Software Architecture Design Patterns in Java

18 VISITOR

This pattern was previously described in GoF95.

DESCRIPTION

The Visitor pattern is useful in designing an operation across a heterogeneous collection of objects of a class hierarchy. The Visitor pattern allows the operation to be defined without changing the class of any of the objects in the collection. To accomplish this, the Visitor pattern suggests defining the operation in a separate class referred to as a visitor class. This separates the operation from the object collection that it operates on. For every new operation to be defined, a new visitor class is created. Since the operation is to be performed across a set of objects, the visitor needs a way of accessing the public members of these objects. This requirement can be ...