The managed object model version used to open the persistent store is incompatible with the one that was used to create the persistent store.

I’ve put the whole error message in the title of this post so that people can find the answer to this problem easier when looking on the web. The first Core Data application I built since starting to learn how to develop applications for Mac OS X Leopard threw me for a loop because I kept getting this error message when I would try to run the application:

The managed object model version used to open the persistent store is incompatible with the one that was used to create the persistent store.

The problem would not happen as long as I hadn’t made any Core Data binding connections in interface builder, so I was puzzled. I looked around on the web for a while and couldn’t find any answers, so then I asked Marcus. He knew exactly what was wrong.

Apparently the Core Data applications create an XML file in which they store the data for your application in:

~/Library/Application Support/ApplicationName/ApplicationName.xml

where ~ means your home directory and ApplicationName and ApplicationName.xml are the name of your actual application.

All you have to do is delete that XML file and rebuild your app. It will then work fine as it regenerates the object model according to what is in XCode.

What happened was I had created a Core Data application and started trying to do things during which I screwed up completely and decided to scrap the whole project. I then went into the finder and deleted the application code directory completely and decided to start over. When I created the new Core Data application, I used the exact same name as the first project. So, now when I went to build the application, it went and looked in:

~/Library/Application Support/ApplicationName/ApplicationName.xml

and found the file there, so it tried to use it. Meanwhile, my data model had changed in the new project. The application didn’t know what to do with the incompatible model and then threw up its hands and gave me this error. Anyhow, it’s an interesting lesson and very helpful. Thanks to Marcus for providing the answer. Meanwhile, take a look at this code that is part of the default Core Data template:
[c]
– (NSString *)applicationSupportFolder {

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSApplicationSupportDirectory, NSUserDomainMask, YES);
NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : NSTemporaryDirectory();
return [basePath stringByAppendingPathComponent:@”ApplicationName”];
}
[/c]
This code is returning the path to the specific Application Support directory for your application.

Hope this helps.