Swift - UIButton overriding setSelected

Like others mentioned you can use willSet to detect changes. In an override, however, you do not need assign the value to super, you are just observing the existing change.

A couple things you can observe from the following playground:

1. Overriding a property for willSet/didSet still calls super for get/set. You can tell because the state changes from .normal to .selected.
2. willSet and didSet are called even when the value is not changing, so you will probably want do the compare the value of selected to either newValue in willSet or oldValue in didSet to determine whether or not to animate.

import UIKitclass MyButton : UIButton {    override var isSelected: Bool {        willSet {            print("changing from \(isSelected) to \(newValue)")        }        didSet {            print("changed from \(oldValue) to \(isSelected)")        }    }}let button = MyButton()button.state == .normalbutton.isSelected = true // Both events fire on change.button.state == .selectedbutton.isSelected = true // Both events still fire.

you'd do it like e.g. this:

class MyButton : UIButton {    // ...    override var isSelected: Bool {        willSet(newValue) {            super.isSelected = newValue;            // do your own business here...        }    }    // ...}

try this

override public var selected: Bool {    willSet(selectedValue) {        self.selected = selectedValue        // Do whatever you want    }}