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])

Looks ok.

There is one line that looks dangerous to me:

attachedTo.unlisten(sleeve: self)

Because attachedTo is AnyObject, it will crash if called on other objects. Maybe wrapping that call with respondsToSelector would be an appropriate thing. Or Change the attachedTo variable to UIControl. However, that would not work if you want to use the ClosureSleeve for other stuff (I use it for example also for UIBarButtonItem and UITapGestureRecognizer). Maybe adding a protocol (like Unlistenable) could be a solution then.

I would also move all the closure parameters as the last parameter, so that trailing closure syntax can be used on call site.

Also, it looks like you cannot unlisten a listenOnce listener.

Wow, super duper feedback! Thanks!