NSCollectionView

NSCollectionView was originally a simple grid layout that didn't really match any layout that any app used, or wanted. In macOS 10.11, it got a bunch of functionality (copied from iOS?) to make it much more flexible and powerful. Unfortunately, it was also so buggy in that release that I've found it completely unusable.

In 10.12, it's much better (but still not perfect). I haven't shipped any 10.12-only apps yet, so I don't have real experience with it, and I can't say whether it's a good choice yet.

NSCollectionView is one of the places that use NSViewController extensively (NSCollectionViewItem is a subclass of NSViewController), so (as per the rule of thumb in NSView), you need to have a dumb NSView with the logic in the controller, in order to use this view.