iOS 原生的 UIButton 點擊事件是不容許帶多參數的，惟一的一個參數就是默認UIButton自己 那麼咱們該怎麼實現傳遞多個參數的點擊事件呢？

UIButton *btn = // create the button
objc_setAssociatedObject(btn, "firstObject", someObject, OBJC_ASSOCIATION_RETAIN_NONATOMIC);   //實際上就是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");        //取參
    id second = objc_setAssociatedObject(btn, "secondObject");
    // etc.
}