Swift3 UIControl extension for adding block event listeners. Adapted from: https://stackoverflow.com/a/44917661/44639

UIControl+ListenBlock.swift

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)
    }
}

Usage.swift

// 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])

Wow, super duper feedback! Thanks!