title: How to make 1 IBOutlet works for different devices?
body: <p>Say I got a general iPhone size and iPad size to work out.</p>
  
  <p>The iPad has a <code>UIButton</code> that links to <code>UIViewController</code> as a <code>IBOutlet</code>. 
  Whereas iPhone doesn't need this <code>UIButton</code> but since iPhone and iPad all in 1 <code>Storyboard</code> and any other <code>IBOutlet</code> are identical. What is the most proper way to deal with this?</p>
  
  <p>What I am thinking is to make the <code>@IBOutlet weak var button:UIButton?</code> optional and only the iPad's button links to it. But every action I do in the code requires <code>button?.xxxxx</code></p>
  
  <p>Any suggestions?</p>