Add NSLayoutConstraint for a view inside a UITableCellView - ios

Question

I would like to have a UIButton centred inside my UITableCellView. I've added the necessary code in the tableView cellForRowAt function but I get the error :
The view hierarchy is not prepared for the constraint: When added to a view, the constraint's items must be descendants of that view (or the view itself). This will crash if the constraint needs to be resolved before the view hierarchy is assembled. Break on
-[UIView(UIConstraintBasedLayout) _viewHierarchyUnpreparedForConstraint:] to debug.
My code is the following :
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
cell = UITableViewCell(
style: .default, reuseIdentifier: Id.settingButtonCellIdentifier)
cell!.backgroundColor = UIColor.clear
cell!.preservesSuperviewLayoutMargins = false
cell!.separatorInset = UIEdgeInsets.zero
let button : UIButton = UIButton(type: UIButtonType.custom) as UIButton
button.backgroundColor = UIColor.red
button.setTitle("Click Me !", for: UIControlState.normal)
cell!.addSubview(button)
button.translatesAutoresizingMaskIntoConstraints = false
button.addConstraint(NSLayoutConstraint(item: button, attribute: .leading, relatedBy: .equal, toItem: cell!, attribute: .leading, multiplier: 1, constant: 10))
button.addConstraint(NSLayoutConstraint(item: button, attribute: .trailing, relatedBy: .equal, toItem: cell!, attribute: .trailing, multiplier: 1, constant: 10))
button.addConstraint(NSLayoutConstraint(item: button, attribute: .top, relatedBy: .equal, toItem: cell!, attribute: .top, multiplier: 1, constant: 10))
button.addConstraint(NSLayoutConstraint(item: button, attribute: .bottom, relatedBy: .equal, toItem: cell!, attribute: .bottom, multiplier: 1, constant: 10))
}
return cell!
}
Any help would be appreciated !

Answer 1

Try this
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
cell = UITableViewCell(
style: .default, reuseIdentifier: Id.settingButtonCellIdentifier)
cell!.backgroundColor = UIColor.clear
cell!.preservesSuperviewLayoutMargins = false
cell!.separatorInset = UIEdgeInsets.zero
let button : UIButton = UIButton(type: UIButtonType.custom) as UIButton
button.backgroundColor = UIColor.red
button.setTitle("Click Me !", for: UIControlState.normal)
button.translatesAutoresizingMaskIntoConstraints = false
cell!.contentView.addSubview(button)
cell.contentView.addConstraint(NSLayoutConstraint(item: button, attribute: .leading, relatedBy: .equal, toItem: cell.contentView, attribute: .leading, multiplier: 1, constant: 10))
cell.contentView.addConstraint(NSLayoutConstraint(item: button, attribute: .trailing, relatedBy: .equal, toItem: cell.contentView, attribute: .trailing, multiplier: 1, constant: 10))
cell.contentView.addConstraint(NSLayoutConstraint(item: button, attribute: .top, relatedBy: .equal, toItem: cell.contentView, attribute: .top, multiplier: 1, constant: 10))
cell.contentView.addConstraint(NSLayoutConstraint(item: button, attribute: .bottom, relatedBy: .equal, toItem: cell.contentView, attribute: .bottom, multiplier: 1, constant: 10))
}
return cell!
}