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

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.