How to delete an old/unused Data Model Version in Xcode

I've just found the need to do this. I created a new model version then realised I didn't need it after all. I was surprised to find there was no way of deleting it (that I could find) from Xcode. Still, to remove it I did the following:

First I made sure it wasn't my current model version. Then I went to Finder and found my *.xcdatamodeld file. Right click and Show Package Contents on that. In there you will find the actual model file and can delete it.

This still doesn't remove it from Xcode and it will show red in the Files and Groups. To stop this from happening go back to Finder and Show Package Contents on your main *.xcodeproj file (you may want to make sure you have a backup of this first). In there open up and edit project.pbxproj do a find on your model version name, in my case "interval 8". For me it appeared on two separate lines. I removed these lines and now it's completely removed from Xcode.

It's a hack, but this worked for me:

1. Set the Current version of the model in Xcode to one that you want to keep
2. Remove the .xcdatamodeld from your project (Right-click -> Delete -> Remove Reference Only)
3. Show the contents of the .xcdatamodeld package in the Finder (Right-click -> Show Package Contents)
4. Delete the .xcdatamodel file(s) that you don't want anymore
5. Re-add the .xcdatamodeld file to your project

This eliminates the need to manually modify any of the project metadata files.