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LLDsystem_design~12 mins

Composite pattern in LLD - Architecture Diagram

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System Overview - Composite pattern

The Composite pattern helps organize objects into tree structures to represent part-whole hierarchies. It lets clients treat individual objects and compositions of objects uniformly, simplifying code that works with complex nested structures.

Key requirements include supporting recursive composition, uniform access to leaf and composite objects, and easy addition/removal of components.

Architecture Diagram
          +----------------+
          |     Client     |
          +--------+-------+
                   |
                   v
          +--------+-------+
          |   Component    |
          | (Interface)    |
          +--------+-------+
                   |
       +-----------+-----------+
       |                       |
+------+-------+       +-------+------+
|   Leaf       |       | Composite    |
| (Single Obj) |       | (Container)  |
+--------------+       +-------+------+
                                |
                     +----------+----------+
                     |                     |
               +-----+-----+         +-----+-----+
               |   Leaf    |         |   Leaf    |
               +-----------+         +-----------+
Components
Client
client
Uses the Component interface to interact with objects in the composition
Component
interface
Defines the common interface for Leaf and Composite objects
Leaf
leaf
Represents end objects with no children
Composite
composite
Holds child Components and implements child-related operations
Request Flow - 5 Hops
Client → Component
Component → Leaf or Composite
Composite → Child Components
Leaf or Composite → Component
Component → Client
Failure Scenario
Component Fails:Composite
Impact:If a Composite fails, its child components become inaccessible, breaking part of the tree structure and causing incomplete operation results.
Mitigation:Design Composite to handle child failures gracefully, e.g., skip failed children or provide fallback behavior. Use error handling in Client to detect incomplete results.
Architecture Quiz - 3 Questions
Test your understanding
Which component in the Composite pattern holds child components?
AComposite
BClient
CLeaf
DComponent Interface
Design Principle
The Composite pattern simplifies client code by allowing uniform treatment of individual objects and compositions. It uses recursive structures to represent hierarchies, enabling flexible and scalable designs for complex nested objects.