iOS 原生的 UIButton 点击事件是不容许带多参数的，惟一的一个参数就是默认UIButton自己 那么咱们该怎么实现传递多个参数的点击事件呢？

UIButton *btn = // create the button
objc_setAssociatedObject(btn, "firstObject", someObject, OBJC_ASSOCIATION_RETAIN_NONATOMIC);   //实际上就是KVC
objc_setAssociatedObject(btn, "secondObject", otherObject, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

[btn addTarget:self action:@selector(click:) forControlEvents:UIControlEventTouchUpInside];

- (void)click:(UIButton *)sender
{
    id first = objc_getAssociatedObject(btn, "firstObject");        //取参
    id second = objc_setAssociatedObject(btn, "secondObject");
    // etc.
}