Visitor pattern in LLD - Architecture Diagram

System Overview - Visitor pattern

The Visitor pattern lets you add new operations to objects without changing their classes. It separates algorithms from the objects they work on, making it easier to add features without modifying existing code.

Key requirements include supporting multiple object types and allowing new operations to be added independently.

Architecture Diagram

  +---------+       +-------------+       +-------------+
  |  Client | ----> |  Object A   | <---- |  Visitor A   |
  +---------+       +-------------+       +-------------+
                         ^   ^
                         |   |
                  +-------------+       +-------------+
                  |  Object B   | <---- |  Visitor B   |
                  +-------------+       +-------------+

Components

Client

client

Starts the operation by accepting visitors on objects

Object A

element

An element that accepts visitors to perform operations

Object B

element

Another element type that accepts visitors

Visitor A

visitor

Defines an operation to perform on Object A

Visitor B

visitor

Defines an operation to perform on Object B

Request Flow - 4 Hops

Client → Object A

Object A → Visitor A

Client → Object B

Object B → Visitor B

Failure Scenario

Component Fails:Visitor A

Impact:Operations on Object A fail or produce incorrect results

Mitigation:Use default visitor implementations or fallback visitors to handle missing operations

Architecture Quiz - 3 Questions

Which component initiates the Visitor pattern operation?

A Client

B Visitor

C Object

D Database

Design Principle

The Visitor pattern separates operations from object structures, enabling new behaviors without modifying existing classes. This promotes open/closed principle and easier maintenance.