C++ Software Design

Chapter 6. The Adapter, Observer, and CRTP Design Patterns

In this chapter, we turn our attention to three must-know design patterns: the two GoF design patterns, Adapter and Observer, and the Curiously Recurring Template Pattern (CRTP) design pattern.

In “Guideline 24: Use Adapters to Standardize Interfaces”, we talk about making incompatible things fit together by adapting interfaces. To achieve this, I will show you the Adapter design pattern and its application in both inheritance hierarchies and generic programming. You will also get an overview of different kinds of Adapters, including object, class, and function Adapters.

In “Guideline 25: Apply Observers as an Abstract Notification Mechanism”, we will deal with how to observe state change and how to get notified about it. In this context, I will introduce you to the Observer design pattern, one of the most famous and most commonly used design patterns. We will talk about the classic, GoF-style Observer, and also how to implement the Observer in modern C++.

In “Guideline 26: Use CRTP to Introduce Static Type Categories”, we will turn our attention to the CRTP. I will show you how to use CRTP to define a compile-time relationship between a family of related types and how to properly implement a CRTP base class.

In “Guideline 27: Use CRTP for Static Mixin Classes”, I will continue the CRTP story by showing you how CRTP can be used to create compile-time mixin classes. We will also see the difference between semantic inheritance, ...