I am not that familiar with iCloud integration. I read numerous bad reports about the integration in iOS 5 and 6. But now I guess it's better in iOS 7 so I decided to add it in one of the new apps I'm working on.
From what I read and saw in the WWDC 2013 CoreData/iCloud video I thought it was as simple as flipping on iCloud in Xcode and configuring the NSPersistentStoreUbiquitousContentNameKey value to something unique in the addPersistentStore call, to get started. But each time I run the app, in the simulator or on a physical iPhone, the console output shows the iCloud setup failed due to URLForUbiquityContainerIdentifier returning nil.
I am using Xcode 6 beta and the iOS 8 beta 2 SDK. I've made sure iCloud is signed in and otherwise functioning on the simulator and physical devices. I've also made sure that the "Documents/Data" switch is on under iCloud setting and the app IS appearing here. I've also browsed to the simulator application directory and I see the SQLite file in the normal documents directory and in an iCloud directory.
Is there something really simple I'm missing?
Not sure what the developer agreements allows to say, but at the time of writing this, it is still beta and most probably is a bug in xcode 6. There may be a few threads on the developer forum on that exact same subject. Search for 'URLForUbiquityContainerIdentifier' and you may find more information.
Try beta 4. My iCloud code is now working.