I have an app that uses iCloud to store a Core Data database of a moderately sized amount of data. I realized that on my test iCloud account, when I converted to iCloud Drive, all the data was wiped out.
I added more sample data, but with the simulator as the second device, I cannot determine if the data is properly syncing between devices.
These may be a consequence of iOS 8 still in beta, but I still have the question:
Do I need to change the way I do my iCloud syncing for iOS 8?
For more information, I am currently using iCloudCoreDataStack in the app. The app only uses iCloud for Core Data, no documents or key value stuff.
I upgraded my phone to iOS 8 GM yesterday, and there was an option to enable iCloud Drive, with the warning that other devices without the same option won't sync anymore. So I did, and my app's iCloud data is still retrieved.
So my guess is now Apple provides migration from old iCloud to the new iCloud Drive, which is a one-way operation. The previous iCloud data won't get lost (otherwise it'd be a disaster for lots of iOS apps), but wouldn't sync to old iCloud devices anymore.