Updating constraints in swift 5 - swift

Question

I have tried deactivating and reactivating... However I cannot seem to find out how to do it... I have code to use as an example but it keeps failing me, if anyone knows how to update a constraint in swift 5 please let me know... I know that the updateConstraint() exists just not sure how to use it.
let constraint1: NSLayoutConstraint? = text.bottomAnchor.constraint(equalTo: view.bottomAnchor)
let constraint2: NSLayoutConstraint? = text.bottomAnchor.constraint (equalTo: view.bottomAnchor, constant: 5)
if acondition {
constraint1?.isActive = false
constraint2.isActive = true
} else {
constraint2.isActive = false
constraint1.isActive = true
}

Answer 1

first declare the variable, after set start constraints variable to true and after call a function that active and dis active constraints, try with my example:
under controller class declare a button and a view do you want to move:
let dummyView = UIView()
let button = UIButton(type: .system)
after declare variable to move your view with constraint:
var up: NSLayoutConstraint?
var down: NSLayoutConstraint?
in ViewDiLoad set the view, the button and the constraints like this:
dummyView.backgroundColor = .yellow
dummyView.translatesAutoresizingMaskIntoConstraints = false
button.setTitle("viewDiwn", for: .normal)
button.backgroundColor = .red
button.setTitleColor(.white, for: .normal)
button.titleLabel?.font = .systemFont(ofSize: 16)
button.addTarget(self, action: #selector(handletapButton), for: .touchUpInside)// button action that call handletapButton func
button.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(dummyView)
up = dummyView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor)
up?.isActive = true // start constraint active
down = dummyView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 100) // constraint to activate for move the view
dummyView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
dummyView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
dummyView.heightAnchor.constraint(equalToConstant: 50).isActive = true
view.addSubview(button)
button.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
button.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
button.heightAnchor.constraint(equalToConstant: 50).isActive = true
button.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor).isActive = true
now write the function to move the view by constraint animation:
#objc func handletapButton() {
UIView.animate(withDuration: 0.5, delay: 0, options: .curveEaseOut, animations: {
self.up?.isActive = false
self.down?.isActive = true
self.view.layoutIfNeeded()
}, completion: nil)
}
this is the result

Answer 2

Probably you can check your #properties and replace weak with strong. Reason is, isActive = false will set self.yourConstraint = nil, hence you wouldn't be able to use self.yourConstraint again.