Value.Required now requires an "initial:" parameter. For previous CoreStoreObject users, use the appropriate empty value for your existing properties (0 for numeric types, false for Bool, "" for String)

Sources/Transformable.swift

@@ -0,0 +1,597 @@
+//
+//  Transformable.swift
+//  CoreStore
+//
+//  Copyright © 2017 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: - DynamicObject
+
+public extension DynamicObject where Self: CoreStoreObject {
+    
+    /**
+     The containing type for transformable properties. `Transformable` properties support types that conforms to `NSCoding & NSCopying`.
+     ```
+     class Animal: CoreStoreObject {
+     let species = Value.Required<String>("species")
+     let nickname = Value.Optional<String>("nickname")
+     let color = Transformable.Optional<UIColor>("color")
+     }
+     ```
+     - Important: `Transformable` properties are required to be stored properties. Computed properties will be ignored, including `lazy` and `weak` properties.
+     */
+    public typealias Transformable = TransformableContainer<Self>
+}
+
+
+// MARK: - TransformableContainer
+
+/**
+ The containing type for transformable properties. Use the `DynamicObject.Transformable` typealias instead for shorter syntax.
+ ```
+ class Animal: CoreStoreObject {
+     let species = Value.Required<String>("species")
+     let nickname = Value.Optional<String>("nickname")
+     let color = Transformable.Optional<UIColor>("color")
+ }
+ ```
+ */
+public enum TransformableContainer<O: CoreStoreObject> {
+
+    // MARK: - Required
+
+    /**
+     The containing type for transformable properties. Any type that conforms to `NSCoding & NSCopying` are supported.
+     ```
+     class Animal: CoreStoreObject {
+         let species = Value.Required<String>("species")
+         let nickname = Value.Optional<String>("nickname")
+         let color = Transformable.Optional<UIColor>("color")
+     }
+     ```
+     - Important: `Transformable.Required` properties are required to be stored properties. Computed properties will be ignored, including `lazy` and `weak` properties.
+     */
+    public final class Required<V: NSCoding & NSCopying>: AttributeProtocol {
+
+        /**
+         Initializes the metadata for the property.
+         ```
+         class Animal: CoreStoreObject {
+             let species = Value.Required<String>("species")
+             let color = Transformable.Required<UIColor>(
+                 "color",
+                 initial: UIColor.clear,
+                 isTransient: true,
+                 customGetter: Animal.getColor(_:)
+             )
+         }
+
+         private static func getColor(_ partialObject: PartialObject<Animal>) -> UIColor {
+             let cachedColor = partialObject.primitiveValue(for: { $0.color })
+             if cachedColor != UIColor.clear {
+
+                 return cachedColor
+             }
+             let color: UIColor
+             switch partialObject.value(for: { $0.species }) {
+
+             case "Swift": color = UIColor.orange
+             case "Bulbasaur": color = UIColor.green
+             default: color = UIColor.black
+             }
+             partialObject.setPrimitiveValue(color, for: { $0.color })
+             return color
+         }
+         ```
+         - parameter keyPath: the permanent attribute name for this property.
+         - parameter initial: the initial value for the property when the object is first created. Defaults to the `ImportableAttributeType`'s empty value if not specified.
+         - parameter isIndexed: `true` if the property should be indexed for searching, otherwise `false`. Defaults to `false` if not specified.
+         - parameter isTransient: `true` if the property is transient, otherwise `false`. Defaults to `false` if not specified. The transient flag specifies whether or not a property's value is ignored when an object is saved to a persistent store. Transient properties are not saved to the persistent store, but are still managed for undo, redo, validation, and so on.
+         - 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 renamingIdentifier: used to resolve naming conflicts between models. When creating an entity mapping between entities in two managed object models, a source entity property and a destination entity property that share the same identifier 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 name.
