Implement dynamic initializers for Field properties (fixes #382)

CoreStoreDemo/CoreStoreDemo/List and Object Observers Demo/CollectionViewDemoViewController.swift

@@ -146,8 +146,7 @@ final class CollectionViewDemoViewController: UICollectionViewController {
         ColorsDemo.stack.perform(
             asynchronous: { (transaction) in
 
-                let palette = transaction.create(Into<Palette>())
+                _ = transaction.create(Into<Palette>())
-                palette.setInitialValues(in: transaction)
             },
             completion: { _ in }
         )
@@ -159,8 +158,8 @@ final class CollectionViewDemoViewController: UICollectionViewController {
 
                 for palette in try transaction.fetchAll(From<Palette>()) {
 
-                    palette.hue .= Palette.randomHue()
+                    palette.hue = Palette.randomHue()
-                    palette.colorName .= nil
+                    palette.colorName = nil
                 }
             },
             completion: { _ in }

CoreStoreDemo/CoreStoreDemo/List and Object Observers Demo/ColorsDemo.swift

@@ -35,8 +35,8 @@ struct ColorsDemo {
             switch self {
                 
             case .all: return .init()
-            case .light: return (\Palette.brightness >= 0.9)
+            case .light: return (\Palette.$brightness >= 0.9)
-            case .dark: return (\Palette.brightness <= 0.4)
+            case .dark: return (\Palette.$brightness <= 0.4)
             }
         }
     }
@@ -47,9 +47,9 @@ struct ColorsDemo {
             
             try! self.palettes.refetch(
                 From<Palette>()
-                    .sectionBy(\.colorName)
+                    .sectionBy(\.$colorName)
                     .where(self.filter.whereClause())
-                    .orderBy(.ascending(\.hue))
+                    .orderBy(.ascending(\.$hue))
             )
         }
     }
@@ -81,8 +81,8 @@ struct ColorsDemo {
 
         return ColorsDemo.stack.publishList(
             From<Palette>()
-                .sectionBy(\.colorName)
+                .sectionBy(\.$colorName)
-                .orderBy(.ascending(\.hue))
+                .orderBy(.ascending(\.$hue))
         )
     }()
 }

CoreStoreDemo/CoreStoreDemo/List and Object Observers Demo/ListObserverDemoViewController.swift

@@ -158,8 +158,7 @@ final class ListObserverDemoViewController: UITableViewController {
         ColorsDemo.stack.perform(
             asynchronous: { (transaction) in
                 
-                let palette = transaction.create(Into<Palette>())
+                _ = transaction.create(Into<Palette>())
-                palette.setInitialValues(in: transaction)
             },
             completion: { _ in }
         )
@@ -171,8 +170,8 @@ final class ListObserverDemoViewController: UITableViewController {
 
                 for palette in try transaction.fetchAll(From<Palette>()) {
 
-                    palette.hue .= Palette.randomHue()
+                    palette.hue = Palette.randomHue()
-                    palette.colorName .= nil
+                    palette.colorName = nil
                 }
             },
             completion: { _ in }

CoreStoreDemo/CoreStoreDemo/List and Object Observers Demo/ObjectObserverDemoViewController.swift

@@ -43,7 +43,7 @@ class ObjectObserverDemoViewController: UIViewController, ObjectObserver {
     
     required init?(coder aDecoder: NSCoder) {
         
-        if let palette = try! ColorsDemo.stack.fetchOne(From<Palette>().orderBy(.ascending(\.hue))) {
+        if let palette = try! ColorsDemo.stack.fetchOne(From<Palette>().orderBy(.ascending(\.$hue))) {
             
             self.monitor = ColorsDemo.stack.monitorObject(palette)
         }
@@ -52,12 +52,11 @@ class ObjectObserverDemoViewController: UIViewController, ObjectObserver {
             _ = try? ColorsDemo.stack.perform(
                 synchronous: { (transaction) in
                     
-                    let palette = transaction.create(Into<Palette>())
+                    _ = transaction.create(Into<Palette>())
-                    palette.setInitialValues(in: transaction)
                 }
             )
             
-            let palette = try! ColorsDemo.stack.fetchOne(From<Palette>().orderBy(.ascending(\.hue)))!
+            let palette = try! ColorsDemo.stack.fetchOne(From<Palette>().orderBy(.ascending(\.$hue)))!
             self.monitor = ColorsDemo.stack.monitorObject(palette)
         }
         
@@ -119,7 +118,7 @@ class ObjectObserverDemoViewController: UIViewController, ObjectObserver {
                 
                 if let palette = transaction.edit(self?.monitor?.object) {
                     
-                    palette.hue .= Int(hue)
+                    palette.hue = Int(hue)
                 }
             },
             completion: { _ in }
@@ -134,7 +133,7 @@ class ObjectObserverDemoViewController: UIViewController, ObjectObserver {
                 
                 if let palette = transaction.edit(self?.monitor?.object) {
                     
-                    palette.saturation .= saturation
+                    palette.saturation = saturation
                 }
             },
             completion: { _ in }
@@ -149,7 +148,7 @@ class ObjectObserverDemoViewController: UIViewController, ObjectObserver {
                 
