NSUbiquityIdentityDidChangeNotification doesn't work?

问题

I'm creating a cloudkit app, and have been trying multiple ways to get the NSUbiquityIdentityDidChangeNotification, but I never am able to get this notification.

I've tried both of these code versions under the delegate didFinish and the viewDidLoad methods. And I tried calling it from another notification - UIApplicationDidBecomeActiveNotification. I also put import Foundation at top of files.

Here's the basic code I've tried:

NSNotificationCenter.defaultCenter().addObserver(self,
        selector: "handleIdentityChanged:",
        name: NSUbiquityIdentityDidChangeNotification,
        object: nil)

// And this one I tried too from another post here on SO:

    var localeChangeObserver = NSNotificationCenter.defaultCenter().addObserverForName(NSUbiquityIdentityDidChangeNotification, object: nil, queue: NSOperationQueue.mainQueue()) { _ in
        println("The user’s iCloud login changed: should refresh all user data.")
    }

Does anyone know how to get this notification to work for only a cloudkit app in swift? I really just want to detect the iCloud status change and then initiate fetching the userID if there's been a change.

Not that I need to access the ubiquityIdentityToken, but I was wondering why not store the token and every-time the app starts compare the current token with the one in local storage to see if it's a different account or nil? Therefore, why is getting the notification necessary?

Also, the code for getting the token only seems to work if I turn on "iCloud Documents", which I don't need. Does anyone know the implications of having that turned on for a social app that doesn't need it? And is there another way to get the token without enabling iCloud Documents?

This is the code I used to get token and placed in the delegate didFinish method, but only works if iCloud documents is turned on:

var token = NSFileManager.defaultManager().ubiquityIdentityToken
    println("token is \(token!)")

回答1:

On iOS, when I sign out of iCloud, my app is killed. So there seems not really to be a need to receive a NSUbiquityIdentityDidChangeNotification. Like you have said, it seems to be sufficient to compare the current token to the saved token.

On the Apple TV though, my app was not killed when I logged out of iCloud. Here I had noticed the notification was not fired, like you described. Since the app is not killed, a notification would be in order. (Did Apple forget to kill apps on Apple TV when iCloud account is changed?)

With Apple TV there is no iCloud documents container available (unless I explicitly share one from an iOS app). I found that on the dev center website, for the app identifier, iCloud was shown as "Configurable" and not "Enabled" if no document container was selected. I wonder if this has an effect on receiving notifications.

Both on the Apple TV and iOS, I can also confirm that the iCloud token is nil when not using documents (here: key-value-store only). Now that makes it difficult for Apple TV apps (because the app is not killed on iCloud account change, like on iOS) to detect account changes.

I have just noticed that my Apple TV app does received several NSUbiquitousKeyValueStoreDidChangeExternallyNotification when I log into another iCloud account, to reflect the changes. I guess this is as good as it gets. These notifications come with the NSUbiquitousKeyValueStoreChangeReasonKey key in userInfo, and a value of NSUbiquitousKeyValueStoreAccountChange indicates the account has changed.

Sorry for not being able to provide a direct solution, maybe it helped to share my experience.

回答2:

To be notified in iOS when a user logs in or out of iCloud while using your app, use CKAccountChangedNotification instead of NSUbiquityIdentityChanged notification.

(Longer explanation: https://stackoverflow.com/a/38689094/54423.)

来源：https://stackoverflow.com/questions/28933569/nsubiquityidentitydidchangenotification-doesnt-work