+         - 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 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 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: KeyPath,
+            initial: @autoclosure @escaping () -> V,
+            isIndexed: Bool = false,
+            isTransient: Bool = false,
+            versionHashModifier: @autoclosure @escaping () -> String? = nil,
+            renamingIdentifier: @autoclosure @escaping () -> String? = nil,
+            customGetter: ((_ partialObject: PartialObject<O>) -> V)? = nil,
+            customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)? = nil,
+            affectedByKeyPaths: @autoclosure @escaping () -> Set<String> = []) {
+
+            self.keyPath = keyPath
+            self.defaultValue = initial
+            self.isIndexed = isIndexed
+            self.isTransient = isTransient
+            self.versionHashModifier = versionHashModifier
+            self.renamingIdentifier = renamingIdentifier
+            self.customGetter = customGetter
+            self.customSetter = customSetter
+            self.affectedByKeyPaths = affectedByKeyPaths
+        }
+
+        /**
+         The property value.
+         */
+        public var value: V {
+
+            get {
+
+                CoreStore.assert(
+                    self.parentObject != nil,
+                    "Attempted to access values from a \(cs_typeName(O.self)) meta object. Meta objects are only used for querying keyPaths and infering types."
+                )
+                return withExtendedLifetime(self.parentObject! as! O) { (object: O) in
+
+                    CoreStore.assert(
+                        object.rawObject!.isRunningInAllowedQueue() == true,
+                        "Attempted to access \(cs_typeName(O.self))'s value outside it's designated queue."
+                    )
+                    if let customGetter = self.customGetter {
+
+                        return customGetter(PartialObject<O>(object.rawObject!))
+                    }
+                    return object.rawObject!.value(forKey: self.keyPath)! as! V
+                }
+            }
+            set {
+
+                CoreStore.assert(
+                    self.parentObject != nil,
+                    "Attempted to access values from a \(cs_typeName(O.self)) meta object. Meta objects are only used for querying keyPaths and infering types."
+                )
+                return withExtendedLifetime(self.parentObject! as! O) { (object: O) in
+
+                    CoreStore.assert(
+                        object.rawObject!.isRunningInAllowedQueue() == true,
+                        "Attempted to access \(cs_typeName(O.self))'s value outside it's designated queue."
+                    )
+                    CoreStore.assert(
+                        object.rawObject!.isEditableInContext() == true,
+                        "Attempted to update a \(cs_typeName(O.self))'s value from outside a transaction."
+                    )
+                    if let customSetter = self.customSetter {
+
+                        return customSetter(PartialObject<O>(object.rawObject!), newValue)
+                    }
+                    object.rawObject!.setValue(
+                        newValue,
+                        forKey: self.keyPath
+                    )
+                }
+            }
+        }
+
+
+        // MARK: AttributeProtocol
+
+        internal static var attributeType: NSAttributeType {
+
+            return .transformableAttributeType
+        }
+
+        public let keyPath: KeyPath
+
+        internal let isOptional = false
+        internal let isIndexed: Bool
+        internal let isTransient: Bool
+        internal let versionHashModifier: () -> String?
+        internal let renamingIdentifier: () -> String?
+        internal let defaultValue: () -> Any?
+        internal let affectedByKeyPaths: () -> Set<String>
+        internal weak var parentObject: CoreStoreObject?
+
+        internal private(set) lazy var getter: CoreStoreManagedObject.CustomGetter? = cs_lazy { [unowned self] in
+
+            guard let customGetter = self.customGetter else {
+
+                return nil
+            }
+            let keyPath = self.keyPath
+            return { (_ id: Any) -> Any? in
+
+                let rawObject = id as! CoreStoreManagedObject
+                rawObject.willAccessValue(forKey: keyPath)
+                defer {
+
+                    rawObject.didAccessValue(forKey: keyPath)
+                }
+                let value = customGetter(PartialObject<O>(rawObject))
+                return value
+            }
+        }
+
+        internal private(set) lazy var setter: CoreStoreManagedObject.CustomSetter? = cs_lazy { [unowned self] in
+
+            guard let customSetter = self.customSetter else {
+
+                return nil
+            }
+            let keyPath = self.keyPath
+            return { (_ id: Any, _ newValue: Any?) -> Void in
+
+                let rawObject = id as! CoreStoreManagedObject
+                rawObject.willChangeValue(forKey: keyPath)
+                defer {
+
+                    rawObject.didChangeValue(forKey: keyPath)
+                }
+                customSetter(
+                    PartialObject<O>(rawObject),
+                    newValue as! V
+                )
+            }
+        }
+
+
+        // MARK: Private
+
+        private let customGetter: ((_ partialObject: PartialObject<O>) -> V)?