                 if let palette = transaction.edit(self?.monitor?.object) {
                     
-                    palette.brightness .= brightness
+                    palette.brightness = brightness
                 }
             },
             completion: { _ in }
@@ -169,7 +168,7 @@ class ObjectObserverDemoViewController: UIViewController, ObjectObserver {
     
     func reloadPaletteInfo(_ palette: Palette, changedKeys: Set<String>?) {
         
-        self.colorNameLabel?.text = palette.colorName.value
+        self.colorNameLabel?.text = palette.colorName
         
         let color = palette.color
         self.colorNameLabel?.textColor = color
@@ -177,17 +176,17 @@ class ObjectObserverDemoViewController: UIViewController, ObjectObserver {
         
         self.hsbLabel?.text = palette.colorText
         
-        if changedKeys == nil || changedKeys?.contains(String(keyPath: \Palette.hue)) == true {
+        if changedKeys == nil || changedKeys?.contains(String(keyPath: \Palette.$hue)) == true {
             
-            self.hueSlider?.value = Float(palette.hue.value)
+            self.hueSlider?.value = Float(palette.hue)
         }
-        if changedKeys == nil || changedKeys?.contains(String(keyPath: \Palette.saturation)) == true {
+        if changedKeys == nil || changedKeys?.contains(String(keyPath: \Palette.$saturation)) == true {
             
-            self.saturationSlider?.value = palette.saturation.value
+            self.saturationSlider?.value = palette.saturation
         }
-        if changedKeys == nil || changedKeys?.contains(String(keyPath: \Palette.brightness)) == true {
+        if changedKeys == nil || changedKeys?.contains(String(keyPath: \Palette.$brightness)) == true {
             
-            self.brightnessSlider?.value = palette.brightness.value
+            self.brightnessSlider?.value = palette.brightness
         }
     }
 }

CoreStoreDemo/CoreStoreDemo/List and Object Observers Demo/Palette.swift

@@ -16,31 +16,29 @@ import CoreStore
 
 final class Palette: CoreStoreObject {
     
-    let hue = Value.Required<Int>("hue", initial: 0)
+    @Field.Stored(
-    let saturation = Value.Required<Float>("saturation", initial: 0)
+        "hue",
-    let brightness = Value.Required<Float>("brightness", initial: 0)
+        dynamicInitialValue: { Palette.randomHue() }
-    
-    let colorName = Value.Optional<String>(
-        "colorName",
-        isTransient: true,
-        customGetter: Palette.getColorName
     )
+    var hue: Int
 
-    static func randomHue() -> Int {
+    @Field.Stored("saturation")
+    var saturation: Float = 1
     
-        return Int(arc4random_uniform(360))
+    @Field.Stored(
-    }
+        "brightness",
-    
+        dynamicInitialValue: { Palette.randomBrightness() }
-    private static func getColorName(_ partialObject: PartialObject<Palette>) -> String? {
+    )
-        
+    var brightness: Float
-        if let colorName = partialObject.primitiveValue(for: { $0.colorName }) {
     
+    @Field.Virtual(
+        "colorName",
+        customGetter: { object, field in
+            if let colorName = field.primitiveValue {
                 return colorName
             }
-        
             let colorName: String
-        switch partialObject.value(for: { $0.hue }) % 360 {
+            switch object.$hue.value % 360 {
-            
             case 0 ..< 20: colorName = "Lower Reds"
             case 20 ..< 57: colorName = "Oranges and Browns"
             case 57 ..< 90: colorName = "Yellow-Greens"
@@ -51,10 +49,21 @@ final class Palette: CoreStoreObject {
             case 297 ..< 331: colorName = "Magentas"
             default: colorName = "Upper Reds"
             }
-        
+            field.primitiveValue = colorName
-        partialObject.setPrimitiveValue(colorName, for: { $0.colorName })
             return colorName
         }
+    )
+    var colorName: String!
+    
+    static func randomHue() -> Int {
+        
+        return Int.random(in: 0 ..< 360)
+    }
+    
+    static func randomBrightness() -> Float {
+        
+        return (Float.random(in: 0 ..< 70) + 30) / 100.0
+    }
 }
 
 extension Palette {
@@ -62,25 +71,15 @@ extension Palette {
     var color: UIColor {
         
         return UIColor(
-            hue: CGFloat(self.hue.value) / 360.0,
+            hue: CGFloat(self.hue) / 360.0,
-            saturation: CGFloat(self.saturation.value),
+            saturation: CGFloat(self.saturation),
-            brightness: CGFloat(self.brightness.value),
+            brightness: CGFloat(self.brightness),
             alpha: 1.0
         )
     }
     
     var colorText: String {
         
-        return "H: \(self.hue.value)˚, S: \(round(self.saturation.value * 100.0))%, B: \(round(self.brightness.value * 100.0))%"
+        return "H: \(self.hue)˚, S: \(round(self.saturation * 100.0))%, B: \(round(self.brightness * 100.0))%"
-    }
-}
-
-extension Palette {
-
-    func setInitialValues(in transaction: BaseDataTransaction) {
-
-        self.hue .= Palette.randomHue()
-        self.saturation .= Float(1.0)
-        self.brightness .= Float(arc4random_uniform(70) + 30) / 100.0
     }
 }

