Refetch monitors when persistent stores are added/removed. Allow unsafe transactions to create their own monitors

CoreStore/Convenience Helpers/NSFetchedResultsController+Convenience.swift

@@ -31,20 +31,31 @@ import CoreData
 
 public extension NSFetchedResultsController {
     
-    public convenience init<T: NSManagedObject>(dataStack: DataStack, fetchRequest: NSFetchRequest, from: From<T>? = nil, sectionBy: SectionBy? = nil, fetchClauses: [FetchClause]) {
+    
+    // MARK: Public
+    
+    public func createForStack<T: NSManagedObject>(dataStack: DataStack, fetchRequest: NSFetchRequest, from: From<T>? = nil, sectionBy: SectionBy? = nil, fetchClauses: [FetchClause]) -> NSFetchedResultsController {
         
-        let context = dataStack.mainContext
-        from?.applyToFetchRequest(fetchRequest, context: context)
-        for clause in fetchClauses {
-            
-            clause.applyToFetchRequest(fetchRequest)
-        }
-        
-        self.init(
+        return CoreStoreFetchedResultsController<T>(
+            context: dataStack.mainContext,
             fetchRequest: fetchRequest,
-            managedObjectContext: context,
-            sectionNameKeyPath: sectionBy?.sectionKeyPath,
-            cacheName: nil
+            from: from,
+            sectionBy: sectionBy,
+            fetchClauses: fetchClauses
+        )
+    }
+    
+    
+    // MARK: Internal
+    
+    internal func createFromContext<T: NSManagedObject>(context: NSManagedObjectContext, fetchRequest: NSFetchRequest, from: From<T>? = nil, sectionBy: SectionBy? = nil, fetchClauses: [FetchClause]) -> NSFetchedResultsController {
+        
+        return CoreStoreFetchedResultsController<T>(
+            context: context,
+            fetchRequest: fetchRequest,
+            from: from,
+            sectionBy: sectionBy,
+            fetchClauses: fetchClauses
         )
     }
 }

CoreStore/Fetching and Querying/Concrete Clauses/From.swift

@@ -36,22 +36,25 @@ public struct From<T: NSManagedObject> {
     
     // MARK: Public
     
+    /**
+    Initializes a `From` clause with the specified entity type and configuration.
+    Sample Usage:
+    
+        let person = transaction.fetchOne(From<MyPersonEntity>())
+    */
     public init(){
         
-        self.entityClass = T.self
-        self.findPersistentStores = { _ in nil }
+        self.init(entityClass: T.self)
     }
     
     public init(_ entity: T.Type) {
         
-        self.entityClass = entity
-        self.findPersistentStores = { _ in nil }
+        self.init(entityClass: entity)
     }
     
     public init(_ entityClass: AnyClass) {
         
-        self.entityClass = entityClass
-        self.findPersistentStores = { _ in nil }
+        self.init(entityClass: entityClass)
     }
     
     public init(_ configuration: String?, otherConfigurations: String?...) {
@@ -147,10 +150,20 @@ public struct From<T: NSManagedObject> {
     
     // MARK: Internal
     
-    internal func applyToFetchRequest(fetchRequest: NSFetchRequest, context: NSManagedObjectContext) {
+    internal func applyToFetchRequest(fetchRequest: NSFetchRequest, context: NSManagedObjectContext, applyAffectedStores: Bool = true) {
         
         fetchRequest.entity = context.entityDescriptionForEntityClass(self.entityClass)
-        fetchRequest.affectedStores = self.findPersistentStores(context: context)
+        if applyAffectedStores {
+            
+            self.applyAffectedStoresForFetchedRequest(fetchRequest, context: context)
+        }
+    }
+    
+    internal func applyAffectedStoresForFetchedRequest(fetchRequest: NSFetchRequest, context: NSManagedObjectContext) -> Bool {
+        
+        let stores = self.findPersistentStores(context: context)
+        fetchRequest.affectedStores = stores
+        return stores?.isEmpty == false
     }
     
     
@@ -160,6 +173,15 @@ public struct From<T: NSManagedObject> {
     
     private let findPersistentStores: (context: NSManagedObjectContext) -> [NSPersistentStore]?
     
