improved API for custom getters and setters in Field properties

CoreStore.xcodeproj/project.pbxproj

@@ -189,6 +189,10 @@
 		B50E17622351FA66004F033C /* Internals.Closure.swift in Sources */ = {isa = PBXBuildFile; fileRef = B50E17602351FA66004F033C /* Internals.Closure.swift */; };
 		B50E17632351FA66004F033C /* Internals.Closure.swift in Sources */ = {isa = PBXBuildFile; fileRef = B50E17602351FA66004F033C /* Internals.Closure.swift */; };
 		B50E17642351FA66004F033C /* Internals.Closure.swift in Sources */ = {isa = PBXBuildFile; fileRef = B50E17602351FA66004F033C /* Internals.Closure.swift */; };
+		B50E42F723FBB91800ED476E /* ObjectProxy.swift in Sources */ = {isa = PBXBuildFile; fileRef = B50E42F623FBB91800ED476E /* ObjectProxy.swift */; };
+		B50E42F823FBB91800ED476E /* ObjectProxy.swift in Sources */ = {isa = PBXBuildFile; fileRef = B50E42F623FBB91800ED476E /* ObjectProxy.swift */; };
+		B50E42F923FBB91800ED476E /* ObjectProxy.swift in Sources */ = {isa = PBXBuildFile; fileRef = B50E42F623FBB91800ED476E /* ObjectProxy.swift */; };
+		B50E42FA23FBB91800ED476E /* ObjectProxy.swift in Sources */ = {isa = PBXBuildFile; fileRef = B50E42F623FBB91800ED476E /* ObjectProxy.swift */; };
 		B50EE14223473C92009B8C47 /* CoreStoreObject+DataSources.swift in Sources */ = {isa = PBXBuildFile; fileRef = B50EE14123473C92009B8C47 /* CoreStoreObject+DataSources.swift */; };
 		B50EE14323473C96009B8C47 /* CoreStoreObject+DataSources.swift in Sources */ = {isa = PBXBuildFile; fileRef = B50EE14123473C92009B8C47 /* CoreStoreObject+DataSources.swift */; };
 		B50EE14423473C97009B8C47 /* CoreStoreObject+DataSources.swift in Sources */ = {isa = PBXBuildFile; fileRef = B50EE14123473C92009B8C47 /* CoreStoreObject+DataSources.swift */; };
@@ -1025,6 +1029,7 @@
 		B50E175623517DE4004F033C /* Differentiable.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Differentiable.swift; sourceTree = "<group>"; };
 		B50E175B2351848E004F033C /* Internals.DiffableDataUIDispatcher.DiffResult.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Internals.DiffableDataUIDispatcher.DiffResult.swift; sourceTree = "<group>"; };
 		B50E17602351FA66004F033C /* Internals.Closure.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Internals.Closure.swift; sourceTree = "<group>"; };
+		B50E42F623FBB91800ED476E /* ObjectProxy.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ObjectProxy.swift; sourceTree = "<group>"; };
 		B50EE14123473C92009B8C47 /* CoreStoreObject+DataSources.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "CoreStoreObject+DataSources.swift"; sourceTree = "<group>"; };
 		B512607E1E97A18000402229 /* CoreStoreObject+Convenience.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "CoreStoreObject+Convenience.swift"; sourceTree = "<group>"; };
 		B51260881E9B252B00402229 /* NSEntityDescription+DynamicModel.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "NSEntityDescription+DynamicModel.swift"; sourceTree = "<group>"; };
@@ -1646,6 +1651,7 @@
 			children = (
 				B5D339D71E9489AB00C880DE /* CoreStoreObject.swift */,
 				B53CA9A11EF1EF1600E0F440 /* PartialObject.swift */,
+				B50E42F623FBB91800ED476E /* ObjectProxy.swift */,
 				B56E4EC823CD9B2E00E1708C /* Field Properties */,
 				B5831B6E1F3355C300A9F647 /* Legacy Properties */,
 				B52F74391E9B8724005F3DAC /* Dynamic Schema */,
@@ -2381,6 +2387,7 @@
 				B5E84F411AFF8CCD0064E85B /* TypeErasedClauses.swift in Sources */,
 				B5E84F0D1AFF847B0064E85B /* BaseDataTransaction+Querying.swift in Sources */,
 				B52F74451E9B8724005F3DAC /* XcodeDataModelSchema.swift in Sources */,
+				B50E42F723FBB91800ED476E /* ObjectProxy.swift in Sources */,
 				B5FAD6AC1B51285300714891 /* Internals.MigrationManager.swift in Sources */,
 				B50EE14223473C92009B8C47 /* CoreStoreObject+DataSources.swift in Sources */,
 				B50C3EE023D062C300B29880 /* FieldCoderType.swift in Sources */,
@@ -2632,6 +2639,7 @@
 				B59851491C90289D00C99590 /* NSPersistentStoreCoordinator+Setup.swift in Sources */,
 				B5E1B5A41CAA4365007FD580 /* CSCoreStore+Observing.swift in Sources */,
 				B596BBB71DD5BC67001DCDD9 /* FetchableSource.swift in Sources */,
+				B50E42F823FBB91800ED476E /* ObjectProxy.swift in Sources */,
 				B5FEC18F1C9166E600532541 /* NSPersistentStore+Setup.swift in Sources */,
 				82BA18B71C4BBD3F00A0916E /* CoreStore+Querying.swift in Sources */,
 				B50C3EE123D062C300B29880 /* FieldCoderType.swift in Sources */,
@@ -2883,6 +2891,7 @@
 				B52DD1A51BE1F92F00949AFE /* ImportableUniqueObject.swift in Sources */,
 				B5E222271CA4E12600BA2E95 /* CSSynchronousDataTransaction.swift in Sources */,
 				B52F74481E9B8724005F3DAC /* XcodeDataModelSchema.swift in Sources */,
+				B50E42FA23FBB91800ED476E /* ObjectProxy.swift in Sources */,
 				B5519A621CA21954002BEF78 /* CSAsynchronousDataTransaction.swift in Sources */,
 				B52DD19C1BE1F92C00949AFE /* Into.swift in Sources */,
 				B50C3EE323D062C300B29880 /* FieldCoderType.swift in Sources */,
@@ -3134,6 +3143,7 @@
 				B52F74471E9B8724005F3DAC /* XcodeDataModelSchema.swift in Sources */,
 				B5FEC1901C9166E700532541 /* NSPersistentStore+Setup.swift in Sources */,
 				B56321A11BD65216006C9394 /* ListMonitor.swift in Sources */,
+				B50E42F923FBB91800ED476E /* ObjectProxy.swift in Sources */,
 				B5E1B5A51CAA4365007FD580 /* CSCoreStore+Observing.swift in Sources */,
 				B596BBB81DD5BC67001DCDD9 /* FetchableSource.swift in Sources */,
 				B50C3EE223D062C300B29880 /* FieldCoderType.swift in Sources */,