CoreStoreDemo/CoreStoreDemo/SwiftUI Demo/SwiftUIContainerViewController.swift

@@ -33,8 +33,8 @@ final class SwiftUIContainerViewController: UIViewController {
                 rootView: SwiftUIView(
                     palettes: ColorsDemo.stack.publishList(
                         From<Palette>()
-                            .sectionBy(\.colorName)
+                            .sectionBy(\.$colorName)
-                            .orderBy(.ascending(\.hue))
+                            .orderBy(.ascending(\.$hue))
                     )
                 )
                 .environment(\.dataStack, ColorsDemo.stack)

CoreStoreDemo/CoreStoreDemo/SwiftUI Demo/SwiftUIView.swift

@@ -61,8 +61,8 @@ struct SwiftUIView: View {
 
                                     for palette in try transaction.fetchAll(From<Palette>()) {
 
-                                        palette.hue .= Palette.randomHue()
+                                        palette.hue = Palette.randomHue()
-                                        palette.colorName .= nil
+                                        palette.colorName = nil
                                     }
                                 },
                                 completion: { _ in }
@@ -79,8 +79,7 @@ struct SwiftUIView: View {
                             self.dataStack.perform(
                                 asynchronous: { transaction in
 
-                                    let palette = transaction.create(Into<Palette>())
+                                    _ = transaction.create(Into<Palette>())
-                                    palette.setInitialValues(in: transaction)
                                 },
                                 completion: { _ in }
                             )
@@ -173,8 +172,8 @@ struct SwiftUIView_Previews: PreviewProvider {
         SwiftUIView(
             palettes: ColorsDemo.stack.publishList(
                 From<Palette>()
-                    .sectionBy(\.colorName)
+                    .sectionBy(\.$colorName)
-                    .orderBy(.ascending(\.hue))
+                    .orderBy(.ascending(\.$hue))
             )
         )
         .environment(\.dataStack, ColorsDemo.stack)

Sources/CoreStoreManagedObject.swift

@@ -33,6 +33,7 @@ import Foundation
     
     internal typealias CustomGetter = @convention(block) (_ rawObject: Any) -> Any?
     internal typealias CustomSetter = @convention(block) (_ rawObject: Any, _ newValue: Any?) -> Void
+    internal typealias CustomInitializer = @convention(block) (_ rawObject: Any) -> Void
     internal typealias CustomGetterSetter = (getter: CustomGetter?, setter: CustomSetter?)
     
     @nonobjc @inline(__always)

Sources/CoreStoreSchema.swift

@@ -209,15 +209,17 @@ public final class CoreStoreSchema: DynamicSchema {
             let rawModel = NSManagedObjectModel()
             var entityDescriptionsByEntity: [DynamicEntity: NSEntityDescription] = [:]
             var allCustomGettersSetters: [DynamicEntity: [KeyPathString: CoreStoreManagedObject.CustomGetterSetter]] = [:]
+            var allCustomInitializers: [DynamicEntity: [KeyPathString: CoreStoreManagedObject.CustomInitializer]] = [:]
             var allFieldCoders: [DynamicEntity: [KeyPathString: Internals.AnyFieldCoder]] = [:]
             for entity in self.allEntities {
                 
-                let (entityDescription, customGetterSetterByKeyPaths, fieldCoders) = self.entityDescription(
+                let (entityDescription, customGetterSetterByKeyPaths, customInitializerByKeyPaths, fieldCoders) = self.entityDescription(
                     for: entity,
                     initializer: CoreStoreSchema.firstPassCreateEntityDescription(from:in:)
                 )
                 entityDescriptionsByEntity[entity] = (entityDescription.copy() as! NSEntityDescription)
                 allCustomGettersSetters[entity] = customGetterSetterByKeyPaths
+                allCustomInitializers[entity] = customInitializerByKeyPaths
                 allFieldCoders[entity] = fieldCoders
             }
             CoreStoreSchema.secondPassConnectRelationshipAttributes(for: entityDescriptionsByEntity)
@@ -225,6 +227,7 @@ public final class CoreStoreSchema: DynamicSchema {
             CoreStoreSchema.fourthPassSynthesizeManagedObjectClasses(
                 for: entityDescriptionsByEntity,
                 allCustomGettersSetters: allCustomGettersSetters,
+                allCustomInitializers: allCustomInitializers,
                 allFieldCoders: allFieldCoders
             )
             
@@ -257,6 +260,7 @@ public final class CoreStoreSchema: DynamicSchema {
     
     private var entityDescriptionsByEntity: [DynamicEntity: NSEntityDescription] = [:]
     private var customGettersSettersByEntity: [DynamicEntity: [KeyPathString: CoreStoreManagedObject.CustomGetterSetter]] = [:]
+    private var customInitializersByEntity: [DynamicEntity: [KeyPathString: CoreStoreManagedObject.CustomInitializer]] = [:]
     private var fieldCodersByEntity: [DynamicEntity: [KeyPathString: Internals.AnyFieldCoder]] = [:]
     private weak var cachedRawModel: NSManagedObjectModel?
     