+    private init(entityClass: AnyClass) {
+        
+        self.entityClass = entityClass
+        self.findPersistentStores = { (context: NSManagedObjectContext) -> [NSPersistentStore]? in
+            
+            return context.parentStack?.persistentStoresForEntityClass(entityClass)
+        }
+    }
+    
     private init(entityClass: AnyClass, configurations: [String?]) {
         
         let configurationsSet = Set(configurations.map { $0 ?? Into.defaultConfigurationName })

CoreStore/Info.plist

@@ -15,7 +15,7 @@
 	<key>CFBundlePackageType</key>
 	<string>FMWK</string>
 	<key>CFBundleShortVersionString</key>
-	<string>1.4.4</string>
+	<string>1.5.0</string>
 	<key>CFBundleSignature</key>
 	<string>????</string>
 	<key>CFBundleVersion</key>

CoreStore/Internal/CoreStoreFetchedResultsController.swift

@@ -0,0 +1,101 @@
+//
+//  CoreStoreFetchedResultsController.swift
+//  CoreStore
+//
+//  Copyright © 2016 John Rommel Estropia
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy
+//  of this software and associated documentation files (the "Software"), to deal
+//  in the Software without restriction, including without limitation the rights
+//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//  copies of the Software, and to permit persons to whom the Software is
+//  furnished to do so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+//
+
+import Foundation
+import CoreData
+
+
+// MARK: - CoreStoreFetchedResultsController
+
+@available(OSX, unavailable)
+internal final class CoreStoreFetchedResultsController<T: NSManagedObject>: NSFetchedResultsController {
+    
+    
+    // MARK: Internal
+    
+    internal convenience init<T>(dataStack: DataStack, fetchRequest: NSFetchRequest, from: From<T>? = nil, sectionBy: SectionBy? = nil, fetchClauses: [FetchClause]) {
+        
+        self.init(
+            context: dataStack.mainContext,
+            fetchRequest: fetchRequest,
+            from: from,
+            sectionBy: sectionBy,
+            fetchClauses: fetchClauses
+        )
+    }
+    
+    internal init<T>(context: NSManagedObjectContext, fetchRequest: NSFetchRequest, from: From<T>? = nil, sectionBy: SectionBy? = nil, fetchClauses: [FetchClause]) {
+        
+        from?.applyToFetchRequest(fetchRequest, context: context, applyAffectedStores: false)
+        for clause in fetchClauses {
+            
+            clause.applyToFetchRequest(fetchRequest)
+        }
+        
+        if let from = from {
+            
+            self.reapplyAffectedStores = {
+                
+                return from.applyAffectedStoresForFetchedRequest(fetchRequest, context: context)
+            }
+        }
+        else {
+            
+            guard let from = (fetchRequest.entity.flatMap { $0.managedObjectClassName }).flatMap(NSClassFromString).flatMap(From.init) else {
+                
+                fatalError("Attempted to create an \(typeName(NSFetchedResultsController)) without a  From clause or an NSEntityDescription.")
+            }
+            
+            self.reapplyAffectedStores = {
+                
+                return from.applyAffectedStoresForFetchedRequest(fetchRequest, context: context)
+            }
+        }
+        
+        super.init(
+            fetchRequest: fetchRequest,
+            managedObjectContext: context,
+            sectionNameKeyPath: sectionBy?.sectionKeyPath,
+            cacheName: nil
+        )
+    }
+    
+    internal func performFetchFromSpecifiedStores() throws {
+        
+        if !self.reapplyAffectedStores() {
+            
+            CoreStore.log(
+                .Warning,
+                message: "Attempted to perform a fetch on an \(typeName(NSFetchedResultsController)) but could not find any persistent store for the entity \(typeName(self.fetchRequest.entityName))"
+            )
+        }
+        try self.performFetch()
+    }
+    
+    
+    // MARK: Private
+    
+    private let reapplyAffectedStores: () -> Bool
+}

CoreStore/Observing/ListMonitor.swift

@@ -882,12 +882,15 @@ public final class ListMonitor<T: NSManagedObject> {
             "Attempted to refetch a \(typeName(self)) outside the main thread."
         )
         
