: title, at: index)
+    }
+
+    @available(*, deprecated, renamed: "index(of:)")
+    public func indexOf(_ object: ObjectType) -> Int? {
+
+        return self.index(of: object)
+    }
+
+    @available(*, deprecated, renamed: "indexPath(of:)")
+    public func indexPathOf(_ object: ObjectType) -> IndexPath? {
+
+        return self.indexPath(of: object)
+    }
 }
 
     
@@ -1192,9 +1243,9 @@ extension ListMonitor where ListMonitor.ObjectType: NSManagedObject {
      - parameter section: the section index. Using an index outside the valid range will raise an exception.
      - returns: all objects in the specified section
      */
-    public func objectsInSection(_ section: Int) -> [ObjectType] {
+    public func objects(in section: Int) -> [ObjectType] {
         
-        return (self.sectionInfoAtIndex(section).objects as! [ObjectType]?) ?? []
+        return (self.sectionInfo(at: section).objects as! [ObjectType]?) ?? []
     }
     
     /**
@@ -1203,9 +1254,24 @@ extension ListMonitor where ListMonitor.ObjectType: NSManagedObject {
      - parameter section: the section index. Using an index outside the valid range will return `nil`.
      - returns: all objects in the specified section
      */
-    public func objectsInSection(safeSectionIndex section: Int) -> [ObjectType]? {
+    public func objects(safelyIn section: Int) -> [ObjectType]? {
         
-        return self.sectionInfoAtIndex(safeSectionIndex: section)?.objects as! [ObjectType]?
+        return self.sectionInfo(safelyAt: section)?.objects as! [ObjectType]?
+    }
+
+
+    // MARK: Deprecated
+
+    @available(*, deprecated, renamed: "objects(in:)")
+    public func objectsInSection(_ section: Int) -> [ObjectType] {
+
+        return self.objects(in: section)
+    }
+
+    @available(*, deprecated, renamed: "objects(safelyIn:)")
+    public func objectsInSection(safeSectionIndex section: Int) -> [ObjectType]? {
+
+        return self.objects(safelyIn: section)
     }
 }
 
@@ -1236,9 +1302,9 @@ extension ListMonitor where ListMonitor.ObjectType: CoreStoreObject {
      - parameter section: the section index. Using an index outside the valid range will raise an exception.
      - returns: all objects in the specified section
      */
-    public func objectsInSection(_ section: Int) -> [ObjectType] {
+    public func objects(in section: Int) -> [ObjectType] {
         
-        return (self.sectionInfoAtIndex(section).objects ?? [])
+        return (self.sectionInfo(at: section).objects ?? [])
             .map({ ObjectType.cs_fromRaw(object: $0 as! NSManagedObject) })
     }
     
@@ -1248,11 +1314,26 @@ extension ListMonitor where ListMonitor.ObjectType: CoreStoreObject {
      - parameter section: the section index. Using an index outside the valid range will return `nil`.
      - returns: all objects in the specified section
      */
-    public func objectsInSection(safeSectionIndex section: Int) -> [ObjectType]? {
+    public func objects(safelyIn section: Int) -> [ObjectType]? {
         
-        return (self.sectionInfoAtIndex(safeSectionIndex: section)?.objects)?
+        return (self.sectionInfo(safelyAt: section)?.objects)?
             .map({ ObjectType.cs_fromRaw(object: $0 as! NSManagedObject) })
     }
+
+
+    // MARK: Deprecated
+
+    @available(*, deprecated, renamed: "objects(in:)")
+    public func objectsInSection(_ section: Int) -> [ObjectType] {
+
+        return self.objects(in: section)
+    }
+
+    @available(*, deprecated, renamed: "objects(safelyIn:)")
+    public func objectsInSection(safeSectionIndex section: Int) -> [ObjectType]? {
+
+        return self.objects(safelyIn: section)
+    }
 }
 
 

Sources/NSManagedObjectContext+ObjectiveC.swift

@@ -34,139 +34,107 @@ internal extension NSManagedObjectContext {
     // MARK: Internal
     
     @nonobjc
-    internal func fetchOne(_ from: CSFrom, _ fetchClauses: [CSFetchClause]) -> NSManagedObject? {
+    internal func fetchOne(_ from: CSFrom, _ fetchClauses: [CSFetchClause]) throws -> NSManagedObject? {
         
         let fetchRequest = CoreStoreFetchRequest()
-        let storeFound = from.bridgeToSwift.applyToFetchRequest(fetchRequest, context: self)
+        try from.bridgeToSwift.applyToFetchRequest(fetchRequest, context: self)
         
         fetchRequest.fetchLimit = 1
         fetchRequest.resultType = .managedObjectResultType
         fetchClauses.forEach { $0.applyToFetchRequest(fetchRequest) }
-        
-        guard storeFound else {
-            
-            return nil
-        }
-        return self.fetchOne(fetchRequest.dynamicCast())
+
+        return try self.fetchOne(fetchRequest.dynamicCast())
     }
     
