ios - Changing label text of second ViewController upon clicking button in first ViewController

Question

I'm new to Swift and to iOS Development. I currently have 2 ViewControllers, a button in the first and a label in the second one. I've connected the first button to the second ViewController and the transition works.

Now, when I try changing the label's text I get the error:

fatal error: unexpectedly found nil while unwrapping an Optional value

.

Here you find my prepare function in the first ViewController:

 override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "mySegue" {
            let vc = segue.destination as! SecondViewController
            vc.secondResultLabel.text = "Testing"
         }
    }

Can it be that the label in the second ViewController is somehow protected ?

Thanks for the help

Answer 1

You need to pass the String to the SecondViewController instead of directing setting it, as the UILabel has not been created yet.

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "mySegue" {
        let vc = segue.destination as! SecondViewController
        vc.secondResultLabelText = "Testing"
    }
}

And in your SecondViewController viewDidLoad method set the UILabel to be the string

var secondResultLabelText : String!

override func viewDidLoad() {

    secondResultLabelText.text = secondResultLabelText
}