如何将视图高度设置为等于其宽度

Question

I created a UIView, then I added a constrain on the uiview that its width is equal to its superview width. Then I want to make this uiview's height to be equal to it's width. I don't know how to add this kind of constrain. I can see that I can add a height constrain on this view but how to set its value to be equal to its width?

Answer 1

Add the Aspect Ratio constraint to your view

Answer 2

Try this:

yourView.translatesAutoresizingMaskIntoConstraints = false
yourView.addConstraint(NSLayoutConstraint(item: yourView, attribute: .Height, relatedBy: .Equal, toItem: yourView, attribute: .Equal, multiplier: 1, constant: yourWidthHere))

Or you can drag IBOutlet of your Width Constraint and Height Constraint to your ViewController:

@IBOutlet weak var heightConstraint: NSLayoutConstraint!
@IBOutlet weak var widthConstraint: NSLayoutConstraint!

and set the height equal to width:

heightConstraint.constant = widthConstraint.constant

Answer 3

you can set a view height to be equal to its width either from storyboard or programmatically for this you need to add the aspect ratio constraint on a view with multiplier 1.

From storyboard you can add the aspect ratio constraint with the help of Pin Tools in storyboard

By programmatically you can try below code, It is working fine.

override func viewDidLoad() {
    super.viewDidLoad()

    let myView = UIView()
    myView.backgroundColor = UIColor.redColor()
    self.view.addSubview(myView)
    myView.translatesAutoresizingMaskIntoConstraints = false

    // here I'm setting the CenterX & CenterY constraint equal to its superview CenterX & CenterY
    view.addConstraint(NSLayoutConstraint(item: myView, attribute: .CenterX, relatedBy: .Equal, toItem: view, attribute: .CenterX, multiplier: 1, constant: 0))
    view.addConstraint(NSLayoutConstraint(item: myView, attribute: .CenterY, relatedBy: .Equal, toItem: view, attribute: .CenterY, multiplier: 1, constant: 0))

    // here I'm setting the width constraint equal to its superview width
    view.addConstraint(NSLayoutConstraint(item: myView, attribute: .Width, relatedBy: .Equal, toItem: view, attribute: .Width, multiplier: 1, constant: 0))

    // here I'm setting the aspect ratio constraint to equal width or height of myView
    // since  aspect ratio constraint belongs to self width or height so add this constraints it self(i.e. myView) but not in its superView
    myView.addConstraint(NSLayoutConstraint(item : myView, attribute: .Width, relatedBy: .Equal, toItem: myView, attribute: .Height, multiplier: 1, constant: 0))
}