CoreStore/Sources/Value.swift

//
//  Value.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 value propertiess. `Value` properties support any type that conforms to `ImportableAttributeType`.
     ```
     class Animal: CoreStoreObject {
         let species = Value.Required<String>("species")
         let nickname = Value.Optional<String>("nickname")
         let color = Transformable.Optional<UIColor>("color")
     }
     ```
     - Important: `Value` properties are required to be stored properties. Computed properties will be ignored, including `lazy` and `weak` properties.
     */
    public typealias Value = ValueContainer<Self>
    
    /**
     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: - ValueContainer

/**
 The containing type for value properties. Use the `DynamicObject.Value` 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 ValueContainer<O: CoreStoreObject> {
    
    // MARK: - Required
    
    /**
     The containing type for required value properties. Any type that conforms to `ImportableAttributeType` are supported.
     ```
     class Animal: CoreStoreObject {
         let species = Value.Required<String>("species")
         let nickname = Value.Optional<String>("nickname")
         let color = Transformable.Optional<UIColor>("color")
     }
     ```
     - Important: `Value.Required` properties are required to be stored properties. Computed properties will be ignored, including `lazy` and `weak` properties.
     */
    public final class Required<V: ImportableAttributeType>: AttributeProtocol {
        
        /**
         Initializes the metadata for the property.
         ```
         class Person: CoreStoreObject {
             let title = Value.Required<String>("title", default: "Mr.")
             let name = Value.Required<String>(
                 "name",
                 customGetter: { (`self`, getValue) in
                    return "\(self.title.value) \(getValue())"
                 }
             )
         }
         ```
         - parameter keyPath: the permanent attribute name for this property.
         - parameter default: the initial value for the property when the object is first created. For types that implement `EmptyableAttributeType`s, this argument may be omitted and the type's "empty" value will be used instead (e.g. `false` for `Bool`, `0` for `Int`, `""` for `String`, etc.)
         - 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 to make final transformations to the property's value before returning from the getter.
         - parameter self: the `CoreStoreObject`
         - parameter getValue: the original getter for the property
         - parameter customSetter: use this closure to make final transformations to the new value before assigning to the property.
         - parameter setValue: the original setter for the property
         - parameter finalNewValue: the transformed new value
         - parameter originalNewValue: the original new value
         */
        public init(_ keyPath: KeyPath, `default`: V, isIndexed: Bool = false, isTransient: Bool = false, versionHashModifier: String? = nil, renamingIdentifier: String? = nil, customGetter: @escaping (_ `self`: O, _ getValue: () -> V) -> V = { $1() }, customSetter: @escaping (_ `self`: O, _ setValue: (_ finalNewValue: V) -> Void, _ originalNewValue: V) -> Void = { $1($2) }) {
            
            self.keyPath = keyPath
            self.isIndexed = isIndexed
            self.isTransient = isTransient
            self.defaultValue = `default`.cs_toImportableNativeType()
            self.versionHashModifier = versionHashModifier
            self.renamingIdentifier = renamingIdentifier
            self.customGetter = customGetter
            self.customSetter = customSetter
        }
        
        /**
         The property value.
         */
        public var value: V {
            
            get {
                
                let object = self.parentObject() as! O
                CoreStore.assert(
                    object.rawObject!.isRunningInAllowedQueue() == true,
                    "Attempted to access \(cs_typeName(O.self))'s value outside it's designated queue."
                )
                return self.customGetter(
                    object,
                    { () -> V in
                        
                        return object.rawObject!.getValue(
                            forKvcKey: self.keyPath,
                            didGetValue: { V.cs_fromImportableNativeType($0 as! V.ImportableNativeType)! }
                        )
                    }
                )
            }
            set {
                
                let object = self.parentObject() as! O
                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."
                )
                self.customSetter(
                    object,
                    { (newValue: V) -> Void in
                        
                        object.rawObject!.setValue(
                            newValue,
                            forKvcKey: self.keyPath,
                            willSetValue: { $0.cs_toImportableNativeType() }
                        )
                    },
                    newValue
                )
            }
        }
        
        
        // MARK: AttributeProtocol
        
        internal static var attributeType: NSAttributeType {
            
            return V.cs_rawAttributeType
        }
        
        public let keyPath: KeyPath
        
        internal let isOptional = false
        internal let isIndexed: Bool
        internal let isTransient: Bool
        internal let defaultValue: Any?
        internal let versionHashModifier: String?
        internal let renamingIdentifier: String?
        
