Template of UIApplicationDelegate without storyboard.

AppDelegate.swif

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

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

        let vc = ViewController()
        let nav = UINavigationController(rootViewController: vc)
        
        let window =  { () -> UIWindow in
            let window = UIWindow(frame: UIScreen.main.bounds)
            window.rootViewController = nav
            
            return window
        }()

        window.makeKeyAndVisible()
        self.window = window

        return true
    }
}