Core Data migration problem: “Persistent store migration failed, missing source managed object model.”

Question

The Background

• A Cocoa Non Document Core Data project with two Managed Object Models.
• Model 1 stays the same. Model 2 has changed, s

Answer 1

I had a similar problem. I have used +modelByMergeingModels:, but I did not use Mapping Model. However merging models does not work with lightweight data migration.

From the Apple Docs:

To perform automatic lightweight migration, Core Data needs to be able to find the source and destination managed object models itself at runtime.

If you use +modelByMergeingModels: than that is used for the destination model. However Core Data will not be able to find source model. Source model has been created using +modelByMergeingModels: in older version of the application and Core Data does try to merge models to find out the source model.

What I ended up doing is that I have (manually) created a new merged .xcdatamodeld by editing the XML files of the models, added it into the project, removed the separate .xcdatamodelds from Compile Sources and instead of using +modelByMergeingModels: use NSManagedObjectModel's -initWithContentsOfURL: with the URL of the new merged model. I'll probably create a script that will automatically merge the models in the future.