Is it possible to intercept iCloud switching on/off in Settings -> iCloud -> Document & Data?

Question

Is it possible to intercept if the user switches from on to off the iCloud support under Settings -> iCloud -> Document & Data<

Answer 1

It's not possible to intercept the changes, but you can programmatically check to see if they have iCloud enabled:

NSFileManager *fileManager = [NSFileManager defaultManager];
NSURL *ubiquityContainerURL = [fileManager URLForUbiquityContainerIdentifier:nil];
if (!ubiquityContainerURL) {
    // iCloud is not enabled
}

When your app enters the background, you could periodically poll this and have your app respond to any change in state.

EDIT: If your app is running and the user changes enables or disable Document & Data iCloud syncing via the settings app, your app will receive the SIGKILL signal. However, the OS can terminate your app for a number of reasons so trapping SIGKILL is not a reliable method of intercepting iCloud sync setting changes. You are still better off periodically polling.