     @nonobjc
-    internal func fetchAll<T: NSManagedObject>(_ from: CSFrom, _ fetchClauses: [CSFetchClause]) -> [T]? {
+    internal func fetchAll<T: NSManagedObject>(_ from: CSFrom, _ fetchClauses: [CSFetchClause]) throws -> [T] {
         
         let fetchRequest = CoreStoreFetchRequest()
-        let storeFound = from.bridgeToSwift.applyToFetchRequest(fetchRequest, context: self)
+        try from.bridgeToSwift.applyToFetchRequest(fetchRequest, context: self)
         
         fetchRequest.fetchLimit = 0
         fetchRequest.resultType = .managedObjectResultType
         fetchClauses.forEach { $0.applyToFetchRequest(fetchRequest) }
-        
-        guard storeFound else {
-            
-            return nil
-        }
-        return self.fetchAll(fetchRequest.dynamicCast())
+
+        return try self.fetchAll(fetchRequest.dynamicCast())
     }
     
     @nonobjc
-    internal func fetchCount(_ from: CSFrom, _ fetchClauses: [CSFetchClause]) -> Int? {
+    internal func fetchCount(_ from: CSFrom, _ fetchClauses: [CSFetchClause]) throws -> Int {
         
         let fetchRequest = CoreStoreFetchRequest()
-        let storeFound = from.bridgeToSwift.applyToFetchRequest(fetchRequest, context: self)
+        try from.bridgeToSwift.applyToFetchRequest(fetchRequest, context: self)
         fetchClauses.forEach { $0.applyToFetchRequest(fetchRequest) }
-        
-        guard storeFound else {
-            
-            return nil
-        }
-        return self.fetchCount(fetchRequest.dynamicCast())
+
+        return try self.fetchCount(fetchRequest.dynamicCast())
     }
     
     @nonobjc
-    internal func fetchObjectID(_ from: CSFrom, _ fetchClauses: [CSFetchClause]) -> NSManagedObjectID? {
+    internal func fetchObjectID(_ from: CSFrom, _ fetchClauses: [CSFetchClause]) throws -> NSManagedObjectID? {
         
         let fetchRequest = CoreStoreFetchRequest()
-        let storeFound = from.bridgeToSwift.applyToFetchRequest(fetchRequest, context: self)
+        try from.bridgeToSwift.applyToFetchRequest(fetchRequest, context: self)
         
         fetchRequest.fetchLimit = 1
         fetchRequest.resultType = .managedObjectIDResultType
         fetchClauses.forEach { $0.applyToFetchRequest(fetchRequest) }
-        
-        guard storeFound else {
-            
-            return nil
-        }
-        return self.fetchObjectID(fetchRequest.dynamicCast())
+
+        return try self.fetchObjectID(fetchRequest.dynamicCast())
     }
     
     @nonobjc
-    internal func fetchObjectIDs(_ from: CSFrom, _ fetchClauses: [CSFetchClause]) -> [NSManagedObjectID]? {
+    internal func fetchObjectIDs(_ from: CSFrom, _ fetchClauses: [CSFetchClause]) throws -> [NSManagedObjectID] {
         
         let fetchRequest = CoreStoreFetchRequest()
-        let storeFound = from.bridgeToSwift.applyToFetchRequest(fetchRequest, context: self)
+        try from.bridgeToSwift.applyToFetchRequest(fetchRequest, context: self)
         
         fetchRequest.fetchLimit = 0
         fetchRequest.resultType = .managedObjectIDResultType
         fetchClauses.forEach { $0.applyToFetchRequest(fetchRequest) }
-        
-        guard storeFound else {
-            
-            return nil
-        }
-        return self.fetchObjectIDs(fetchRequest.dynamicCast())
+
+        return try self.fetchObjectIDs(fetchRequest.dynamicCast())
     }
     
     @nonobjc
-    internal func deleteAll(_ from: CSFrom, _ deleteClauses: [CSDeleteClause]) -> Int? {
+    internal func deleteAll(_ from: CSFrom, _ deleteClauses: [CSDeleteClause]) throws -> Int {
         
         let fetchRequest = CoreStoreFetchRequest()
-        let storeFound = from.bridgeToSwift.applyToFetchRequest(fetchRequest, context: self)
+        try from.bridgeToSwift.applyToFetchRequest(fetchRequest, context: self)
         
         fetchRequest.fetchLimit = 0
         fetchRequest.resultType = .managedObjectResultType
         fetchRequest.returnsObjectsAsFaults = true
         fetchRequest.includesPropertyValues = false
         deleteClauses.forEach { $0.applyToFetchRequest(fetchRequest) }
-        
-        guard storeFound else {
-            
-            return nil
-        }
-        return self.deleteAll(fetchRequest.dynamicCast())
+
+        return try self.deleteAll(fetchRequest.dynamicCast())
     }
     
