Recently I was trying to link a static objective-c library to a swift framework. My initial thought was I needed to create a bridging header. However, after reviewing the Mix and Match documentation, it was clear that only app targets support bridging headers, frameworks need to use an umbrella header. But there is a catch. The frameworks/libraries you are attempting to import need to have a module defined. I was out of luck, I had a binary library file and a bunch of headers.
Prior to iOS 5 if you wanted to maintain a particular order in a core data relationship, you had to create an additional index attribute for the entity and track this value manually. This was a royal pain and prone to errors. NSOrderedSet was introduced in iOS 5, it gives the benefit of items having an index like an array, but also having the added benefit of guaranteeing all items are unique