-        self.isPendingRefetch = true
-        
-        NSNotificationCenter.defaultCenter().postNotificationName(
-            ListMonitorWillRefetchListNotification,
-            object: self
-        )
+        if !self.isPendingRefetch {
+            
+            self.isPendingRefetch = true
+            
+            NSNotificationCenter.defaultCenter().postNotificationName(
+                ListMonitorWillRefetchListNotification,
+                object: self
+            )
+        }
         
         self.taskGroup.notify(.Main) { [weak self] () -> Void in
             
@@ -904,14 +907,14 @@ public final class ListMonitor<T: NSManagedObject> {
                 clause.applyToFetchRequest(fetchRequest)
             }
             
-            strongSelf.parentStack?.childTransactionQueue.async {
+            strongSelf.transactionQueue.async {
                 
                 guard let strongSelf = self else {
                     
                     return
                 }
                 
-                try! strongSelf.fetchedResultsController.performFetch()
+                try! strongSelf.fetchedResultsController.performFetchFromSpecifiedStores()
                 
                 GCDQueue.Main.async { () -> Void in
                     
@@ -938,36 +941,54 @@ public final class ListMonitor<T: NSManagedObject> {
     internal convenience init(dataStack: DataStack, from: From<T>, sectionBy: SectionBy?, fetchClauses: [FetchClause]) {
      
         self.init(
-            dataStack: dataStack,
+            context: dataStack.mainContext,
+            transactionQueue: dataStack.childTransactionQueue,
             from: from,
             sectionBy: sectionBy,
             fetchClauses: fetchClauses,
-            prepareFetch: { _, performFetch in performFetch() }
+            createAsynchronously: nil
         )
     }
     
     internal convenience init(dataStack: DataStack, from: From<T>, sectionBy: SectionBy?, fetchClauses: [FetchClause], createAsynchronously: (ListMonitor<T>) -> Void) {
         
+        let queue = dataStack.childTransactionQueue
         self.init(
-            dataStack: dataStack,
+            context: dataStack.mainContext,
+            transactionQueue: queue,
             from: from,
             sectionBy: sectionBy,
             fetchClauses: fetchClauses,
-            prepareFetch: { listMonitor, performFetch in
-                
-                dataStack.childTransactionQueue.async {
-                    
-                    performFetch()
-                    GCDQueue.Main.async {
-                        
-                        createAsynchronously(listMonitor)
-                    }
-                }
-            }
+            createAsynchronously: createAsynchronously
         )
     }
     
-    private init(dataStack: DataStack, from: From<T>, sectionBy: SectionBy?, fetchClauses: [FetchClause], prepareFetch: (ListMonitor<T>, () -> Void) -> Void) {
+    internal convenience init(unsafeTransaction: UnsafeDataTransaction, from: From<T>, sectionBy: SectionBy?, fetchClauses: [FetchClause]) {
+        
+        self.init(
+            context: unsafeTransaction.context,
+            transactionQueue: unsafeTransaction.transactionQueue,
+            from: from,
+            sectionBy: sectionBy,
+            fetchClauses: fetchClauses,
+            createAsynchronously: nil
+        )
+    }
+    
+    internal convenience init(unsafeTransaction: UnsafeDataTransaction, from: From<T>, sectionBy: SectionBy?, fetchClauses: [FetchClause], createAsynchronously: (ListMonitor<T>) -> Void) {
+        
+        let queue = unsafeTransaction.transactionQueue
+        self.init(
+            context: unsafeTransaction.context,
+            transactionQueue: queue,
+            from: from,
+            sectionBy: sectionBy,
+            fetchClauses: fetchClauses,
+            createAsynchronously: createAsynchronously
+        )
+    }
+    
+    private init(context: NSManagedObjectContext, transactionQueue: GCDQueue, from: From<T>, sectionBy: SectionBy?, fetchClauses: [FetchClause], createAsynchronously: ((ListMonitor<T>) -> Void)?) {
         
         let fetchRequest = NSFetchRequest()
         fetchRequest.fetchLimit = 0
@@ -976,8 +997,8 @@ public final class ListMonitor<T: NSManagedObject> {
         fetchRequest.includesPendingChanges = false
         fetchRequest.shouldRefreshRefetchedObjects = true
         
