Closure syntax for UIButton's addTarget

UIButton+Blocks.swift

import UIKit

extension UIButton {
    typealias BlockType = (UIButton) -> ()
    private static var controlStatesBlockKey = "controlStatesBlockKey"

    func add(block: @escaping BlockType, forControlEvents controlEvents: UIControlEvents) {
        UIButton.controlStatesBlockKey += "\(controlEvents)"
        var blocks = (objc_getAssociatedObject(self, &UIButton.controlStatesBlockKey) as? [BlockType]) ?? []
        blocks.append(block)
        objc_setAssociatedObject(self, &UIButton.controlStatesBlockKey, blocks, .OBJC_ASSOCIATION_COPY_NONATOMIC)
        addTarget(self, action: #selector(action(_:)), for: controlEvents)
    }

    @objc private func action(_ sender: UIButton) {
        guard let blocks = objc_getAssociatedObject(self, &UIButton.controlStatesBlockKey) as? [BlockType] else { return }
        for block in blocks {
            block(self)
        }
    }

}