CoreStoreTests/DynamicModelTests.swift

@@ -94,22 +94,43 @@ enum Job: String {
 
 class Person: CoreStoreObject {
 
-    @Field.Stored("title", customSetter: Person.setTitle(_:_:))
+    @Field.Stored(
+        "title",
+        customSetter: { (object, field, newValue) in
+            field.primitiveValue = newValue
+            object.$displayName.primitiveValue = nil
+        }
+    )
     var title: String = "Mr."
 
-    @Field.Stored("name", customSetter: Person.setName(_:_:))
+    @Field.Stored(
+        "name",
+        customSetter: { (object, field, newValue) in
+            field.primitiveValue = newValue
+            object.$displayName.primitiveValue = nil
+        }
+    )
     var name: String = ""
 
     @Field.Virtual(
         "displayName",
-        customGetter: Person.getDisplayName(_:),
+        customGetter: Person.getDisplayName(_:_:),
         affectedByKeyPaths: Person.keyPathsAffectingDisplayName()
     )
     var displayName: String?
 
     @Field.Virtual(
         "customType",
-        customGetter: Person.getCustomField(_:)
+        customGetter: { (object, field) in
+
+            if let value = field.primitiveValue {
+
+                return value
+            }
+            let value = CustomType()
+            field.primitiveValue = value
+            return value
+        }
     )
     var customField: CustomType
 
@@ -131,40 +152,17 @@ class Person: CoreStoreObject {
     @Field.Relationship("_spouseInverse", inverse: \.$spouse)
     private var spouseInverse: Person?
     
-    private static func setTitle(_ partialObject: PartialObject<Person>, _ newValue: String) {
+    static func getDisplayName(_ object: ObjectProxy<Person>, _ field: ObjectProxy<Person>.FieldProxy<String?>) -> String? {
-        
-        partialObject.setPrimitiveValue(newValue, for: \.$title)
-        partialObject.setPrimitiveValue(nil, for: \.$displayName)
-    }
-    
-    private static func setName(_ partialObject: PartialObject<Person>, _ newValue: String) {
-        
-        partialObject.setPrimitiveValue(newValue, for: \.$name)
-        partialObject.setPrimitiveValue(nil, for: \.$displayName)
-    }
 
-    static func getCustomField(_ partialObject: PartialObject<Person>) -> CustomType {
+        if let value = field.primitiveValue {
 
-        if let customField = partialObject.primitiveValue(for: \.$customField) {
+            return value
-
-            return customField
         }
-        let customField = CustomType()
+        let title = object.$title.value
-        partialObject.setPrimitiveValue(customField, for: \.$customField)
+        let name = object.$name.value
-        return customField
+        let value = "\(title) \(name)"
-    }
+        field.primitiveValue = value
-    
+        return value
-    static func getDisplayName(_ partialObject: PartialObject<Person>) -> String? {
-        
-        if let displayName = partialObject.primitiveValue(for: \.$displayName) {
-            
-            return displayName
-        }
-        let title = partialObject.value(for: \.$title)
-        let name = partialObject.value(for: \.$name)
-        let displayName = "\(title) \(name)"
-        partialObject.setPrimitiveValue(displayName, for: \.$displayName)
-        return displayName
     }
     
     static func keyPathsAffectingDisplayName() -> Set<String> {

Sources/Field.Coded.swift

@@ -65,15 +65,15 @@ extension FieldContainer {
              @Field.Virtual("displayName", customGetter: Person.getName(_:))
              var displayName: String = ""
 