@@ -265,11 +269,13 @@ public final class CoreStoreSchema: DynamicSchema {
         initializer: (DynamicEntity, ModelVersion) -> (
             entity: NSEntityDescription,
             customGetterSetterByKeyPaths: [KeyPathString: CoreStoreManagedObject.CustomGetterSetter],
+            customInitializersByEntity: [KeyPathString: CoreStoreManagedObject.CustomInitializer],
             fieldCoders: [KeyPathString: Internals.AnyFieldCoder]
         )
     ) -> (
         entity: NSEntityDescription,
         customGetterSetterByKeyPaths: [KeyPathString: CoreStoreManagedObject.CustomGetterSetter],
+        customInitializerByKeyPaths: [KeyPathString: CoreStoreManagedObject.CustomInitializer],
         fieldCoders: [KeyPathString: Internals.AnyFieldCoder]
     ) {
         
@@ -278,23 +284,31 @@ public final class CoreStoreSchema: DynamicSchema {
             return (
                 cachedEntityDescription,
                 self.customGettersSettersByEntity[entity] ?? [:],
+                self.customInitializersByEntity[entity] ?? [:],
                 self.fieldCodersByEntity[entity] ?? [:]
             )
         }
         let modelVersion = self.modelVersion
-        let (entityDescription, customGetterSetterByKeyPaths, fieldCoders) = withoutActuallyEscaping(
+        let (entityDescription, customGetterSetterByKeyPaths, customInitializerByKeyPaths, fieldCoders) = withoutActuallyEscaping(
             initializer,
             do: { $0(entity, modelVersion) }
         )
         self.entityDescriptionsByEntity[entity] = entityDescription
         self.customGettersSettersByEntity[entity] = customGetterSetterByKeyPaths
+        self.customInitializersByEntity[entity] = customInitializerByKeyPaths
         self.fieldCodersByEntity[entity] = fieldCoders
-        return (entityDescription, customGetterSetterByKeyPaths, fieldCoders)
+        return (
+            entityDescription,
+            customGetterSetterByKeyPaths,
+            customInitializerByKeyPaths,
+            fieldCoders
+        )
     }
 
     private static func firstPassCreateEntityDescription(from entity: DynamicEntity, in modelVersion: ModelVersion) -> (
         entity: NSEntityDescription,
         customGetterSetterByKeyPaths: [KeyPathString: CoreStoreManagedObject.CustomGetterSetter],
+        customInitializerByKeyPaths: [KeyPathString: CoreStoreManagedObject.CustomInitializer],
         fieldCoders: [KeyPathString: Internals.AnyFieldCoder]
     ) {
         
@@ -306,6 +320,7 @@ public final class CoreStoreSchema: DynamicSchema {
         entityDescription.managedObjectClassName = CoreStoreManagedObject.cs_subclassName(for: entity, in: modelVersion)
         
         var keyPathsByAffectedKeyPaths: [KeyPathString: Set<KeyPathString>] = [:]
+        var customInitialValuesByKeyPaths: [KeyPathString: CoreStoreManagedObject.CustomInitializer] = [:]
         var customGetterSetterByKeyPaths: [KeyPathString: CoreStoreManagedObject.CustomGetterSetter] = [:]
         var fieldCoders: [KeyPathString: Internals.AnyFieldCoder] = [:]
         func createProperties(for type: CoreStoreObject.Type) -> [NSPropertyDescription] {
@@ -338,6 +353,7 @@ public final class CoreStoreSchema: DynamicSchema {
 
                     keyPathsByAffectedKeyPaths[attribute.keyPath] = entityDescriptionValues.affectedByKeyPaths
                     customGetterSetterByKeyPaths[attribute.keyPath] = (attribute.getter, attribute.setter)
+                    customInitialValuesByKeyPaths[attribute.keyPath] = attribute.initializer
                     fieldCoders[attribute.keyPath] = valueTransformer
 
                 case let relationship as FieldRelationshipProtocol:
@@ -401,7 +417,12 @@ public final class CoreStoreSchema: DynamicSchema {
         }
         entityDescription.properties = createProperties(for: entity.type as! CoreStoreObject.Type)
         entityDescription.keyPathsByAffectedKeyPaths = keyPathsByAffectedKeyPaths
-        return (entityDescription, customGetterSetterByKeyPaths, fieldCoders)
+        return (
+            entityDescription,
+            customGetterSetterByKeyPaths,
+            customInitialValuesByKeyPaths,
+            fieldCoders
+        )
     }
     
     private static func secondPassConnectRelationshipAttributes(for entityDescriptionsByEntity: [DynamicEntity: NSEntityDescription]) {
@@ -597,10 +618,15 @@ public final class CoreStoreSchema: DynamicSchema {
     private static func fourthPassSynthesizeManagedObjectClasses(
         for entityDescriptionsByEntity: [DynamicEntity: NSEntityDescription],
         allCustomGettersSetters: [DynamicEntity: [KeyPathString: CoreStoreManagedObject.CustomGetterSetter]],
+        allCustomInitializers: [DynamicEntity: [KeyPathString: CoreStoreManagedObject.CustomInitializer]],
         allFieldCoders: [DynamicEntity: [KeyPathString: Internals.AnyFieldCoder]]
     ) {
         
