Behavioral

Visitor

Separates algorithms from the objects on which they operate.

AST processingDocument exportReport generation

Understanding Visitor

The Visitor pattern lets you define new operations on elements of an object structure without changing the classes of the elements. It separates algorithms from the objects they operate on.

How It Works

Elements

Circle

Accept(v)

Rectangle

Accept(v)

Triangle

Accept(v)

Visitor

AreaCalc

VisitCircle()

VisitRectangle()

VisitTriangle()

Different element types

Element Structure

Objects with different types in a structure.

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Basic Implementation

Area calculator visiting different shapes:

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Real-World Example: Document Export

Document nodes with HTML and plain text exporters:

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