Mac OS X 10.7 brought ordered relationships to Core Data. Unfortunately Apple didn't update any of their binding enabled controllers ( NSArrayController, NSTreeController ) to support ordered relationships. DDOutlineView is a fully functional example using a subclassed NSTreeController and a standard NSOutlineView with ordered Core Data relationships.
DDOutlineView is 10.7+ only and requires Xcode 4.2 with LLVM 3.0 compiler to work as it is an ARC enabled project.
- Drag & Drop support has been added but it is well tested but does not work "cleanly" with the Pasteboard. You should adjust the drag and drop code as needed.