Design Patterns: Structural

Master patterns for organizing object composition—Adapter, Decorator, Facade, Proxy.

75 minutes

5Detailed Sections

Senior Level

Structural patterns define how classes and objects combine to form larger structures while keeping them flexible. They solve: How do we compose objects without tight coupling?

How do we add functionality without modifying code (OCP)? How do we provide unified interfaces to complex subsystems?

Adapter bridges incompatible interfaces. Decorator adds features dynamically.

Facade hides complexity. Proxy controls access.

Benefits: composition over inheritance, flexible, extensible without modification. Real-world: Express middleware (Decorator), database adapters, API gateways (Facade), caching proxies.

Key Takeaways

Structural patterns organize object composition

Adapter: Make incompatible interfaces compatible

Decorator: Add behavior dynamically, composition-based inheritance

Facade: Simplify complex subsystems

Proxy: Control access (caching, validation, lazy loading)

Bridge: Decouple abstraction from implementation

Composite: Tree structures (files/folders, UI components)

Common theme: Composition over inheritance, flexibility

Visual Diagram

Adapter: incompatible ←→ adapter ←→ expected | Decorator: adds behavior dynamically | Facade: hides complexity

All Tutorials Practice Questions

Design Patterns: Structural

Table of Contents

Structural Patterns: Object Composition and Relationships

Key Takeaways

Visual Diagram

Adapter Pattern: Bridging Incompatible Interfaces

Decorator Pattern: Dynamic Behavior Addition

Facade Pattern: Simplifying Complexity

Proxy Pattern: Controlled Access and Lazy Loading