-             private static func getName(_ partialObject: PartialObject<Person>) -> String {
+             private static func getName(_ object: ObjectProxy<Person>) -> String {
-                 let cachedDisplayName = partialObject.primitiveValue(for: \.$displayName)
+                 let cachedDisplayName = object.primitiveValue(for: \.$displayName)
                  if !cachedDisplayName.isEmpty {
                      return cachedDisplayName
                  }
-                 let title = partialObject.value(for: \.$title)
+                 let title = object.value(for: \.$title)
-                 let name = partialObject.value(for: \.$name)
+                 let name = object.value(for: \.$name)
                  let displayName = "\(title) \(name)"
-                 partialObject.setPrimitiveValue(displayName, for: { $0.displayName })
+                 object.setPrimitiveValue(displayName, for: { $0.displayName })
                  return displayName
              }
          }
@@ -82,8 +82,8 @@ extension FieldContainer {
          - parameter keyPath: the permanent attribute name for this property.
          - parameter versionHashModifier: used to mark or denote a property as being a different "version" than another even if all of the values which affect persistence are equal. (Such a difference is important in cases where the properties are unchanged but the format or content of its data are changed.)
          - parameter previousVersionKeyPath: used to resolve naming conflicts between models. When creating an entity mapping between entities in two managed object models, a source entity property's `keyPath` with a matching destination entity property's `previousVersionKeyPath` indicate that a property mapping should be configured to migrate from the source to the destination. If unset, the identifier will be the property's `keyPath`.
-         - parameter customGetter: use this closure as an "override" for the default property getter. The closure receives a `PartialObject<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `PartialObject<O>`, make sure to use `PartialObject<O>.primitiveValue(for:)` instead of `PartialObject<O>.value(for:)`, which would unintentionally execute the same closure again recursively.
+         - parameter customGetter: use this closure as an "override" for the default property getter. The closure receives a `ObjectProxy<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `ObjectProxy<O>`, make sure to use `ObjectProxy<O>.primitiveValue(for:)` instead of `ObjectProxy<O>.value(for:)`, which would unintentionally execute the same closure again recursively.
-         - parameter customSetter: use this closure as an "override" for the default property setter. The closure receives a `PartialObject<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `PartialObject<O>`, make sure to use `PartialObject<O>.setPrimitiveValue(_:for:)` instead of `PartialObject<O>.setValue(_:for:)`, which would unintentionally execute the same closure again recursively.
+         - parameter customSetter: use this closure as an "override" for the default property setter. The closure receives a `ObjectProxy<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `ObjectProxy<O>`, make sure to use `ObjectProxy<O>.$property.primitiveValue` instead of `ObjectProxy<O>.$property.value`, which would unintentionally execute the same closure again recursively.
          - parameter affectedByKeyPaths: a set of key paths for properties whose values affect the value of the receiver. This is similar to `NSManagedObject.keyPathsForValuesAffectingValue(forKey:)`.
          */
         public init<Coder: FieldCoderType>(
@@ -92,8 +92,8 @@ extension FieldContainer {
             versionHashModifier: @autoclosure @escaping () -> String? = nil,
             previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
             coder fieldCoderType: Coder.Type,
-            customGetter: ((_ partialObject: PartialObject<O>) -> V)? = nil,
+            customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
-            customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)? = nil,
+            customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
             affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = []
         ) where Coder.FieldStoredValue == V {
 
@@ -116,8 +116,8 @@ extension FieldContainer {
             versionHashModifier: @autoclosure @escaping () -> String? = nil,
             previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
             coder: (encode: (V) -> Data?, decode: (Data?) -> V),
-            customGetter: ((_ partialObject: PartialObject<O>) -> V)? = nil,
+            customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
-            customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)? = nil,
+            customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
             affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = []
         ) {
 
@@ -209,7 +209,10 @@ extension FieldContainer {
             let field = field as! Self
             if let customGetter = field.customGetter {
 
-                return customGetter(PartialObject<O>(rawObject))
+                return customGetter(
+                    ObjectProxy<O>(rawObject),
+                    ObjectProxy<O>.FieldProxy<V>(rawObject: rawObject, field: field)
+                )
             }
             let keyPath = field.keyPath
             switch rawObject.value(forKey: keyPath) {
@@ -237,7 +240,11 @@ extension FieldContainer {
             let keyPath = field.keyPath
             if let customSetter = field.customSetter {
 
-                return customSetter(PartialObject<O>(rawObject), newValue)
+                return customSetter(
+                    ObjectProxy<O>(rawObject),
+                    ObjectProxy<O>.FieldProxy<V>(rawObject: rawObject, field: field),
+                    newValue
+                )
             }
             return rawObject.setValue(newValue, forKey: keyPath)
         }
@@ -279,7 +286,10 @@ extension FieldContainer {
 
                     rawObject.didAccessValue(forKey: keyPath)
                 }
-                let value = customGetter(PartialObject<O>(rawObject))
+                let value = customGetter(
+                    ObjectProxy<O>(rawObject),
+                    ObjectProxy<O>.FieldProxy<V>(rawObject: rawObject, field: self)
+                )
                 return value
             }
         }
@@ -300,7 +310,8 @@ extension FieldContainer {
                     rawObject.didChangeValue(forKey: keyPath)
                 }
                 customSetter(
-                    PartialObject<O>(rawObject),
+                    ObjectProxy<O>(rawObject),
+                    ObjectProxy<O>.FieldProxy<V>(rawObject: rawObject, field: self),
                     newValue as! V
                 )
             }
@@ -316,8 +327,8 @@ extension FieldContainer {
             versionHashModifier: @escaping () -> String?,
             renamingIdentifier: @escaping () -> String?,
             valueTransformer: @escaping () -> Internals.AnyFieldCoder?,
-            customGetter: ((_ partialObject: PartialObject<O>) -> V)?,
+            customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)?,
-            customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)? ,
+            customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? ,
             affectedByKeyPaths: @escaping () -> Set<KeyPathString>) {
 
             self.keyPath = keyPath
@@ -346,8 +357,8 @@ extension FieldContainer {
 
         // MARK: Private
 
-        private let customGetter: ((_ partialObject: PartialObject<O>) -> V)?
+        private let customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)?
-        private let customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)?
+        private let customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)?
     }
 }
 
@@ -369,15 +380,15 @@ extension FieldContainer.Coded where V: FieldOptionalType {
          @Field.Virtual("displayName", customGetter: Person.getName(_:))
          var displayName: String = ""
 
