SWIFT

swift create uinavigationcontroller programmatically

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
   self.window = UIWindow(frame: UIScreen.mainScreen().bounds)
   var nav1 = UINavigationController()
   var mainView = ViewController(nibName: nil, bundle: nil) //ViewController = Name of your controller
   nav1.viewControllers = [mainView]
   self.window!.rootViewController = nav1
   self.window?.makeKeyAndVisible()
}

swift create uinavigationcontroller programmatically

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

    window?.windowScene = windowScene
    window?.makeKeyAndVisible()

    let viewController = ViewController()
    let navViewController = UINavigationController(rootViewController: viewController)
    window?.rootViewController = navViewController
}

swift create uinavigationcontroller programmatically

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
   self.window = UIWindow(frame: UIScreen.main.bounds)
   let nav1 = UINavigationController()
   let mainView = ViewController(nibName: nil, bundle: nil) //ViewController = Name of your controller
   nav1.viewControllers = [mainView]
   self.window!.rootViewController = nav1
   self.window?.makeKeyAndVisible()
}