        internal var parentObject: () -> CoreStoreObject = {
            
            CoreStore.abort("Attempted to access values from a \(cs_typeName(O.self)) meta object. Meta objects are only used for querying keyPaths and infering types.")
        }
        
        
        // MARK: Private
        
        private let customGetter: (_ `self`: O, _ getValue: () -> V) -> V
        private let customSetter: (_ `self`: O, _ setValue: (V) -> Void, _ newValue: V) -> Void
    }
    
    
    // MARK: - Optional
    
    /**
     The containing type for optional value properties. Any type that conforms to `ImportableAttributeType` are supported.
     ```
     class Animal: CoreStoreObject {
         let species = Value.Required<String>("species")
         let nickname = Value.Optional<String>("nickname")
         let color = Transformable.Optional<UIColor>("color")
     }
     ```
     - Important: `Value.Optional` properties are required to be stored properties. Computed properties will be ignored, including `lazy` and `weak` properties.
     */
    public final class Optional<V: ImportableAttributeType>: AttributeProtocol {
        
        /**
         Initializes the metadata for the property.
         ```
         class Person: CoreStoreObject {
             let title = Value.Required<String>("title", default: "Mr.")
             let name = Value.Required<String>(
                 "name",
                 customGetter: { (`self`, getValue) in
                     return "\(self.title.value) \(getValue())"
                 }
             )
         }
         ```
         - parameter keyPath: the permanent attribute name for this property.
         - parameter default: the initial value for the property when the object is first created. Defaults to `nil` 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 to make final transformations to the property's value before returning from the getter.
         - parameter self: the `CoreStoreObject`
         - parameter getValue: the original getter for the property
         - parameter customSetter: use this closure to make final transformations to the new value before assigning to the property.
         - parameter setValue: the original setter for the property
         - parameter finalNewValue: the transformed new value
         - parameter originalNewValue: the original new value
         */
        public init(_ keyPath: KeyPath, `default`: V? = nil, isIndexed: Bool = false, isTransient: Bool = false, versionHashModifier: String? = nil, renamingIdentifier: String? = nil, customGetter: @escaping (_ `self`: O, _ getValue: () -> V?) -> V? = { $1() }, customSetter: @escaping (_ `self`: O, _ setValue: (_ finalNewValue: V?) -> Void, _ originalNewValue: V?) -> Void = { $1($2) }) {
            
            self.keyPath = keyPath
            self.isIndexed = isIndexed
            self.isTransient = isTransient
            self.defaultValue = `default`?.cs_toImportableNativeType()
            self.versionHashModifier = versionHashModifier
            self.renamingIdentifier = renamingIdentifier
            self.customGetter = customGetter
            self.customSetter = customSetter
        }
        
        /**
         The property value.
         */
        public var value: V? {
            
            get {
                
                let object = self.parentObject() as! O
                CoreStore.assert(
                    object.rawObject!.isRunningInAllowedQueue() == true,
                    "Attempted to access \(cs_typeName(O.self))'s value outside it's designated queue."
                )
                return self.customGetter(
                    object,
                    { () -> V? in
                        
                        return object.rawObject!.getValue(
                            forKvcKey: self.keyPath,
                            didGetValue: { ($0 as! V.ImportableNativeType?).flatMap(V.cs_fromImportableNativeType) }
                        )
                    }
                )
            }
            set {
                
                let object = self.parentObject() as! O
                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."
                )
                self.customSetter(
                    object,
                    { (newValue: V?) -> Void in
                        
                        object.rawObject!.setValue(
                            newValue,
                            forKvcKey: self.keyPath,
                            willSetValue: { $0?.cs_toImportableNativeType() }
                        )
                    },
                    newValue
                )
            }
        }
        
        
        // MARK: AttributeProtocol
        
        internal static var attributeType: NSAttributeType {
            
            return V.cs_rawAttributeType
        }
        
        public let keyPath: KeyPath
        internal let isOptional = true
        internal let isIndexed: Bool
        internal let isTransient: Bool
        internal let defaultValue: Any?
        internal let versionHashModifier: String?
        internal let renamingIdentifier: String?
        
        internal var parentObject: () -> CoreStoreObject = {
            
            CoreStore.abort("Attempted to access values from a \(cs_typeName(O.self)) meta object. Meta objects are only used for querying keyPaths and infering types.")
        }
        
