Programming iOS 6, 3rd Edition

iCloud

Once your app is operating through UIDocument, iCloud compatibility falls right into your lap. You have just two steps to perform:

Register for iCloud entitlements

In the Portal (Chapter 9), register your app and configure it to be enabled for iCloud (a simple checkbox); then create a provisioning profile for the app (obviously, while developing, this would be a Development profile), download it, and hand it over to Xcode.

Back in your project, edit the target; under Summary, check Enable Entitlements in the Entitlements section. This causes the entire entitlements mechanism to spring to life. The entitlements file is added to the project. The Enable iCloud checkbox is enabled; check it if it isn’t checked. You’ll also need one Ubiquity Container (listed just below the iCloud checkbox); if there isn’t one, add one, which will automatically be assigned your app’s bundle id.

Obtain an iCloud-compatible directory

Early in your app’s lifetime, call NSFileManager’s URLForUbiquityContainerIdentifier: (typically passing nil as the argument), on a background thread, to obtain the URL of a cloud-shared directory. It will probably be an app-specific directory inside file://localhost/private/var/mobile/Library/Mobile%20Documents/; you are given sandbox access to this directory even though strictly speaking it isn’t inside your sandbox area. Any documents your app puts here by way of a UIDocument subclass will be automatically shared into the cloud.

Thus, for example, having registered ...