     @nonobjc
-    internal func queryValue(_ from: CSFrom, _ selectClause: CSSelect, _ queryClauses: [CSQueryClause]) -> Any? {
+    internal func queryValue(_ from: CSFrom, _ selectClause: CSSelect, _ queryClauses: [CSQueryClause]) throws -> Any? {
         
         let fetchRequest = CoreStoreFetchRequest()
-        let storeFound = from.bridgeToSwift.applyToFetchRequest(fetchRequest, context: self)
+        try from.bridgeToSwift.applyToFetchRequest(fetchRequest, context: self)
         
         fetchRequest.fetchLimit = 0
         
         selectClause.applyToFetchRequest(fetchRequest)
         queryClauses.forEach { $0.applyToFetchRequest(fetchRequest) }
-        
-        guard storeFound else {
-            
-            return nil
-        }
-        return self.queryValue(selectClause.selectTerms, fetchRequest: fetchRequest.dynamicCast())
+
+        return try self.queryValue(selectClause.selectTerms, fetchRequest: fetchRequest.dynamicCast())
     }
     
     @nonobjc
-    internal func queryAttributes(_ from: CSFrom, _ selectClause: CSSelect, _ queryClauses: [CSQueryClause]) -> [[String: Any]]? {
+    internal func queryAttributes(_ from: CSFrom, _ selectClause: CSSelect, _ queryClauses: [CSQueryClause]) throws -> [[String: Any]] {
         
         let fetchRequest = CoreStoreFetchRequest()
-        let storeFound = from.bridgeToSwift.applyToFetchRequest(fetchRequest, context: self)
+        try from.bridgeToSwift.applyToFetchRequest(fetchRequest, context: self)
         
         fetchRequest.fetchLimit = 0
         
         selectClause.applyToFetchRequest(fetchRequest)
         queryClauses.forEach { $0.applyToFetchRequest(fetchRequest) }
-        
-        guard storeFound else {
-            
-            return nil
-        }
-        return self.queryAttributes(fetchRequest.dynamicCast())
+
+        return try self.queryAttributes(fetchRequest.dynamicCast())
     }
 }

Sources/NSManagedObjectContext+Querying.swift

@@ -101,152 +101,130 @@ extension NSManagedObjectContext: FetchableSource, QueryableSource {
     }
     
     @nonobjc
-    public func fetchOne<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> D? {
+    public func fetchOne<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> D? {
         
-        return self.fetchOne(from, fetchClauses)
+        return try self.fetchOne(from, fetchClauses)
     }
     
     @nonobjc
-    public func fetchOne<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> D? {
+    public func fetchOne<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> D? {
         
         let fetchRequest = CoreStoreFetchRequest()
-        let storeFound = from.applyToFetchRequest(fetchRequest, context: self)
+        try from.applyToFetchRequest(fetchRequest, context: self)
         
         fetchRequest.fetchLimit = 1
         fetchRequest.resultType = .managedObjectResultType
         fetchClauses.forEach { $0.applyToFetchRequest(fetchRequest) }
-        
-        guard storeFound else {
-            
-            return nil
-        }
-        return self.fetchOne(fetchRequest.dynamicCast()).flatMap(from.entityClass.cs_fromRaw)
+
+        return try self.fetchOne(fetchRequest.dynamicCast()).flatMap(from.entityClass.cs_fromRaw)
     }
     
     @nonobjc
-    public func fetchOne<B: FetchChainableBuilderType>(_ clauseChain: B) -> B.ObjectType? {
+    public func fetchOne<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> B.ObjectType? {
         
-        return self.fetchOne(clauseChain.from, clauseChain.fetchClauses)
+        return try self.fetchOne(clauseChain.from, clauseChain.fetchClauses)
     }
     
     @nonobjc
-    public func fetchAll<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> [D]? {
+    public func fetchAll<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> [D] {
         
-        return self.fetchAll(from, fetchClauses)
+        return try self.fetchAll(from, fetchClauses)
     }
     
     @nonobjc
-    public func fetchAll<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> [D]? {
+    public func fetchAll<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> [D] {
         
         let fetchRequest = CoreStoreFetchRequest()
-        let storeFound = from.applyToFetchRequest(fetchRequest, context: self)
+        try from.applyToFetchRequest(fetchRequest, context: self)
         
         fetchRequest.fetchLimit = 0
         fetchRequest.resultType = .managedObjectResultType
         fetchClauses.forEach { $0.applyToFetchRequest(fetchRequest) }
-        
-        guard storeFound else {
-            
-            return nil
-        }
+
         let entityClass = from.entityClass
-        return self.fetchAll(fetchRequest.dynamicCast())?.map(entityClass.cs_fromRaw)
+        return try self.fetchAll(fetchRequest.dynamicCast()).map(entityClass.cs_fromRaw)
     }
     
     @nonobjc
-    public func fetchAll<B: FetchChainableBuilderType>(_ clauseChain: B) -> [B.ObjectType]? {
+    public func fetchAll<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> [B.ObjectType] {
         
-        return self.fetchAll(clauseChain.from, clauseChain.fetchClauses)
+        return try self.fetchAll(clauseChain.from, clauseChain.fetchClauses)
     }
     
     @nonobjc
-    public func fetchCount<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> Int? {
+    public func fetchCount<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> Int {
     