-         private static func getName(_ partialObject: PartialObject<Person>) -> String {
+         private static func getName(_ object: ObjectProxy<Person>) -> String {
-             let cachedDisplayName = partialObject.primitiveValue(for: \.$displayName)
+             let cachedDisplayName = object.primitiveValue(for: \.$displayName)
              if !cachedDisplayName.isEmpty {
                  return cachedDisplayName
              }
-             let title = partialObject.value(for: \.$title)
+             let title = object.value(for: \.$title)
-             let name = partialObject.value(for: \.$name)
+             let name = object.value(for: \.$name)
              let displayName = "\(title) \(name)"
-             partialObject.setPrimitiveValue(displayName, for: { $0.displayName })
+             object.setPrimitiveValue(displayName, for: { $0.displayName })
              return displayName
          }
      }
@@ -386,8 +397,8 @@ extension FieldContainer.Coded where V: FieldOptionalType {
      - parameter keyPath: the permanent attribute name for this property.
      - parameter versionHashModifier: used to mark or denote a property as being a different "version" than another even if all of the values which affect persistence are equal. (Such a difference is important in cases where the properties are unchanged but the format or content of its data are changed.)
      - parameter previousVersionKeyPath: used to resolve naming conflicts between models. When creating an entity mapping between entities in two managed object models, a source entity property's `keyPath` with a matching destination entity property's `previousVersionKeyPath` indicate that a property mapping should be configured to migrate from the source to the destination. If unset, the identifier will be the property's `keyPath`.
-     - parameter customGetter: use this closure as an "override" for the default property getter. The closure receives a `PartialObject<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `PartialObject<O>`, make sure to use `PartialObject<O>.primitiveValue(for:)` instead of `PartialObject<O>.value(for:)`, which would unintentionally execute the same closure again recursively.
+     - parameter customGetter: use this closure as an "override" for the default property getter. The closure receives a `ObjectProxy<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `ObjectProxy<O>`, make sure to use `ObjectProxy<O>.primitiveValue(for:)` instead of `ObjectProxy<O>.value(for:)`, which would unintentionally execute the same closure again recursively.
-     - parameter customSetter: use this closure as an "override" for the default property setter. The closure receives a `PartialObject<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `PartialObject<O>`, make sure to use `PartialObject<O>.setPrimitiveValue(_:for:)` instead of `PartialObject<O>.setValue(_:for:)`, which would unintentionally execute the same closure again recursively.
+     - parameter customSetter: use this closure as an "override" for the default property setter. The closure receives a `ObjectProxy<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `ObjectProxy<O>`, make sure to use `ObjectProxy<O>.$property.primitiveValue` instead of `ObjectProxy<O>.$property.value`, which would unintentionally execute the same closure again recursively.
      - parameter affectedByKeyPaths: a set of key paths for properties whose values affect the value of the receiver. This is similar to `NSManagedObject.keyPathsForValuesAffectingValue(forKey:)`.
      */
     public init<Coder: FieldCoderType>(
@@ -396,8 +407,8 @@ extension FieldContainer.Coded where V: FieldOptionalType {
         versionHashModifier: @autoclosure @escaping () -> String? = nil,
         previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
         coder: Coder.Type,
-        customGetter: ((_ partialObject: PartialObject<O>) -> V)? = nil,
+        customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
-        customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)? = nil,
+        customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
         affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = []
     ) where Coder.FieldStoredValue == V.Wrapped {
 
@@ -420,8 +431,8 @@ extension FieldContainer.Coded where V: FieldOptionalType {
         versionHashModifier: @autoclosure @escaping () -> String? = nil,
         previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
         coder: (encode: (V) -> Data?, decode: (Data?) -> V),
-        customGetter: ((_ partialObject: PartialObject<O>) -> V)? = nil,
+        customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
-        customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)? = nil,
+        customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
         affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = []
     ) {
 
@@ -457,15 +468,15 @@ extension FieldContainer.Coded where V: DefaultNSSecureCodable {
          @Field.Virtual("displayName", customGetter: Person.getName(_:))
          var displayName: String = ""
 
-         private static func getName(_ partialObject: PartialObject<Person>) -> String {
+         private static func getName(_ object: ObjectProxy<Person>) -> String {
-             let cachedDisplayName = partialObject.primitiveValue(for: \.$displayName)
+             let cachedDisplayName = object.primitiveValue(for: \.$displayName)
              if !cachedDisplayName.isEmpty {
                  return cachedDisplayName
              }
-             let title = partialObject.value(for: \.$title)
+             let title = object.value(for: \.$title)
-             let name = partialObject.value(for: \.$name)
+             let name = object.value(for: \.$name)
              let displayName = "\(title) \(name)"
-             partialObject.setPrimitiveValue(displayName, for: { $0.displayName })
+             object.setPrimitiveValue(displayName, for: { $0.displayName })
              return displayName
          }
      }
@@ -474,8 +485,8 @@ extension FieldContainer.Coded where V: DefaultNSSecureCodable {
      - parameter keyPath: the permanent attribute name for this property.
      - parameter versionHashModifier: used to mark or denote a property as being a different "version" than another even if all of the values which affect persistence are equal. (Such a difference is important in cases where the properties are unchanged but the format or content of its data are changed.)
      - parameter previousVersionKeyPath: used to resolve naming conflicts between models. When creating an entity mapping between entities in two managed object models, a source entity property's `keyPath` with a matching destination entity property's `previousVersionKeyPath` indicate that a property mapping should be configured to migrate from the source to the destination. If unset, the identifier will be the property's `keyPath`.
-     - parameter customGetter: use this closure as an "override" for the default property getter. The closure receives a `PartialObject<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `PartialObject<O>`, make sure to use `PartialObject<O>.primitiveValue(for:)` instead of `PartialObject<O>.value(for:)`, which would unintentionally execute the same closure again recursively.
+     - parameter customGetter: use this closure as an "override" for the default property getter. The closure receives a `ObjectProxy<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `ObjectProxy<O>`, make sure to use `ObjectProxy<O>.primitiveValue(for:)` instead of `ObjectProxy<O>.value(for:)`, which would unintentionally execute the same closure again recursively.
-     - parameter customSetter: use this closure as an "override" for the default property setter. The closure receives a `PartialObject<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `PartialObject<O>`, make sure to use `PartialObject<O>.setPrimitiveValue(_:for:)` instead of `PartialObject<O>.setValue(_:for:)`, which would unintentionally execute the same closure again recursively.
+     - parameter customSetter: use this closure as an "override" for the default property setter. The closure receives a `ObjectProxy<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `ObjectProxy<O>`, make sure to use `ObjectProxy<O>.$property.primitiveValue` instead of `ObjectProxy<O>.$property.value`, which would unintentionally execute the same closure again recursively.
      - parameter affectedByKeyPaths: a set of key paths for properties whose values affect the value of the receiver. This is similar to `NSManagedObject.keyPathsForValuesAffectingValue(forKey:)`.
      */
     public init(
@@ -483,8 +494,8 @@ extension FieldContainer.Coded where V: DefaultNSSecureCodable {
         _ keyPath: KeyPathString,
         versionHashModifier: @autoclosure @escaping () -> String? = nil,
         previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
-        customGetter: ((_ partialObject: PartialObject<O>) -> V)? = nil,
+        customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
-        customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)? = nil,
+        customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
         affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = []
     ) {
 
