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.
I suggest you to not add constraints in viewDidLoad, because the view hierarchy is set, but not constraints.You should prefer updateViewConstraints or viewWillLayoutSubviews
Please add the view to superview before adding constraints for the view in superview.
superView?.addSubview(view)superView?.addConstraints([topConstraint,leftConstraint,bottomConstraint,rightConstraint])