iOS App Lifecycle

1. Managing your app's life cycle

   App states: not running, inactive, active, background and suspended.

2. UIApplicationDelegate

   App-level launch and state callbacks.

3. UISceneDelegate

   Scene lifecycle callbacks such as sceneDidBecomeActive and sceneWillResignActive.

4. Scenes

   Multiple scenes and iPadOS windows.

5. Background Tasks

   Scheduling refresh and processing tasks.

6. Extending your app's background execution time

   beginBackgroundTask and finite-length background work.

7. SwiftUI ScenePhase

   Observing active, inactive and background phases in SwiftUI.

8. User Notifications

   Local and remote notification scheduling and handling.

9. Preparing your UI to run in the background

   Hiding sensitive data and saving state before snapshots are taken.

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