title: How can I addSubview to UIButton in Interface Builder
body: <p>Like I said, I add a UIButton in Interface Builder, I want add a UILabel、UIImageView as the button's subviews, but I can't add any object on it in IB. IS anybody know how to do this? Thank you very much.</p>
  
  <p>I can use code to achieve that, but I want achieve it in IB, so I can use it in any class I want.</p>