I\'m trying to figure this out since last week without going any step further. Ok, so I need to apply some constraints programmatically
The error is caused by constrains automatically created from autoresizing mask, they are created because UIView property translatesAutoresizingMaskIntoConstraints is true by default.
Consider using BoxView to get rid of all manual constraint creation boilerplate, and make your code concize and readable. To make layout in question with BoxView is very easy:
boxView.items = [
new_view.boxed.centerX().centerY().relativeWidth(1.0).relativeHeight(1.0)
]