You need to first change the constraint and then animate the update.
This should be in the superview.
self.nameInputConstraint.constant = 8
Swift 2
UIView.animateWithDuration(0.5) {
self.view.layoutIfNeeded()
}
Swift 3, 4, 5
UIView.animate(withDuration: 0.5) {
self.view.layoutIfNeeded()
}