如何使用 Core Data 和 iCloud 在两台设备之间同步数据？

Question

我想要实现的是，当用户在persistent store 上创建、更改或删除数据时，它将与iCloud store 同步，然后更新登录到同一 iCloud 帐户的其他设备。

我使用 Objective-C 资源创建了一个Core Data Stack，并尝试用 Swift 编写我自己的，但我在使用登录到同一个 iCloud 帐户的两台设备同步数据时遇到问题。

例如当 iDevice A 登录到 iCloud 时，它会将数据备份到 iCloud，但是当 iDevice B 登录到 iCloud 时，应用程序会删除永久存储中已有的所有数据以保存 iCloud up，并且商店设备之间的任何更改都不会出现在另一台设备上，但似乎作为最新备份保存到 iCloud 商店，因此如果删除并重新安装该应用程序，我会看到另一台设备所做的最新备份 - 有了这个请注意，如果 iDevice B 已经登录，它不会使用来自 iDevice A 的数据，除非重新安装了该应用程序并且最后一次备份是由另一台设备进行的。

有人知道我在Core data stack 中哪里出了问题，以便使用同一个 iCloud 帐户在两台设备之间同步数据吗？

核心数据栈：

// MARK: - Core Data stack
// All the following code is in my appDelgate Core data stack 

func observeCloudActions(persistentStoreCoordinator psc:      NSPersistentStoreCoordinator?) {
// Register iCloud notifications observers for;

//Stores Will change 
//Stores Did Change 
//persistentStoreDidImportUbiquitousContentChanges
//mergeChanges

}

//Functions for notifications

func mergeChanges(notification: NSNotification) {
NSLog("mergeChanges notif:\(notification)")
if let moc = managedObjectContext {
    moc.performBlock {
        moc.mergeChangesFromContextDidSaveNotification(notification)
        self.postRefetchDatabaseNotification()
    }
 }
}

  func persistentStoreDidImportUbiquitousContentChanges(notification: NSNotification) {
self.mergeChanges(notification);
 }    

func storesWillChange(notification: NSNotification) {
NSLog("storesWillChange notif:\(notification)");
if let moc = self.managedObjectContext {
    moc.performBlockAndWait {
        var error: NSError? = nil;
        if moc.hasChanges && !moc.save(&error) {
            NSLog("Save error: \(error)");
        } else {
            // drop any managed objects
        }
        moc.reset();
    }

       NSNotificationCenter.defaultCenter().postNotificationName("storeWillChange", object: nil)

 }
}

 func storesDidChange(notification: NSNotification) {
NSLog("storesDidChange posting notif");
self.postRefetchDatabaseNotification();
//Sends notification to view controllers to reload data      NSNotificationCenter.defaultCenter().postNotificationName("storeDidChange", object: nil)

 }

func postRefetchDatabaseNotification() {
dispatch_async(dispatch_get_main_queue(), { () -> Void in
          NSNotificationCenter.defaultCenter().postNotificationName("storeDidChange", object: nil)

 })
 }


// Core data stack 

lazy var applicationDocumentsDirectory: NSURL = {
// The directory the application uses to store the Core Data store file. This code uses a directory named "hyouuu.pendo" in the application's documents Application Support directory.
let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
return urls[urls.count-1] as! NSURL
}()

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 = NSBundle.mainBundle().URLForResource("AppName", withExtension: "momd")!
NSLog("modelURL:\(modelURL)")
return NSManagedObjectModel(contentsOfURL: modelURL)!
}()

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)


let documentsDirectory = NSFileManager.defaultManager().URLsForDirectory(NSSearchPathDirectory.DocumentDirectory, inDomains: NSSearchPathDomainMask.UserDomainMask).last as! NSURL


let storeURL = documentsDirectory.URLByAppendingPathComponent("CoreData.sqlite")

NSLog("storeURL:\(storeURL)")

let storeOptions = [NSPersistentStoreUbiquitousContentNameKey:"AppStore"]

var error: NSError? = nil
var failureReason = "There was an error creating or loading the application's saved data."

if coordinator!.addPersistentStoreWithType(
    NSSQLiteStoreType,
    configuration: nil,
    URL: storeURL,
    options: storeOptions,
    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: "Pendo_Error_Domain", code: 9999, userInfo: dict as [NSObject : AnyObject])
    // 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("AddPersistentStore error \(error), \(error!.userInfo)")
}

self.observeCloudActions(persistentStoreCoordinator: coordinator)

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
if coordinator == nil {
    return nil
}
var managedObjectContext = NSManagedObjectContext(concurrencyType: NSManagedObjectContextConcurrencyType.MainQueueConcurrencyType)
managedObjectContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
managedObjectContext.persistentStoreCoordinator = coordinator
return managedObjectContext
}()

Answer 1

我发现对我有用的代码和你的代码之间的区别是：

1) 我没有看到您在代码中为 NSPersistentStoreDidImportUbiquitousContentChangesNotification 添加了观察者的位置：

let nc : NSNotificationCenter = NSNotificationCenter.defaultCenter();
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
nc.addObserver(self, selector: "dataUpdated:",
        name: NSPersistentStoreDidImportUbiquitousContentChangesNotification,
        object: self.managedObjectContext?.persistentStoreCoordinator)

2) 在我捕获通知的函数代码中（在本例中为 dataUpdated），它在更新显示以显示新数据之前使用以下代码重置托管 objext 上下文：

let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
if let managedObjectContext = appDelegate.managedObjectContext {
     managedObjectContext.reset()
}

重置托管对象上下文后，我再次使用代码获取实体：

let fetchRequest = NSFetchRequest(entityName: "ClassNameHere")
let sortDescriptor = NSSortDescriptor(key: "name", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
let fetchResults = managedObjectContext!.executeFetchRequest(fetchRequest, error: nil) as! [ClassNameHere]

Answer 2

这就是我的设置，它同步我的核心数据并保持同步更改。

这来自我的 AppDelegate。

    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)
    let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("APPNAME.sqlite")
    var error: NSError? = nil
    var failureReason = "There was an error creating or loading the application's saved data."
    // iCloud store
    var storeOptions = [NSPersistentStoreUbiquitousContentNameKey : "APPNAMEStore",NSMigratePersistentStoresAutomaticallyOption: true,
        NSInferMappingModelAutomaticallyOption: true]
    // iCloud storeOptions need to be added to the if statement
    do {
        try coordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: NSURL.fileURLWithPath(url.path!), options: storeOptions)
    } catch var error1 as NSError {
        error = error1
        coordinator = nil
        // Report any error we got.
        var dict = [String: AnyObject]()
        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()
    } catch {
        fatalError()
    }

    return coordinator
}()

    // MARK: - iCloud
// This handles the updates to the data via iCLoud updates

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)
}