iOS iCloud not restoring after deleting App - icloud

Question

I'm trying to get the key value store in iCloud to work and I'm running into an odd problem.
I store data using:
[[NSUbiquitousKeyValueStore defaultStore] setObject:#"SomeValue" forKey:#"SomeKey"];
[[NSUbiquitousKeyValueStore defaultStore] synchronize];
I read the data using:
someValue = [[NSUbiquitousKeyValueStore defaultStore] objectForKey:#"SomeKey"];
This all works great when I start and stop the App. Values are stored and I see the values being read. Everything is fine.
Then I delete the App from my device and load it again (via xcode). Now, I don't see any data come down from the cloud.
Isn't one of the main points of iCloud that you can delete an App and then recover data (in my case, game save state)?
Why does deleting my App and reinstall it (running it in xcode) cause all the iCloud data to vanish?
I am running this on the device, not the simulator. I've tried it on iOS 5 and iOS 6 with the same results.
NSUbiquitousKeyValueStore seems really simple to use, but I'm clearly doing something wrong.

Answer 1

First, try synchronizing before you read the data to make sure the latest updates have come in from iCloud.
Do you have another device on which you can test? If so, run the writing code on one device and then run the reading code on another device. It could be that even though you're using NSUbiquitiousKeyValueStore, it isn't actually syncing when you think it is. The reason that it would work on your device is that the key value store is available locally, but not in iCloud. So when you delete your app you're deleting the local (and also your only) copy of the data.

Answer 2

I found you need to register for the NSUbiquitousKeyValueStoreDidChangeExternallyNotification notification to make the sync work. It wouldn't persist data after a reinstall without it.
- (void)iCloudKeyStateChanged:(NSNotification*)n {
}
- (BOOL)application:(UIApplication*)application didFinishLaunchingWithOptions:(NSDictionary*)launchOptions {
...
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(iCloudKeyStateChanged:) name:NSUbiquitousKeyValueStoreDidChangeExternallyNotification object:nil];
}