XCode 4.3.2, as configured on my box, does not show NSObject in the list of subclasses, only NSViewController and NSWindowController, among others.
You should be able to just type in NSObject.
Thanks, I’ll try that next time. I just modified the class after it was created. What’s behind the change in the selections in XCode since you wrote the book?
Only Apple knows. I’m running 4.5 (developer preview) which has quite a lengthy list of selections in that combo box. My guess is that at one point they were only listing classes for which they had Xcode file templates.