Swift add constraint programmatically

Question

I add a UILabel (amountLabel) in UIViewController in storyboard editor. And then in swift file, viewDidLoad, I programatically create a

Answer 1

let nameLabel: UILabel = {

   let label = UILabel()
    label.translatesAutoresizingMaskIntoConstraints = false
    return label
}()

if you forgot setting this label.translatesAutoresizingMaskIntoConstraints = false or if you add subview after constraints this problem arises

Answer 2

I ran into the same problem that you described earlier. In order to make the programmatic subview, (in your case the paymentTextField) you have to add this to the subview first and then apply your constraints.

By adding the subview to view first, this ensures both views have the same parent.

Answer 3

Make sure you added the paymentTextField to your view:

paymentTextField.translatesAutoResizingMaskIntoConstraints = false
view.addSubview(paymentTextField)

...

Add your constraints, for example paymentTextField.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true

Answer 4

Checklist for this ISSUE:

• Check whether you added the programmatically created view to its parent before activating constraints
• Check whether you write constraints activation code inside viewDidLoad() / viewWillAppear(). You should write constraints activation code in updateViewConstraints or viewWillLayoutSubviews. ( suggested by vmeyer )
• Check whether you turn off translatesAutoresizingMaskIntoConstraints.

Answer 5

The error states that "because they have no common ancestor", which means that they don't share the same parent. In order to relate constraint between two items, they have to have a child-parent relationship or a sibling one.

In your case just make sure they have the same parent view before adding the constraint programmatically.