deltachat-ios/Pods/KK-ALCameraViewController/ALCameraViewController/Utilities/UIButtonExtensions.swift

//
//  UIButtonExtensions.swift
//  ALCameraViewController
//
//  Created by Alex Littlejohn on 2016/03/26.
//  Copyright © 2016 zero. All rights reserved.
//

import UIKit

typealias ButtonAction = () -> Void

extension UIButton {
    
    private struct AssociatedKeys {
        static var ActionKey = "ActionKey"
    }
    
    private class ActionWrapper {
        let action: ButtonAction
        init(action: @escaping ButtonAction) {
            self.action = action
        }
    }
    
    var action: ButtonAction? {
        set(newValue) {
            removeTarget(self, action: #selector(performAction), for: .touchUpInside)
            var wrapper: ActionWrapper? = nil
            if let newValue = newValue {
                wrapper = ActionWrapper(action: newValue)
                addTarget(self, action: #selector(performAction), for: .touchUpInside)
            }
            
            objc_setAssociatedObject(self, &AssociatedKeys.ActionKey, wrapper, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        }
        get {
            guard let wrapper = objc_getAssociatedObject(self, &AssociatedKeys.ActionKey) as? ActionWrapper else {
                return nil
            }
            
            return wrapper.action
        }
    }
    
    @objc func performAction() {
        guard let action = action else {
            return
        }

        action()
    }
}