@@ -512,8 +523,8 @@ extension FieldContainer.Coded where V: FieldOptionalType, V.Wrapped: DefaultNSS
         _ keyPath: KeyPathString,
         versionHashModifier: @autoclosure @escaping () -> String? = nil,
         previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
-        customGetter: ((_ partialObject: PartialObject<O>) -> V)? = nil,
+        customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
-        customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)? = nil,
+        customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
         affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = []
     ) {
 

Sources/Field.Stored.swift

@@ -62,28 +62,26 @@ extension FieldContainer {
              @Field.Stored("name")
              var name: String = ""
 
-             @Field.Virtual("displayName", customGetter: Person.getName(_:))
+             @Field.Virtual(
-             var displayName: String = ""
+                 "displayName",
-
+                 customGetter: { (object, field) in
-             private static func getName(_ partialObject: PartialObject<Person>) -> String {
+                     if let cached = field.primitiveValue, !cached.isEmpty {
-                 let cachedDisplayName = partialObject.primitiveValue(for: \.$displayName)
+                         return cached
-                 if !cachedDisplayName.isEmpty {
+                     }
-                     return cachedDisplayName
+                     let value = "\(object.$title.value) \(object.$name.value)"
+                     field.primitiveValue = value
+                     return value
                  }
-                 let title = partialObject.value(for: \.$title)
+             )
-                 let name = partialObject.value(for: \.$name)
+             var displayName: String = ""
-                 let displayName = "\(title) \(name)"
-                 partialObject.setPrimitiveValue(displayName, for: { $0.displayName })
-                 return displayName
-             }
          }
          ```
          - parameter initial: the initial value for the property when the object is first create
          - parameter keyPath: the permanent attribute name for this property.
          - parameter versionHashModifier: used to mark or denote a property as being a different "version" than another even if all of the values which affect persistence are equal. (Such a difference is important in cases where the properties are unchanged but the format or content of its data are changed.)
          - parameter previousVersionKeyPath: used to resolve naming conflicts between models. When creating an entity mapping between entities in two managed object models, a source entity property's `keyPath` with a matching destination entity property's `previousVersionKeyPath` indicate that a property mapping should be configured to migrate from the source to the destination. If unset, the identifier will be the property's `keyPath`.
-         - parameter customGetter: use this closure as an "override" for the default property getter. The closure receives a `PartialObject<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `PartialObject<O>`, make sure to use `PartialObject<O>.primitiveValue(for:)` instead of `PartialObject<O>.value(for:)`, which would unintentionally execute the same closure again recursively.
+         - parameter customGetter: use this closure as an "override" for the default property getter. The closure receives a `ObjectProxy<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `ObjectProxy<O>`, make sure to use `ObjectProxy<O>.primitiveValue(for:)` instead of `ObjectProxy<O>.value(for:)`, which would unintentionally execute the same closure again recursively.
-         - parameter customSetter: use this closure as an "override" for the default property setter. The closure receives a `PartialObject<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `PartialObject<O>`, make sure to use `PartialObject<O>.setPrimitiveValue(_:for:)` instead of `PartialObject<O>.setValue(_:for:)`, which would unintentionally execute the same closure again recursively.
+         - parameter customSetter: use this closure as an "override" for the default property setter. The closure receives a `ObjectProxy<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `ObjectProxy<O>`, make sure to use `ObjectProxy<O>.$property.primitiveValue` instead of `ObjectProxy<O>.$property.value`, which would unintentionally execute the same closure again recursively.
          - parameter affectedByKeyPaths: a set of key paths for properties whose values affect the value of the receiver. This is similar to `NSManagedObject.keyPathsForValuesAffectingValue(forKey:)`.
          */
         public init(
@@ -91,8 +89,8 @@ extension FieldContainer {
             _ keyPath: KeyPathString,
             versionHashModifier: @autoclosure @escaping () -> String? = nil,
             previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
-            customGetter: ((_ partialObject: PartialObject<O>) -> V)? = nil,
+            customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
-            customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)? = nil,
+            customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
             affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = []
         ) {
 
@@ -183,7 +181,10 @@ extension FieldContainer {
             let field = field as! Self
             if let customGetter = field.customGetter {
 
-                return customGetter(PartialObject<O>(rawObject))
+                return customGetter(
+                    ObjectProxy<O>(rawObject),
+                    ObjectProxy<O>.FieldProxy<V>(rawObject: rawObject, field: field)
+                )
             }
             let keyPath = field.keyPath
             switch rawObject.value(forKey: keyPath) {
@@ -211,7 +212,11 @@ extension FieldContainer {
             let keyPath = field.keyPath
             if let customSetter = field.customSetter {
 
-                return customSetter(PartialObject<O>(rawObject), newValue)
+                return customSetter(
+                    ObjectProxy<O>(rawObject),
+                    ObjectProxy<O>.FieldProxy<V>(rawObject: rawObject, field: field),
+                    newValue
+                )
             }
             return rawObject.setValue(
                 newValue.cs_toFieldStoredNativeType(),
@@ -239,7 +244,10 @@ extension FieldContainer {
 