-        func createManagedObjectSubclass(for entityDescription: NSEntityDescription, customGetterSetterByKeyPaths: [KeyPathString: CoreStoreManagedObject.CustomGetterSetter]?) {
+        func createManagedObjectSubclass(
+            for entityDescription: NSEntityDescription,
+            customGetterSetterByKeyPaths: [KeyPathString: CoreStoreManagedObject.CustomGetterSetter]?,
+            customInitializers: [KeyPathString: CoreStoreManagedObject.CustomInitializer]?
+        ) {
             
             let superEntity = entityDescription.superentity
             let className = entityDescription.managedObjectClassName!
@@ -612,7 +638,8 @@ public final class CoreStoreSchema: DynamicSchema {
                 
                 createManagedObjectSubclass(
                     for: superEntity,
-                    customGetterSetterByKeyPaths: superEntity.coreStoreEntity.flatMap({ allCustomGettersSetters[$0] })
+                    customGetterSetterByKeyPaths: superEntity.coreStoreEntity.flatMap({ allCustomGettersSetters[$0] }),
+                    customInitializers: superEntity.coreStoreEntity.flatMap({ allCustomInitializers[$0] })
                 )
             }
             let superClass = Internals.with { () -> CoreStoreManagedObject.Type in
@@ -675,6 +702,7 @@ public final class CoreStoreSchema: DynamicSchema {
                         }
                     }
             }
+            swizzle_keyPathsForValuesAffectingValueForKey: do {
 
                 let newSelector = NSSelectorFromString("cs_keyPathsForValuesAffectingValueForKey:")
                 let keyPathsByAffectedKeyPaths = entityDescription.keyPathsByAffectedKeyPaths
@@ -704,11 +732,50 @@ public final class CoreStoreSchema: DynamicSchema {
                     method_exchangeImplementations(origMethod, newMethod)
                 }
             }
+            swizzle_awakeFromInsert: do {
+
+                let newSelector = NSSelectorFromString("cs_awakeFromInsert")
+                let awakeFromInsertValue: @convention(block) (Any) -> Void
+                if let customInitializers = customInitializers,
+                    !customInitializers.isEmpty {
+                    
+                    let initializers = Array(customInitializers.values)
+                    awakeFromInsertValue = { (instance) in
+                        
+                        initializers.forEach {
+                            
+                            $0(instance)
+                        }
+                    }
+                }
+                else {
+                    
+                    awakeFromInsertValue = { _ in }
+                }
+                let origSelector = #selector(CoreStoreManagedObject.awakeFromInsert)
+                
+                let origMethod = class_getInstanceMethod(managedObjectClass, origSelector)!
+                
+                let origImp = method_getImplementation(origMethod)
+                let newImp = imp_implementationWithBlock(awakeFromInsertValue)
+                
+                if class_addMethod(managedObjectClass, origSelector, newImp, method_getTypeEncoding(origMethod)) {
+                    
+                    class_replaceMethod(managedObjectClass, newSelector, origImp, method_getTypeEncoding(origMethod))
+                }
+                else {
+                    
+                    let newMethod = class_getInstanceMethod(managedObjectClass, newSelector)!
+                    method_exchangeImplementations(origMethod, newMethod)
+                }
+            }
+        }
         for (dynamicEntity, entityDescription) in entityDescriptionsByEntity {
             
             createManagedObjectSubclass(
                 for: entityDescription,
-                customGetterSetterByKeyPaths: allCustomGettersSetters[dynamicEntity]
+                customGetterSetterByKeyPaths: allCustomGettersSetters[dynamicEntity],
+                customInitializers: allCustomInitializers[dynamicEntity]
             )
         }
 

Sources/Field.Coded.swift

@@ -94,6 +94,32 @@ extension FieldContainer {
                 valueTransformer: { Internals.AnyFieldCoder(fieldCoderType) },
                 customGetter: customGetter,
                 customSetter: customSetter,
+                dynamicInitialValue: nil,
+                affectedByKeyPaths: affectedByKeyPaths
+            )
+        }
+        
+        public init<Coder: FieldCoderType>(
+            _ keyPath: KeyPathString,
+            versionHashModifier: @autoclosure @escaping () -> String? = nil,
+            previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
+            coder fieldCoderType: Coder.Type,
+            customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
+            customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
+            affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = [],
+            dynamicInitialValue: @escaping () -> V
+        ) where Coder.FieldStoredValue == V {
+
+            self.init(
+                defaultValue: nil,
+                keyPath: keyPath,
+                isOptional: false,
+                versionHashModifier: versionHashModifier,
+                renamingIdentifier: previousVersionKeyPath,
+                valueTransformer: { Internals.AnyFieldCoder(fieldCoderType) },
+                customGetter: customGetter,
+                customSetter: customSetter,
+                dynamicInitialValue: dynamicInitialValue,
                 affectedByKeyPaths: affectedByKeyPaths
             )
         }
@@ -142,6 +168,32 @@ extension FieldContainer {
                 valueTransformer: { Internals.AnyFieldCoder(tag: UUID(), encode: coder.encode, decode: coder.decode) },
                 customGetter: customGetter,
                 customSetter: customSetter,
+                dynamicInitialValue: nil,
+                affectedByKeyPaths: affectedByKeyPaths
+            )
+        }
+        
+        public init(
+            _ keyPath: KeyPathString,
+            versionHashModifier: @autoclosure @escaping () -> String? = nil,
+            previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
+            coder: (encode: (V) -> Data?, decode: (Data?) -> V),
+            customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
+            customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
+            affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = [],
+            dynamicInitialValue: @escaping () -> V
+        ) {
+
+            self.init(
+                defaultValue: nil,
+                keyPath: keyPath,
+                isOptional: false,
+                versionHashModifier: versionHashModifier,
+                renamingIdentifier: previousVersionKeyPath,
+                valueTransformer: { Internals.AnyFieldCoder(tag: UUID(), encode: coder.encode, decode: coder.decode) },
+                customGetter: customGetter,
+                customSetter: customSetter,
+                dynamicInitialValue: dynamicInitialValue,
                 affectedByKeyPaths: affectedByKeyPaths
             )
         }
@@ -334,11 +386,28 @@ extension FieldContainer {
             }
         }
         
