title: instantiateControllerWithIdentifier always return nil
body: <p>I try to choose an instance NSCollectionView item from the storyboard and fail. Always receive nil.</p>
  
  <pre><code>- (void)viewDidLoad {
      NSCollectionViewItem *collectionViewItem = [self.storyboard instantiateControllerWithIdentifier:@"collectionItem"];
      [super viewDidLoad];
  }
  </code></pre>
  
  <p>Probably I don't know where to set the identifier "collectionItem", directly on NSCollectionViewItem or NSView in NSCollectionViewItem. For NSCollectionViewItem I did not find the identifier. There is only a Storyboard ID or ID Restoration and neither worked. I am using Xcode 6.1.1</p>