ios - UIView.animateWithDuration swift loop animation

Question

In ViewController.Swift I managed to make a box animate from one point to another. I thought it would be easy to loop this so the box will animate to one point and then animate back to its original position and then loop again. I have managed to move the object to a position and in "complete" move it back again, but that doesn't make i loop. How can this be achieved?

I thought maybe this could work but i honestly don't know:

let boxmoves = [CGRect(x: 120, y: 220, width: 100, height: 100), CGRect(x: 120, y: 120, width: 100, height: 100)]
for boxmove in boxmoves {
    coloredSquare.frame = boxmove
}

How could I center it based on the device-width (I assume there are some math involved?)?

My code:

let coloredSquare = UIView()

coloredSquare.backgroundColor = UIColor.blueColor()

coloredSquare.frame = CGRect(x: 120, y: 120, width: 100, height: 100)

self.view.addSubview(coloredSquare)

// found repeate but this will not animate as I want.
//UIView.animateWithDuration(2.0, delay: 0.2, options: UIViewAnimationOptions.Repeat, animations: {
UIView.animateWithDuration(2.0, animations: {

    coloredSquare.frame = CGRect(x: 120, y: 220, width: 100, height: 100)

    }, completion: { finished in
        UIView.animateWithDuration(2.0, animations: {
        coloredSquare.frame = CGRect(x: 120, y: 120, width: 100, height: 100)
        })
})

Answer 1

No need to do the completion block approach, just use the animation options argument:

updated for Swift 3.0

UIView.animate(withDuration: 2.0, delay: 0, options: [.repeat, .autoreverse], animations: {

    coloredSquare.frame = CGRect(x: 120, y: 220, width: 100, height: 100)

}, completion: nil)

If for any reason you want to stop the animation later, just use:

coloredSquare.layer.removeAllAnimations()