composite

The Composite Pattern allows you to compose objects into tree structures to represent part-whole hierarchies. Composite lets clients treat individual objects and compositions of objects uniformly.

Using a composite structure, we can apply the same operations over both composites and individual objects. In other words, in most cases we can ignore the differences compositions of objects and individual objects.

Note that, Composite Pattern does not adhere to the Single Responsibility Principle, and trades it for transparency. This is a classic case of tradeoff.

Use case

In Chapter 9 of HFDP Book, we want to add a dessert submenu, and such structural bears resemblance to node-leaf in a tree.