UIStackView bounds is zero after creation

Question

I have a subclass of UIStackView

final class MyStack : UIStackView {
  required init(coder: NSCoder) {
    super.init(coder: coder)
    setup()
  }
  
  override init(frame: CGRect) {
    super.init(frame: frame)
    setup()
  }
  
  private func setup() {
    backgroundColor = .clear
    axis = .horizontal
    contentMode = .scaleAspectFit
    
    alignment = .fill
    distribution = .fillProportionally
    spacing = 0
    
    contentMode = .scaleToFill
    isUserInteractionEnabled = true
    
    autoresizingMask = [.flexibleLeftMargin, .flexibleRightMargin, .flexibleTopMargin, .flexibleBottomMargin, .flexibleWidth, .flexibleHeight]
    translatesAutoresizingMaskIntoConstraints = true
    
  }

func setupSymbols(_ amount:Int) {
  let large = UIImage.SymbolConfiguration(scale: .large)

  for index in 0..< number {
    let image = UIImage(systemName: "trash", withConfiguration: large)
    let highlightedImage = UIImage(systemName: "trash.fill", withConfiguration: large)

    let imageView = UIImageView(image: image, highlightedImage: highlightedImage)
    self.addArrangedSubview(oneStar)
  }
}

On the ViewController I create an instance of this class

let myStack = MyStack()

myStack.setupSymbols(5)
self.view.addSubview(myStack)

print (myStack.frame)

the last line gives me width and height equal to zero!!!

why?

score 1 · Accepted Answer · answered May 16 '22 at 17:56

The frame of the view won't be updated until the next layout pass. The frame doesn't get calculated immediately after adding the view to the view hierarchy, that's why you see it being zero.

If you override the view controller's viewDidLayoutSubviews method and check the frame there, it will likely be non-zero.

UIStackView bounds is zero after creation

1 Answers1