title: App delegate must implement the window property if it wants to use a main storyboard file
body: <p>I've already tried all solutions I've been able to find in stackoverflow and none of them work.</p>
  
  <p>This is my current AppDelegate.swift file, I think that I'm implementing the window property, some way or another:</p>
  
  <pre><code>import UIKit
  
  @UIApplicationMain
  class AppDelegate: UIResponder, UIApplicationDelegate {
  
  var window: UIWindow?
  
  func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -&gt; Bool {
      // Override point for customization after application launch.
      window = UIWindow()
      window?.makeKeyAndVisible()
      let mainVC = UIViewController()
      window?.rootViewController = mainVC
  
      return true
  }
  
  // MARK: UISceneSession Lifecycle
  @available(iOS 13.0, *)
  func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -&gt; UISceneConfiguration {
      // Called when a new scene session is being created.
      // Use this method to select a configuration to create the new scene with.
      window = UIWindow()
            window?.makeKeyAndVisible()
            let mainVC = UIViewController()
            window?.rootViewController = mainVC
      return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)
  }
  
  @available(iOS 13.0, *)
  func application(_ application: UIApplication, didDiscardSceneSessions sceneSessions: Set&lt;UISceneSession&gt;) {
      // Called when the user discards a scene session.
      // If any sessions were discarded while the application was not running, this will be called shortly after application:didFinishLaunchingWithOptions.
      // Use this method to release any resources that were specific to the discarded scenes, as they will not return.
      window = UIWindow()
            window?.makeKeyAndVisible()
            let mainVC = UIViewController()
            window?.rootViewController = mainVC
  }
  </code></pre>
  
  <p>}</p>
  
  <p>What can be happening so the warning still appears and my app keeps on showing a black screen?</p>