-        return self.fetchCount(from, fetchClauses)
+        return try self.fetchCount(from, fetchClauses)
     }
     
     @nonobjc
-    public func fetchCount<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> Int? {
+    public func fetchCount<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> Int {
         
         let fetchRequest = CoreStoreFetchRequest()
-        let storeFound = from.applyToFetchRequest(fetchRequest, context: self)
+        try from.applyToFetchRequest(fetchRequest, context: self)
         fetchClauses.forEach { $0.applyToFetchRequest(fetchRequest) }
-        
-        guard storeFound else {
-            
-            return nil
-        }
-        return self.fetchCount(fetchRequest.dynamicCast())
+
+        return try self.fetchCount(fetchRequest.dynamicCast())
     }
     
     @nonobjc
-    public func fetchCount<B: FetchChainableBuilderType>(_ clauseChain: B) -> Int? {
+    public func fetchCount<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> Int {
         
-        return self.fetchCount(clauseChain.from, clauseChain.fetchClauses)
+        return try self.fetchCount(clauseChain.from, clauseChain.fetchClauses)
     }
     
     @nonobjc
-    public func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> NSManagedObjectID? {
+    public func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> NSManagedObjectID? {
         
-        return self.fetchObjectID(from, fetchClauses)
+        return try self.fetchObjectID(from, fetchClauses)
     }
     
     @nonobjc
-    public func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> NSManagedObjectID? {
+    public func fetchObjectID<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> NSManagedObjectID? {
         
         let fetchRequest = CoreStoreFetchRequest()
-        let storeFound = from.applyToFetchRequest(fetchRequest, context: self)
+        try from.applyToFetchRequest(fetchRequest, context: self)
         
         fetchRequest.fetchLimit = 1
         fetchRequest.resultType = .managedObjectIDResultType
         fetchClauses.forEach { $0.applyToFetchRequest(fetchRequest) }
-        
-        guard storeFound else {
-            
-            return nil
-        }
-        return self.fetchObjectID(fetchRequest.dynamicCast())
+
+        return try self.fetchObjectID(fetchRequest.dynamicCast())
     }
-    
-    // TODO: docs
+
     @nonobjc
-    public func fetchObjectID<B: FetchChainableBuilderType>(_ clauseChain: B) -> NSManagedObjectID? {
+    public func fetchObjectID<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> NSManagedObjectID? {
         
-        return self.fetchObjectID(clauseChain.from, clauseChain.fetchClauses)
+        return try self.fetchObjectID(clauseChain.from, clauseChain.fetchClauses)
     }
     
     @nonobjc
-    public func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> [NSManagedObjectID]? {
+    public func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: FetchClause...) throws -> [NSManagedObjectID] {
         
-        return self.fetchObjectIDs(from, fetchClauses)
+        return try self.fetchObjectIDs(from, fetchClauses)
     }
     
     @nonobjc
-    public func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) -> [NSManagedObjectID]? {
+    public func fetchObjectIDs<D>(_ from: From<D>, _ fetchClauses: [FetchClause]) throws -> [NSManagedObjectID] {
         
         let fetchRequest = CoreStoreFetchRequest()
-        let storeFound = from.applyToFetchRequest(fetchRequest, context: self)
+        try from.applyToFetchRequest(fetchRequest, context: self)
         
         fetchRequest.fetchLimit = 0
         fetchRequest.resultType = .managedObjectIDResultType
         fetchClauses.forEach { $0.applyToFetchRequest(fetchRequest) }
-        
-        guard storeFound else {
-            
-            return nil
-        }
-        return self.fetchObjectIDs(fetchRequest.dynamicCast())
+
+        return try self.fetchObjectIDs(fetchRequest.dynamicCast())
     }
-    
-    // TODO: docs
+
     @nonobjc
-    public func fetchObjectIDs<B: FetchChainableBuilderType>(_ clauseChain: B) -> [NSManagedObjectID]? {
+    public func fetchObjectIDs<B: FetchChainableBuilderType>(_ clauseChain: B) throws -> [NSManagedObjectID] {
         
-        return self.fetchObjectIDs(clauseChain.from, clauseChain.fetchClauses)
+        return try self.fetchObjectIDs(clauseChain.from, clauseChain.fetchClauses)
     }
     
     @nonobjc
-    internal func fetchObjectIDs(_ fetchRequest: NSFetchRequest<NSManagedObjectID>) -> [NSManagedObjectID]? {
+    internal func fetchObjectIDs(_ fetchRequest: NSFetchRequest<NSManagedObjectID>) throws -> [NSManagedObjectID] {
         
         var fetchResults: [NSManagedObjectID]?
         var fetchError: Error?
@@ -261,77 +239,70 @@ extension NSManagedObjectContext: FetchableSource, QueryableSource {
                 fetchError = error
             }
         }
-        if fetchResults == nil {
-            
-            CoreStore.log(
-                CoreStoreError(fetchError),
-                "Failed executing fetch request."
-            )
-            return nil
+        if let fetchResults = fetchResults {
+
+            return fetchResults
         }
-        return fetchResults
+        let coreStoreError = CoreStoreError(fetchError)
+        CoreStore.log(
+            coreStoreError,
+            "Failed executing fetch request."
+        )
+        throw coreStoreError
     }
     
