Summary

In this chapter, we covered multiple fundamental GoF structural design patterns. They help us extend our systems from the outside without modifying the actual classes, leading to a higher degree of cohesion by composing our object graph dynamically.

We started with the Decorator pattern, a powerful tool that allows us to dynamically add new functionality to an object without altering its original code. Decorators can also be chained, allowing even greater flexibility (decorating other decorators). We learned that this pattern adheres to the Open-Closed principle and promotes the separation of responsibilities into smaller, manageable pieces.

We also used an open-source tool named Scrutor that simplifies the decorator pattern usage by extending the built-in ASP.NET Core dependency injection system.

Then, we covered the Composite pattern, which allows us to create complex, non-linear, and self-managed data structures with minimal effort. That hierarchical data structure...