Scala Design Patterns - Second Edition

Example class diagram

Let's imagine that we are building a system for a school where each student can take multiple classes and each class is taken by multiple students. We might want to have a functionality that notifies all the students of a specific class that it is canceled, or we might want to easily add or remove users from classes. We can impulsively start writing our code and have a list of classes as a part of the student class and a list of students in the group class. This way, however, our objects will become interconnected and not really reusable. This is a good use case for the mediator pattern.

Let's take a look at our class diagram:

As you can see from the preceding diagram, the school is the mediator and it contains information ...