Not performing segue

Question

I am testing a simple login system for an iOS app.

This is the code where I want to check if the user was logged in previosly:

 override func viewDidLoad() {
        super.viewDidLoad()

        let logeado = UserDefaults.standard.string(forKey: "logeado")
        let men = "SI"

        if logeado == men {
            showToast(message: logeado!)
            self.performSegue(withIdentifier: "entrar_segue", sender: self)
        }


    }

    func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        if segue.identifier == "entrar_segue"{
            var vc = segue.destination as! HomeViewController

        }
    }

The Toast is shown, but the segue is not performed. There is a button that uses the same function:

self.performSegue(withIdentifier: "entrar_segue", sender: self)

and there it works.

What is wrong in the code?

Answer 1

You need to call this self.performSegue method in dispatch_async block:

override func viewDidLoad() {
    super.viewDidLoad()

    DispatchQueue.main.async {
        self.performSegue(withIdentifier: "seg", sender: self)
    }
}

That's because viewDidLoad() runs in background thread and all UI updates and transitions must be done on Main Thread.