     
     // MARK: QueryableSource
     
     @nonobjc
-    public func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: QueryClause...) -> U? {
+    public func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: QueryClause...) throws -> U? {
         
-        return self.queryValue(from, selectClause, queryClauses)
+        return try self.queryValue(from, selectClause, queryClauses)
     }
     
     @nonobjc
-    public func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: [QueryClause]) -> U? {
+    public func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: [QueryClause]) throws -> U? {
         
         let fetchRequest = CoreStoreFetchRequest()
-        let storeFound = from.applyToFetchRequest(fetchRequest, context: self)
+        try from.applyToFetchRequest(fetchRequest, context: self)
         
         fetchRequest.fetchLimit = 0
         
         selectClause.applyToFetchRequest(fetchRequest)
         queryClauses.forEach { $0.applyToFetchRequest(fetchRequest) }
-        
-        guard storeFound else {
-            
-            return nil
-        }
-        return self.queryValue(selectClause.selectTerms, fetchRequest: fetchRequest)
+
+        return try self.queryValue(selectClause.selectTerms, fetchRequest: fetchRequest)
     }
     
     @nonobjc
-    public func queryValue<B>(_ clauseChain: B) -> B.ResultType? where B: QueryChainableBuilderType, B.ResultType: QueryableAttributeType {
+    public func queryValue<B>(_ clauseChain: B) throws -> B.ResultType? where B: QueryChainableBuilderType, B.ResultType: QueryableAttributeType {
         
-        return self.queryValue(clauseChain.from, clauseChain.select, clauseChain.queryClauses)
+        return try self.queryValue(clauseChain.from, clauseChain.select, clauseChain.queryClauses)
     }
     
     @nonobjc
-    public func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: QueryClause...) -> [[String: Any]]? {
+    public func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: QueryClause...) throws -> [[String: Any]] {
         
-        return self.queryAttributes(from, selectClause, queryClauses)
+        return try self.queryAttributes(from, selectClause, queryClauses)
     }
     
     @nonobjc
-    public func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: [QueryClause]) -> [[String: Any]]? {
+    public func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: [QueryClause]) throws -> [[String: Any]] {
         
         let fetchRequest = CoreStoreFetchRequest()
-        let storeFound = from.applyToFetchRequest(fetchRequest, context: self)
+        try from.applyToFetchRequest(fetchRequest, context: self)
         
         fetchRequest.fetchLimit = 0
         
         selectClause.applyToFetchRequest(fetchRequest)
         queryClauses.forEach { $0.applyToFetchRequest(fetchRequest) }
-        
-        guard storeFound else {
-            
-            return nil
-        }
-        return self.queryAttributes(fetchRequest)
+
+        return try self.queryAttributes(fetchRequest)
     }
     
-    public func queryAttributes<B>(_ clauseChain: B) -> [[String : Any]]? where B : QueryChainableBuilderType, B.ResultType == NSDictionary {
+    public func queryAttributes<B>(_ clauseChain: B) throws -> [[String : Any]] where B : QueryChainableBuilderType, B.ResultType == NSDictionary {
         
-        return self.queryAttributes(clauseChain.from, clauseChain.select, clauseChain.queryClauses)
+        return try self.queryAttributes(clauseChain.from, clauseChain.select, clauseChain.queryClauses)
     }
     
     
@@ -347,22 +318,18 @@ extension NSManagedObjectContext: FetchableSource, QueryableSource {
     // MARK: Deleting
     
     @nonobjc
-    internal func deleteAll<D>(_ from: From<D>, _ deleteClauses: [FetchClause]) -> Int? {
+    internal func deleteAll<D>(_ from: From<D>, _ deleteClauses: [FetchClause]) throws -> Int {
         
         let fetchRequest = CoreStoreFetchRequest()
-        let storeFound = from.applyToFetchRequest(fetchRequest, context: self)
+        try from.applyToFetchRequest(fetchRequest, context: self)
         
         fetchRequest.fetchLimit = 0
         fetchRequest.resultType = .managedObjectResultType
         fetchRequest.returnsObjectsAsFaults = true
         fetchRequest.includesPropertyValues = false
         deleteClauses.forEach { $0.applyToFetchRequest(fetchRequest) }
-        
-        guard storeFound else {
-            
-            return nil
-        }
-        return self.deleteAll(fetchRequest.dynamicCast())
+
+        return try self.deleteAll(fetchRequest.dynamicCast())
     }
     
     
@@ -383,7 +350,7 @@ internal extension NSManagedObjectContext {
     // MARK: Fetching
     
