title: Can standard iOS UIBarButtonSystemItem icons be referenced through storyboard Attributes Inspector?
body: <p>The app that I am writing uses a navigation bar and I need to put a standard 'Add' (plus) icon as a bar button item. These standard icons are described <a href="https://developer.apple.com/library/prerelease/ios/documentation/UserExperience/Conceptual/MobileHIG/Bars.html#//apple_ref/doc/uid/TP40006556-CH12-SW33" rel="nofollow">here</a> and their use is described <a href="https://developer.apple.com/library/prerelease/ios/documentation/UIKit/Reference/UIBarButtonItem_Class/index.html#//apple_ref/c/tdef/UIBarButtonSystemItem" rel="nofollow">here</a>, but the documentation only describes how to reference the icons from code (objective-c or swift).  </p>
  
  <p>None of the resources I can find on the subject covers how to specify the image source through the Attributes inspector, where I would set the icon source if it was based on a custom image. Is it not possible to reference default system icons through the Attributes inspector for the Bar Button Item?</p>