18.UIButton传参

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