xcdatamodel Contents Disappears

I've had this happen a few times.

The contents of proj.xcdatamodeld/proj.xcdatamodel/ randomly disappear off my hard drive. However, Xcode will open the model file just fine.

Sometimes all three f开发者_Python百科iles disappear (elements, layout, contents). Other times only a subset of the files disappear.

I've done a filesystem check with Disk Utility which detected no problems.

I've checked that all the build settings etc. for the xcdatamodel are correct.

Are you perhaps confusing *.xcdatamodel and *.xcdatamodeld?

What's the problem if everything works?

I believe I've figured out what the problem is.

The core data file is incompatible across Snow Leopard Xcode 4.0 and Lion Xcode 4.1.

Edit: You can fix this problem by clicking on .xcdatamodel, and in the right-hand panel under "Tools Version" minimum set it to "Xcode 3.2".