[Alternative] NSControl extension for closure version of `.action`

NSControl+Extension.swift

class SelectorWrapper<T> {
	let selector: Selector
	let closure: (T) -> Void

	init(withClosure closure: @escaping (T) -> Void) {
		self.selector = #selector(callClosure)
		self.closure = closure
	}

	@objc
	private func callClosure(sender: AnyObject) {
		closure(sender as! T)
	}
}

var handle: Int = 0

extension NSControl {
	typealias ActionClosure = (NSControl) -> Void

	var onAction: ActionClosure? {
		get {
			return nil
		}
		set {
			if let newValue = newValue {
				let selectorWrapper = SelectorWrapper<NSControl>(withClosure: newValue)
				objc_setAssociatedObject(self, &handle, selectorWrapper, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
				action = selectorWrapper.selector
				target = selectorWrapper
			} else {
				action = nil
				target = nil
			}
		}
	}
}

nice implementation