Arranging buttons programmatically with constraints - ios

Question

I have an array of buttons that I am iterating through and adding the buttons onto the view. Each button should be adjacent to the previous button, so I'm setting the leading constraint to the previous button's trailing. But the buttons end up layered on top of each other with only the top one displayed.
for k in 0 ..< buttons.count {
view.addSubview(buttons[k])
if k > 0 {
buttons[k].leadingAnchor.constraint(equalTo: buttons[k-1].trailingAnchor).isActive = true
}
}
Edit:
I don't know if this is part of the problem, but here's how I'm creating the buttons. I set each to (0,0) because I don't know where they'll end up. I assume the constraint would reposition them as needed (first time use programmatic constraints).
let size = CGRect(x: 0, y: 0, width: buttonWidth, height: buttonHeight)
let button: UIButton = UIButton(frame: size)

Answer 1

Here a simple playground that works with a UIStackView. You can play a bit and accommodate for your goal.
UIStackViews are very flexible components if you want avoid creating constraints manually.
//: A UIKit based Playground for presenting user interface
import UIKit
import PlaygroundSupport
class MyViewController: UIViewController {
override func loadView() {
let view = UIView()
view.backgroundColor = .white
let buttons = createButtons()
let stackView = createStackView(with: UILayoutConstraintAxis.vertical)
buttons.forEach { button in
stackView.addArrangedSubview(button)
}
view.addSubview(stackView)
stackView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
stackView.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
self.view = view
}
func createStackView(with layout: UILayoutConstraintAxis) -> UIStackView {
let stackView = UIStackView()
stackView.translatesAutoresizingMaskIntoConstraints = false
stackView.axis = layout
stackView.distribution = .equalSpacing
stackView.spacing = 0
return stackView
}
func createButtons() -> [UIButton] {
var buttons = [UIButton]()
for x in 0..<5 {
let button = UIButton(type: .custom)
button.backgroundColor = .red
button.translatesAutoresizingMaskIntoConstraints = false
button.widthAnchor.constraint(equalToConstant: 50).isActive = true
button.heightAnchor.constraint(equalToConstant: 100).isActive = true
button.setTitle("Title \(x)", for: .normal)
buttons.append(button)
}
return buttons
}
}
// Present the view controller in the Live View window
PlaygroundPage.current.liveView = MyViewController()

Answer 2

The key problem is you should use isActive to active constraint.
The following is example
var buttons: [UIButton] = []
for index in 0...5 {
let button = UIButton(frame: .zero)
button.setTitleColor(.black, for: .normal)
button.setTitle("button \(index)", for: .normal)
button.layer.borderColor = UIColor.gray.cgColor
button.layer.borderWidth = 1.0
button.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(button)
buttons.append(button)
}
for index in 0...5 {
let button = buttons[index]
if index == 0 {
button.leadingAnchor.constraint(equalTo: self.view.leadingAnchor, constant: 8.0).isActive = true
button.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 20.0).isActive = true
} else {
let preButton = buttons[index - 1]
button.leadingAnchor.constraint(equalTo: preButton.trailingAnchor, constant: 8.0).isActive = true
button.topAnchor.constraint(equalTo: preButton.topAnchor, constant: 0.0).isActive = true
}
}