A mixin is a class designed to inject specific functionality into other classes through inheritance, allowing developers to add behaviors without relying on deep or rigid inheritance hierarchies. Unlike traditional base classes, mixins are often small, focused, and flexible, providing methods or properties that can be combined to enhance functionality across diverse classes. In C++, mixins are often implemented with templates and the Curiously Recurring Template Pattern (CRTP), allowing for compile-time efficiency and minimal overhead.
The Curiously Recurring Template Pattern (CRTP) is a C++ technique that allows for static polymorphism. In CRTP, a class inherits from a template that takes the inheriting class itself as a parameter. This way, behavior can be defined at compile-time, eliminating the runtime overhead of virtual function calls.
Here, Derived inherits from Base<Derived>, allowing it to provide its own implementation at compile-time. This boosts performance by avoiding virtual calls.