In Hacking with Swift, Project 7, I discovered an error which took me a while to understand and come up with a fix, but here it is.

In the tutorial you say to add the following to AppDelegate…

 if let tabBarController = window?.rootViewController as? UITabBarController {

      let storyboard = UIStoryboard(name: "Main", bundle: nil)
      let vc = storyboard.instantiateViewController(withIdentifier: "NavController")
      vc.tabBarItem = UITabBarItem(tabBarSystemItem: .topRated, tag: 1)

      tabBarController.viewControllers?.append(vc)
    }

I believe that this code must be placed in SceneDelegate.swift.

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
}

Yeah, just hit the same thing. var window: UIWindow? is no longer declared in AppDelegate, but SceneDelegate. i agree with the suggested method, adding the code there works as expected.

@ThomasLeeEvans - Thank you so much for posting this! I was wondering why my second tab bar item was not showing up. This solved my issue!

@tarasis - also noticed that var window: UIWindow? wasn't in AppDelegate.swift so I declared it my elf but ran into the problem of the code having no effect of adding the second button.

Much appreciated!

I did what you did but the other tabBarController doesnt show up, i already checked the code and it's everything ok! does anyone has the same problem? thanks.

@ThomasLeeEvans is correct.

Place the code in SceneDelegate.swift in the func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) after guard let _ = (scene as? UIWindowScene) else { return }