Add UIButton targets using closure

UIButton+AddTargetClosure.swift

import UIKit

typealias UIButtonTargetClosure = UIButton -> ()

class ClosureWrapper: NSObject {
    let closure: UIButtonTargetClosure
    init(_ closure: UIButtonTargetClosure) {
        self.closure = closure
    }
}

extension UIButton {
    
    private struct AssociatedKeys {
        static var targetClosure = "targetClosure"
    }
    
    private var targetClosure: UIButtonTargetClosure? {
        get {
            guard let closureWrapper = objc_getAssociatedObject(self, &AssociatedKeys.targetClosure) as? ClosureWrapper else { return nil }
            return closureWrapper.closure
        }
        set(newValue) {
            guard let newValue = newValue else { return }
            objc_setAssociatedObject(self, &AssociatedKeys.targetClosure, ClosureWrapper(newValue), objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        }
    }
    
    func addTargetClosure(closure: UIButtonTargetClosure) {
        targetClosure = closure
        addTarget(self, action: #selector(UIButton.closureAction), forControlEvents: .TouchUpInside)
    }
    
    func closureAction() {
        guard let targetClosure = targetClosure else { return }
        targetClosure(self)
    }
}

Swift 4.1

//
// Created by Tommy Sadiq Hinrichsen on 28/04/2018.
// Copyright (c) 2018. All rights reserved.
//

import Foundation
import UIKit

typealias UIButtonTargetClosure = (UIButton) -> ()

class ClosureWrapper: NSObject {
    let closure: UIButtonTargetClosure

    init(_ closure: @escaping UIButtonTargetClosure) {
        self.closure = closure
    }
}

extension UIButton {

    fileprivate struct AssociatedKeys {
        static var touchUpInsideClosure = "targetClosure"
    }

    fileprivate var touchUpInsideClosure: UIButtonTargetClosure? {
        get {
            guard let closureWrapper = objc_getAssociatedObject(self, &AssociatedKeys.touchUpInsideClosure) as? ClosureWrapper else { return nil }
            return closureWrapper.closure
        }
        set(newValue) {
            guard let newValue = newValue else { return }
            objc_setAssociatedObject(self, &AssociatedKeys.touchUpInsideClosure, ClosureWrapper(newValue), objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        }
    }

    func onTouchUpInside(_ closure: @escaping UIButtonTargetClosure) {
        touchUpInsideClosure = closure
        addTarget(self, action: #selector(UIButton.touchUpInsideAction), for: .touchUpInside)
    }

    @objc
    fileprivate func touchUpInsideAction() {
        guard let touchUpInsideClosure = touchUpInsideClosure else { return }
        touchUpInsideClosure(self)
    }
}