There are questions related to SO such as this one , and although this question is mentioned, this is not the essence of this question or any other. can find.
I wrote an iOS 8.1 app called Cloudy, which is just a test bed for learning Core Data for iCloud. The documentation says that to detect an iCloud account state change, you should listen NSUbiquityIdentityDidChangeNotificationand then examine the value of the property NSFileManager ubiquityIdentityToken. Conceptually, this is very simple and understandable. The problem is that this never happens.
Instead, my application always gets SIGKILLwhen I exit iCloud or disable iCloud Documents. In some comments on the related SO question above, some have guessed that this only happens when debugging through Xcode, but I can assure you that this is not the case. This also happens when you simply launch the application without connecting a debugger.
Now SIGKILLjust fine. In fact, it makes my life easier. The problem is that I cannot find this behavior anywhere, so I do not trust him. However, since I could never capture NSUbiquityIdentityDidChangeNotification, it is impossible to verify any code written to process it.
While iCloud is a great technology, the documentation for it is probably half higher than the awful one.