+        internal var initializer: CoreStoreManagedObject.CustomInitializer? {
+            
+            guard let dynamicInitialValue = self.dynamicInitialValue else {
+                
+                return nil
+            }
+            let keyPath = self.keyPath
+            return { (_ id: Any) -> Void in
+                
+                let rawObject = id as! CoreStoreManagedObject
+                rawObject.setPrimitiveValue(
+                    dynamicInitialValue(),
+                    forKey: keyPath
+                )
+            }
+        }
+
 
         // MARK: FilePrivate
 
         fileprivate init(
-            defaultValue: @escaping () -> Any?,
+            defaultValue: (() -> Any?)?,
             keyPath: KeyPathString,
             isOptional: Bool,
             versionHashModifier: @escaping () -> String?,
@@ -346,6 +415,7 @@ extension FieldContainer {
             valueTransformer: @escaping () -> Internals.AnyFieldCoder?,
             customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)?,
             customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? ,
+            dynamicInitialValue: (() -> V)?,
             affectedByKeyPaths: @escaping () -> Set<KeyPathString>) {
 
             self.keyPath = keyPath
@@ -361,14 +431,17 @@ extension FieldContainer {
                     renamingIdentifier: renamingIdentifier(),
                     valueTransformer: fieldCoder,
                     affectedByKeyPaths: affectedByKeyPaths(),
-                    defaultValue: Internals.AnyFieldCoder.TransformableDefaultValueCodingBox(
+                    defaultValue: defaultValue.map {
-                        defaultValue: defaultValue(),
+                        Internals.AnyFieldCoder.TransformableDefaultValueCodingBox(
+                            defaultValue: $0(),
                             fieldCoder: fieldCoder
-                    )
+                        ) as Any
+                    }
                 )
             }
             self.customGetter = customGetter
             self.customSetter = customSetter
+            self.dynamicInitialValue = dynamicInitialValue
         }
 
 
@@ -376,6 +449,7 @@ extension FieldContainer {
 
         private let customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)?
         private let customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)?
+        private let dynamicInitialValue: (() -> V)?
     }
 }
 
@@ -422,6 +496,32 @@ extension FieldContainer.Coded where V: FieldOptionalType {
             valueTransformer: { Internals.AnyFieldCoder(coder) },
             customGetter: customGetter,
             customSetter: customSetter,
+            dynamicInitialValue: nil,
+            affectedByKeyPaths: affectedByKeyPaths
+        )
+    }
+    
+    public init<Coder: FieldCoderType>(
+        _ keyPath: KeyPathString,
+        versionHashModifier: @autoclosure @escaping () -> String? = nil,
+        previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
+        coder: Coder.Type,
+        customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
+        customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
+        affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = [],
+        dynamicInitialValue: @escaping () -> V
+    ) where Coder.FieldStoredValue == V.Wrapped {
+
+        self.init(
+            defaultValue: nil,
+            keyPath: keyPath,
+            isOptional: true,
+            versionHashModifier: versionHashModifier,
+            renamingIdentifier: previousVersionKeyPath,
+            valueTransformer: { Internals.AnyFieldCoder(coder) },
+            customGetter: customGetter,
+            customSetter: customSetter,
+            dynamicInitialValue: dynamicInitialValue,
             affectedByKeyPaths: affectedByKeyPaths
         )
     }
@@ -470,6 +570,32 @@ extension FieldContainer.Coded where V: FieldOptionalType {
             valueTransformer: { Internals.AnyFieldCoder(tag: UUID(), encode: coder.encode, decode: coder.decode) },
             customGetter: customGetter,
             customSetter: customSetter,
+            dynamicInitialValue: nil,
+            affectedByKeyPaths: affectedByKeyPaths
+        )
+    }
+    
+    public init(
+        _ keyPath: KeyPathString,
+        versionHashModifier: @autoclosure @escaping () -> String? = nil,
+        previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
+        coder: (encode: (V) -> Data?, decode: (Data?) -> V),
+        customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
+        customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
+        affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = [],
+        dynamicInitialValue: @escaping () -> V
+    ) {
+
+        self.init(
+            defaultValue: nil,
+            keyPath: keyPath,
+            isOptional: true,
+            versionHashModifier: versionHashModifier,
+            renamingIdentifier: previousVersionKeyPath,
+            valueTransformer: { Internals.AnyFieldCoder(tag: UUID(), encode: coder.encode, decode: coder.decode) },
+            customGetter: customGetter,
+            customSetter: customSetter,
+            dynamicInitialValue: dynamicInitialValue,
             affectedByKeyPaths: affectedByKeyPaths
         )
     }
@@ -516,6 +642,31 @@ extension FieldContainer.Coded where V: DefaultNSSecureCodable {
             valueTransformer: { Internals.AnyFieldCoder(FieldCoders.DefaultNSSecureCoding<V>.self) },
             customGetter: customGetter,
             customSetter: customSetter,
+            dynamicInitialValue: nil,
+            affectedByKeyPaths: affectedByKeyPaths
+        )
+    }
+    
+    public init(
+        _ keyPath: KeyPathString,
+        versionHashModifier: @autoclosure @escaping () -> String? = nil,
+        previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
+        customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
+        customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
+        affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = [],
+        dynamicInitialValue: @escaping () -> V
+    ) {
+
+        self.init(
+            defaultValue: nil,
+            keyPath: keyPath,
+            isOptional: false,
+            versionHashModifier: versionHashModifier,
+            renamingIdentifier: previousVersionKeyPath,
+            valueTransformer: { Internals.AnyFieldCoder(FieldCoders.DefaultNSSecureCoding<V>.self) },
+            customGetter: customGetter,
+            customSetter: customSetter,
+            dynamicInitialValue: dynamicInitialValue,
             affectedByKeyPaths: affectedByKeyPaths
         )
     }
@@ -562,6 +713,31 @@ extension FieldContainer.Coded where V: FieldOptionalType, V.Wrapped: DefaultNSS
             valueTransformer: { Internals.AnyFieldCoder(FieldCoders.DefaultNSSecureCoding<V.Wrapped>.self) },
             customGetter: customGetter,
             customSetter: customSetter,
+            dynamicInitialValue: nil,
+            affectedByKeyPaths: affectedByKeyPaths
+        )
+    }
+    
+    public init(
+        _ keyPath: KeyPathString,
+        versionHashModifier: @autoclosure @escaping () -> String? = nil,
+        previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
+        customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
+        customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
+        affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = [],
+        dynamicInitialValue: @escaping () -> V
+    ) {
+
+        self.init(
+            defaultValue: nil,
+            keyPath: keyPath,
+            isOptional: true,
+            versionHashModifier: versionHashModifier,
+            renamingIdentifier: previousVersionKeyPath,
+            valueTransformer: { Internals.AnyFieldCoder(FieldCoders.DefaultNSSecureCoding<V.Wrapped>.self) },
+            customGetter: customGetter,
+            customSetter: customSetter,
+            dynamicInitialValue: dynamicInitialValue,
             affectedByKeyPaths: affectedByKeyPaths
         )
     }

