Getting Exception: “Impossible to set up layout with view hierarchy unprepared for constraint”

Try adding passwordTextField to its superview before binding any constraints to it.

UPD (thanks @vmeyer and @MacMark): please notice that it’s safer to add constraints not in viewDidLoad or viewWillAppear/viewDidAppear but in updateViewConstraints or viewWillLayoutSubviews since the view hierarchy might be unprepared for this operation.