The BNR Core Data stack provides what we consider best practices for using Core Data in our applications.
It takes the place of the boilerplate setup code from Xcode's template and focuses on efficient performance and change management.
Deferred is an asynchronous promise-style API that can be used as an alternative to the "block callback" pattern. It lets you work with values that haven't been determined yet, like an array that's coming later (one day!) from a web service call. It was originally inspired by OCaml's Deferred library.