willDeactivateNotification
A notification that indicates that the scene is about to resign the active state and stop responding to user events.
Declaration
nonisolated class let willDeactivateNotification: NSNotification.NameDiscussion
UIKit posts this notification for temporary interruptions, such as when displaying system alerts. It also posts this notification before transitioning your app to the background state. UIKit places the scene object in the object property of the notification.
Use this notification to quiet your interface and prepare it to stop interacting with the user. Specifically, pause ongoing tasks, disable timers, and decrease frame rates or stop updating your interface altogether. Games should use this notification to pause the game. By the time your handler method returns, your app should be doing minimal work while it waits to transition to the background or to the foreground again.
If your scene has unsaved user data, save that data here to ensure that it isn’t lost. However, never save data solely from your notification handler. Instead, save it at appropriate points from your view controllers, usually in response to user actions. For example, save data when the user dismisses a data-entry screen. Do not rely on specific app transitions to save all of your app’s critical data.
UIKit also calls the sceneWillResignActive(_:) method of your scene delegate object.
For more information about what to do when your app resigns the active state, see Preparing your UI to run in the background.