在Swift 3中启用核心数据轻量级迁移

根据文章我已阅读正确的方式来启用核心数据轻量级迁移是通过传递选项addPersistentStoreWithType ：

 let mOptions = [NSMigratePersistentStoresAutomaticallyOption: true, NSInferMappingModelAutomaticallyOption: true] try coordinator!.addPersistentStoreWithType( NSSQLiteStoreType, configuration: nil, URL: url, options: mOptions) 

但是在我的Xcode 8 Swift 3项目中我找不到addPersistentStoreWithType被调用的地方。 这是我创build项目时生成的唯一core data代码：

  // MARK: - Core Data stack lazy var persistentContainer: NSPersistentContainer = { /* The persistent container for the application. This implementation creates and returns a container, having loaded the store for the application to it. This property is optional since there are legitimate error conditions that could cause the creation of the store to fail. */ let container = NSPersistentContainer(name: "Habits") container.loadPersistentStores(completionHandler: { (storeDescription, error) in if let error = error as NSError? { // Replace this implementation with code to handle the error appropriately. // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. /* Typical reasons for an error here include: * The parent directory does not exist, cannot be created, or disallows writing. * The persistent store is not accessible, due to permissions or data protection when the device is locked. * The device is out of space. * The store could not be migrated to the current model version. Check the error message to determine what the actual problem was. */ fatalError("Unresolved error \(error), \(error.userInfo)") } }) return container }() // MARK: - Core Data Saving support func saveContext () { let context = persistentContainer.viewContext if context.hasChanges { do { try context.save() } catch { // Replace this implementation with code to handle the error appropriately. // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. let nserror = error as NSError fatalError("Unresolved error \(nserror), \(nserror.userInfo)") } } } 

如何使用Swift 3在Xcode 8中启用轻量级迁移？

Answer 1

您可以使用NSPersistentStoreDescription完成这个NSPersistentStoreDescription ，这是Swift 3更新中的所有选项。 在调用loadPersistentStores之前执行此loadPersistentStores ：

 let description = NSPersistentStoreDescription() description.shouldInferMappingModelAutomatically = true description.shouldMigrateStoreAutomatically = true container.persistentStoreDescriptions = [description] 

Answer 2

您可以在Xcode 7中开始一个新项目，并将生成的核心数据代码复制并粘贴到新的新项目中！

我在Xcode 7中创build了一个项目，并将其移植到Xcode 8，这是生成的代码。 （我已经添加了启用轻量级堆栈迁移的两个选项）

 // MARK: - Core Data stack lazy var applicationDocumentsDirectory: URL = { // The directory the application uses to store the Core Data store file. This code uses a directory named "com.MyApp" in the application's documents Application Support directory. let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask) return urls[urls.count-1] }() lazy var managedObjectModel: NSManagedObjectModel = { // The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model. let modelURL = Bundle.main.url(forResource: "MyApp", withExtension: "momd")! return NSManagedObjectModel(contentsOf: modelURL)! }() lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = { // The persistent store coordinator for the application. This implementation creates and returns a coordinator, having added the store for the application to it. This property is optional since there are legitimate error conditions that could cause the creation of the store to fail. // Create the coordinator and store let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel) let url = self.applicationDocumentsDirectory.appendingPathComponent("SingleViewCoreData.sqlite") var failureReason = "There was an error creating or loading the application's saved data." do { try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: [NSMigratePersistentStoresAutomaticallyOption: true,NSInferMappingModelAutomaticallyOption: true]) } catch { // Report any error we got. var dict = [String: AnyObject]() dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data" as AnyObject? dict[NSLocalizedFailureReasonErrorKey] = failureReason as AnyObject? dict[NSUnderlyingErrorKey] = error as NSError let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict) // Replace this with code to handle the error appropriately. // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. NSLog("Unresolved error \(wrappedError), \(wrappedError.userInfo)") abort() } return coordinator }() lazy var managedObjectContext: NSManagedObjectContext = { // Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail. let coordinator = self.persistentStoreCoordinator var managedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType) managedObjectContext.persistentStoreCoordinator = coordinator return managedObjectContext }() // MARK: - Core Data Saving support func saveContext () { if managedObjectContext.hasChanges { do { try managedObjectContext.save() } catch { // Replace this implementation with code to handle the error appropriately. // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. let nserror = error as NSError NSLog("Unresolved error \(nserror), \(nserror.userInfo)") abort() } } } 

你可以复制上面的代码并粘贴到你的App Delegate中。

有一点需要注意的是，请编辑这一行，以便获取您的数据模型的URL：

 let modelURL = Bundle.main.url(forResource: "MyApp", withExtension: "momd")! 

Answer 3

请注意， NSPersistentStore的shouldInferMappingModelAutomatically和shouldMigrateStoreAutomatically默认为true 。

苹果参考资料：

• shouldInferMappingModelAutomatically

• shouldMigrateStoreAutomatically

Answer 4

在我的情况下，我附加到新的说明，而不是replace

 let description = NSPersistentStoreDescription() description.shouldInferMappingModelAutomatically = true description.shouldMigrateStoreAutomatically = true container.persistentStoreDescriptions.append(description)