I have an app that has been running fine on the iPhone simulator for some time. Recently, I decided I wanted to re-use the data model and related classes in another project - so I dragged them from this project window to the other then told Xcode not to copy, just to make references. At first this didn't work so I jumped through a number of hoops to try to fix it (I may be asking more about that in another post). After all this, I re-compiled and tried to run the original app -- and it's not working any more. On further investigation, I discovered that when I re-compile the original app, I end up with a bundle that contains a .momd package but it contains only a Versioninfo.plist file - no .mom file, no .omo file like I'm expecting to see. I don't recall making any changes to the original app. I don't get any warnings. I just get an incomplete .momd package (and, not surprisingly, my app now crashes).
What's going on here?
BTW, the app now crashes with this message: Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* -[__NSArrayM insertObject:atIndex:]: object cannot be nil'
Which I get when executing this line of code:
self.productRegistry = [[UIManagedDocument alloc] initWithFileURL:self.productRegistryURL];
I figured this out by looking more closely at the file locations in the project directory using Finder. In the Xcode window, everything looks normal but in the actual project directory I found that the .datamodeld package had ended up at the top level of the project directory -- at the same level as the project package itself. Xcode apparently did not like this but unfortunately it did not complain -- it just created a partial build output. Once I moved the .datamodeld package into the same folder as the rest of the project's code, everything worked just fine.
This would appear to be just a quirk. I would expect that Xcode would either see that all is well and build correctly OR it would see that things weren't quite as they should be and fail. In this case, it did not build correctly but was silent about it.
Hope this answer helps someone else someday.