Hands-On Design Patterns with C++

Visiting composite objects

The general idea of visiting complex objects is quite straightforward—when visiting the object itself, we generally do not know all the details of how to handle each component or contained object. But there is something else that does—the visitor for that object type is written specifically to handle that class and nothing else. This observation suggests that the correct way to handle the component objects is to simply visit each one, and thus delegate the problem to someone else (a generally powerful technique, in programming and otherwise).

Let's first demonstrate this idea on the example of a simple container class, such as the Shelter class, which can contain any number of pet objects representing the pets ...