        
        // MARK: Private
        
        private let customGetter: (_ `self`: O, _ getValue: () -> V?) -> V?
        private let customSetter: (_ `self`: O, _ setValue: (V?) -> Void, _ newValue: V?) -> Void
    }
}

public extension ValueContainer.Required where V: EmptyableAttributeType {
    
    /**
     Initializes the metadata for the property. This convenience initializer uses the `EmptyableAttributeType`'s "empty" value as the initial value for the property when the object is first created (e.g. `false` for `Bool`, `0` for `Int`, `""` for `String`, etc.)
     ```
     class Person: CoreStoreObject {
         let title = Value.Required<String>("title") // initial value defaults to empty string
     }
     ```
     - parameter keyPath: the permanent attribute name for this property.
     - 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 to make final transformations to the property's value before returning from the getter.
     - parameter self: the `CoreStoreObject`
     - parameter getValue: the original getter for the property
     - parameter customSetter: use this closure to make final transformations to the new value before assigning to the property.
     - parameter setValue: the original setter for the property
     - parameter finalNewValue: the transformed new value
     - parameter originalNewValue: the original new value
     */
    public convenience init(_ keyPath: KeyPath, isIndexed: Bool = false, isTransient: Bool = false, versionHashModifier: String? = nil, renamingIdentifier: String? = nil, customGetter: @escaping (_ `self`: O, _ getValue: () -> V) -> V = { $1() }, customSetter: @escaping (_ `self`: O, _ setValue: (_ finalNewValue: V) -> Void, _ originalNewValue: V) -> Void = { $1($2) }) {
        
        self.init(
            keyPath,
            default: V.cs_emptyValue(),
            isIndexed: isIndexed,
            isTransient: isTransient,
            versionHashModifier: versionHashModifier,
            renamingIdentifier: renamingIdentifier,
            customGetter: customGetter,
            customSetter: customSetter
        )
    }
}


// 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 color = Transformable.Optional<UIColor>("color")
         }
         ```
         - parameter keyPath: the permanent attribute name for this property.
         - parameter default: 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 to make final transformations to the property's value before returning from the getter.
         - parameter self: the `CoreStoreObject`
         - parameter getValue: the original getter for the property
         - parameter customSetter: use this closure to make final transformations to the new value before assigning to the property.
         - parameter setValue: the original setter for the property
         - parameter finalNewValue: the transformed new value
         - parameter originalNewValue: the original new value
         */
        public init(_ keyPath: KeyPath, `default`: V, isIndexed: Bool = false, isTransient: Bool = false, versionHashModifier: String? = nil, renamingIdentifier: String? = nil, customGetter: @escaping (_ `self`: O, _ getValue: () -> V) -> V = { $1() }, customSetter: @escaping (_ `self`: O, _ setValue: (_ finalNewValue: V) -> Void, _ originalNewValue: V) -> Void = { $1($2) }) {
            
            self.keyPath = keyPath
            self.defaultValue = `default`
            self.isIndexed = isIndexed
            self.isTransient = isTransient
            self.versionHashModifier = versionHashModifier
            self.renamingIdentifier = renamingIdentifier
            self.customGetter = customGetter
            self.customSetter = customSetter
        }
        
        /**
         The property value.
         */
        public var value: V {
            
            get {
                
                let object = self.parentObject() as! O
                CoreStore.assert(
                    object.rawObject!.isRunningInAllowedQueue() == true,
                    "Attempted to access \(cs_typeName(O.self))'s value outside it's designated queue."
                )
                return self.customGetter(
                    object,
                    { () -> V in
                        
                        return object.rawObject!.getValue(
                            forKvcKey: self.keyPath,
                            didGetValue: { $0 as! V }
                        )
                    }
                )
            }
            set {
                
                let object = self.parentObject() as! O
                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."
                )
                self.customSetter(
                    object,
                    { (newValue: V) -> Void in
                        
                        object.rawObject!.setValue(
                            newValue,
                            forKvcKey: self.keyPath
                        )
                    },
                    newValue
                )
            }
        }
        
        
        // 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 defaultValue: Any?
        internal let versionHashModifier: String?
        internal let renamingIdentifier: String?
        
        internal var parentObject: () -> CoreStoreObject = {
            
            CoreStore.abort("Attempted to access values from a \(cs_typeName(O.self)) meta object. Meta objects are only used for querying keyPaths and infering types.")
        }
        
