folder structure

Sources/Importing/ImportableUniqueObject.swift

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+//
+//  ImportableUniqueObject.swift
+//  CoreStore
+//
+//  Copyright © 2015 John Rommel Estropia
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy
+//  of this software and associated documentation files (the "Software"), to deal
+//  in the Software without restriction, including without limitation the rights
+//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//  copies of the Software, and to permit persons to whom the Software is
+//  furnished to do so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+//
+
+import Foundation
+import CoreData
+
+
+// MARK: - ImportableUniqueObject
+
+/**
+ `NSManagedObject` subclasses that conform to the `ImportableUniqueObject` protocol can be imported from a specified `ImportSource`. This allows transactions to either update existing objects or create new instances this way:
+ ```
+ class MyPersonEntity: NSManagedObject, ImportableUniqueObject {
+     typealias ImportSource = NSDictionary
+     typealias UniqueIDType = NSString
+     // ...
+ }
+ 
+ CoreStore.beginAsynchronous { (transaction) -> Void in
+     let json: NSDictionary = // ...
+     let person = try! transaction.importUniqueObject(
+         Into(MyPersonEntity),
+         source: json
+     )
+     // ...
+     transaction.commit()
+ }
+ ```
+ */
+public protocol ImportableUniqueObject: ImportableObject {
+    
+    /**
+     The data type for the import source. This is most commonly an `NSDictionary` or another external source such as an `NSUserDefaults`.
+     */
+    associatedtype ImportSource
+    
+    /**
+     The data type for the entity's unique ID attribute
+     */
+    associatedtype UniqueIDType: NSObject
+    
+    /**
+     The keyPath to the entity's unique ID attribute
+     */
+    static var uniqueIDKeyPath: String { get }
+    
+    /**
+     The object's unique ID value
+     */
+    var uniqueIDValue: UniqueIDType { get set }
+    
+    /**
+     Return `true` if an object should be created from `source`. Return `false` to ignore and skip `source`. The default implementation returns the value returned by the `shouldUpdateFromImportSource(:inTransaction:)` implementation.
+     
+     - parameter source: the object to import from
+     - parameter transaction: the transaction that invoked the import. Use the transaction to fetch or create related objects if needed.
+     - returns: `true` if an object should be created from `source`. Return `false` to ignore.
+     */
+    static func shouldInsertFromImportSource(source: ImportSource, inTransaction transaction: BaseDataTransaction) -> Bool
+    
+    /**
+     Return `true` if an object should be updated from `source`. Return `false` to ignore and skip `source`. The default implementation returns `true`.
+     
+     - parameter source: the object to import from
+     - parameter transaction: the transaction that invoked the import. Use the transaction to fetch or create related objects if needed.
+     - returns: `true` if an object should be updated from `source`. Return `false` to ignore.
+     */
+    static func shouldUpdateFromImportSource(source: ImportSource, inTransaction transaction: BaseDataTransaction) -> Bool
+    
+    /**
+     Return the unique ID as extracted from `source`. This method is called before `shouldInsertFromImportSource(...)` or `shouldUpdateFromImportSource(...)`. Return `nil` to skip importing from `source`. Note that throwing from this method will cause subsequent imports that are part of the same `importUniqueObjects(:sourceArray:)` call to be cancelled.
+     
+     - parameter source: the object to import from
+     - parameter transaction: the transaction that invoked the import. Use the transaction to fetch or create related objects if needed.
+     - returns: the unique ID as extracted from `source`, or `nil` to skip importing from `source`.
+     */
+    static func uniqueIDFromImportSource(source: ImportSource, inTransaction transaction: BaseDataTransaction) throws -> UniqueIDType?
+    
+    /**
+     Implements the actual importing of data from `source`. This method is called just after the object is created and assigned its unique ID as returned from `uniqueIDFromImportSource(...)`. Implementers should pull values from `source` and assign them to the receiver's attributes. Note that throwing from this method will cause subsequent imports that are part of the same `importUniqueObjects(:sourceArray:)` call to be cancelled. The default implementation simply calls `updateFromImportSource(...)`.
+     
+     - parameter source: the object to import from
+     - parameter transaction: the transaction that invoked the import. Use the transaction to fetch or create related objects if needed.
+     */
+    func didInsertFromImportSource(source: ImportSource, inTransaction transaction: BaseDataTransaction) throws
+    
+    /**
+     Implements the actual importing of data from `source`. This method is called just after the existing object is fetched using its unique ID. Implementers should pull values from `source` and assign them to the receiver's attributes. Note that throwing from this method will cause subsequent imports that are part of the same `importUniqueObjects(:sourceArray:)` call to be cancelled.
+     
+     - parameter source: the object to import from
+     - parameter transaction: the transaction that invoked the import. Use the transaction to fetch or create related objects if needed.
+     */
+    func updateFromImportSource(source: ImportSource, inTransaction transaction: BaseDataTransaction) throws
+}
+
+
+// MARK: - ImportableUniqueObject (Default Implementations)
+
+public extension ImportableUniqueObject {
+    
+    static func shouldInsertFromImportSource(source: ImportSource, inTransaction transaction: BaseDataTransaction) -> Bool {
+        
+        return self.shouldUpdateFromImportSource(source, inTransaction: transaction)
+    }
+    
+    static func shouldUpdateFromImportSource(source: ImportSource, inTransaction transaction: BaseDataTransaction) -> Bool {
+        
+        return true
+    }
+    
+    func didInsertFromImportSource(source: ImportSource, inTransaction transaction: BaseDataTransaction) throws {
+        
+        try self.updateFromImportSource(source, inTransaction: transaction)
+    }
+}