     @nonobjc
-    internal func fetchOne<D: NSManagedObject>(_ fetchRequest: NSFetchRequest<D>) -> D? {
+    internal func fetchOne<D: NSManagedObject>(_ fetchRequest: NSFetchRequest<D>) throws -> D? {
         
         var fetchResults: [D]?
         var fetchError: Error?
@@ -398,19 +365,20 @@ internal extension NSManagedObjectContext {
                 fetchError = error
             }
         }
-        if fetchResults == nil {
-            
-            CoreStore.log(
-                CoreStoreError(fetchError),
-                "Failed executing fetch request."
-            )
-            return nil
+        if let fetchResults = fetchResults {
+
+            return fetchResults.first
         }
-        return fetchResults?.first
+        let coreStoreError = CoreStoreError(fetchError)
+        CoreStore.log(
+            coreStoreError,
+            "Failed executing fetch request."
+        )
+        throw coreStoreError
     }
     
     @nonobjc
-    internal func fetchAll<D: NSManagedObject>(_ fetchRequest: NSFetchRequest<D>) -> [D]? {
+    internal func fetchAll<D: NSManagedObject>(_ fetchRequest: NSFetchRequest<D>) throws -> [D] {
         
         var fetchResults: [D]?
         var fetchError: Error?
@@ -425,19 +393,20 @@ internal extension NSManagedObjectContext {
                 fetchError = error
             }
         }
-        if fetchResults == nil {
-            
-            CoreStore.log(
-                CoreStoreError(fetchError),
-                "Failed executing fetch request."
-            )
-            return nil
+        if let fetchResults = fetchResults {
+
+            return fetchResults
         }
-        return fetchResults
+        let coreStoreError = CoreStoreError(fetchError)
+        CoreStore.log(
+            coreStoreError,
+            "Failed executing fetch request."
+        )
+        throw coreStoreError
     }
     
     @nonobjc
-    internal func fetchCount(_ fetchRequest: NSFetchRequest<NSFetchRequestResult>) -> Int? {
+    internal func fetchCount(_ fetchRequest: NSFetchRequest<NSFetchRequestResult>) throws -> Int {
         
         var count = 0
         var countError: Error?
@@ -453,18 +422,19 @@ internal extension NSManagedObjectContext {
             }
         }
         if count == NSNotFound {
-            
+
+            let coreStoreError = CoreStoreError(countError)
             CoreStore.log(
-                CoreStoreError(countError),
+                coreStoreError,
                 "Failed executing count request."
             )
-            return nil
+            throw coreStoreError
         }
         return count
     }
     
     @nonobjc
-    internal func fetchObjectID(_ fetchRequest: NSFetchRequest<NSManagedObjectID>) -> NSManagedObjectID? {
+    internal func fetchObjectID(_ fetchRequest: NSFetchRequest<NSManagedObjectID>) throws -> NSManagedObjectID? {
         
         var fetchResults: [NSManagedObjectID]?
         var fetchError: Error?
@@ -479,22 +449,23 @@ internal extension NSManagedObjectContext {
                 fetchError = error
             }
         }
-        if fetchResults == nil {
-            
-            CoreStore.log(
-                CoreStoreError(fetchError),
-                "Failed executing fetch request."
-            )
-            return nil
+        if let fetchResults = fetchResults {
+
+            return fetchResults.first
         }
-        return fetchResults?.first
+        let coreStoreError = CoreStoreError(fetchError)
+        CoreStore.log(
+            coreStoreError,
+            "Failed executing fetch request."
+        )
+        throw coreStoreError
     }
     
     
     // MARK: Querying
     
     @nonobjc
-    internal func queryValue<D, U: QueryableAttributeType>(_ selectTerms: [SelectTerm<D>], fetchRequest: NSFetchRequest<NSFetchRequestResult>) -> U? {
+    internal func queryValue<D, U: QueryableAttributeType>(_ selectTerms: [SelectTerm<D>], fetchRequest: NSFetchRequest<NSFetchRequestResult>) throws -> U? {
         
         var fetchResults: [Any]?
         var fetchError: Error?
@@ -518,16 +489,16 @@ internal extension NSManagedObjectContext {
             }
             return nil
         }
-        
+        let coreStoreError = CoreStoreError(fetchError)
         CoreStore.log(
-            CoreStoreError(fetchError),
+            coreStoreError,
             "Failed executing fetch request."
         )
-        return nil
+        throw coreStoreError
     }
     
     @nonobjc
-    internal func queryValue<D>(_ selectTerms: [SelectTerm<D>], fetchRequest: NSFetchRequest<NSFetchRequestResult>) -> Any? {
+    internal func queryValue<D>(_ selectTerms: [SelectTerm<D>], fetchRequest: NSFetchRequest<NSFetchRequestResult>) throws -> Any? {
         
         var fetchResults: [Any]?
         var fetchError: Error?
@@ -551,16 +522,16 @@ internal extension NSManagedObjectContext {
             }
             return nil
         }
-        
+        let coreStoreError = CoreStoreError(fetchError)
         CoreStore.log(
-            CoreStoreError(fetchError),
+            coreStoreError,
             "Failed executing fetch request."
         )
-        return nil
+        throw coreStoreError
     }
     
