Build failed--attribute must have a defined type

Question

My app crashes on build. Here's the error in it's entirety:

DataModelVersionCompile /Users/AAAAAAA/Library/Developer/Xcode/DerivedData/XXXXXXXXXX-envirswdnpegjccdpxakhoykfnfq/Build/Products/Debug-iphonesimulator/XXXXXXXXXX.app/WMMGDataModel.momd XXXXXXXXXX/WMMGDataModel.xcdatamodeld
    cd "/Users/AAAAAAA/Desktop/Everything from DT 1:20:15/App projects/WMMG/XXXXXXXXXX"
    export PATH="/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin:/Applications/Xcode.app/Contents/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin"
    /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/momc -XD_MOMC_SDKROOT=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator8.1.sdk -XD_MOMC_IOS_TARGET_VERSION=8.1 -MOMC_PLATFORMS iphonesimulator /Users/AAAAAAA/Desktop/Everything\ from\ DT\ 1:20:15/App\ projects/WMMG/XXXXXXXXXX/XXXXXXXXXX/WMMGDataModel.xcdatamodeld /Users/AAAAAAA/Library/Developer/Xcode/DerivedData/XXXXXXXXXX-envirswdnpegjccdpxakhoykfnfq/Build/Products/Debug-iphonesimulator/XXXXXXXXXX.app/WMMGDataModel.momd

/Users/AAAAAAA/Desktop/Everything from DT 1:20:15/App projects/WMMG/XXXXXXXXXX/XXXXXXXXXX/WMMGDataModel.xcdatamodeld/WMMGDataModel 5.xcdatamodel:WMMGAccount.attribute: error: WMMGAccount.attribute must have a defined type
/Users/AAAAAAA/Desktop/Everything from DT 1:20:15/App projects/WMMG/XXXXXXXXXX/XXXXXXXXXX/WMMGDataModel.xcdatamodeld:0: error: Compilation failed for data model at path '/Users/AAAAAAA/Library/Developer/Xcode/DerivedData/XXXXXXXXXX-envirswdnpegjccdpxakhoykfnfq/Build/Products/Debug-iphonesimulator/XXXXXXXXXX.app/WMMGDataModel.momd/WMMGDataModel 5.mom'
Command /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/momc failed with exit code 1

The relevant part seems to be:

/Users/AAAAAAA/Desktop/Everything from DT 1:20:15/App projects/WMMG/XXXXXXXXXX/XXXXXXXXXX/WMMGDataModel.xcdatamodeld/WMMGDataModel 5.xcdatamodel:WMMGAccount.attribute: error: WMMGAccount.attribute must have a defined type

I've gone into my xcdatamodel, but can't find any attributes that aren't properly defined by type. One suspicious thing I'm seeing is the reference to WMMGDataModel 5. I'm up to version 8 in my model, and can't even find version 5.

This crash began after a recent automatic migration (using MagicalRecord) in which I added an attribute to one of the entities and then recreated the Managed Object Subclass (yes, the new subclass contains the new, properly defined attribute). I've added attributes before, but this is the first time I've encountered this issue.

I've cleaned the thing, quit and restarted Xcode, still crashes. Anybody have any ideas? I also deleted the DerivedData folder for the project. Still won't build.

Edit:

I just recreated all my managed subclass files. Still no dice--same error message.

Edit:

I tried running another project as a control, and got this message:

Unable to run app in Simulator An error was encountered while running (Domain = FBSOpenApplicationErrorDomain, Code = 4)

So I quit Xcode and the simulator, restarted Xcode. Same error.

Yet more info

I restarted the computer and tried again, but am still getting "Build Failed" with the same error message.

If anyone else has run into anything like this, I sure would appreciate some guidance here... :)

Final edit

Please see solution in my answer below...

Answer 1

Ok, I finally cured the problem with a decision to delete my xcdatamodeld and rebuild the entire model. Some research into how to do this yielded a less destructive and less risky method in this answer.

Here's hoping it will help someone else with this problem.

Thanks to all who took a look!

Answer 2

I've never had the problem you describe, but have a few suggestions. Apologies if you've already tried these:

First, in the model editor, can you access the model version 5 that you suspect is the problem, eg.:

If it's there, you can hopefully fix the attribute error. If it doesn't appear there, have you tried right-click in the Project Navigator and select "Show in Finder":

Then in Finder looking for the version 5?