Rotating a UIButton by 90 degrees every time the button is clicked

Question

How do you rotate a UIButton by 90 degrees each time the button is clicked and also keep track of each rotated position/angle?

Here is the code I have so far but it only

Answer 1

Swift 4:

@IBOutlet weak var expandButton: UIButton!

var sectionIsExpanded: Bool = true {
    didSet {
        UIView.animate(withDuration: 0.25) {
            if self.sectionIsExpanded {
                self.expandButton.transform = CGAffineTransform.identity
            } else {
                self.expandButton.transform = CGAffineTransform(rotationAngle: -CGFloat.pi / 2.0)
            }
        }
    }
}

@IBAction func expandButtonTapped(_ sender: UIButton) {
    sectionIsExpanded = !sectionIsExpanded
}