Confused about class relationships

[Craig Allen]

what you have is a totally acceptable factory system.  Not sure why
you are using a generator, but that's another matter.

I agree with the previous replies regarding inheritance... this is not
a case for inheritance.  You could, however, have Bar be a borg with
the Bar factory built in as a class method to the Bar class itself if
you want the whole job done by one component.  Questions to lead to or
away from that: will Engine every create things besides Bars?