Swift - 用 iCloud 核心数据替换核心数据

Question

如何用 iCloud Core Data 替换我现有的 Core Data ？ 这是我的persistentStoreCoordinator：

lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator? = {
    // The persistent store coordinator for the application. This implementation creates and return 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
    var coordinator: NSPersistentStoreCoordinator? = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)

    var notificacionCenter: NSNotificationCenter = NSNotificationCenter.defaultCenter()
    notificacionCenter.addObserver(self, selector: "storesWillChange:", name:NSPersistentStoreCoordinatorStoresWillChangeNotification, object: coordinator)
    notificacionCenter.addObserver(self, selector: "storesDidChange:", name:NSPersistentStoreCoordinatorStoresDidChangeNotification, object: coordinator)
    notificacionCenter.addObserver(self, selector: "persistentStoreDidImportUbiquitousContentChanges:", name:NSPersistentStoreDidImportUbiquitousContentChangesNotification, object: coordinator)

    let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("MyApp.sqlite")
    var error: NSError? = nil
    var failureReason = "There was an error creating or loading the application's saved data."
    var options: NSDictionary = [NSMigratePersistentStoresAutomaticallyOption : NSNumber(bool: true), NSInferMappingModelAutomaticallyOption : NSNumber(bool: true),
        NSPersistentStoreUbiquitousContentNameKey : "iCloudStore"]
    if coordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: options, error: &error) == nil {
        coordinator = nil
        // Report any error we got.
        let dict = NSMutableDictionary()
        dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
        dict[NSLocalizedFailureReasonErrorKey] = failureReason
        dict[NSUnderlyingErrorKey] = error
        error = 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 \(error), \(error!.userInfo)")
        abort()
    }

    return coordinator
}()

我添加了通知，然后呢？怎么换？

Answer 1

您无需执行任何操作即可让 iCloud 存储的数据替换本地存储的数据。也就是说，本地核心数据会使用 iCloud 下载的数据进行更新，并在之后保持一致。

但是，如果您在 UI 中显示了数据，那么当“新 iCloud 数据”到达时，“旧本地数据”可能仍会显示。 Using the SQLite Store with iCould 的 Apple 文档描述了如何通过通知处理更新。总结该参考：在NSPersistentStoreCoordinatorStoresWillChangeNotification 的处理程序中，如果存在任何未决更改，则保存它们，否则您将重置托管对象上下文并禁用用户界面。然后在 NSPersistentStoreCoordinatorStoresDidChangeNotification 处理程序中更新您显示的（和其他）数据并重新启用您的 UI。

这是我用于带有 iCloud 的 Core Data 的。 storeOptions 是关键点。对于您的 Xcode 目标，您需要启用 iCloud 功能并确保您已选择“iCloud Documents”。

{
  // ...

  lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator? = {
    // The persistent store coordinator for the application. This implementation
    // creates and return 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
    var coordinator: NSPersistentStoreCoordinator =
      NSPersistentStoreCoordinator (managedObjectModel: self.managedObjectModel)

    var storeURL =
      self.applicationDocumentsDirectory
        .URLByAppendingPathComponent("iAppSwift.sqlite")

    var storeOptions =
      [NSPersistentStoreUbiquitousContentNameKey : "iAppSwiftStore"
      // NSPersistentStoreRebuildFromUbiquitousContentOption: @(true)
        ]

    // 
    self.registerCoordinatorForStoreNotifications (coordinator)

    var error : NSError? = nil
    var store : NSPersistentStore! =
      coordinator.addPersistentStoreWithType (NSSQLiteStoreType,
        configuration: nil,
        URL: storeURL,
        options: storeOptions,
        error: &error)

    if nil == store {
      // handle error
    }

    return coordinator
  }()

  func registerCoordinatorForStoreNotifications (coordinator : NSPersistentStoreCoordinator) {
    let nc : NSNotificationCenter = NSNotificationCenter.defaultCenter();

    nc.addObserver(self, selector: "handleStoresWillChange:",
      name: NSPersistentStoreCoordinatorStoresWillChangeNotification,
      object: coordinator)

    nc.addObserver(self, selector: "handleStoresDidChange:",
      name: NSPersistentStoreCoordinatorStoresDidChangeNotification,
      object: coordinator)

    nc.addObserver(self, selector: "handleStoresWillRemove:",
      name: NSPersistentStoreCoordinatorWillRemoveStoreNotification,
      object: coordinator)

    nc.addObserver(self, selector: "handleStoreChangedUbiquitousContent:",
      name: NSPersistentStoreDidImportUbiquitousContentChangesNotification,
      object: coordinator)
  }

  // ...
}