+        private let customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)?
+
+
+        // MARK: Deprecated
+
+        @available(*, deprecated: 3.1, renamed: "init(_:initial:isIndexed:isTransient:versionHashModifier:renamingIdentifier:customGetter:customSetter:affectedByKeyPaths:)")
+        public convenience init(
+            _ keyPath: KeyPath,
+            `default`: @autoclosure @escaping () -> V,
+            isIndexed: Bool = false,
+            isTransient: Bool = false,
+            versionHashModifier: @autoclosure @escaping () -> String? = nil,
+            renamingIdentifier: @autoclosure @escaping () -> String? = nil,
+            customGetter: ((_ partialObject: PartialObject<O>) -> V)? = nil,
+            customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V) -> Void)? = nil,
+            affectedByKeyPaths: @autoclosure @escaping () -> Set<String> = []) {
+
+            self.init(
+                keyPath,
+                initial: `default`,
+                isIndexed: isIndexed,
+                isTransient: isTransient,
+                versionHashModifier: versionHashModifier,
+                renamingIdentifier: renamingIdentifier,
+                customGetter: customGetter,
+                customSetter: customSetter,
+                affectedByKeyPaths: affectedByKeyPaths
+            )
+        }
+    }
+
+
+    // MARK: - Optional
+
+    /**
+     The containing type for optional transformable properties. Any type that conforms to `NSCoding & NSCopying` are supported.
+     ```
+     class Animal: CoreStoreObject {
+         let species = Value.Required<String>("species")
+         let nickname = Value.Optional<String>("nickname")
+         let color = Transformable.Optional<UIColor>("color")
+     }
+     ```
+     - Important: `Transformable.Optional` properties are required to be stored properties. Computed properties will be ignored, including `lazy` and `weak` properties.
+     */
+    public final class Optional<V: NSCoding & NSCopying>: AttributeProtocol {
+
+        /**
+         Initializes the metadata for the property.
+         ```
+         class Animal: CoreStoreObject {
+             let species = Value.Required<String>("species")
+             let color = Transformable.Optional<UIColor>(
+                 "color",
+                 isTransient: true,
+                 customGetter: Animal.getColor(_:)
+             )
+         }
+
+         private static func getColor(_ partialObject: PartialObject<Animal>) -> UIColor? {
+             if let cachedColor = partialObject.primitiveValue(for: { $0.color }) {
+                 return cachedColor
+             }
+             let color: UIColor?
+             switch partialObject.value(for: { $0.species }) {
+
+             case "Swift": color = UIColor.orange
+             case "Bulbasaur": color = UIColor.green
+             default: return nil
+             }
+             partialObject.setPrimitiveValue(color, for: { $0.color })
+             return color
+         }
+         ```
+         - parameter keyPath: the permanent attribute name for this property.
+         - parameter initial: the initial value for the property when the object is first created. Defaults to the `ImportableAttributeType`'s empty value if not specified.
+         - parameter isIndexed: `true` if the property should be indexed for searching, otherwise `false`. Defaults to `false` if not specified.
+         - parameter isTransient: `true` if the property is transient, otherwise `false`. Defaults to `false` if not specified. The transient flag specifies whether or not a property's value is ignored when an object is saved to a persistent store. Transient properties are not saved to the persistent store, but are still managed for undo, redo, validation, and so on.
+         - 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 renamingIdentifier: used to resolve naming conflicts between models. When creating an entity mapping between entities in two managed object models, a source entity property and a destination entity property that share the same identifier 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 name.
