Animate view height with Swift

Question

I have view sView inside my ViewController. It height has constraint - I created IBOutlet for this constraint - sViewHeightConstraint. I want to decrease height of sView with animation.

I created function

UIView.animateWithDuration(5.5, animations: {
                self.sViewHeightConstraint.constant = 50
            })

Height of view is changing but i don't see any animation. What I am doing wrong?

Solution

use layoutIfNeeded()

 view.layoutIfNeeded() // force any pending operations to finish

 UIView.animateWithDuration(0.2, animations: { () -> Void in
    self.sViewHeightConstraint.constant = 50
    self.view.layoutIfNeeded()
})

swift 3

view.layoutIfNeeded() 
sViewHeightConstraint.constant = 50

UIView.animate(withDuration: 1.0, animations: { 
     self.view.layoutIfNeeded() 
})

Comments

[Bhavin Bhadani]

@moonvader layoutIfNeeded on the view force any pending operations to finish and then in the animation block capture the frame changes.

[Bhavin Bhadani]

for more info. check stackoverflow.com/questions/1182945/how-is-layoutifneeded-us‌​ed