Swift - UIButton overriding setSelected
32,670
Solution 1
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:
- Overriding a property for
willSet/didSet
still calls super forget/set
. You can tell because the state changes from.normal
to.selected
. - 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 eithernewValue
inwillSet
oroldValue
indidSet
to determine whether or not to animate.
import UIKit
class 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 == .normal
button.isSelected = true // Both events fire on change.
button.state == .selected
button.isSelected = true // Both events still fire.
Solution 2
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...
}
}
// ...
}
Author by
LorTush
Updated on June 21, 2020Comments
-
LorTush almost 4 years
I'm making a UIButton subclass in Swift to perform custom drawing and animation on selection
What would be the equivalent in Swift of overriding
- (void)setSelected:(BOOL)selected
in ObjC?I tried
override var selected: Bool
so I could implement an observer but I get
Cannot override with a stored property 'selected'