Sources/Field.Stored.swift

@@ -85,6 +85,30 @@ extension FieldContainer {
                 renamingIdentifier: previousVersionKeyPath,
                 customGetter: customGetter,
                 customSetter: customSetter,
+                dynamicInitialValue: nil,
+                affectedByKeyPaths: affectedByKeyPaths
+            )
+        }
+        
+        public init(
+            _ keyPath: KeyPathString,
+            versionHashModifier: @autoclosure @escaping () -> String? = nil,
+            previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
+            customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
+            customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
+            affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = [],
+            dynamicInitialValue: @escaping () -> V
+        ) {
+
+            self.init(
+                wrappedValue: nil,
+                keyPath: keyPath,
+                isOptional: false,
+                versionHashModifier: versionHashModifier,
+                renamingIdentifier: previousVersionKeyPath,
+                customGetter: customGetter,
+                customSetter: customSetter,
+                dynamicInitialValue: dynamicInitialValue,
                 affectedByKeyPaths: affectedByKeyPaths
             )
         }
@@ -263,17 +287,35 @@ extension FieldContainer {
             }
         }
         
+        internal var initializer: CoreStoreManagedObject.CustomInitializer? {
+            
+            guard let dynamicInitialValue = self.dynamicInitialValue else {
+                
+                return nil
+            }
+            let keyPath = self.keyPath
+            return { (_ id: Any) -> Void in
+                
+                let rawObject = id as! CoreStoreManagedObject
+                rawObject.setPrimitiveValue(
+                    dynamicInitialValue().cs_toFieldStoredNativeType(),
+                    forKey: keyPath
+                )
+            }
+        }
+
 
         // MARK: FilePrivate
 
         fileprivate init(
-            wrappedValue initial: @escaping () -> V,
+            wrappedValue initial: (() -> V)?,
             keyPath: KeyPathString,
             isOptional: Bool,
             versionHashModifier: @escaping () -> String?,
             renamingIdentifier: @escaping () -> String?,
             customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)?,
-            customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? ,
+            customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)?,
+            dynamicInitialValue: (() -> V)?,
             affectedByKeyPaths: @escaping () -> Set<KeyPathString>) {
 
             self.keyPath = keyPath
@@ -287,11 +329,12 @@ extension FieldContainer {
                     renamingIdentifier: renamingIdentifier(),
                     valueTransformer: nil,
                     affectedByKeyPaths: affectedByKeyPaths(),
-                    defaultValue: initial().cs_toFieldStoredNativeType()
+                    defaultValue: initial?().cs_toFieldStoredNativeType()
                 )
             }
             self.customGetter = customGetter
             self.customSetter = customSetter
+            self.dynamicInitialValue = dynamicInitialValue
         }
 
 
@@ -299,6 +342,7 @@ extension FieldContainer {
 
         private let customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)?
         private let customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)?
+        private let dynamicInitialValue: (() -> V)?
     }
 }
 