-        let fetchedResultsController = NSFetchedResultsController(
-            dataStack: dataStack,
+        let fetchedResultsController = CoreStoreFetchedResultsController<T>(
+            context: context,
             fetchRequest: fetchRequest,
             from: from,
             sectionBy: sectionBy,
@@ -988,7 +1009,6 @@ public final class ListMonitor<T: NSManagedObject> {
         
         self.fetchedResultsController = fetchedResultsController
         self.fetchedResultsControllerDelegate = fetchedResultsControllerDelegate
-        self.parentStack = dataStack
         
         if let sectionIndexTransformer = sectionBy?.sectionIndexTransformer {
             
@@ -998,26 +1018,118 @@ public final class ListMonitor<T: NSManagedObject> {
             
             self.sectionIndexTransformer = { $0 }
         }
+        self.transactionQueue = transactionQueue
         
         fetchedResultsControllerDelegate.handler = self
         fetchedResultsControllerDelegate.fetchedResultsController = fetchedResultsController
         
-        prepareFetch(self, { try! fetchedResultsController.performFetch() })
+        guard let coordinator = context.parentStack?.coordinator else {
+            
+            return
+        }
+        
+        self.observerForWillChangePersistentStore = NotificationObserver(
+            notificationName: NSPersistentStoreCoordinatorStoresWillChangeNotification,
+            object: coordinator,
+            closure: { [weak self] (note) -> Void in
+                
+                guard let `self` = self else {
+                        
+                    return
+                }
+                
+                self.isPersistentStoreChanging = true
+                
+                guard let removedStores = (note.userInfo?[NSRemovedPersistentStoresKey] as? [NSPersistentStore]).flatMap(Set.init)
+                    where !Set(self.fetchedResultsController.fetchRequest.affectedStores ?? []).intersect(removedStores).isEmpty else {
+                        
+                        return
+                }
+                self.refetch(fetchClauses)
+            }
+        )
+        
+        self.observerForDidChangePersistentStore = NotificationObserver(
+            notificationName: NSPersistentStoreCoordinatorStoresDidChangeNotification,
+            object: coordinator,
+            closure: { [weak self] (note) -> Void in
+                
+                guard let `self` = self else {
+                    
+                    return
+                }
+                
+                if !self.isPendingRefetch {
+                    
+                    let previousStores = Set(self.fetchedResultsController.fetchRequest.affectedStores ?? [])
+                    let currentStores = previousStores
+                        .subtract(note.userInfo?[NSRemovedPersistentStoresKey] as? [NSPersistentStore] ?? [])
+                        .union(note.userInfo?[NSAddedPersistentStoresKey] as? [NSPersistentStore] ?? [])
+                    
+                    if previousStores != currentStores {
+                        
+                        self.refetch(fetchClauses)
+                    }
+                }
+                
+                self.isPersistentStoreChanging = false
+            }
+        )
+        
+        if let createAsynchronously = createAsynchronously {
+            
+            transactionQueue.async {
+                
+                try! fetchedResultsController.performFetchFromSpecifiedStores()
+                self.taskGroup.notify(.Main) {
+                    
+                    createAsynchronously(self)
+                }
+            }
+        }
+        else {
+            
+            try! fetchedResultsController.performFetchFromSpecifiedStores()
+        }
     }
     
     deinit {
         
         self.fetchedResultsControllerDelegate.fetchedResultsController = nil
+        self.isPersistentStoreChanging = false
+    }
+    
+    private var isPersistentStoreChanging: Bool = false {
+        
+        didSet {
+            
+            let newValue = self.isPersistentStoreChanging
+            guard newValue != oldValue else {
+                
+                return
+            }
+            
+            if newValue {
+                
+                self.taskGroup.enter()
+            }
+            else {
+                
+                self.taskGroup.leave()
+            }
+        }
     }
     
     
     // MARK: Private
     
-    private let fetchedResultsController: NSFetchedResultsController
+    private let fetchedResultsController: CoreStoreFetchedResultsController<T>
     private let fetchedResultsControllerDelegate: FetchedResultsControllerDelegate
     private let sectionIndexTransformer: (sectionName: KeyPath?) -> String?
+    private var observerForWillChangePersistentStore: NotificationObserver!
+    private var observerForDidChangePersistentStore: NotificationObserver!
     private let taskGroup = GCDGroup()
-    private weak var parentStack: DataStack?
+    private let transactionQueue: GCDQueue
     
     private var willChangeListKey: Void?
     private var didChangeListKey: Void?

