addSubview doesn't work in UIView - Swift Programmatically - ios

Question

I need to add a UIButton as a subview on a UIView but it actually doesn't appear at runtime.
This is my code:
let moreButton : UIButton = {
let button = UIButton()
button.setImage(#imageLiteral(resourceName: "more"), for: .normal)
button.translatesAutoresizingMaskIntoConstraints = false
return button
}()
override init(frame: CGRect) {
super.init(frame: frame)
addSubview(moreButton)
moreButton.trailingAnchor.constraint(equalTo: self.trailingAnchor).isActive = true
moreButton.topAnchor.constraint(equalTo: self.topAnchor).isActive = true
moreButton.heightAnchor.constraint(equalToConstant: 30).isActive = true
moreButton.widthAnchor.constraint(equalToConstant: 20).isActive = true
}
The button isn't added eventually to the view. I'm sure this is an easy fix but I can't wrap my head around it.

Answer 1

First of all, make sure you the viewController is showing anything since you're doing it without storyboards, check out this simple tutorial:
https://medium.com/better-programming/creating-a-project-without-storyboard-in-2020-and-without-swifui-82080eb6d13b
If the problem is with that UIButton, try to set up the subviews in viewDidLoad:
final class ViewController: UIViewController {
let cardView = CardView()
override func viewDidLoad() {
super.viewDidLoad()
view.addSubview(cardView)
/// Constraints
let margins = view.layoutMarginsGuide
cardView.trailingAnchor.constraint(equalTo: margins.trailingAnchor).isActive = true
cardView.leadingAnchor.constraint(equalTo: margins.leadingAnchor).isActive = true
cardView.topAnchor.constraint(equalTo: margins.topAnchor).isActive = true
cardView.heightAnchor.constraint(equalToConstant: 30).isActive = true
cardView.widthAnchor.constraint(equalToConstant: 20).isActive = true
}
}
final class CardView: UIView {
let moreButton : UIButton = {
let button = UIButton()
button.setTitle("Button title", for: .normal)
button.translatesAutoresizingMaskIntoConstraints = false
return button
}()
required init(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)!
}
override init(frame: CGRect) {
super.init(frame:frame)
self.translatesAutoresizingMaskIntoConstraints = false
self.addSubview(moreButton)
/// Constraints
let margins = self.layoutMarginsGuide
moreButton.trailingAnchor.constraint(equalTo: margins.trailingAnchor).isActive = true
moreButton.leadingAnchor.constraint(equalTo: margins.leadingAnchor).isActive = true
moreButton.topAnchor.constraint(equalTo: margins.topAnchor).isActive = true
moreButton.heightAnchor.constraint(equalToConstant: 30).isActive = true
moreButton.widthAnchor.constraint(equalToConstant: 20).isActive = true
}
}
I've set up margins for the constraints and also added a leadingAnchor constraint, that might have been the issue as well.