                     rawObject.didAccessValue(forKey: keyPath)
                 }
-                let value = customGetter(PartialObject<O>(rawObject))
+                let value = customGetter(
+                    ObjectProxy<O>(rawObject),
+                    ObjectProxy<O>.FieldProxy<V>(rawObject: rawObject, field: self)
+                )
                 return value.cs_toFieldStoredNativeType()
             }
         }
@@ -260,7 +268,8 @@ extension FieldContainer {
                     rawObject.didChangeValue(forKey: keyPath)
                 }
                 customSetter(
-                    PartialObject<O>(rawObject),
+                    ObjectProxy<O>(rawObject),
+                    ObjectProxy<O>.FieldProxy<V>(rawObject: rawObject, field: self),
                     V.cs_fromFieldStoredNativeType(newValue as! V.FieldStoredNativeType)
                 )
             }
@@ -275,8 +284,8 @@ extension FieldContainer {
             isOptional: Bool,
             versionHashModifier: @escaping () -> String?,
             renamingIdentifier: @escaping () -> String?,
-            customGetter: ((_ partialObject: PartialObject<O>) -> V)?,
+            customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)?,
-            customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)? ,
+            customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? ,
             affectedByKeyPaths: @escaping () -> Set<KeyPathString>) {
 
             self.keyPath = keyPath
@@ -300,8 +309,8 @@ extension FieldContainer {
 
         // MARK: Private
 
-        private let customGetter: ((_ partialObject: PartialObject<O>) -> V)?
+        private let customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)?
-        private let customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)?
+        private let customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)?
     }
 }
 
@@ -323,15 +332,15 @@ extension FieldContainer.Stored where V: FieldOptionalType {
          @Field.Virtual("displayName", customGetter: Person.getName(_:))
          var displayName: String = ""
 
-         private static func getName(_ partialObject: PartialObject<Person>) -> String {
+         private static func getName(_ object: ObjectProxy<Person>) -> String {
-             let cachedDisplayName = partialObject.primitiveValue(for: \.$displayName)
+             let cachedDisplayName = object.primitiveValue(for: \.$displayName)
              if !cachedDisplayName.isEmpty {
                  return cachedDisplayName
              }
-             let title = partialObject.value(for: \.$title)
+             let title = object.value(for: \.$title)
-             let name = partialObject.value(for: \.$name)
+             let name = object.value(for: \.$name)
              let displayName = "\(title) \(name)"
-             partialObject.setPrimitiveValue(displayName, for: { $0.displayName })
+             object.setPrimitiveValue(displayName, for: { $0.displayName })
              return displayName
          }
      }
@@ -340,8 +349,8 @@ extension FieldContainer.Stored where V: FieldOptionalType {
      - parameter keyPath: the permanent attribute name for this property.
      - parameter versionHashModifier: used to mark or denote a property as being a different "version" than another even if all of the values which affect persistence are equal. (Such a difference is important in cases where the properties are unchanged but the format or content of its data are changed.)
      - parameter previousVersionKeyPath: used to resolve naming conflicts between models. When creating an entity mapping between entities in two managed object models, a source entity property's `keyPath` with a matching destination entity property's `previousVersionKeyPath` indicate that a property mapping should be configured to migrate from the source to the destination. If unset, the identifier will be the property's `keyPath`.
-     - parameter customGetter: use this closure as an "override" for the default property getter. The closure receives a `PartialObject<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `PartialObject<O>`, make sure to use `PartialObject<O>.primitiveValue(for:)` instead of `PartialObject<O>.value(for:)`, which would unintentionally execute the same closure again recursively.
+     - parameter customGetter: use this closure as an "override" for the default property getter. The closure receives a `ObjectProxy<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `ObjectProxy<O>`, make sure to use `ObjectProxy<O>.primitiveValue(for:)` instead of `ObjectProxy<O>.value(for:)`, which would unintentionally execute the same closure again recursively.
-     - parameter customSetter: use this closure as an "override" for the default property setter. The closure receives a `PartialObject<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `PartialObject<O>`, make sure to use `PartialObject<O>.setPrimitiveValue(_:for:)` instead of `PartialObject<O>.setValue(_:for:)`, which would unintentionally execute the same closure again recursively.
+     - parameter customSetter: use this closure as an "override" for the default property setter. The closure receives a `ObjectProxy<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `ObjectProxy<O>`, make sure to use `ObjectProxy<O>.$property.primitiveValue` instead of `ObjectProxy<O>.$property.value`, which would unintentionally execute the same closure again recursively.
      - parameter affectedByKeyPaths: a set of key paths for properties whose values affect the value of the receiver. This is similar to `NSManagedObject.keyPathsForValuesAffectingValue(forKey:)`.
      */
     public init(
@@ -349,8 +358,8 @@ extension FieldContainer.Stored where V: FieldOptionalType {
         _ keyPath: KeyPathString,
         versionHashModifier: @autoclosure @escaping () -> String? = nil,
         previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
-        customGetter: ((_ partialObject: PartialObject<O>) -> V)? = nil,
+        customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
-        customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)? = nil,
+        customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
         affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = []) {
 
         self.init(

Sources/Field.Virtual.swift

@@ -65,28 +65,28 @@ extension FieldContainer {
              @Field.Virtual("displayName", customGetter: Person.getName(_:))
              var displayName: String = ""
 
