sceneWillResignActive

sceneWillResignActive is a notification that is posted by the UIApplication object when the application is transitioning from an active state to a background state. This transition occurs when the user, for example, presses the home button on an iOS device or switches to another application. The notification signifies that the application is about to lose focus and its UI will no longer be visible or interactive.

When an application receives the sceneWillResignActive notification, it is an opportunity to perform necessary cleanup or state-saving operations. This might include saving user data, pausing ongoing tasks like network requests or media playback, or deactivating timers. It's crucial to handle this notification gracefully to ensure a smooth user experience and prevent data loss. Applications should aim to complete any critical operations within a short timeframe after receiving this notification, as the operating system may eventually terminate the application to free up resources.

Applications can observe this notification using `NotificationCenter.default.addObserver`. When the notification is received, a designated method will be called, allowing the developer to implement custom logic for responding to the application entering the background. This notification is part of the application lifecycle management provided by the operating system.