How to change outlet properties from global scope?

Question

I need a function from global scope change a label on the storyboard.

When I try running this code, the error I get is:

fatal error: unexpectedly found nil while unwrapping an Optional value

The problem is that viewController.congratulations is null.

How to fix that? Thanks in advance!

func myAlert ()
{
    // how to change 'configuration.text' from here?

    let storyboard = UIStoryboard(name: "Main", bundle: nil);
    let viewController : ViewController = storyboard.instantiateViewController(withIdentifier: "ViewController") as! ViewController;

    viewController.congratulations.text = "test";
}

class ViewController: UIViewController
{
    @IBOutlet weak var congratulations: UILabel!;

    override func viewDidLoad()
    {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        myAlert();
    }

    override func didReceiveMemoryWarning()
    {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

}

After nib load, the outlet gets the reference of the UI so it is always nil. — Salman Ghumsani, Jul 31 '17 at 08:53
Here you are making again as per my understanding in `viewDidLoad` `myAlert();` — Salman Ghumsani, Jul 31 '17 at 08:54

score 1 · Answer 1 · answered Jul 31 '17 at 08:54

1

You shouldn't directly try to access a UILabel from outside the class where it is defined. Labels are only created once viewDidLoad is called on the specific instance of your UIViewController subclass.

What you should do is store the text you want to display on your label in another variable and change that variable from outside your class.

answered Jul 31 '17 at 08:54

Dávid Pásztor

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Should I use a timer to check whether it has changed? – A. Bhakta Jul 31 '17 at 09:03
Definitely not. You can use property observers for this. – Dávid Pásztor Jul 31 '17 at 09:05

score 0 · Answer 2 · answered Jul 31 '17 at 08:54

The IBOutlet named congratulations is nil in viewDidLoad. So make a String property at ViewController (say stringValue). Set that string property while navigation

In your viewController's viewDidLoad method, get the stringValue and set its value to label

self.congratulations.text = stringValue;

score 0 · Answer 3 · answered Jul 31 '17 at 09:07

Adding myAlert() into ViewController class solved the problem.

class ViewController: UIViewController
{
    func myAlert ()
    {
        self.congratulations.text = "vrebreberbfrbb";
    }

    @IBOutlet weak var congratulations: UILabel!;

    override func viewDidLoad()
    {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        myAlert();
    }

    override func didReceiveMemoryWarning()
    {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

}

How to change outlet properties from global scope?

3 Answers3