-             private static func getName(_ partialObject: PartialObject<Person>) -> String {
+             private static func getName(_ object: ObjectProxy<Person>) -> String {
-                 let cachedDisplayName = partialObject.primitiveValue(for: \.$displayName)
+                 let cachedDisplayName = object.primitiveValue(for: \.$displayName)
                  if !cachedDisplayName.isEmpty {
                      return cachedDisplayName
                  }
-                 let title = partialObject.value(for: \.$title)
+                 let title = object.value(for: \.$title)
-                 let name = partialObject.value(for: \.$name)
+                 let name = object.value(for: \.$name)
                  let displayName = "\(title) \(name)"
-                 partialObject.setPrimitiveValue(displayName, for: { $0.displayName })
+                 object.setPrimitiveValue(displayName, for: { $0.displayName })
                  return displayName
              }
          }
          ```
          - parameter keyPath: the permanent attribute name for this property.
-         - parameter customGetter: use this closure as an "override" for the default property getter. The closure receives a `PartialObject<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `PartialObject<O>`, make sure to use `PartialObject<O>.primitiveValue(for:)` instead of `PartialObject<O>.value(for:)`, which would unintentionally execute the same closure again recursively.
+         - parameter customGetter: use this closure as an "override" for the default property getter. The closure receives a `ObjectProxy<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `ObjectProxy<O>`, make sure to use `ObjectProxy<O>.primitiveValue(for:)` instead of `ObjectProxy<O>.value(for:)`, which would unintentionally execute the same closure again recursively.
-         - parameter customSetter: use this closure as an "override" for the default property setter. The closure receives a `PartialObject<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `PartialObject<O>`, make sure to use `PartialObject<O>.setPrimitiveValue(_:for:)` instead of `PartialObject<O>.setValue(_:for:)`, which would unintentionally execute the same closure again recursively.
+         - parameter customSetter: use this closure as an "override" for the default property setter. The closure receives a `ObjectProxy<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info everytime KVO invokes this accessor method incurs a cumulative performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `ObjectProxy<O>`, make sure to use `ObjectProxy<O>.$property.primitiveValue` instead of `ObjectProxy<O>.$property.value`, which would unintentionally execute the same closure again recursively.
          - parameter affectedByKeyPaths: a set of key paths for properties whose values affect the value of the receiver. This is similar to `NSManagedObject.keyPathsForValuesAffectingValue(forKey:)`.
          */
         public init(
             _ keyPath: KeyPathString,
-            customGetter: @escaping (_ partialObject: PartialObject<O>) -> V,
+            customGetter: @escaping (_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V,
-            customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)? = nil,
+            customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
             affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = []) {
 
             self.init(
@@ -106,8 +106,8 @@ extension FieldContainer {
             wrappedValue initial: @autoclosure @escaping () -> V,
             _ keyPath: KeyPathString,
             versionHashModifier: @autoclosure @escaping () -> String? = nil,
-            customGetter: ((_ partialObject: PartialObject<O>) -> V)? = nil,
+            customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
-            customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)? = nil,
+            customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
             affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = []) {
 
             fatalError()
@@ -188,7 +188,10 @@ extension FieldContainer {
             let field = field as! Self
             if let customGetter = field.customGetter {
 
-                return customGetter(PartialObject<O>(rawObject))
+                return customGetter(
+                    ObjectProxy<O>(rawObject),
+                    ObjectProxy<O>.FieldProxy<V>(rawObject: rawObject, field: field)
+                )
             }
             let keyPath = field.keyPath
             switch rawObject.value(forKey: keyPath) {
@@ -216,7 +219,11 @@ extension FieldContainer {
             let keyPath = field.keyPath
             if let customSetter = field.customSetter {
 
-                return customSetter(PartialObject<O>(rawObject), newValue)
+                return customSetter(
+                    ObjectProxy<O>(rawObject),
+                    ObjectProxy<O>.FieldProxy<V>(rawObject: rawObject, field: field),
+                    newValue
+                )
             }
             return rawObject.setValue(newValue, forKey: keyPath)
         }
@@ -241,7 +248,10 @@ extension FieldContainer {
 
                     rawObject.didAccessValue(forKey: keyPath)
                 }
-                return customGetter(PartialObject<O>(rawObject))
+                return customGetter(
+                    ObjectProxy<O>(rawObject),
+                    ObjectProxy<O>.FieldProxy<V>(rawObject: rawObject, field: self)
+                )
             }
         }
 
@@ -260,7 +270,11 @@ extension FieldContainer {
 
                     rawObject.didChangeValue(forKey: keyPath)
                 }
-                return customSetter(PartialObject<O>(rawObject), newValue as! V)
+                return customSetter(
+                    ObjectProxy<O>(rawObject),
+                    ObjectProxy<O>.FieldProxy<V>(rawObject: rawObject, field: self),
+                    newValue as! V
+                )
             }
         }
 
@@ -270,8 +284,8 @@ extension FieldContainer {
         fileprivate init(
             keyPath: KeyPathString,
             isOptional: Bool,
-            customGetter: ((_ partialObject: PartialObject<O>) -> V)?,
+            customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)?,
-            customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)? ,
+            customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? ,
             affectedByKeyPaths: @escaping () -> Set<KeyPathString>) {
 
             self.keyPath = keyPath
@@ -295,8 +309,8 @@ extension FieldContainer {
 
         // MARK: Private
 
-        private let customGetter: ((_ partialObject: PartialObject<O>) -> V)?
+        private let customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)?
-        private let customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)?
+        private let customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)?
     }
 }
 
@@ -305,8 +319,8 @@ extension FieldContainer.Virtual where V: FieldOptionalType {
 
     public init(
         _ keyPath: KeyPathString,
-        customGetter: ((_ partialObject: PartialObject<O>) -> V)? = nil,
+        customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
-        customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)? = nil,
+        customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
         affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = []) {
 
