Hands-On Design Patterns with C++

What is the Visitor pattern?

The Visitor pattern is a pattern that separates the algorithm from the object structure, which is the data for this algorithm. Using the Visitor pattern, we can add a new operation to the class hierarchy without modifying the classes themselves. The use of the Visitor pattern follows the open/closed principle of the software design—a class (or another unit of code, such as a module) should be closed for modifications; once the class presents an interface to its clients, the clients come to depend on this interface and the functionality it provides. This interface should remain stable; it should not be necessary to modify the classes in order to maintain the software and continue its development. At the same time, ...