I have in XCode a main project that relies on a subproject to work. The subproject is basically a library that also define a database model, and the way to interact with it.
To use the subproject in the main project, I just dropped the subproject xcodeproj file in the main project, did some setup (like specifying header search path), and that's it.
I'm using core data, but if I try to use the .xcdatamodelId files directly, by creating managed object context, it fails : looks like the main project can't find the subproject ressources (except .h and .m files).
The only solution I found so far is to copy the .xcdatamodelId file from the subproject in the main project, and it does the trick. But it's not satisfactory, as I have to maintain two files if my model evolves.