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 interactions.

Figure 1: A UML class diagram representing the Visitor structure