Design Patterns: Behavioral

Master patterns that define how objects interact—Observer for events, Strategy for algorithms, Command for actions.

80 minutes

5Detailed Sections

Senior Level

Behavioral patterns solve: How do objects collaborate without tight coupling? How do we encapsulate behavior (algorithms, actions)?

How do we handle requests that may need delegation? Observer enables pub-sub.

Strategy enables pluggable algorithms. Command enables action encapsulation (undo/redo, queuing).

Chain of Responsibility enables request routing through handlers. State enables state machines.

Common theme: Decouple sender from receiver, enable new behaviors without modifying existing code. Real-world: Netflix uses Observer for service events.

Uber uses Strategy for surge-pricing algorithms. Netflix UI uses Command for action history.

Understanding behavioral patterns is critical for event-driven systems and loosely-coupled microservices.

Key Takeaways

Behavioral patterns define object communication and collaboration

Observer: Pub-sub, loose coupling, event-driven

Strategy: Pluggable algorithms, runtime selection

Command: Action encapsulation, undo/redo, queuing

Chain of Responsibility: Request routing through handlers

State: Behavior changes based on internal state

Common benefit: New behaviors without modifying existing code (OCP)

Critical for: Microservices, event-driven architecture, testing

Visual Diagram

Observer: Subject broadcasts to Observers | Strategy: Context delegates to Strategy | Command: Invoker queues Commands

All Tutorials Practice Questions

Design Patterns: Behavioral

Table of Contents

Behavioral Patterns: Object Communication

Key Takeaways

Visual Diagram

Observer Pattern: Event-Driven Loose Coupling

Strategy Pattern: Pluggable Algorithms

Command Pattern: Action Encapsulation

Chain of Responsibility: Request Routing