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Swift3 UIControl extension for adding block event listeners. Adapted from: https://stackoverflow.com/a/44917661/44639
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import Foundation | |
import UIKit | |
extension UIControl { | |
func listen(_ action: @escaping () -> (), for controlEvents: UIControlEvents) -> AnyObject { | |
let sleeve = ClosureSleeve(attachTo: self, closure: action, controlEvents: controlEvents) | |
addTarget(sleeve, action: #selector(ClosureSleeve.invoke), for: controlEvents) | |
return sleeve | |
} | |
func listenOnce(_ action: @escaping () -> (), for controlEvents: UIControlEvents) { | |
let sleeve = ClosureSleeve(attachTo: self, closure: action, controlEvents: controlEvents) | |
addTarget(sleeve, action: #selector(ClosureSleeve.invokeOnce), for: controlEvents) | |
} | |
func unlisten(sleeve: AnyObject) { | |
guard let sleeve = sleeve as? ClosureSleeve else { return } | |
self.removeTarget(sleeve, action: #selector(ClosureSleeve.invoke), for: sleeve.controlEvents) | |
} | |
} | |
private class ClosureSleeve { | |
let closure: () -> () | |
let controlEvents:UIControlEvents | |
let attachedTo: AnyObject | |
init(attachTo: AnyObject, closure: @escaping () -> (), controlEvents:UIControlEvents) { | |
self.attachedTo = attachTo | |
self.closure = closure | |
self.controlEvents = controlEvents | |
objc_setAssociatedObject(attachTo, "[\(arc4random())]", self, .OBJC_ASSOCIATION_RETAIN) | |
} | |
@objc func invoke() { | |
closure() | |
} | |
@objc func invokeOnce() { | |
closure() | |
attachedTo.unlisten(sleeve: self) | |
} | |
} |
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// Register listener, keep the reference to unregister the listener | |
let listener = button.listenOnce({ | |
print("I will say this every time you tap the button") | |
}, for: [.touchUpInside]) | |
// … later … | |
button.unlisten(listener) | |
// Listen once for the control events, automatically unlisten when the block is performed | |
button.listenOnce({ | |
print("I will only say this once") | |
}, for: [.touchUpInside, .touchDragExit]) |
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