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Understanding the Differences Between Patterns

✅ Purpose of This Chapter​

Many design patterns share similar structures or intentions.
This chapter aims to clearly compare such patterns side by side and help you understand when and why to choose one over the other during design decisions.

Have you ever wondered:

  • "How is Strategy different from Template Method?"
  • "Aren’t Adapter and Bridge structurally the same?"
  • "Isn't Command just another form of Strategy?"

To answer these questions, we analyze patterns from key perspectives such as structure, flexibility, reusability, runtime adaptability, and testability.

✅ What This Chapter Covers​

This chapter provides side-by-side comparisons for 10 commonly confused pairs of design patterns:

  • Strategy vs Template Method
  • Adapter vs Bridge
  • Factory Method vs Abstract Factory
  • Decorator vs Proxy
  • State vs Strategy
  • Command vs Strategy
  • Observer vs Mediator
  • Proxy vs Facade
  • Singleton vs Dependency Injection
  • Command vs Template Method

Each comparison page follows a consistent format with the following sections:

  • ✅ Purpose of Comparison
  • ✅ Comparison Overview
  • ✅ Similarities
  • ✅ Key Differences
  • ✅ When to Choose Which
  • ✅ UML Class Diagram (to visualize structural differences)
  • ✅ Practical Tips for Implementation
  • ✅ Summary

✅ How to Use This Chapter​

This chapter is designed to be useful in the following scenarios:

  • When reviewing designs and evaluating pattern choices
  • When you know the pattern names but want to better articulate their differences
  • When you want to explain design rationale clearly to team members

The focus is not on code refactoring, but rather on understanding conceptual and structural differences.

The goal of this chapter is to develop the ability to articulate pattern choices clearly and confidently.
It is not just about learning names—it is about strengthening your design reasoning and communication.