NSLayoutConstraints to limit label width - ios

Question

I am struggling to set the necessary constraints to limit the width of a label to the leading anchor of a button in a tableview cell.
Desired Result
Label to the left, button to the right. Label wraps before button if needed.
Current Result
The label is pulling the red button to the left.
Code
[button.centerYAnchor constraintEqualToAnchor:cell.contentView.centerYAnchor constant:0].active = YES;
[button.trailingAnchor constraintEqualToAnchor:cell.contentView.trailingAnchor constant:-5].active = YES;
[label.leadingAnchor constraintEqualToAnchor:cell.contentView.leadingAnchor constant:10].active = YES;
[label.trailingAnchor constraintEqualToAnchor:button.leadingAnchor constant:0].active = YES;
I have tried various things like adding another label constraint to the right of the cell but that squeezed the button (I tried to fix by setting its compression resistance priority but that had no effect)
What constraints do I need to achieve the desired result please?

Answer 1

Just change
[label.trailingAnchor constraintEqualToAnchor:button.leadingAnchor constant:0].active = YES;
into
[label.trailingAnchor constraintLessThanOrEqualToAnchor:button.leadingAnchor constant:0].active = YES;
import UIKit
final class ViewController: UIViewController {
lazy var tableView: UITableView = {
let val = UITableView(frame: self.view.bounds, style: .plain)
val.dataSource = self
val.delegate = self
val.estimatedRowHeight = 44
val.register(MyCell.self, forCellReuseIdentifier: "MyCell")
return val
}()
let data: [String] = [
"LayoutDemo",
"LayoutDemo LayoutDemo LayoutDemo LayoutDemo LayoutDemo LayoutDemo LayoutDemo LayoutDemo LayoutDemo LayoutDemo LayoutDemo LayoutDemo",
"LayoutDemoLayoutDemoLayoutDemoLayoutDemo"
]
override func viewDidLoad() {
super.viewDidLoad()
view.addSubview(tableView)
}
}
extension ViewController: UITableViewDataSource {
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
data.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
guard let cell = tableView.dequeueReusableCell(withIdentifier: "MyCell", for: indexPath) as? MyCell else { fatalError() }
cell.dataText = data[indexPath.row]
return cell
}
}
extension ViewController: UITableViewDelegate {
func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
return UITableView.automaticDimension
}
}
class MyCell: UITableViewCell {
var dataText: String? {
didSet {
label.text = dataText
}
}
lazy var label: UILabel = {
let val = UILabel(frame: .zero)
val.translatesAutoresizingMaskIntoConstraints = false
val.numberOfLines = 0
val.backgroundColor = .gray
return val
}()
lazy var button: UIButton = {
let val = UIButton(type: .custom)
val.translatesAutoresizingMaskIntoConstraints = false
val.backgroundColor = .red
return val
}()
override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
super.init(style: style, reuseIdentifier: reuseIdentifier)
contentView.addSubview(label)
contentView.addSubview(button)
NSLayoutConstraint.activate([
button.centerYAnchor.constraint(equalTo: contentView.centerYAnchor),
button.trailingAnchor.constraint(equalTo: contentView.trailingAnchor, constant: -5),
button.heightAnchor.constraint(equalToConstant: 20),
button.widthAnchor.constraint(equalToConstant: 20),
label.topAnchor.constraint(equalTo: contentView.topAnchor, constant: 5),
label.bottomAnchor.constraint(equalTo: contentView.bottomAnchor, constant: -5),
label.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 10),
label.trailingAnchor.constraint(lessThanOrEqualTo: button.leadingAnchor, constant: -10)
])
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}