How to set a constraint using percentage?

Question

Just a very direct question, but we had spent many hours trying to find a working solution but faild.

In Xcode, storyboard, how to set a constraint so one view can be located 30% of total window height from the top of the superview? And we need it to be that way for ALL supported iOS devices of all orientations.

Please see my illustration attached.

Answer 1

I demonstrate this below - you just have to change the value of multiplier.

Answer 2

Update

Sorry, I have misunderstood your problem.

You'll need to add the constraints from code like so (the xConstraint is totally arbitrary, but you must need to define x, y positions, width and height, for an unambiguous layout):

@IBOutlet weak var imageView: UIImageView!      override func viewDidLayoutSubviews() {         super.viewDidLayoutSubviews()          let yConstraint = NSLayoutConstraint(item: imageView, attribute: .Top, relatedBy: .Equal, toItem: view, attribute: .Top, multiplier: 1, constant: view.bounds.height / 3)          let xConstraint = NSLayoutConstraint(item: imageView, attribute: .Leading, relatedBy: .Equal, toItem: view, attribute: .Leading, multiplier: 1, constant: 30)          NSLayoutConstraint.activateConstraints([yConstraint, xConstraint])     } 

This way, the equation will be:

imageView.top = 1 * view.top + (view.width / 3) 

Original answer

Auto Layout uses the following equation for constraints:

aView.property = Multiplier * bView.property + Constant 

Based on this, you can simply add an equal width/height constraint, then add a multiplier:

So the equation will be:

view.height = 0.3 * superView.height + 0