Visitor

Introduction

The Visitor is a behavioural pattern. It allows the designer to define new operations on an object structure and its elements, without modifying the object structure itself.

Description

The Visitor describes three distinct components:

• Object Structure - Provides a visitor with access to its elements.
• Element - Accepts visits.
• Visitor - Accesses an element to perform operations.

Figure 1 graphically describes these Visitor pattern relationships.

Figure 1: A UML class diagram representing the Visitor structure