UIGestureRecognizer 添加 Block.swift

extension UIGestureRecognizer {
  
  private struct AssociatedKeys {
    static var action = "action"
  }
  
  private typealias GestureAction = ((UIGestureRecognizer) -> Void)
  
  private var action: GestureAction? {
    get {
      return objc_getAssociatedObject(self, &AssociatedKeys.action) as? GestureAction
    }
    set {
      objc_setAssociatedObject(self, &AssociatedKeys.action, newValue, .OBJC_ASSOCIATION_COPY_NONATOMIC)
    }
  }
  
  @objc private func handleGesture(sender: UIGestureRecognizer) {
    self.action?(sender)
  }
  
  func addTargetBlock(_ block: @escaping (UIGestureRecognizer) -> Void) {
    self.action = block
    self.addTarget(self, action: #selector(handleGesture(sender:)))
  }
  
}