The Non-Virtual Interface

The implementation of the dynamically customizable parts of the templated algorithm is usually done with virtual functions. For a general Template Method pattern, this is not a requirement, but in C++, we rarely need another way. Now, we are going to focus specifically on using the virtual functions and improve on what we have learned.

Virtual functions and access

Let's start with a general question—should virtual functions be public or private? The textbook object-oriented design style uses public virtual functions, so we often make them public without a second thought. Within the Template Method, this practice needs to be reevaluated—a public function is part of the class interface...