@@ -331,7 +375,8 @@ extension FieldContainer.Stored where V: FieldOptionalType {
         previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
         customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
         customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
-        affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = []) {
+        affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = []
+    ) {
 
         self.init(
             wrappedValue: initial,
@@ -341,6 +386,30 @@ extension FieldContainer.Stored where V: FieldOptionalType {
             renamingIdentifier: previousVersionKeyPath,
             customGetter: customGetter,
             customSetter: customSetter,
+            dynamicInitialValue: nil,
+            affectedByKeyPaths: affectedByKeyPaths
+        )
+    }
+    
+    public init(
+        _ keyPath: KeyPathString,
+        versionHashModifier: @autoclosure @escaping () -> String? = nil,
+        previousVersionKeyPath: @autoclosure @escaping () -> String? = nil,
+        customGetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>) -> V)? = nil,
+        customSetter: ((_ object: ObjectProxy<O>, _ field: ObjectProxy<O>.FieldProxy<V>, _ newValue: V) -> Void)? = nil,
+        affectedByKeyPaths: @autoclosure @escaping () -> Set<KeyPathString> = [],
+        dynamicInitialValue: @escaping () -> V
+    ) {
+
+        self.init(
+            wrappedValue: nil,
+            keyPath: keyPath,
+            isOptional: true,
+            versionHashModifier: versionHashModifier,
+            renamingIdentifier: previousVersionKeyPath,
+            customGetter: customGetter,
+            customSetter: customSetter,
+            dynamicInitialValue: dynamicInitialValue,
             affectedByKeyPaths: affectedByKeyPaths
         )
     }

Sources/Field.Virtual.swift

@@ -276,6 +276,8 @@ extension FieldContainer {
             }
         }
         
+        let initializer: CoreStoreManagedObject.CustomInitializer? = nil
+
 
         // MARK: FilePrivate
 

Sources/FieldAttributeProtocol.swift

@@ -48,4 +48,5 @@ internal protocol FieldAttributeProtocol: FieldProtocol {
     var entityDescriptionValues: () -> EntityDescriptionValues { get }
     var getter: CoreStoreManagedObject.CustomGetter? { get }
     var setter: CoreStoreManagedObject.CustomSetter? { get }
+    var initializer: CoreStoreManagedObject.CustomInitializer? { get }
 }

Sources/From+Querying.swift

@@ -345,6 +345,30 @@ extension From where O: CoreStoreObject {
         return self.select(R.self, [SelectTerm<O>.attribute(keyPath)])
     }
     
+    /**
+     Creates a `SectionMonitorChainBuilder` with the key path to use to group `ListMonitor` objects into sections
+     
+     - parameter sectionKeyPath: the `KeyPath` to use to group the objects into sections
+     - returns: a `SectionMonitorChainBuilder` that is sectioned by the specified key path
+     */
+    @available(macOS 10.12, *)
+    public func sectionBy<T>(_ sectionKeyPath: KeyPath<O, FieldContainer<O>.Stored<T>>) -> SectionMonitorChainBuilder<O> {
+        
+        return self.sectionBy(O.meta[keyPath: sectionKeyPath].keyPath, { $0 })
+    }
+    
+    /**
+     Creates a `SectionMonitorChainBuilder` with the key path to use to group `ListMonitor` objects into sections
+     
+     - parameter sectionKeyPath: the `KeyPath` to use to group the objects into sections
+     - returns: a `SectionMonitorChainBuilder` that is sectioned by the specified key path
+     */
+    @available(macOS 10.12, *)
+    public func sectionBy<T>(_ sectionKeyPath: KeyPath<O, FieldContainer<O>.Virtual<T>>) -> SectionMonitorChainBuilder<O> {
+        
+        return self.sectionBy(O.meta[keyPath: sectionKeyPath].keyPath, { $0 })
+    }
+    
     /**
      Creates a `SectionMonitorChainBuilder` with the key path to use to group `ListMonitor` objects into sections
      

Sources/NSEntityDescription+DynamicModel.swift

@@ -115,27 +115,6 @@ extension NSEntityDescription {
         }
     }
     
-    @nonobjc
-    internal var customGetterSetterByKeyPaths: [KeyPathString: CoreStoreManagedObject.CustomGetterSetter] {
-        
-        get {
-            
-            if let userInfo = self.userInfo,
-                let value = userInfo[UserInfoKey.CoreStoreManagedObjectCustomGetterSetterByKeyPaths] {
-                
-                return value as! [KeyPathString: CoreStoreManagedObject.CustomGetterSetter]
-            }
-            return [:]
-        }
-        set {
-            
-            cs_setUserInfo { (userInfo) in
-                
-                userInfo[UserInfoKey.CoreStoreManagedObjectCustomGetterSetterByKeyPaths] = newValue
-            }
-        }
-    }
-    
     
     // MARK: Private
     
@@ -151,7 +130,6 @@ extension NSEntityDescription {
         fileprivate static let CoreStoreManagedObjectUniqueConstraints = "CoreStoreManagedObjectUniqueConstraints"
         
         fileprivate static let CoreStoreManagedObjectKeyPathsByAffectedKeyPaths = "CoreStoreManagedObjectKeyPathsByAffectedKeyPaths"
-        fileprivate static let CoreStoreManagedObjectCustomGetterSetterByKeyPaths = "CoreStoreManagedObjectCustomGetterSetterByKeyPaths"
         
     }