+         - 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 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 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: KeyPath,
+            initial: @autoclosure @escaping () -> V? = nil,
+            isIndexed: Bool = false,
+            isTransient: Bool = false,
+            versionHashModifier: @autoclosure @escaping () -> String? = nil,
+            renamingIdentifier: @autoclosure @escaping () -> String? = nil,
+            customGetter: ((_ partialObject: PartialObject<O>) -> V?)? = nil,
+            customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V?) -> Void)? = nil,
+            affectedByKeyPaths: @autoclosure @escaping () -> Set<String> = []) {
+
+            self.keyPath = keyPath
+            self.defaultValue = initial
+            self.isIndexed = isIndexed
+            self.isTransient = isTransient
+            self.versionHashModifier = versionHashModifier
+            self.renamingIdentifier = renamingIdentifier
+            self.customGetter = customGetter
+            self.customSetter = customSetter
+            self.affectedByKeyPaths = affectedByKeyPaths
+        }
+
+        /**
+         The property value.
+         */
+        public var value: V? {
+
+            get {
+
+                CoreStore.assert(
+                    self.parentObject != nil,
+                    "Attempted to access values from a \(cs_typeName(O.self)) meta object. Meta objects are only used for querying keyPaths and infering types."
+                )
+                return withExtendedLifetime(self.parentObject! as! O) { (object: O) in
+
+                    CoreStore.assert(
+                        object.rawObject!.isRunningInAllowedQueue() == true,
+                        "Attempted to access \(cs_typeName(O.self))'s value outside it's designated queue."
+                    )
+                    if let customGetter = self.customGetter {
+
+                        return customGetter(PartialObject<O>(object.rawObject!))
+                    }
+                    return object.rawObject!.value(forKey: self.keyPath) as! V?
+                }
+            }
+            set {
+
+                CoreStore.assert(
+                    self.parentObject != nil,
+                    "Attempted to access values from a \(cs_typeName(O.self)) meta object. Meta objects are only used for querying keyPaths and infering types."
+                )
+                return withExtendedLifetime(self.parentObject! as! O) { (object: O) in
+
+                    CoreStore.assert(
+                        object.rawObject!.isRunningInAllowedQueue() == true,
+                        "Attempted to access \(cs_typeName(O.self))'s value outside it's designated queue."
+                    )
+                    CoreStore.assert(
+                        object.rawObject!.isEditableInContext() == true,
+                        "Attempted to update a \(cs_typeName(O.self))'s value from outside a transaction."
+                    )
+                    if let customSetter = self.customSetter {
+
+                        return customSetter(PartialObject<O>(object.rawObject!), newValue)
+                    }
+                    object.rawObject!.setValue(
+                        newValue,
+                        forKey: self.keyPath
+                    )
+                }
+            }
+        }
+
+
+        // MARK: AttributeProtocol
+
+        internal static var attributeType: NSAttributeType {
+
+            return .transformableAttributeType
+        }
+
+        public let keyPath: KeyPath
+
+        internal let isOptional = true
+        internal let isIndexed: Bool
+        internal let isTransient: Bool
+        internal let versionHashModifier: () -> String?
+        internal let renamingIdentifier: () -> String?
+        internal let defaultValue: () -> Any?
+        internal let affectedByKeyPaths: () -> Set<String>
+        internal weak var parentObject: CoreStoreObject?
+
+        internal private(set) lazy var getter: CoreStoreManagedObject.CustomGetter? = cs_lazy { [unowned self] in
+
+            guard let customGetter = self.customGetter else {
+
+                return nil
+            }
+            let keyPath = self.keyPath
+            return { (_ id: Any) -> Any? in
+
+                let rawObject = id as! CoreStoreManagedObject
+                rawObject.willAccessValue(forKey: keyPath)
+                defer {
+
+                    rawObject.didAccessValue(forKey: keyPath)
+                }
+                let value = customGetter(PartialObject<O>(rawObject))
+                return value
+            }
+        }
+
+        internal private(set) lazy var setter: CoreStoreManagedObject.CustomSetter? = cs_lazy { [unowned self] in
+
+            guard let customSetter = self.customSetter else {
+
+                return nil
+            }
+            let keyPath = self.keyPath
+            return { (_ id: Any, _ newValue: Any?) -> Void in
+
+                let rawObject = id as! CoreStoreManagedObject
+                rawObject.willChangeValue(forKey: keyPath)
+                defer {
+
+                    rawObject.didChangeValue(forKey: keyPath)
+                }
+                customSetter(
+                    PartialObject<O>(rawObject),
+                    newValue as! V?
