n-b/ObjcCollectionsKeyValueFiltering — pull request #2 by joelmartinez (2013-06-26 20:01:12+00:00)
Title: New category methods: [indexedDictionaryByKeyPath:] for NSArray and NSSet, and [NSMutableSet exceptSet:]

Added a few more helpful methods and figured I'd write some unit tests and contribute them back in case you find them helpful as well :)