Swift iOS -Constraint isn't animating even though view.layoutIfNeeded() is called - ios

Question

I have a rounded likeButton that is behind a rounded moreButton. The likeButton is pinned to the centerX and centerY of the moreButton. When I press the moreButton I want to animate the likeButton 200 points above the moreButton.
I use a NSLayoutConstraint to keep track of the likeButton's centerY and to make changes to it. When I call UIView.animate and inside it's closure I call self.view.layoutIfNeeded() the view isn't updating.
#objc func moreButtonTapped(){
likeButtonCenterY?.isActive = false
likeButton.centerYAnchor.constraint(equalTo: self.moreButton.centerYAnchor, constant: -200)
likeButtonCenterY?.isActive = true
UIView.animate(withDuration: 0.3) {
self.view.layoutIfNeeded()
}
}
Where am I going wrong?
let moreButton: UIButton = {
let button = UIButton(type: .system)
button.translatesAutoresizingMaskIntoConstraints = false
button.setImage(UIImage(named: "more"), for: .normal)
button.tintColor = .red
button.clipsToBounds = true
button.addTarget(self, action: #selector(moreButtonTapped), for: .touchUpInside)
return button
}()
let likeButton: UIButton = {
let button = UIButton(type: .system)
button.translatesAutoresizingMaskIntoConstraints = false
button.setImage(UIImage(named: "like"), for: .normal)
button.tintColor = .blue
button.clipsToBounds = true
return button
}()
var likeButtonCenterY: NSLayoutConstraint?
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .white
setAnchors()
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
moreButton.layer.cornerRadius = moreButton.frame.size.width / 2
likeButton.layer.cornerRadius = likeButton.frame.size.width / 2
}
#objc func moreButtonTapped(){
likeButtonCenterY?.isActive = false
likeButton.centerYAnchor.constraint(equalTo: self.moreButton.centerYAnchor, constant: -200)
likeButtonCenterY?.isActive = true
UIView.animate(withDuration: 0.3) {
self.view.layoutIfNeeded()
}
}
func setAnchors(){
view.addSubview(likeButton)
view.addSubview(moreButton)
moreButton.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
moreButton.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -200).isActive = true
moreButton.widthAnchor.constraint(equalToConstant: 100).isActive = true
moreButton.heightAnchor.constraint(equalToConstant: 100).isActive = true
likeButtonCenterY = likeButton.centerYAnchor.constraint(equalTo: moreButton.centerYAnchor)
likeButtonCenterY?.isActive = true
likeButton.centerXAnchor.constraint(equalTo: moreButton.centerXAnchor).isActive = true
likeButton.widthAnchor.constraint(equalToConstant: 100).isActive = true
likeButton.heightAnchor.constraint(equalToConstant: 100).isActive = true
}

Answer 1

Try this
#objc func moreButtonTapped(){
likeButtonCenterY?.isActive = false
likeButtonCenterY = likeButton.centerYAnchor.constraint(equalTo: self.moreButton.centerYAnchor, constant: -200)
likeButtonCenterY?.isActive = true
UIView.animate(withDuration: 0.3) {
self.view.layoutIfNeeded()
}
}
You have forgotten to write likeButtonCenterY =

Answer 2

If you are activating/deactivating multiple constraints at the same time (like a batch), you might need to override the updateConstraints() method. More information is here: https://developer.apple.com/documentation/uikit/uiview/1622512-updateconstraints
Basically your code in the moreButtonTapped() will go in the overridden implementation of the updateConstraints() method. Don't forget to call super() in the last line of the method.
Then your animation code should look like look like:
UIView.animate(withDuration: 0.3) {
self.view.setNeedsUpdateConstraints()
self.view.layoutIfNeeded()
})