Bad Metaphors

The standard way to teach beginner OO programmers about classes is to make a metaphor to the real world. And indeed, I do this all the time in this blog, usually to the animal kingdom. A "class" in real life codifies a commonality amongst a certain set of objects: mammals, for example, have many things in common; they have backbones, can grow hair, can make their own heat, and so on. A class in a programming language does the same thing: codifies a commonality amongst a certain set of objects v