CoreData - Update model class instead of creating new

Question

I am using CoreData in my iOS application. I face a problem most of the times while creating NSManagedObject classes.

This is what I do:

1. I create an Entity in .xcdatamodeld file.
2. Create attributes and relationships.
3. Choose option Editor->Create NSManagedObject Class to create .h and .m classes.
4. In .h and .m classes, I create some of my custom methods for fetching/saving objects.

So far so good. But afterwards in future if I have to change some attributes, I repeat step 2 and 3. But this time all of my custom code written in step 4 are removed automatically.

So my question is how can I update the existing classes? Instead of using option Editor->Create NSManagedObject Class which removes all my custom code.

Any help is appreciated.

Update:

Tested both approaches (Categories and Mogernator) and looks fine to me. But I have choosen Categories of being a pure Xcode approach. I don't want to take the risk of any 3rd party which may break in future due to XCode updates or can cause problem of data migration.

Thanks to @Tom Harrington, and @Valentin Shamardin for guiding me :)

Answer 1

To make some additional methods or other stuff for your Core Data model classes you have to create Categories. This approach is used by Paul Hegarty in Core Data lections.