Unable to satisfy Bottom Constraint of UILabel to ContentView of Dynamic UITableViewCell - ios

Question

All implementations done programmatically(No Storyboards!).
I have created dynamic tableView with UITableView.automaticDimension with all custom Cells. All Cells are working fine and this one too but this one is generating Constraint warnings in debug.
Though, the layout is perfect and displaying as it should.
It has just one label and 3 CAShapeLayers. Below is the implementation Code:
//BadCustomTableViewCell
override func layoutSubviews() {
super.layoutSubviews()
setUpViews()
setUpConstraints()
}
let badLabel:UILabel = {
let label = UILabel()
label.font = UIFont.systemFont(ofSize: 40, weight: UIFont.Weight.light)
label.text = "899"
label.textColor = .black
label.textAlignment = .center
label.translatesAutoresizingMaskIntoConstraints = false
return label
}()
func setUpViews() {
contentView.addSubview(badLabel)
}
func setUpConstraints() {
badLabel.centerXAnchor.constraint(equalTo: contentView.centerXAnchor).isActive = true
badLabel.layoutIfNeeded()
let safeMargin:CGFloat = badLabel.frame.size.width - 15
badLabel.topAnchor.constraint(equalTo: contentView.topAnchor, constant: safeMargin).isActive = true
badLabel.bottomAnchor.constraint(equalTo: contentView.bottomAnchor, constant: -safeMargin).isActive = true
}
Everything is fine according to me, but I don't what's breaking the constraints!
The log shows this -
(
"<NSLayoutConstraint:0x282729720 V:|-(77.6667)-[UILabel:0x103179a60'65.89 %'] (active, names: '|':UITableViewCellContentView:0x10317a150 )>",
"<NSLayoutConstraint:0x282729950 UILabel:0x103179a60'65.89 %'.bottom == UITableViewCellContentView:0x10317a150.bottom - 77.6667 (active)>",
"<NSLayoutConstraint:0x2827297c0 'UIView-Encapsulated-Layout-Height' UITableViewCellContentView:0x10317a150.height == 48.6667 (active)>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x282729950 UILabel:0x103179a60'65.89 %'.bottom == UITableViewCellContentView:0x10317a150.bottom - 77.6667 (active)>
Any Idea what I might be missing here?

Answer 1

Lower the bottom constraint
let con = badLabel.bottomAnchor.constraint(equalTo: contentView.bottomAnchor, constant: -safeMargin)
con.priority = UILayoutPriority(999)
con.isActive = true
and add the setup & constraints inside
override init(style: UITableViewCell.CellStyle,reuseIdentifier: String?)
as
override func layoutSubviews()
is called multiple times
`

Answer 2

Although it is quite late, I'm posting this answer anyway. Most of the times, you don't need to re-setup your constraints and re-add your subviews to your super/parent view. So your setUpViews() and setUpConstraints() should be indeed inside override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) like so:
override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
super.init(style: style, reuseIdentifier: reuseIdentifier)
setUpViews()
setUpConstraints()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
Also, you don't need (most of the times, again), at least for me, to setup priorities to your constraints. As much as possible, solve the constraints issues/warnings without lowering priorities.
badLabel.layoutIfNeeded() isn't needed too, unless you're actually modifying some constants of your constraints or re-making your constraint. Well it makes sense to use such line if you REALLY want to setup everything in your layoutSubviews()
This whole class similar to your cell worked for me:
class BadCustomTableViewCell: UITableViewCell {
override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
super.init(style: style, reuseIdentifier: reuseIdentifier)
setUpViews()
setUpConstraints()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
let badLabel:UILabel = {
let label = UILabel()
label.font = UIFont.systemFont(ofSize: 40, weight: UIFont.Weight.light)
label.text = "899"
label.textColor = .black
label.textAlignment = .center
label.translatesAutoresizingMaskIntoConstraints = false
return label
}()
func setUpViews() {
contentView.addSubview(badLabel)
}
func setUpConstraints() {
badLabel.centerXAnchor.constraint(equalTo: contentView.centerXAnchor).isActive = true
let safeMargin:CGFloat = badLabel.frame.size.width - 15
badLabel.topAnchor.constraint(equalTo: contentView.topAnchor, constant: -safeMargin).isActive = true
badLabel.bottomAnchor.constraint(equalTo: contentView.bottomAnchor, constant: safeMargin).isActive = true
}
}