无法实例化视图控制器。 - 斯威夫特

Question

So, I'm trying to instantiate my view controller programmatically using storyboard references.

I've put this code in the AppDelegate:

var window: UIWindow?

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

    window = UIWindow(frame: UIScreen.main.bounds)

    let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
    let initialController: WelcomePageViewController = mainStoryboard.instantiateViewController(withIdentifier: "WelcomePageViewController") as! UITabBarController
        window?.rootViewController = initialController        
    window?.makeKeyAndVisible()
    return true
}

And set this inside my view controller's storyboard:

However when I run the application, only a black screen is shown and this message: "Failed to instantiate the default view controller for UIMainStoryboardFile 'Main' - perhaps the designated entry point is not set?"

I've used this exact code in other apps and it works just fine.

I've tried to clean build folder, to run it on an actual device and to create and instantiate a different storyboard file but nothing worked.

Answer 1

Open your Main.storyboard file and find WelcomePageViewController . When it's selected, go to the attributes inspector and check the box marked Is Initial View Controller .

You should see a right-facing arrow appear to the left of WelcomePageViewController , showing that it's your storyboard's entry point.

Now you're all set to go!!!

Answer 2

Ok So i think here is something you can do if it suits:

• set entry point to the navigation controller
• class that navigation controller with a file like rootNavigationVC.swift which is subclass of UINavigationController
• now in didLoad() you can set it's viewController or push one based on your condition

trust me its better than coding in AppDelegate.swift which never worked for me.