swift - Set rootViewController iOS 13

Question

After upgrading Xcode a critical part of my application has stopped working.

When my app launches I run a function to check boolean flags and set the correct rootViewController.

But the code I have been using to set this has now stopped working

class func setLoginAsInitialViewContoller(window:UIWindow) {
    print("SET LOGIN") 
    let storyboard = UIStoryboard(name: "Login", bundle: nil)
    let controller = storyboard.instantiateViewController(withIdentifier: "LoginViewController")
    controller.modalPresentationStyle = .overFullScreen
    window.rootViewController = controller
    window.makeKeyAndVisible()
}

Specifically when the app gets the the second last line window.rootViewController = controller it crashes with a libc++abi.dylib: terminating with uncaught exception of type NSException error.

The above function is in a class called Utilities.swift and I am calling the function from within my AppDelegate.swift as shown below:

class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
    var storyboard: UIStoryboard? = nil

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

        UIApplication.shared.isIdleTimerDisabled = true
        Utilities.decideInitialViewController(window: self.window!)

        return true
    }

Any solutions or fixes on how I can set the root controller is much appreciated.

Thank!

Answer 1

This is because AppDelegate doesn't have window property anymore. Now you must use SceneDelegate's scene(_:willConnectTo:options:) method to change root view controller. Like shown in this example:

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

        // Instantiate UIWindow with scene
        let window = UIWindow(windowScene: scene)
        // Assign window to SceneDelegate window property
        self.window = window
        // Set initial view controller from Main storyboard as root view controller of UIWindow
        self.window?.rootViewController = UIStoryboard(name: "Main", bundle: nil).instantiateInitialViewController()
        // Present window to screen
        self.window?.makeKeyAndVisible()
    }