In xcode 3 there was a helpful feature in the data model builder where you could highlight some attributes/relationships in an entity, right-click, and choose to copy method and property declarations to the clipboard. (You could choose if you wanted objective-c 2.0 property declarations also). Then you could paste them into your NSManagedObject subclass.
I see how you can still generate the entire class file; but this isn't helpful if you are adding attributes to an existing entity. Have they removed this feature from xcode 4? I used it all the time!
See the Core Data Model Editor Help: Creating Objective-C Accessor Methods for a Managed Object
You may find MoGenerator useful.
Watch out for the fact that the special paste menu item only appears in the Edit menu not the contextual menu in the source editor.
来源：https://stackoverflow.com/questions/5327600/generate-code-for-core-data-attributes-in-xcode-4