Core Data in Objective-C, 3rd Edition

A Simple Migration

To demonstrate a simple migration, let’s add the ability to attribute recipes to authors. To begin the versioning, the first thing we need to do is create a new managed object model (MOM) based on the first one. To do that, we select the existing model in Xcode and then choose Design > Data Model > Add Model Version.

Your First Data Model Version

When you first set up versioning, be sure to look inside the target in Xcode and update the Compile Sources section. If you don’t see the .xcdatamodeld file inside the target, remove the xcdatamodel references from it and drag the entire xcdatamodeld bundle into the target. Otherwise, your application may complain about being unable to merge entities because it will treat each version ...