     @nonobjc
-    internal func queryAttributes(_ fetchRequest: NSFetchRequest<NSFetchRequestResult>) -> [[String: Any]]? {
+    internal func queryAttributes(_ fetchRequest: NSFetchRequest<NSFetchRequestResult>) throws -> [[String: Any]] {
         
         var fetchResults: [Any]?
         var fetchError: Error?
@@ -579,19 +550,19 @@ internal extension NSManagedObjectContext {
             
             return NSDictionary.cs_fromQueryResultsNativeType(fetchResults)
         }
-        
+        let coreStoreError = CoreStoreError(fetchError)
         CoreStore.log(
-            CoreStoreError(fetchError),
+            coreStoreError,
             "Failed executing fetch request."
         )
-        return nil
+        throw coreStoreError
     }
     
     
     // MARK: Deleting
     
     @nonobjc
-    internal func deleteAll<D: NSManagedObject>(_ fetchRequest: NSFetchRequest<D>) -> Int? {
+    internal func deleteAll<D: NSManagedObject>(_ fetchRequest: NSFetchRequest<D>) throws -> Int {
         
         var numberOfDeletedObjects: Int?
         var fetchError: Error?
@@ -614,14 +585,15 @@ internal extension NSManagedObjectContext {
                 }
             }
         }
-        if numberOfDeletedObjects == nil {
-            
-            CoreStore.log(
-                CoreStoreError(fetchError),
-                "Failed executing fetch request."
-            )
-            return nil
+        if let numberOfDeletedObjects = numberOfDeletedObjects {
+
+            return numberOfDeletedObjects
         }
-        return numberOfDeletedObjects
+        let coreStoreError = CoreStoreError(fetchError)
+        CoreStore.log(
+            coreStoreError,
+            "Failed executing delete request."
+        )
+        throw coreStoreError
     }
 }

Sources/QueryableSource.swift

@@ -42,9 +42,10 @@ public protocol QueryableSource: class {
      - parameter from: a `From` clause indicating the entity type
      - parameter selectClause: a `Select<U>` clause indicating the properties to fetch, and with the generic type indicating the return type.
      - parameter queryClauses: a series of `QueryClause` instances for the query request. Accepts `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
-     - returns: the result of the the query. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - returns: the result of the the query, or `nil` if no match was found. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: QueryClause...) -> U?
+    func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: QueryClause...) throws -> U?
 
     /**
      Queries aggregate values as specified by the `QueryClause`s. Requires at least a `Select` clause, and optional `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
@@ -54,9 +55,10 @@ public protocol QueryableSource: class {
      - parameter from: a `From` clause indicating the entity type
      - parameter selectClause: a `Select<U>` clause indicating the properties to fetch, and with the generic type indicating the return type.
      - parameter queryClauses: a series of `QueryClause` instances for the query request. Accepts `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
-     - returns: the result of the the query. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - returns: the result of the the query, or `nil` if no match was found. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: [QueryClause]) -> U?
+    func queryValue<D, U: QueryableAttributeType>(_ from: From<D>, _ selectClause: Select<D, U>, _ queryClauses: [QueryClause]) throws -> U?
     
     /**
      Queries a property value or aggregate as specified by the `QueryChainableBuilderType` built from a chain of clauses.
@@ -70,9 +72,10 @@ public protocol QueryableSource: class {
      )
      ```
      - parameter clauseChain: a `QueryChainableBuilderType` indicating the property/aggregate to fetch and the series of queries for the request.
-     - returns: the result of the the query as specified by the `QueryChainableBuilderType`
+     - returns: the result of the the query as specified by the `QueryChainableBuilderType`, or `nil` if no match was found.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func queryValue<B: QueryChainableBuilderType>(_ clauseChain: B) -> B.ResultType? where B.ResultType: QueryableAttributeType
+    func queryValue<B: QueryChainableBuilderType>(_ clauseChain: B) throws -> B.ResultType? where B.ResultType: QueryableAttributeType
 
     /**
      Queries a dictionary of attribute values as specified by the `QueryClause`s. Requires at least a `Select` clause, and optional `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
@@ -83,8 +86,9 @@ public protocol QueryableSource: class {
      - parameter selectClause: a `Select<U>` clause indicating the properties to fetch, and with the generic type indicating the return type.
      - parameter queryClauses: a series of `QueryClause` instances for the query request. Accepts `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
      - returns: the result of the the query. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: QueryClause...) -> [[String: Any]]?
+    func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: QueryClause...) throws -> [[String: Any]]
 
     /**
      Queries a dictionary of attribute values as specified by the `QueryClause`s. Requires at least a `Select` clause, and optional `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
@@ -95,8 +99,9 @@ public protocol QueryableSource: class {
      - parameter selectClause: a `Select<U>` clause indicating the properties to fetch, and with the generic type indicating the return type.
      - parameter queryClauses: a series of `QueryClause` instances for the query request. Accepts `Where`, `OrderBy`, `GroupBy`, and `Tweak` clauses.
      - returns: the result of the the query. The type of the return value is specified by the generic type of the `Select<U>` parameter.
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: [QueryClause]) -> [[String: Any]]?
+    func queryAttributes<D>(_ from: From<D>, _ selectClause: Select<D, NSDictionary>, _ queryClauses: [QueryClause]) throws -> [[String: Any]]
     
