Instance Method

application(_:shouldSaveApplicationState:)

Asks the delegate whether the app’s state should be preserved.

Declaration

optional func application(_ application: UIApplication, shouldSaveApplicationState coder: NSCoder) -> Bool

Parameters

application

Your singleton app object.

coder

The keyed archiver into which you can put high-level state information.

Return Value

true if the app’s state should be preserved or false if it should not.

Discussion

Apps must implement this method and the application(_:shouldRestoreApplicationState:) method for state preservation to occur. In addition, your implementation of this method must return true each time UIKit tries to preserve the state of your app. You can return false to disable state preservation temporarily. For example, during testing, you could disable state preservation to test specific code paths.

You can add version information or any other contextual data to the provided coder object as needed. During restoration, you can use that information to help decide whether or not to proceed with restoring your app to its previous state.

See Also

Managing App State Restoration

func application(UIApplication, shouldRestoreApplicationState: NSCoder) -> Bool

Asks the delegate whether the app’s saved state information should be restored.

func application(UIApplication, willEncodeRestorableStateWith: NSCoder)

Tells your delegate to save any high-level state information at the beginning of the state preservation process.

func application(UIApplication, didDecodeRestorableStateWith: NSCoder)

Tells your delegate to restore any high-level state information as part of the state restoration process.

class let stateRestorationBundleVersionKey: String

The version of your app responsible for creating the restoration archive.

class let stateRestorationSystemVersionKey: String

The version of the system on which your app created the restoration archive.

class let stateRestorationTimestampKey: String

The time at which your app created the restoration archive.

class let stateRestorationUserInterfaceIdiomKey: String

The user interface idiom that was in effect when your app created the restoration archive.

class let stateRestorationViewControllerStoryboardKey: String

A reference to the storyboard that contains the view controller.