title: How to align UIBarButtonItem in UIToolbar in iOS universal app?
body: <p>I want to put two <code>UIBarButtonItem</code> instances to <code>UIToolbar</code> in my iOS universal app, on which the first item is on the left-edge of the toolbar and the second is on the center. However, it looks like this cannot be done in Interface Builder, <a href="https://stackoverflow.com/questions/14982302/ios-autolayout-and-uitoolbar-uibarbuttonitems">because the auto layout doesn't support forcing constraints on <code>UIBarButtonItem</code> class due to the fact that it is not a subclass from <code>UIView</code></a>.</p>
  
  <p>Notice that I don't want to put the first on the left-edge and the second is on the right-edge - I have to put the second button <strong>at the center</strong>. Also, I don't have a plan to use the third button in order to align them as left, center, and right at equal interval.</p>
  
  <p>Is it still possible to add such constraint in this situation in storyboard? I use Xcode 6 beta 5.</p>