Unknown type name 'string'

I am attempting to run the iosNativeARCExample in XCode 7.0 on Yosemite and I’m getting a host of these errors:

Unknown type name ‘string’

alternately:

No type name 'string' in namespace 'std'

Make sure you have libc++ selected in your project build settings.

Thanks, but it was selected that way already, so this is apparently not the solution.