UIView Animation just work one time than it doesn't work - swift

Question

I try to do an animation for my view but if just work in first time which is isOpen = true it work but when I call my function again isOpen = false nothing changes?
Perent view is self (UIView). Child is label(UILabel).
private func expansionView(isOpen: Bool) {
if isOpen {
label.backgroundColor = .white
NSLayoutConstraint.activate([
label.centerYAnchor.constraint(equalTo: self.topAnchor),
label.leadingAnchor.constraint(equalTo: self.leadingAnchor, constant: 15),
])
UIView.animate(withDuration: 1, animations: {
self.layoutIfNeeded()
}) { (_) in
}
} else {
label.backgroundColor = .clear
NSLayoutConstraint.activate([
label.centerYAnchor.constraint(equalTo: self.centerYAnchor),
label.leadingAnchor.constraint(equalTo: self.leadingAnchor , constant: 15),
])
UIView.animate(withDuration: 1, animations: {
self.layoutIfNeeded()
}) { (_) in
print("Animation Completed!!!")
}
}
}

Answer 1

You need to have two constraints to make one of them active.
You can also animate changing label's background color to clear. And you can simplify your function like below.
// define both vertical constraints
var constraintToCenterYAnchor: NSLayoutConstraint!
var constraintToTopAnchor: NSLayoutConstraint!
// where you init your view..
init() {
// init your constraints
constraintToTopAnchor = label.centerYAnchor.constraint(equalTo: topAnchor)
constraintToCenterYAnchor = label.centerYAnchor.constraint(equalTo: centerYAnchor)
// set and activate other constraints once.
label.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 15).isActive = true
// update background color of the label
label.backgroundColor = .clear
label.layer.backgroundColor = UIColor.white.cgColor
}
// simplify your function
private func expansionView(_ isOpen: Bool) {
constraintToTopAnchor.isActive = isOpen
constraintToCenterYAnchor.isActive = !isOpen
UIView.animate(withDuration: 1) {
self.label.layer.opacity = isOpen ? 1.0 : 0.0
self.layoutIfNeeded()
}
}

Answer 2

You need to have two contraints to activate and deactivate ...
lazy var centerXConstraint = label.centerYAnchor.constraint(equalTo: self.centerYAnchor)
lazy var topConstraint = label.leadingAnchor.constraint(equalTo: self.leadingAnchor , constant: 15)
init() {
label.leadingAnchor.constraint(equalTo: self.leadingAnchor, constant: 15).isActive = true
}
private func expansionView(isOpen: Bool) {
if isOpen {
label.backgroundColor = .white
centerXConstraint.isActive = false
topConstraint.isActive = true
UIView.animate(withDuration: 1, animations: {
self.layoutIfNeeded()
}) { (_) in
}
} else {
label.backgroundColor = .clear
centerXConstraint.isActive = true
topConstraint.isActive = false
UIView.animate(withDuration: 1, animations: {
self.layoutIfNeeded()
}) { (_) in
print("Animation Completed!!!")
}
}
}