Passing variable back to parent in Swift

Question

I am re-writing a tutorial converting the code from Objective-C to swift. The app moves from VC one where there is 3 sliders (Red, Green and Blue) that set the background colour

Answer 1

ViewController() actually creates a new instance of your ViewController. This is not a reference to the already existing ViewController. What you can do is create a weak variable pointing to first ViewController inside the second ViewController and set it at prepareForSegue or when the second View controller is shown.

class SecondViewController : UIViewController {
    weak var firstViewController : ViewController?

    // Other code

    func textFieldShouldReturn(nameEntry: UITextField) -> Bool
    {
        firstViewController?.colourLabel.text = nameEntry.text
        nameEntry.resignFirstResponder()
        dismissViewControllerAnimated(true, completion: nil)
        return true
    }
}

Inside First View Controller prepareForSegue

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == "SecondViewController" {

        let secondViewController = segue.destinationViewController as SecondViewController
        secondViewController.firstViewController = self
    }
}

Answer 2

It's possible that the view controller returned by ViewController() has not yet loaded its views. You could try checking this in a setter function and storing it for later use once the views have been loaded.

class VC : UIViewController {
    @IBOutlet weak var colourLabel: UILabel!
    var savedLabelText: String?

    override func viewDidLoad() {
        super.viewDidLoad()

        self.colourLabel.text = self.savedLabelText
    }

    func setColorLabelText(label: String) {
        if self.isViewLoaded() {
            self.colourLabel.text = label
        }
        else {
            self.savedLabelText = label
        }
    }
}