AppDelegate & SceneDelegate

AppDelegate

• This is still main entry point for iOS 13+ application. System calls appdelegate methods for application level life cycle events.

• In apple’s default templet, you can find below three methods

func application(_:didFinishLaunchingWithOptions:) -> Bool

• This method is used to perform application setup.
• In iOS 12 or earlier, you might have used this method to create and configure a UIWindow object and assigned a UIViewController instance to the window to make it appear.Now appdelegate is no longer responsible for this

func application(_:configurationForConnecting:options:) -> UISceneConfiguration

• This method is called whenever your application is expected to supply a new scene, or window for iOS to display.
• This method is not called when your app launches initially, it’s only called to obtain and create new scenes

func application(_:didDiscardSceneSessions:)

• This method is called whenever a user discards a scene.

• You can use this function to dispose of resources that these scenes used, because they’re not needed anymore.

SceneDelegate

There are several methods in the SceneDelegate.swift file by default:

• sceneDidDisconnect(_:)
  is called when a scene has been disconnected from the app (Note that it can reconnect later on.)

• sceneDidBecomeActive(_:)
  is called when the user starts interacting with a scene, such as selecting it from the app switcher

• sceneWillResignActive(_:)
  is called when the user stops interacting with a scene, for example by switching to another scene

• sceneWillEnterForeground(_:)
  is called when a scene enters the foreground, i.e. starts or resumes from a background state

• sceneDidEnterBackground(_:)
  is called when a scene enters the background, i.e. the app is minimised but still present in the background.

sample