Why does UILabel TapGesture only work after label initialization?

Question

I have the following code to initialize a label:

let forgotPasswordLabel: UILabel = {
        let label = UILabel()
        label.text = "Forgot password?"
        label.font = ApplicationScheme.instance.containerScheme.typographyScheme.subtitle1
        label.textColor = ApplicationScheme.instance.containerScheme.colorScheme.onPrimaryColor
        label.textAlignment = .right
        label.sizeToFit()
        label.accessibilityRespondsToUserInteraction = true
        label.isUserInteractionEnabled = true
        label.translatesAutoresizingMaskIntoConstraints = false
        return label
    }()

And later on I add it to the subview as such:

let passwordLabel = forgotPasswordLabel
let tapGesture = UITapGestureRecognizer(target: self, action: #selector(onForgotPasswordClick))
passwordLabel.addGestureRecognizer(tapGesture)
self.view.addSubview(passwordLabel)

If I do the code as such then it works fine, however if I put the tapGesture code inside the label forgotPasswordLabel initialization, the tap gesture does not fire. Why is that?

Code that does not work:

let forgotPasswordLabel: UILabel = {
        let label = UILabel()
        label.text = "Forgot password?"
        label.font = ApplicationScheme.instance.containerScheme.typographyScheme.subtitle1
        label.textColor = ApplicationScheme.instance.containerScheme.colorScheme.onPrimaryColor
        label.textAlignment = .right
        label.sizeToFit()
        label.isUserInteractionEnabled = true
        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(onForgotPasswordClick))
        label.addGestureRecognizer(tapGesture)
        label.translatesAutoresizingMaskIntoConstraints = false
        return label
    }()

Does this have something to do with the garbage collector? Unrecognized bounds for the UILabel? Or something else?

Can you tell where do you use forgotPasswordLabel in the case when it does not work? — Harshal Bhavsar, Feb 06 '20 at 03:28
I add to the subview in the viewDidLoad method as the simple line self.view.addSubview(forgotPasswordLabel) — uioporqwerty, Feb 06 '20 at 03:29
see the following explanation should help you to understand the reason behind it — Harshal Bhavsar, Feb 06 '20 at 03:53

Harshal Bhavsar · Accepted Answer · 2020-02-06T03:55:12.003

The tapGesture in following code is added inside the Closure initializer, and with that you assign target as self which is not valid. Coz self here is not the ViewController

let forgotPasswordLabel: UILabel = {
        let label = UILabel()
        label.text = "Forgot password?"
        label.font = ApplicationScheme.instance.containerScheme.typographyScheme.subtitle1
        label.textColor = ApplicationScheme.instance.containerScheme.colorScheme.onPrimaryColor
        label.textAlignment = .right
        label.sizeToFit()
        label.isUserInteractionEnabled = true
        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(onForgotPasswordClick))
        label.addGestureRecognizer(tapGesture)
        label.translatesAutoresizingMaskIntoConstraints = false
        return label
    }()

Where as in the following code where the tapGesture is working as expected you are setting target as self which is the ViewController and that is valid.

let forgotPasswordLabel: UILabel = {
    let label = UILabel()
    label.text = "Forgot password?"
    label.font = ApplicationScheme.instance.containerScheme.typographyScheme.subtitle1
    label.textColor = ApplicationScheme.instance.containerScheme.colorScheme.onPrimaryColor
    label.textAlignment = .right
    label.sizeToFit()
    label.accessibilityRespondsToUserInteraction = true
    label.isUserInteractionEnabled = true
    label.translatesAutoresizingMaskIntoConstraints = false
    return label
}()

let passwordLabel = forgotPasswordLabel
let tapGesture = UITapGestureRecognizer(target: self, action: #selector(onForgotPasswordClick))
passwordLabel.addGestureRecognizer(tapGesture)
self.view.addSubview(passwordLabel)

In case of tapGesture when you set the target it tells that where to look for the action when the gesture happens

Is there a method of doing the gesture initialization inside the closure instead of outside of it? — uioporqwerty, Feb 06 '20 at 04:12
I would say that the approach will create more issue but will let you know here if i find a best way to do it — Harshal Bhavsar, Feb 06 '20 at 05:00

Why does UILabel TapGesture only work after label initialization?

1 Answers1