         self.init(

Sources/ObjectProxy.swift

@@ -0,0 +1,235 @@
+//
+//  ObjectProxy.swift
+//  CoreStore
+//
+//  Copyright © 2020 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 CoreData
+import Foundation
+
+
+// MARK: - ObjectProxy
+
+/**
+ An `ObjectProxy` is only used when overriding getters and setters for `CoreStoreObject` properties. Custom getters and setters are implemented as a closure that "overrides" the default property getter/setter. The closure receives an `ObjectProxy<O>`, which acts as a fast, type-safe KVC interface for `CoreStoreObject`. The reason a `CoreStoreObject` instance is not passed directly is because the Core Data runtime is not aware of `CoreStoreObject` properties' static typing, and so loading those info every time KVO invokes this accessor method incurs a heavy performance hit (especially in KVO-heavy operations such as `ListMonitor` observing.) When accessing the property value from `ObjectProxy<O>`, make sure to use `ObjectProxy<O>.$property.primitiveValue` instead of `ObjectProxy<O>.$property.value`, which would execute the same accessor again recursively.
+ */
+@dynamicMemberLookup
+public struct ObjectProxy<O: CoreStoreObject> {
+
+    /**
+     Returns the value for the property identified by a given key.
+     */
+    public subscript<OBase, V>(dynamicMember member: KeyPath<O, FieldContainer<OBase>.Stored<V>>) -> FieldProxy<V> {
+
+        return .init(rawObject: self.rawObject, keyPath: member)
+    }
+
+    /**
+     Returns the value for the property identified by a given key.
+     */
+    public subscript<OBase, V>(dynamicMember member: KeyPath<O, FieldContainer<OBase>.Virtual<V>>) -> FieldProxy<V> {
+
+        return .init(rawObject: self.rawObject, keyPath: member)
+    }
+
+    /**
+     Returns the value for the property identified by a given key.
+     */
+    public subscript<OBase, V>(dynamicMember member: KeyPath<O, FieldContainer<OBase>.Coded<V>>) -> FieldProxy<V> {
+
+        return .init(rawObject: self.rawObject, keyPath: member)
+    }
+
+
+    // MARK: Internal
+
+    internal let rawObject: CoreStoreManagedObject
+
+    internal init(_ rawObject: CoreStoreManagedObject) {
+
+        self.rawObject = rawObject
+    }
+
+
+    // MARK: - FieldProxy
+
+    public struct FieldProxy<V> {
+
+        // MARK: Public
+
+        /**
+         Returns the value for the specified property from the object’s private internal storage.
+
+         Accessing this property does not invoke the access notification methods (`willAccessValue(forKey:)` and `didAccessValue(forKey:)`). This method is used primarily to implement custom accessor methods that need direct access to the object's private storage.
+         */
+        public var primitiveValue: V? {
+
+            get {
+
+                return self.getPrimitiveValue()
+            }
+            nonmutating set {
+
+                self.setPrimitiveValue(newValue)
+            }
+        }
+
+        /**
+         Returns the value for the property identified by a given key.
+
+         Accessing this property triggers the access notification methods (`willAccessValue(forKey:)` and `didAccessValue(forKey:)`).
+         */
+        public var value: V {
+
+            get {
+
+                return self.getValue()
+            }
+            nonmutating set {
+
+                self.setValue(newValue)
+            }
+        }
+
+
+        // MARK: Internal
+
+        internal init<OBase>(rawObject: CoreStoreManagedObject, keyPath: KeyPath<O, FieldContainer<OBase>.Stored<V>>) {
+
+            self.init(rawObject: rawObject, field: O.meta[keyPath: keyPath])
+        }
+
+        internal init<OBase>(rawObject: CoreStoreManagedObject, keyPath: KeyPath<O, FieldContainer<OBase>.Virtual<V>>) {
+
+            self.init(rawObject: rawObject, field: O.meta[keyPath: keyPath])
+        }
+
+        internal init<OBase>(rawObject: CoreStoreManagedObject, keyPath: KeyPath<O, FieldContainer<OBase>.Coded<V>>) {
+
+            self.init(rawObject: rawObject, field: O.meta[keyPath: keyPath])
+        }
+
+        internal init<OBase>(rawObject: CoreStoreManagedObject, field: FieldContainer<OBase>.Stored<V>) {
+
+            let keyPathString = field.keyPath
+            self.getValue = {
+
+                return FieldContainer<O>.Stored<V>.read(field: field, for: rawObject) as! V
+            }
+            self.setValue = {
+
+                FieldContainer<O>.Stored<V>.modify(field: field, for: rawObject, newValue: $0)
+            }
+            self.getPrimitiveValue = {
+
+                return V.cs_fromFieldStoredNativeType(
+                    rawObject.primitiveValue(forKey: keyPathString) as! V.FieldStoredNativeType
+                )
+            }
+            self.setPrimitiveValue = {
+
+                rawObject.setPrimitiveValue(
+                    $0.cs_toFieldStoredNativeType(),
+                    forKey: keyPathString
+                )
+            }
+        }
+
+        internal init<OBase>(rawObject: CoreStoreManagedObject, field: FieldContainer<OBase>.Virtual<V>) {
+
+            let keyPathString = field.keyPath
+            self.getValue = {
+
+                return FieldContainer<O>.Virtual<V>.read(field: field, for: rawObject) as! V
+            }
+            self.setValue = {
+
+                FieldContainer<O>.Virtual<V>.modify(field: field, for: rawObject, newValue: $0)
+            }
+            self.getPrimitiveValue = {
+
+                switch rawObject.primitiveValue(forKey: keyPathString) {
+
+                case let value as V:
+                    return value
+
+                case nil,
+                     is NSNull,
+                     _? /* any other unrelated type */ :
+                    return nil
+                }
+            }
+            self.setPrimitiveValue = {
+
+                rawObject.setPrimitiveValue(
+                    $0,
+                    forKey: keyPathString
+                )
+            }
+        }
+
+        internal init<OBase>(rawObject: CoreStoreManagedObject, field: FieldContainer<OBase>.Coded<V>) {
+
+            let keyPathString = field.keyPath
+            self.getValue = {
+
+                return FieldContainer<O>.Coded<V>.read(field: field, for: rawObject) as! V
+            }
+            self.setValue = {
+
+                FieldContainer<O>.Coded<V>.modify(field: field, for: rawObject, newValue: $0)
+            }
+            self.getPrimitiveValue = {
+
+                switch rawObject.primitiveValue(forKey: keyPathString) {
+
+                case let valueBox as Internals.AnyFieldCoder.TransformableDefaultValueCodingBox:
+                    rawObject.setPrimitiveValue(valueBox.value, forKey: keyPathString)
+                    return valueBox.value as? V
+
+                case let value as V:
+                    return value
+
+                case nil,
+                     is NSNull,
+                      _? /* any other unrelated type */ :
+                     return nil
+                }
+            }
+            self.setPrimitiveValue = {
+
+                rawObject.setPrimitiveValue(
+                    $0,
+                    forKey: keyPathString
+                )
+            }
+        }
+
+
+        // MARK: Private
+
+        private let getValue: () -> V
+        private let setValue: (V) -> Void
+        private let getPrimitiveValue: () -> V?
+        private let setPrimitiveValue: (V?) -> Void
+    }
+}