        
        // MARK: Private
        
        private let customGetter: (_ `self`: O, _ getValue: () -> V) -> V
        private let customSetter: (_ `self`: O, _ setValue: (V) -> Void, _ newValue: V) -> Void
    }
    
    
    // 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 color = Transformable.Optional<UIColor>("color")
         }
         ```
         - parameter keyPath: the permanent attribute name for this property.
         - parameter default: 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 to make final transformations to the property's value before returning from the getter.
         - parameter self: the `CoreStoreObject`
         - parameter getValue: the original getter for the property
         - parameter customSetter: use this closure to make final transformations to the new value before assigning to the property.
         - parameter setValue: the original setter for the property
         - parameter finalNewValue: the transformed new value
         - parameter originalNewValue: the original new value
         */
        public init(_ keyPath: KeyPath, `default`: V? = nil, isIndexed: Bool = false, isTransient: Bool = false, versionHashModifier: String? = nil, renamingIdentifier: String? = nil, customGetter: @escaping (_ `self`: O, _ getValue: () -> V?) -> V? = { $1() }, customSetter: @escaping (_ `self`: O, _ setValue: (_ finalNewValue: V?) -> Void, _ originalNewValue: V?) -> Void = { $1($2) }) {
            
            self.keyPath = keyPath
            self.defaultValue = `default`
            self.isIndexed = isIndexed
            self.isTransient = isTransient
            self.versionHashModifier = versionHashModifier
            self.renamingIdentifier = renamingIdentifier
            self.customGetter = customGetter
            self.customSetter = customSetter
        }
        
        /**
         The property value.
         */
        public var value: V? {
            
            get {
                
                let object = self.parentObject() as! O
                CoreStore.assert(
                    object.rawObject!.isRunningInAllowedQueue() == true,
                    "Attempted to access \(cs_typeName(O.self))'s value outside it's designated queue."
                )
                return self.customGetter(
                    object,
                    { () -> V? in
                        
                        return object.rawObject!.getValue(
                            forKvcKey: self.keyPath,
                            didGetValue: { $0 as! V? }
                        )
                    }
                )
            }
            set {
                
                let object = self.parentObject() as! O
                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."
                )
                self.customSetter(
                    object,
                    { (newValue: V?) -> Void in
                        
                        object.rawObject!.setValue(
                            newValue,
                            forKvcKey: self.keyPath
                        )
                    },
                    newValue
                )
            }
        }
        
        
        // 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 defaultValue: Any?
        internal let versionHashModifier: String?
        internal let renamingIdentifier: String?
        
        internal var parentObject: () -> CoreStoreObject = {
            
            CoreStore.abort("Attempted to access values from a \(cs_typeName(O.self)) meta object. Meta objects are only used for querying keyPaths and infering types.")
        }
        
        
        // MARK: Private
        
        private let customGetter: (_ `self`: O, _ getValue: () -> V?) -> V?
        private let customSetter: (_ `self`: O, _ setValue: (V?) -> Void, _ newValue: V?) -> Void
    }
}


// MARK: - Operations

infix operator .= : AssignmentPrecedence
infix operator .== : ComparisonPrecedence

extension ValueContainer.Required {
    
    /**
     Assigns a value to the property. The operation
     ```
     animal.species .= "Swift"
     ```
     is equivalent to
     ```
     animal.species.value = "Swift"
     ```
     */
    public static func .= (_ property: ValueContainer<O>.Required<V>, _ newValue: V) {
        
        property.value = newValue
    }
    
    /**
     Assigns a value from another property. The operation
     ```
     animal.species .= anotherAnimal.species
     ```
     is equivalent to
     ```
     animal.species.value = anotherAnimal.species.value
     ```
     */
    public static func .= <O2: CoreStoreObject>(_ property: ValueContainer<O>.Required<V>, _ property2: ValueContainer<O2>.Required<V>) {
        
        property.value = property2.value
    }
    
    /**
     Compares equality between a property's value and another value
     ```
     if animal.species .== "Swift" { ... }
     ```
     is equivalent to
     ```
     if animal.species.value == "Swift" { ... }
     ```
     */
    public static func .== (_ property: ValueContainer<O>.Required<V>, _ value: V?) -> Bool {
        
        return property.value == value
    }
    
    /**
     Compares equality between a value and a property's value
     ```
     if "Swift" .== animal.species { ... }
     ```
     is equivalent to
     ```
     if "Swift" == animal.species.value { ... }
     ```
     */
    public static func .== (_ value: V?, _ property: ValueContainer<O>.Required<V>) -> Bool {
        