CoreStore/Observing/ObjectMonitor.swift

@@ -165,7 +165,17 @@ public final class ObjectMonitor<T: NSManagedObject> {
     
     // MARK: Internal
     
-    internal init(dataStack: DataStack, object: T) {
+    internal convenience init(dataStack: DataStack, object: T) {
+        
+        self.init(context: dataStack.mainContext, object: object)
+    }
+    
+    internal convenience init(unsafeTransaction: UnsafeDataTransaction, object: T) {
+        
+        self.init(context: unsafeTransaction.context, object: object)
+    }
+    
+    private init(context: NSManagedObjectContext, object: T) {
         
         let fetchRequest = NSFetchRequest()
         fetchRequest.entity = object.entity
@@ -175,8 +185,8 @@ public final class ObjectMonitor<T: NSManagedObject> {
         fetchRequest.includesPendingChanges = false
         fetchRequest.shouldRefreshRefetchedObjects = true
         
-        let fetchedResultsController = NSFetchedResultsController(
-            dataStack: dataStack,
+        let fetchedResultsController = CoreStoreFetchedResultsController<T>(
+            context: context,
             fetchRequest: fetchRequest,
             fetchClauses: [Where("SELF", isEqualTo: object.objectID)]
         )
@@ -185,11 +195,10 @@ public final class ObjectMonitor<T: NSManagedObject> {
         
         self.fetchedResultsController = fetchedResultsController
         self.fetchedResultsControllerDelegate = fetchedResultsControllerDelegate
-        self.parentStack = dataStack
         
         fetchedResultsControllerDelegate.handler = self
         fetchedResultsControllerDelegate.fetchedResultsController = fetchedResultsController
-        try! fetchedResultsController.performFetch()
+        try! fetchedResultsController.performFetchFromSpecifiedStores()
         
         self.lastCommittedAttributes = (self.object?.committedValuesForKeys(nil) as? [String: NSObject]) ?? [:]
     }
@@ -202,10 +211,9 @@ public final class ObjectMonitor<T: NSManagedObject> {
     
     // MARK: Private
     
-    private let fetchedResultsController: NSFetchedResultsController
+    private let fetchedResultsController: CoreStoreFetchedResultsController<T>
     private let fetchedResultsControllerDelegate: FetchedResultsControllerDelegate
     private var lastCommittedAttributes = [String: NSObject]()
-    private weak var parentStack: DataStack?
     
     private var willChangeObjectKey: Void?
     private var didDeleteObjectKey: Void?

