Creating NSManagedObject subclass leads to linker error duplicate symbols

Question

I am trying to create a nsmanagedobject (User) by going to the Editor menu and then selecting Create NSManagedObject Subclass...this generates four files:

User+CoreDataClass.h
User+CoreDataClass.m
User+CoreDataProperties.h
User+CoreDataProperties.m

In one of my viewcontrollers I import User+CoreDataClass.h and then have this code:

//create new account entity
    User* thisUser = [NSEntityDescription
                            insertNewObjectForEntityForName:@"User"
                            inManagedObjectContext:self.myController.myDataManager.managedObjectContext];

When I then build the app, I get the following clang error:

duplicate symbol _OBJC_CLASS_$_User in:
    /Users/xxxxxxxxxxxx/Library/Developer/Xcode/DerivedData/StarDate-fzkjccyoiwhfvvczdwkvkmtbioqw/Build/Intermediates/StarDate.build/Debug-iphonesimulator/StarDate.build/Objects-normal/x86_64/User+CoreDataClass.o
duplicate symbol _OBJC_METACLASS_$_User in:
    /Users/xxxxxxxxxxxx/Library/Developer/Xcode/DerivedData/StarDate-fzkjccyoiwhfvvczdwkvkmtbioqw/Build/Intermediates/StarDate.build/Debug-iphonesimulator/StarDate.build/Objects-normal/x86_64/User+CoreDataClass.o
ld: 2 duplicate symbols for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

I tried cleaning the app and deleting my derived data but that had no results. The only way I can clear the error is to delete the generated files. Which obviously is not going to be what I need. Why is XCode creating duplicate files off this menu command? Is there a setting that I missed?

Thanks

Answer 1

You are manually creating NSManagedObject subclasses, that Xcode 8 already has created for you and thus get duplicated symbols.

You can find detailed information how to solve this in this answer.