Unexpected frame of subview (Swift) - swift

Question

My code displays my view initialview as a subview of the container containerView.
I'm expecting initialView.frame to be the frame in the coordinates of the superview (that is the containerview) - which is reported int he playground to be (0,0,0,0) - but it is then displayed in the container so how can the width and height possibly be zero, as reported?
The playground code -
final class InitialView: UIView {
let traverseButton = UIButton(type: .custom)
let networkButton = UIButton(type: .custom)
let networkLabel = UILabel()
override init(frame: CGRect) {
super.init(frame: frame)
setup()
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
private func setup() {
self.backgroundColor = .red
traverseButton.frame = CGRect(x: 0, y: 0, width: 200, height: 100)
traverseButton.setTitle("Go to Detail", for: .normal)
traverseButton.setTitleColor(.black, for: .normal)
traverseButton.isUserInteractionEnabled = true
self.addSubview(traverseButton)
traverseButton.translatesAutoresizingMaskIntoConstraints = false
traverseButton.centerXAnchor.constraint(equalTo: self.centerXAnchor).isActive = true
traverseButton.centerYAnchor.constraint(equalTo: self.centerYAnchor).isActive = true
networkButton.frame = CGRect(x: 0, y: 0, width: 200, height: 100)
networkButton.setTitle("Make Network Call", for: .normal)
networkButton.setTitleColor(.black, for: .normal)
networkButton.isUserInteractionEnabled = true
self.addSubview(networkButton)
networkButton.translatesAutoresizingMaskIntoConstraints = false
networkButton.centerXAnchor.constraint(equalTo: self.centerXAnchor).isActive = true
networkButton.centerYAnchor.constraint(equalTo: self.centerYAnchor, constant: 100).isActive = true
networkLabel.text = "No network calls made"
networkLabel.backgroundColor = .purple
self.addSubview(networkLabel)
networkLabel.translatesAutoresizingMaskIntoConstraints = false
networkLabel.centerXAnchor.constraint(equalTo: self.centerXAnchor).isActive = true
networkLabel.centerYAnchor.constraint(equalTo: self.centerYAnchor, constant: 200).isActive = true
networkLabel.widthAnchor.constraint(equalToConstant: 300).isActive = true
networkLabel.heightAnchor.constraint(equalToConstant: 100).isActive = true
}
func setNetworkLabel(text: String){
networkLabel.text = text
}
}
var initialView: InitialView?
initialView = InitialView()
let containerView = UIView(frame: CGRect(x: 10, y: 0, width: 500, height: 1000))
containerView.addSubview(initialView!)
initialView?.translatesAutoresizingMaskIntoConstraints = false
initialView?.leadingAnchor.constraint(equalTo: containerView.leadingAnchor).isActive = true
initialView?.trailingAnchor.constraint(equalTo: containerView.trailingAnchor).isActive = true
initialView?.topAnchor.constraint(equalTo: containerView.topAnchor).isActive = true
initialView?.bottomAnchor.constraint(equalTo: containerView.bottomAnchor).isActive = true

Answer 1

You have probably put the initialView?.frame line before the containerView line.
Although you have added the constraints, before Xcode playgrounds actually renders the containerView, its subviews are not laid out. That's why initialView's frame remains at its default value of (0, 0, 0, 0). If you actually manually tell containerView that it should lay out its subviews, initialView's frame will be set correctly.
There are many ways to do this:
move the line where you inspect initialView?.frame after the line where you inspect containerView
call containerView.setNeedsLayout() first
call containerView.layoutIfNeeded() first