Cesare Cesare - 5 months ago 8
Swift Question

How to update the constant of a constraint programmatically in Swift?

I want to animate an object, so I declare a constraint and add it to the view. I then update the

constant
property of the constraint inside a standard animation. Why doesn't this code move the object?

UIView.animateWithDuration(1, animations: {
myConstraint.constant = 0
self.view.updateConstraints(myConstraint)
})

Answer

In order to declare an animation, you cannot re-define the constraint and call updateConstraints. You are supposed to change the constant of your constraint and follow the format below:

self.view.layoutIfNeeded()
UIView.animateWithDuration(1, animations: {
    self.sampleConstraint.constant = 20
    self.view.layoutIfNeeded()
})
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