如何从父UIStackView引用和修改子视图UILabel

Question

I have a UIStackView object to which I have added a UILabel as the first subview. Here is what my code looks like:

func createStackView() -> UIStackView? {
  var displayLabel = UILabel()
  // Set properties of displayLabel
  ...
  let myStackView = UIStackView(arrangedSubviews: [displayLabel, stackViewRow1, stackViewRow2]
  return myStackView
}

Now, I wish to obtain a reference to the displayLabel object later on so I can modify it's text field. The only way I could do this was somewhat of a hack:

var displayPanel = topStackView.arrangedSubviews[0]
if let displayLabel = displayPanel as? UILabel {
      displayLabel.text = "Ready"
}

Is there a better way to do this ?

Answer 1

If displayLabel should be not instance variable, then setting a tag value for it might be useful:

An integer that you can use to identify view objects in your application.

What you can do:

// declaring a global constant for holding the label tag value
let displayLabelTageValue = 101

func createStackView() -> UIStackView? {
    var displayLabel = UILabel()
    // setting tag
    displayLabel.tag = displayLabelTageValue
    // Set properties of displayLabel
    ...
    let myStackView = UIStackView(arrangedSubviews: [displayLabel, stackViewRow1, stackViewRow2]
        return myStackView
}

And for getting identified displayLabel label:

if let displayLabel = view.viewWithTag(displayLabelTageValue) as? UILabel {
    // displayLabel is wanted label!
} else {
    // make sure that the tag value is matched
}

Answer 2

Store a reference to the label in a property:

var displayLabel: UILabel?

// then when you create the stack view
self.displayLabel = displayLabel

// to access it later
if let displayLabel = displayLabel {
    displayLabel.text = "Ready"
}

Answer 3

It depends on what your goals are.

If you want to set the text of the view in position 0 of your stack view to a specific string, the code you posted is the right way to go.

If you have a label that you want to be able to change regardless of it's position in the stack view then you should save a reference to it in an instance variable of your view controller, and then you can set it's text to a new string at any time.