Calcul height of uiview after animating this one - ios

Question

I have an animation who modify the constraint of an UIView and i need to know the size of this UIView after animate this, but before the animation begin...
storyboard
When the user scroll the UITableView I update the heightConstraint of the black UIView, I need the height after update the UIView because i need in the function viewDidLayoutSubviews to fixe the height of the Yellow UIview.
this is the code I use for animate the UIView:
self.headerIsCollapsed = true
self.heightProfilView.constant -= (self.view.bounds.height / 5)
UIView.animate(withDuration: 0.3, animations: {
self.view.layoutIfNeeded()
self.imageUserProfil.layer.opacity = 0
})
and i need the value here :
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
heightTopBar.constant = // here i need the height of the UIView after animating this
}
So, the question is: How I can pre-calculate the height of the UIView after animating this ?

Answer 1

Simply use a completion block of UIView.animate()
UIView.animate(withDuration: 0.3, animations: {
self.view.layoutIfNeeded()
self.imageUserProfil.layer.opacity = 0
}) { (finished) in
// get the view's height after animation here
}
Unless you specified duration as 0, the completion block will execute after animation sequence ends.

Answer 2

Try this:
self.headerIsCollapsed = true
//create this property at instance level in your viewcontroller class
self.heightBeforeAnimation = self.heightProfileView.frame.size.height
self.heightProfilView.constant -= (self.view.bounds.height / 5)
UIView.animate(withDuration: 0.3, animations: {
self.view.layoutIfNeeded()
self.imageUserProfil.layer.opacity = 0
}){ (isCompleted) in
//create this property at instance level in your viewcontroller class
self.heightAfterAnimation = self.heightProfileView.frame.size.height
}
and call whatever function and use the value of two variables containing value of height before and after animating your view.