Why does initial viewcontroller crash with instantiateInitialViewController from the storyboard?

Question

I’m trying to use dependency injection with instantiateInitialViewController for the initial view controller in a storyboard. My goal is to inject a ViewModel into my ViewController when it is instantiated. However, my app crashes with the error Fatal error: init(coder:) has not been implemented. Here’s my setup:

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
    guard let windowScene = (scene as? UIWindowScene) else { return }
    
    window = UIWindow(windowScene: windowScene)
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    
    let viewController = storyboard.instantiateInitialViewController(creator: { coder in
        ViewController(coder: coder, viewModel: ViewModel())
    })
    
    window?.rootViewController = viewController
    window?.makeKeyAndVisible()
}

Here is the viewcontroller

final class ViewController: UIViewController {
    private let viewModel: ViewModel

    init?(coder: NSCoder, viewModel: ViewModel) {
        self.viewModel = viewModel
        super.init(coder: coder)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        viewModel.fetchUsers { users in
            print(users)
        }
    }
}

Answer 1

The problem is that even though you are fetching the storyboard yourself and instantiating the initial view controller yourself...

let storyboard = UIStoryboard(name: "Main", bundle: nil)

let viewController = storyboard.instantiateInitialViewController(creator: { coder in
    ViewController(coder: coder, viewModel: ViewModel())
})

... nevertheless, you forgot to prevent the runtime from independently fetching the storyboard and instantiating the initial view controller. Therefore, your initial view controller is being instantiated twice — and the first time, your init?(coder:) override is called and you crash.

To fix the problem, just go into the Info.plist and delete the line that sets the storyboard as Main:

See that line that I've highlighted? Select it and hit Delete.

Now your app will launch successfully and you'll be doing the dependency injection you were aiming at.