trying to animate a constraint in swift

I have a UITextField that I want to enlarge its width when tapped on. I set up the constraints and made sure the constraint on the left has the lower priority then the one that I am trying to animate on the right side.

Here is the code that I am trying to use.

// move the input box
UIView.animateWithDuration(10.5, animations: {
    self.nameInputConstraint.constant = 8
    }, completion: {
        (value: Bool) in
        println(">>> move const")
})

This works, but it seems to just happen instantly and there doesn't seem to be any movement. I tried to set it 10 seconds to make sure I wasn't missing anything, but I got the same results.

nameInputConstraint is the name of the constraint that I control dragged to connect into my class from IB.

Solution 1:

You need to first change the constraint and then animate the update.
This should be in the superview.

self.nameInputConstraint.constant = 8

Swift 2

UIView.animateWithDuration(0.5) {
    self.view.layoutIfNeeded()
}

Swift 3, 4, 5

UIView.animate(withDuration: 0.5) {
    self.view.layoutIfNeeded()
}

Solution 2:

SWIFT 4 and above:

self.mConstraint.constant = 100.0
UIView.animate(withDuration: 0.3) {
        self.view.layoutIfNeeded()
}

Example with completion:

self.mConstraint.constant = 100
UIView.animate(withDuration: 0.3, animations: {
        self.view.layoutIfNeeded()
    }, completion: {res in
        //Do something
})

Solution 3:

It's very important to point out that view.layoutIfNeeded() applies to the view subviews only.

Therefore to animate the view constraint, it is important to call it on the view-to-animate superview as follows:

    topConstraint.constant = heightShift

    UIView.animate(withDuration: 0.3) {

        // request layout on the *superview*
        self.view.superview?.layoutIfNeeded()
    }

An example for a simple layout as follows:

class MyClass {

    /// Container view
    let container = UIView()
        /// View attached to container
        let view = UIView()

    /// Top constraint to animate
    var topConstraint = NSLayoutConstraint()


    /// Create the UI hierarchy and constraints
    func createUI() {
        container.addSubview(view)

        // Create the top constraint
        topConstraint = view.topAnchor.constraint(equalTo: container.topAnchor, constant: 0)


        view.translatesAutoresizingMaskIntoConstraints = false

        // Activate constaint(s)
        NSLayoutConstraint.activate([
           topConstraint,
        ])
    }

    /// Update view constraint with animation
    func updateConstraint(heightShift: CGFloat) {
        topConstraint.constant = heightShift

        UIView.animate(withDuration: 0.3) {

            // request layout on the *superview*
            self.view.superview?.layoutIfNeeded()
        }
    }
}