viewcontroller lifecycle in UIWindowSceneDelegate

I have tested in an app with a scenedelegate.

In the UIViewController, I included:

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        print("will disappear")
    }

It gets called when I close the view which was presented through a segue.

How do you present this "next" view ?

Note.

In appDelegate, I have:

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool { }

    func applicationWillEnterForeground(_ application: UIApplication) { }

    func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration { }

    func application(_ application: UIApplication, didDiscardSceneSessions sceneSessions: Set) { }

And in SceneDelegate:

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) { }

    func sceneDidDisconnect(_ scene: UIScene) {
        guard let _ = (scene as? UIWindowScene) else { return }
    }

    func sceneDidBecomeActive(_ scene: UIScene) { }

    func sceneWillResignActive(_ scene: UIScene) { }

    func sceneWillEnterForeground(_ scene: UIScene) { }

In my scene delegate, I instantiate the view controller which I then embed in a Navgiation controller (I need a nav bar); see lines 22, 24 and 40 below.

  func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
    guard let windowScene = (scene as? UIWindowScene) else { return }
    
    let rootViewController: UIViewController
    
    if let shortcutItem = connectionOptions.shortcutItem {
      dPrint("\(#function) \(shortcutItem)")
    }
    
    closeWindow = nil
    
    let persistentId = scene.session.persistentIdentifier
    if let activity = connectionOptions.userActivities.first ?? session.stateRestorationActivity,
      let identifier = getIdentifier(from: activity) {
      scene.title = activity.title ?? identifier
      if isMultiScenesSupported {
        closeWindow = UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(closeWindowAction))
        closeWindow?.setAccessibilityProperties("CloseWindow")
      }
      
      // The identifier corresponds to the storyboard ID for a detail viewcontroller.
      let detailViewController = instantiateViewController(with: identifier)
      // Embed in a navigation controller to provide title and Done button.
      rootViewController = UINavigationController(rootViewController: detailViewController)
      detailViewController.restorable?.restore(from: activity, isStandalone: isMultiScenesSupported, persistentId: persistentId)
    } else {
      let identifier = AppMainFeatureData.calculator.storyboardIdentifier
      // The identifier corresponds to the storyboard ID for a detail viewcontroller.
      let detailViewController = instantiateViewController(with: identifier)
      // Embed in a navigation controller to provide title and Done button.
      rootViewController = UINavigationController(rootViewController: detailViewController)
      detailViewController.restorable?.restore(from: NSUserActivity(activityType: AppMainFeatureData.calculator.activityType), isStandalone: isMultiScenesSupported, persistentId: persistentId)
    }
    
    window = UIWindow(windowScene: windowScene)
    window?.rootViewController = rootViewController
    window?.makeKeyAndVisible()
  }
  
  public func instantiateViewController(with identifier: String) -> UIViewController {
    UIStoryboard(name: storyboardName, bundle: nil).instantiateViewController(withIdentifier: identifier)
  }

I tested by creating the child views in storyboard.

Works OK as well.

I cannot test your code as sevaral var or functions are not declared:

- dPrint

- closeWindow

- getIdentifier

- isMultiSceneSupported

- …

Sorry about that ...

I should have also also mentioned that the lack of calls to trailing view controller life cycle methods appears to be when I create new scenes. That's why I posted that code.

I have all those SceneDelegate methods you mentioned above implemented and they work fine as far scene life cycle is concerned.

I need to support iOS < 13 and I typically add/remove observers in viewWillAppear()/viewWillDisappear(). I can certainly handle the removing of observers in one of the SceneDelegate methods. But I just find it strange that the view controller life cycle methods area called when the view is appearing (creating a new scence) but now when the view is dissapearing (removing a scene in Expose).

Are you creating a new scene and are able to see calls to viewWillDisappear() and/or viewDidDisappear() when you disconnect the scene? By, for example, swiping up in Expose?

Thanks!

To support older iOS version, you have to test iOS:

Such as:

1. In Scene Delegate

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow?

    @available(iOS 13.0, *)
    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        guard let _ = (scene as? UIWindowScene) else { return }
    }

What I usually do :

2. In AppDelegate, I create a window property as well

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    // MARK: - Application lifecycle

    var window: UIWindow?   // For iOS 12

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
          // …
     }

As well as for scene related in AppDelegate:

    @available(iOS 13.0, *)
    func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {
     return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)
    }

    @available(iOS 13.0, *)
    func application(_ application: UIApplication, didDiscardSceneSessions sceneSessions: Set) {
     }

Thanks for the reply. I have all that!

I guess I still have one basic question: are ViewController life cycle methods viewWillDisappear() and viewDidDisappear() still supposed to be called in iOS 13 when supporting scenes and closing a scene?

If that's the case it's not happening in my app and I'll dig into "why".

I just wanted to make sure that is the case before chasing my tail too long.

Thank!

Yes, viewWillDisappear is fired on iOS 13 with scene management in my sample code.