userId coming to appdelegate still not going to Mainviewcontroller why? in swift

Question

NavigationController is isinitial viewcontroller in storyboard, NavigationController embedded to LoginViewcontroller

in project storyboard navigation willbe like below

NavigationController->LoginViewcontroller-> RegistrationViewcontroller -> MainViewcontroller

in successful registration with PhNUmber i am getting userId which i have stored in KeychainWrapper

in RegistrationViewcontroller: i am storing userId like below:

 let userID: String=jsonObj?["userId"] as? String ?? "" 
 KeychainWrapper.standard.set(userID, forKey: "USERID")

which i am checking in appdelegate like below to go Mainviewcontroller:

class AppDelegate: UIResponder, UIApplicationDelegate {

var window: UIWindow?
var savedUserId: String?

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

    savedUserId = KeychainWrapper.standard.string(forKey: "USERID")
    print("appdelegate userid \(savedUserId)")
    if savedUserId != nil{
        print("saveuserid \(savedUserId)")
        let mainStoryBoard = UIStoryboard(name: "Main", bundle: nil)
        window?.rootViewController = mainStoryBoard.instantiateViewController(withIdentifier: "MainViewController")
    }
    return true
}
}

here savedUserId coming then why i am not going to MainViewcontroller, all the time LoginViewcontroller appears

Answer 1

You need to initialize the window. Give this line above setting the rootViewController:

class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
    var savedUserId: String?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        savedUserId = KeychainWrapper.standard.string(forKey: "USERID")
        print("appdelegate userid \(savedUserId)")
        if savedUserId != nil{
            print("saveuserid \(savedUserId)")
            let mainStoryBoard = UIStoryboard(name: "Main", bundle: nil)
            window = UIWindow()
            window?.rootViewController = mainStoryBoard.instantiateViewController(withIdentifier: "MainViewController")
        }
        return true
    }
}

Update: If you're using SceneDelegate you should use this:

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow?

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        guard let windowScene = scene as? UIWindowScene else { return }
        window = UIWindow(windowScene: windowScene)print("appdelegate userid \(savedUserId)")
        if savedUserId != nil{
            print("saveuserid \(savedUserId)")
            let mainStoryBoard = UIStoryboard(name: "Main", bundle: nil)
            window = UIWindow()
            window?.rootViewController = mainStoryBoard.instantiateViewController(withIdentifier: "MainViewController")
        }
    }
}