The Pragmatic Programmer: your journey to mastery, 20th Anniversary Edition, 2nd Edition

Topic 31

Inheritance Tax

You wanted a banana but what you got was a gorilla holding the banana and the entire jungle.

Joe Armstrong

Do you program in an object-oriented language? Do you use inheritance?

If so, stop! It probably isn't what you want to do.

Let's see why.

Some Background

Inheritance first appeared in Simula 67 in 1969. It was an elegant solution to the problem of queuing multiple types of events on the same list. The Simula approach was to use something called prefix classes. You could write something like this:

link CLASS car;
  ... implementation of car

link CLASS bicycle;
  ... implementation of bicycle

The link is a prefix class that adds the functionality of linked lists. This lets you add both cars and bicycles to the ...