        return value == property.value
    }
    
    /**
     Compares equality between a property's value and another property's value
     ```
     if animal.species .== anotherAnimal.species { ... }
     ```
     is equivalent to
     ```
     if animal.species.value == anotherAnimal.species.value { ... }
     ```
     */
    public static func .== (_ property: ValueContainer<O>.Required<V>, _ property2: ValueContainer<O>.Required<V>) -> Bool {
        
        return property.value == property2.value
    }
    
    /**
     Compares equality between a property's value and another property's value
     ```
     if animal.species .== anotherAnimal.species { ... }
     ```
     is equivalent to
     ```
     if animal.species.value == anotherAnimal.species.value { ... }
     ```
     */
    public static func .== (_ property: ValueContainer<O>.Required<V>, _ property2: ValueContainer<O>.Optional<V>) -> Bool {
        
        return property.value == property2.value
    }
}

extension ValueContainer.Optional {
    
    /**
     Assigns an optional value to the property. The operation
     ```
     animal.nickname .= "Taylor"
     ```
     is equivalent to
     ```
     animal.nickname.value = "Taylor"
     ```
     */
    public static func .= (_ property: ValueContainer<O>.Optional<V>, _ newValue: V?) {
        
        property.value = newValue
    }
    
    /**
     Assigns an optional value from another property. The operation
     ```
     animal.nickname .= anotherAnimal.nickname
     ```
     is equivalent to
     ```
     animal.nickname.value = anotherAnimal.nickname.value
     ```
     */
    public static func .= <O2: CoreStoreObject>(_ property: ValueContainer<O>.Optional<V>, _ property2: ValueContainer<O2>.Optional<V>) {
        
        property.value = property2.value
    }
    
    /**
     Assigns a value from another property. The operation
     ```
     animal.nickname .= anotherAnimal.species
     ```
     is equivalent to
     ```
     animal.nickname.value = anotherAnimal.species.value
     ```
     */
    public static func .= <O2: CoreStoreObject>(_ property: ValueContainer<O>.Optional<V>, _ property2: ValueContainer<O2>.Required<V>) {
        
        property.value = property2.value
    }
    
    /**
     Compares equality between a property's value and another value
     ```
     if animal.species .== "Swift" { ... }
     ```
     is equivalent to
     ```
     if animal.species.value == "Swift" { ... }
     ```
     */
    public static func .== (_ property: ValueContainer<O>.Optional<V>, _ value: V?) -> Bool {
        
        return property.value == value
    }
    
    /**
     Compares equality between a property's value and another property's value
     ```
     if "Swift" .== animal.species { ... }
     ```
     is equivalent to
     ```
     if "Swift" == animal.species.value { ... }
     ```
     */
    public static func .== (_ value: V?, _ property: ValueContainer<O>.Optional<V>) -> Bool {
        
        return value == property.value
    }
    
    /**
     Compares equality between a property's value and another property's value
     ```
     if animal.species .== anotherAnimal.species { ... }
     ```
     is equivalent to
     ```
     if animal.species.value == anotherAnimal.species.value { ... }
     ```
     */
    public static func .== (_ property: ValueContainer<O>.Optional<V>, _ property2: ValueContainer<O>.Optional<V>) -> Bool {
        
        return property.value == property2.value
    }
    
    /**
     Compares equality between a property's value and another property's value
     ```
     if animal.species .== anotherAnimal.species { ... }
     ```
     is equivalent to
     ```
     if animal.species.value == anotherAnimal.species.value { ... }
     ```
     */
    public static func .== (_ property: ValueContainer<O>.Optional<V>, _ property2: ValueContainer<O>.Required<V>) -> Bool {
        
        return property.value == property2.value
    }
}

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: CoreStoreObject>(_ 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: CoreStoreObject>(_ 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: CoreStoreObject>(_ property: TransformableContainer<O>.Optional<V>, _ property2: TransformableContainer<O2>.Required<V>) {
        
        property.value = property2.value
    }
}


// MARK: - AttributeProtocol

internal protocol AttributeProtocol: class {
    
    static var attributeType: NSAttributeType { get }
    
    var keyPath: KeyPath { get }
    var isOptional: Bool { get }
    var isIndexed: Bool { get }
    var isTransient: Bool { get }
    var defaultValue: Any? { get }
    var versionHashModifier: String? { get }
    var renamingIdentifier: String? { get }
    var parentObject: () -> CoreStoreObject { get set }
}