     /**
      Queries a dictionary of attribute values or  as specified by the `QueryChainableBuilderType` built from a chain of clauses.
@@ -120,8 +125,9 @@ public protocol QueryableSource: class {
      ```
      - parameter clauseChain: a `QueryChainableBuilderType` indicating the properties to fetch and the series of queries for the request.
      - returns: the result of the the query as specified by the `QueryChainableBuilderType`
+     - throws: a `CoreStoreError` value indicating the failure if the specified entity could not be found in any store's schema.
      */
-    func queryAttributes<B: QueryChainableBuilderType>(_ clauseChain: B) -> [[String: Any]]? where B.ResultType == NSDictionary
+    func queryAttributes<B: QueryChainableBuilderType>(_ clauseChain: B) throws -> [[String: Any]] where B.ResultType == NSDictionary
     
     /**
      The internal `NSManagedObjectContext` managed by this `QueryableSource`. Using this context directly should typically be avoided, and is provided by CoreStore only for extremely specialized cases.

Sources/Select.swift

@@ -298,6 +298,9 @@ public enum SelectTerm<D: DynamicObject>: ExpressibleByStringLiteral, Hashable {
     }
 }
 
+
+// MARK: - SelectTerm where D: NSManagedObject
+
 extension SelectTerm where D: NSManagedObject {
     
     /**
@@ -366,6 +369,9 @@ extension SelectTerm where D: NSManagedObject {
     }
 }
 
+
+// MARK: - SelectTerm where D: CoreStoreObject
+
 extension SelectTerm where D: CoreStoreObject {
     
     /**

Sources/UnsafeDataTransaction+Observing.swift

@@ -142,8 +142,23 @@ public extension UnsafeDataTransaction {
             createAsynchronously: createAsynchronously
         )
     }
-    
-    // TODO: docs
+
+    /**
+     Asynchronously creates a `ListMonitor` for a list of `DynamicObject`s that satisfy the specified `FetchChainableBuilderType` built from a chain of clauses. Since `NSFetchedResultsController` greedily locks the persistent store on initial fetch, you may prefer this method instead of the synchronous counterpart to avoid deadlocks while background updates/saves are being executed.
+
+     ```
+     dataStack.monitorList(
+         createAsynchronously: { (monitor) in
+             self.monitor = monitor
+         },
+         From<MyPersonEntity>()
+             .where(\.age > 18)
+             .orderBy(.ascending(\.age))
+     )
+     ```
+     - parameter createAsynchronously: the closure that receives the created `ListMonitor` instance
+     - parameter clauseChain: a `FetchChainableBuilderType` built from a chain of clauses
+     */
     public func monitorList<B: FetchChainableBuilderType>(createAsynchronously: @escaping (ListMonitor<B.ObjectType>) -> Void, _ clauseChain: B) {
         
         self.monitorList(
@@ -267,8 +282,8 @@ public extension UnsafeDataTransaction {
              .orderBy(.ascending(\.age))
      )
      ```
+     - parameter createAsynchronously: the closure that receives the created `ListMonitor` instance
      - parameter clauseChain: a `SectionMonitorBuilderType` built from a chain of clauses
-     - returns: a `ListMonitor` for a list of `DynamicObject`s that satisfy the specified `SectionMonitorBuilderType`
      */
     public func monitorSectionedList<B: SectionMonitorBuilderType>(createAsynchronously: @escaping (ListMonitor<B.ObjectType>) -> Void, _ clauseChain: B) {
         

Sources/Where.swift

@@ -541,7 +541,7 @@ public extension Sequence where Iterator.Element: WhereClauseType {
 
 public extension Where {
     
-    @available(*, deprecated: 4.0, renamed: "&&?")
+    @available(*, deprecated, renamed: "&&?")
     public static func && (left: Where<D>, right: Where<D>?) -> Where<D> {
         
         if let right = right {
@@ -551,7 +551,7 @@ public extension Where {
         return left
     }
     
-    @available(*, deprecated: 4.0, renamed: "&&?")
+    @available(*, deprecated, renamed: "&&?")
     public static func && (left: Where<D>?, right: Where<D>) -> Where<D> {
         
         if let left = left {
@@ -561,7 +561,7 @@ public extension Where {
         return right
     }
     
-    @available(*, deprecated: 4.0, renamed: "||?")
+    @available(*, deprecated, renamed: "||?")
     public static func || (left: Where<D>, right: Where<D>?) -> Where<D> {
         
         if let right = right {
@@ -571,7 +571,7 @@ public extension Where {
         return left
     }
     
-    @available(*, deprecated: 4.0, renamed: "||?")
+    @available(*, deprecated, renamed: "||?")
     public static func || (left: Where<D>?, right: Where<D>) -> Where<D> {
         
         if let left = left {