Programming Ruby 3.3

Chapter 6Sharing Functionality: Inheritance, Modules, and Mixins

One of the principles of good software design is the elimination of unnecessary duplication. We work hard to make sure that each concept in our application is expressed only once in our code. Why? Because the world changes. And when you adapt your application to each change, you want to know that you’ve changed exactly the code you need to change. If each real-world concept is implemented at a single point in the code, this becomes vastly easier.

We’ve already seen how classes help reduce duplication. All the methods in a class are automatically accessible to instances of that class. But we want to do other, more general types of sharing. Maybe we’re dealing with an application ...