I can't add UIProgressView in StackView

Question

According to this code, I need to add 4 UIProgressViews to the StackView, but only 1 UIProgressView is added to the StackView. I am using Horizontal StackView.

Code:

class ViewController: UIViewController {
  
  @IBOutlet weak var imageView: UIImageView!
  @IBOutlet weak var stackView: UIStackView!
  
  var progressView: UIProgressView = {
    var view = UIProgressView()
    view.tintColor = .white
    view.progress = 0.5
    return view
  }()
  
  override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
    for _ in 1...4 {
      stackView.addArrangedSubview(progressView)
    }
  }
}

Answer 1

You're adding the same UIProgressView four times. But when you add a subview to a view, the subview is first removed from its existing superview, because a subview can only have a single superview and can only occupy a single slot in its superview's subviews array.

You need to create four UIProgressViews.

let progressViews: [UIProgressView] = (0 ..< 4).map { _ in
    let view = UIProgressView()
    view.tintColor = .white
    view.progress = 0.5
    return view
}

override func viewDidLoad() {
    super.viewDidLoad()

    for progressView in progressViews {
        stackView.addArrangedSubview(progressView)
    }
}