+                )
+            }
+        }
+
+
+        // MARK: Private
+
+        private let customGetter: ((_ partialObject: PartialObject<O>) -> V?)?
+        private let customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V?) -> Void)?
+
+
+        // MARK: Deprecated
+
+        @available(*, deprecated: 3.1, renamed: "init(_:initial:isIndexed:isTransient:versionHashModifier:renamingIdentifier:customGetter:customSetter:affectedByKeyPaths:)")
+        public convenience init(
+            _ keyPath: KeyPath,
+            `default`: @autoclosure @escaping () -> V?,
+            isIndexed: Bool = false,
+            isTransient: Bool = false,
+            versionHashModifier: @autoclosure @escaping () -> String? = nil,
+            renamingIdentifier: @autoclosure @escaping () -> String? = nil,
+            customGetter: ((_ partialObject: PartialObject<O>) -> V?)? = nil,
+            customSetter: ((_ partialObject: PartialObject<O>, _ newValue: V?) -> Void)? = nil,
+            affectedByKeyPaths: @autoclosure @escaping () -> Set<String> = []) {
+
+            self.init(
+                keyPath,
+                initial: `default`,
+                isIndexed: isIndexed,
+                isTransient: isTransient,
+                versionHashModifier: versionHashModifier,
+                renamingIdentifier: renamingIdentifier,
+                customGetter: customGetter,
+                customSetter: customSetter,
+                affectedByKeyPaths: affectedByKeyPaths
+            )
+        }
+    }
+}
+
+
+// MARK: - Operations
+
+infix operator .= : AssignmentPrecedence
+infix operator .== : ComparisonPrecedence
+
+extension TransformableContainer.Required {
+    
+    /**
+     Assigns a transformable value to the property. The operation
+     ```
+     animal.color .= UIColor.red
+     ```
+     is equivalent to
+     ```
+     animal.color.value = UIColor.red
+     ```
+     */
+    public static func .= (_ property: TransformableContainer<O>.Required<V>, _ newValue: V) {
+        
+        property.value = newValue
+    }
+    
+    /**
+     Assigns a transformable value from another property. The operation
+     ```
+     animal.nickname .= anotherAnimal.species
+     ```
+     is equivalent to
+     ```
+     animal.nickname.value = anotherAnimal.species.value
+     ```
+     */
+    public static func .= <O2>(_ property: TransformableContainer<O>.Required<V>, _ property2: TransformableContainer<O2>.Required<V>) {
+        
+        property.value = property2.value
+    }
+}
+
+extension TransformableContainer.Optional {
+    
+    /**
+     Assigns an optional transformable value to the property. The operation
+     ```
+     animal.color .= UIColor.red
+     ```
+     is equivalent to
+     ```
+     animal.color.value = UIColor.red
+     ```
+     */
+    public static func .= (_ property: TransformableContainer<O>.Optional<V>, _ newValue: V?) {
+        
+        property.value = newValue
+    }
+    
+    /**
+     Assigns an optional transformable value from another property. The operation
+     ```
+     animal.color .= anotherAnimal.color
+     ```
+     is equivalent to
+     ```
+     animal.color.value = anotherAnimal.color.value
+     ```
+     */
+    public static func .= <O2>(_ property: TransformableContainer<O>.Optional<V>, _ property2: TransformableContainer<O2>.Optional<V>) {
+        
+        property.value = property2.value
+    }
+    
+    /**
+     Assigns a transformable value from another property. The operation
+     ```
+     animal.color .= anotherAnimal.color
+     ```
+     is equivalent to
+     ```
+     animal.color.value = anotherAnimal.color.value
+     ```
+     */
+    public static func .= <O2>(_ property: TransformableContainer<O>.Optional<V>, _ property2: TransformableContainer<O2>.Required<V>) {
+        
+        property.value = property2.value
+    }
+}