NSUbiquityIdentityDidChangeNotification doesn't work?

Question

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.

Answer 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.

Answer 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.)