I'm not sure how else to note this, but in Xcode 9+ NSManagedObject entities are (by default) set to have their class autogenerated. This is a departure from the way things were done (manual generation via the Editor > Create NSManagedObject Subclass ... as noted in the Managed Object Subclasses section of chapter 1 of the book. It might be worth it to note the difference and how to set the automatic code generation to none.
I'm not sure how else to note this, but in Xcode 9+
NSManagedObjectentities are (by default) set to have their class autogenerated. This is a departure from the way things were done (manual generation via the Editor > Create NSManagedObject Subclass ... as noted in the Managed Object Subclasses section of chapter 1 of the book. It might be worth it to note the difference and how to set the automatic code generation to none.