iOS 13: Swift - 'Set application root view controller programmatically' does not work

Question

I have following code in my AppDelegate.swift to setup root view controller for an iOS application. But it does not work. It follows Target structure (defined under General

Answer 1

var window: UIWindow?

has been moved from AppdDelegate.swift to SceneDelegate.swift.

So I used rootViewController in the Scene Delegate class and it works -

   func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
        // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
        // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).
        guard let _ = (scene as? UIWindowScene) else { return }

        if let tabBarController = window?.rootViewController as? UITabBarController {
                  let storyboard = UIStoryboard(name: "Main", bundle: nil)
                  let vc = storyboard.instantiateViewController(identifier: "NavController")

                  vc.tabBarItem = UITabBarItem(tabBarSystemItem: .topRated, tag: 1)
                  tabBarController.viewControllers?.append(vc)
              }
    }

Answer 2

    let MainViewController  = mainStoryboard.instantiateViewController(withIdentifier: "MainViewController") as! MainViewController

                    let nvc:rootNavigation  = mainStoryboard.instantiateViewController(withIdentifier: "rootNavigation") as! rootNavigation
                    nvc.viewControllers = [Mainmap]
                   
                    leftViewController.mainViewController = nvc

UIApplication.shared.windows.first?.backgroundColor = UIColor(red: 236.0, green: 238.0, blue: 241.0, alpha: 1.0)
                    UIApplication.shared.windows.first?.rootViewController = nvc
                    UIApplication.shared.windows.first?.makeKeyAndVisible()