Tells the app that your code has finished any asynchronous state restoration.
- iOS 6.0+
- Mac Catalyst 13.0+
- tvOS 9.0+
UIKit restores your app’s state synchronously on the main thread. If you choose to perform additional state restoration on a secondary thread, call the
extend method to inform UIKit of that fact. Call this method after you finish with your background work to let the system know that state restoration is complete.