调用方法

but.addClickEvent(click: { (but) in
                print("点击事件")
            })

添加扩展方法

typealias butAction = (UIButton)->()
extension UIButton{
    
    private struct butKeys{
        static var action = "click"
    }
    
    @objc dynamic var click: butAction? {
        set{
            objc_setAssociatedObject(self,&butKeys.action, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_COPY)
        }
        get{
            if let action = objc_getAssociatedObject(self, &butKeys.action) as? butAction{
                return action
            }
            return nil
        }
    }
    
    func addClickEvent(click:@escaping  butAction) {
        self.click = click
        self.addTarget(self, action: #selector(touchUpInSideFun), for: UIButton.Event.touchUpInside)
        
    }
    
    @objc func touchUpInSideFun(but: UIButton) {
        if let click = self.click {
            click(but)
        }
    }
}