Presenting View Controller is too slow

Question

I have implemented a Firebase Google login into my Swift App. I want to check in the beginning if its already a logged in user or not. I do this like that:

override func viewDidLoad() {
        super.viewDidLoad()
        GIDSignIn.sharedInstance()?.presentingViewController = self
        GIDSignIn.sharedInstance().delegate = self

    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(false)

        if Auth.auth().currentUser != nil {

          let storyboard = UIStoryboard(name: "Main", bundle: nil)
          let vc = storyboard.instantiateViewController(withIdentifier: "feedVC")
          vc.modalPresentationStyle = .fullScreen
          self.present(vc, animated: false)

        }
    }

Now my problem is: It works how I want, but its pretty slow. I can still get a quick look at the login screen, before my main page gets presented.

Now if I want to add the currentUser check to the viewDidLoad, the App doesnt check if the User has already logged in before.

Any recommendations?

Answer 1

Do it on main thread

 override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(false)

        if Auth.auth().currentUser != nil {
    DispatchQueue.main.async {
     let storyboard = UIStoryboard(name: "Main", bundle: nil)
              let vc = storyboard.instantiateViewController(withIdentifier: "feedVC")
              vc.modalPresentationStyle = .fullScreen
              self.present(vc, animated: false)
    }
}