How to update the constant height constraint of a UIView programmatically?

Question

I have a UIView and I set the constraints using Xcode Interface Builder.

Now I need to update that UIView instance\'s height constant progra

Answer 1

To update a layout constraint you only need to update the constant property and call layoutIfNeeded after.

myConstraint.constant = newValue
myView.layoutIfNeeded()

Answer 2

If the above method does not work then make sure you update it in Dispatch.main.async{} block. You do not need to call layoutIfNeeded() method then.

Answer 3

If you have a view with multiple constrains, a much easier way without having to create multiple outlets would be:

In interface builder, give each constraint you wish to modify an identifier:

Then in code you can modify multiple constraints like so:

for constraint in self.view.constraints {
    if constraint.identifier == "myConstraint" {
       constraint.constant = 50
    }
}
myView.layoutIfNeeded()

You can give multiple constrains the same identifier thus allowing you to group together constrains and modify all at once.

Answer 4

Drag the constraint into your VC as an IBOutlet. Then you can change its associated value (and other properties; check the documentation):

@IBOutlet myConstraint : NSLayoutConstraint!
@IBOutlet myView : UIView!

func updateConstraints() {
    // You should handle UI updates on the main queue, whenever possible
    DispatchQueue.main.async {
        self.myConstraint.constant = 10
        self.myView.layoutIfNeeded()
    }
}

Answer 5

Create an IBOutlet of NSLayoutConstraint of yourView and update the constant value accordingly the condition specifies.

//Connect them from Interface 
@IBOutlet viewHeight: NSLayoutConstraint! 
@IBOutlet view: UIView!

private func updateViewHeight(height:Int){
   guard let aView = view, aViewHeight = viewHeight else{
      return
   }
   aViewHeight.constant = height
   aView.layoutIfNeeded()
}

Answer 6

You can update your constraint with a smooth animation if you want, see the chunk of code below:

heightOrWidthConstraint.constant = 100
UIView.animate(withDuration: animateTime, animations:{
self.view.layoutIfNeeded()
})