CoreStore/Observing/UnsafeDataTransaction+Observing.swift

@@ -0,0 +1,201 @@
+//
+//  UnsafeDataTransaction+Observing.swift
+//  CoreStore
+//
+//  Copyright © 2016 John Rommel Estropia
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy
+//  of this software and associated documentation files (the "Software"), to deal
+//  in the Software without restriction, including without limitation the rights
+//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//  copies of the Software, and to permit persons to whom the Software is
+//  furnished to do so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+//
+
+import Foundation
+import CoreData
+#if USE_FRAMEWORKS
+    import GCDKit
+#endif
+
+
+// MARK: - UnsafeDataTransaction
+
+@available(OSX, unavailable)
+public extension UnsafeDataTransaction {
+    
+    
+    // MARK: Public
+    
+    /**
+    Creates a `ObjectMonitor` for the specified `NSManagedObject`. Multiple `ObjectObserver`s may then register themselves to be notified when changes are made to the `NSManagedObject`.
+    
+    - parameter object: the `NSManagedObject` to observe changes from
+    - returns: a `ObjectMonitor` that monitors changes to `object`
+    */
+    @warn_unused_result
+    public func monitorObject<T: NSManagedObject>(object: T) -> ObjectMonitor<T> {
+        
+        return ObjectMonitor(
+            unsafeTransaction: self,
+            object: object
+        )
+    }
+    
+    /**
+     Creates a `ListMonitor` for a list of `NSManagedObject`s that satisfy the specified fetch clauses. Multiple `ListObserver`s may then register themselves to be notified when changes are made to the list.
+     
+     - parameter from: a `From` clause indicating the entity type
+     - parameter fetchClauses: a series of `FetchClause` instances for fetching the object list. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
+     - returns: a `ListMonitor` instance that monitors changes to the list
+     */
+    @warn_unused_result
+    public func monitorList<T: NSManagedObject>(from: From<T>, _ fetchClauses: FetchClause...) -> ListMonitor<T> {
+        
+        return self.monitorList(from, fetchClauses)
+    }
+    
+    /**
+     Creates a `ListMonitor` for a list of `NSManagedObject`s that satisfy the specified fetch clauses. Multiple `ListObserver`s may then register themselves to be notified when changes are made to the list.
+     
+     - parameter from: a `From` clause indicating the entity type
+     - parameter fetchClauses: a series of `FetchClause` instances for fetching the object list. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
+     - returns: a `ListMonitor` instance that monitors changes to the list
+     */
+    @warn_unused_result
+    public func monitorList<T: NSManagedObject>(from: From<T>, _ fetchClauses: [FetchClause]) -> ListMonitor<T> {
+        
+        CoreStore.assert(
+            fetchClauses.filter { $0 is OrderBy }.count > 0,
+            "A ListMonitor requires an OrderBy clause."
+        )
+        
+        return ListMonitor(
+            unsafeTransaction: self,
+            from: from,
+            sectionBy: nil,
+            fetchClauses: fetchClauses
+        )
+    }
+    
+    /**
+     Asynchronously creates a `ListMonitor` for a list of `NSManagedObject`s that satisfy the specified fetch clauses. Multiple `ListObserver`s may then register themselves to be notified when changes are made to the list. 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.
+     
+     - parameter createAsynchronously: the closure that receives the created `ListMonitor` instance
+     - parameter from: a `From` clause indicating the entity type
+     - parameter fetchClauses: a series of `FetchClause` instances for fetching the object list. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
+     */
+    public func monitorList<T: NSManagedObject>(createAsynchronously createAsynchronously: (ListMonitor<T>) -> Void, _ from: From<T>, _ fetchClauses: FetchClause...) {
+        
+        self.monitorList(createAsynchronously: createAsynchronously, from, fetchClauses)
+    }
+    
+    /**
+     Asynchronously creates a `ListMonitor` for a list of `NSManagedObject`s that satisfy the specified fetch clauses. Multiple `ListObserver`s may then register themselves to be notified when changes are made to the list. 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.
+     
+     - parameter createAsynchronously: the closure that receives the created `ListMonitor` instance
+     - parameter from: a `From` clause indicating the entity type
+     - parameter fetchClauses: a series of `FetchClause` instances for fetching the object list. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
+     */
+    public func monitorList<T: NSManagedObject>(createAsynchronously createAsynchronously: (ListMonitor<T>) -> Void, _ from: From<T>, _ fetchClauses: [FetchClause])  {
+        
+        CoreStore.assert(
+            fetchClauses.filter { $0 is OrderBy }.count > 0,
+            "A ListMonitor requires an OrderBy clause."
+        )
+        
+        _ = ListMonitor(
+            unsafeTransaction: self,
+            from: from,
+            sectionBy: nil,
+            fetchClauses: fetchClauses,
+            createAsynchronously: createAsynchronously
+        )
+    }
+    
+    /**
+     Creates a `ListMonitor` for a sectioned list of `NSManagedObject`s that satisfy the specified fetch clauses. Multiple `ListObserver`s may then register themselves to be notified when changes are made to the list.
