Editing Visitor pattern (section)

== Definition ==
The [[Design Patterns|Gang of Four]] defines the Visitor as:
{{quote|Represent[ing] an operation to be performed on elements of an object structure. Visitor lets you define a new operation without changing the classes of the elements on which it operates.}}

The nature of the Visitor makes it an ideal pattern to plug into public APIs, thus allowing its clients to perform operations on a class using a "visiting" class without having to modify the source.<ref>{{Cite web |last=Coogan |first=Corey |date=June 16, 2009 |title=Visitor Pattern: A Real World Example |url=https://coreycoogan.wordpress.com/2009/06/16/visitor-pattern-real-world-example |via=[[WordPress.com]]}}</ref>