+     
+     - parameter from: a `From` clause indicating the entity type
+     - parameter sectionBy: a `SectionBy` clause indicating the keyPath for the attribute to use when sorting the list into sections.
+     - parameter fetchClauses: a series of `FetchClause` instances for fetching the object list. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
+     - returns: a `ListMonitor` instance that monitors changes to the list
+     */
+    @warn_unused_result
+    public func monitorSectionedList<T: NSManagedObject>(from: From<T>, _ sectionBy: SectionBy, _ fetchClauses: FetchClause...) -> ListMonitor<T> {
+        
+        return self.monitorSectionedList(from, sectionBy, fetchClauses)
+    }
+    
+    /**
+     Creates a `ListMonitor` for a sectioned list of `NSManagedObject`s that satisfy the specified fetch clauses. Multiple `ListObserver`s may then register themselves to be notified when changes are made to the list.
+     
+     - parameter from: a `From` clause indicating the entity type
+     - parameter sectionBy: a `SectionBy` clause indicating the keyPath for the attribute to use when sorting the list into sections.
+     - parameter fetchClauses: a series of `FetchClause` instances for fetching the object list. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
+     - returns: a `ListMonitor` instance that monitors changes to the list
+     */
+    @warn_unused_result
+    public func monitorSectionedList<T: NSManagedObject>(from: From<T>, _ sectionBy: SectionBy, _ fetchClauses: [FetchClause]) -> ListMonitor<T> {
+        
+        CoreStore.assert(
+            fetchClauses.filter { $0 is OrderBy }.count > 0,
+            "A ListMonitor requires an OrderBy clause."
+        )
+        
+        return ListMonitor(
+            unsafeTransaction: self,
+            from: from,
+            sectionBy: sectionBy,
+            fetchClauses: fetchClauses
+        )
+    }
+    
+    /**
+     Asynchronously creates a `ListMonitor` for a sectioned list of `NSManagedObject`s that satisfy the specified fetch clauses. Multiple `ListObserver`s may then register themselves to be notified when changes are made to the list. 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.
+     
+     - parameter createAsynchronously: the closure that receives the created `ListMonitor` instance
+     - parameter from: a `From` clause indicating the entity type
+     - parameter sectionBy: a `SectionBy` clause indicating the keyPath for the attribute to use when sorting the list into sections.
+     - parameter fetchClauses: a series of `FetchClause` instances for fetching the object list. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
+     */
+    public func monitorSectionedList<T: NSManagedObject>(createAsynchronously createAsynchronously: (ListMonitor<T>) -> Void, _ from: From<T>, _ sectionBy: SectionBy, _ fetchClauses: FetchClause...) {
+        
+        self.monitorSectionedList(createAsynchronously: createAsynchronously, from, sectionBy, fetchClauses)
+    }
+    
+    /**
+     Asynchronously creates a `ListMonitor` for a sectioned list of `NSManagedObject`s that satisfy the specified fetch clauses. Multiple `ListObserver`s may then register themselves to be notified when changes are made to the list. 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.
+     
+     - parameter createAsynchronously: the closure that receives the created `ListMonitor` instance
+     - parameter from: a `From` clause indicating the entity type
+     - parameter sectionBy: a `SectionBy` clause indicating the keyPath for the attribute to use when sorting the list into sections.
+     - parameter fetchClauses: a series of `FetchClause` instances for fetching the object list. Accepts `Where`, `OrderBy`, and `Tweak` clauses.
+     */
+    public func monitorSectionedList<T: NSManagedObject>(createAsynchronously createAsynchronously: (ListMonitor<T>) -> Void, _ from: From<T>, _ sectionBy: SectionBy, _ fetchClauses: [FetchClause]) {
+        
+        CoreStore.assert(
+            fetchClauses.filter { $0 is OrderBy }.count > 0,
+            "A ListMonitor requires an OrderBy clause."
+        )
+        
+        _ = ListMonitor(
+            unsafeTransaction: self,
+            from: from,
+            sectionBy: sectionBy,
+            fetchClauses: fetchClauses,
+            createAsynchronously: createAsynchronously
+        )
+    }
+}

CoreStore/Setting Up/DataStack.swift

@@ -367,11 +367,12 @@ public final class DataStack {
             self.configurationStoreMapping[configurationName] = persistentStore
             for entityDescription in (self.coordinator.managedObjectModel.entitiesForConfiguration(configurationName) ?? []) {
                 
-                if self.entityConfigurationsMapping[entityDescription.managedObjectClassName] == nil {
+                let managedObjectClassName = entityDescription.managedObjectClassName
+                if self.entityConfigurationsMapping[managedObjectClassName] == nil {
                     
-                    self.entityConfigurationsMapping[entityDescription.managedObjectClassName] = []
+                    self.entityConfigurationsMapping[managedObjectClassName] = []
                 }
-                self.entityConfigurationsMapping[entityDescription.managedObjectClassName]?.insert(configurationName)
+                self.entityConfigurationsMapping[managedObjectClassName]?.insert(configurationName)
             }
         }
     }