Expanding Design Power Through Combination
This chapter focuses on the intentional combination of two design patterns to achieve enhanced flexibility, modularity, and control in your application architecture. In real-world systems, design patterns are rarely used in isolation — they often appear in complementary pairs that strengthen each other’s role in solving complex design problems.
By examining these common composite patterns, we aim to deepen structural understanding and illustrate how such pairings lead to more maintainable and scalable solutions.
Goals of This Chapter
- Understand how and why certain patterns are frequently combined in real-world applications.
- Learn to improve system design by separating concerns and enhancing reusability through structural composition.
- Develop the ability to identify recurring composite structures and apply them proactively in your own designs.
Covered Pattern Combinations (7 Key Pairs)
| Combination | Description |
|---|---|
Strategy × Template Method | Fixed flow with flexible behavior injection |
Observer × Mediator | Decoupled notification and orchestration control |
Command × Memento | Command history tracking and state restoration |
Facade × Iterator | Unified interface for traversing complex collections |
Proxy × Strategy | Transparent control with swappable execution logic |
State × Strategy | State-driven behavior delegation |
Bridge × Strategy | Decoupled abstraction and implementation with injection |
Page Structure
Each combination is presented with:
- Intent of the Combination – What makes these patterns work well together
- Common Use Cases – Typical practical scenarios where this pair is applied
- UML Class Diagram – To visualize the structure
- Code Example: Concrete implementation (TypeScript / PHP / Python) — final form only.
- Explanation – Highlighting the motivation, structure, and benefits
Supplement: Multi-Pattern Design (3 or more)
In production-grade systems, it is common to find combinations of three or more patterns working in unison. However, for clarity and learnability, this chapter focuses on two-pattern combinations as a practical baseline.
We provide an overview of more advanced multi-pattern compositions in the supplemental section:
Appendix: Evolution Maps of Composite Patterns
This appendix includes mermaid-style graphs showing common progression paths and pattern relationship diagrams.
Summary
Combining design patterns is not simply about adding features — it’s about designing a system where each part reinforces the overall structure. These composite patterns offer practical templates for building systems that are robust, flexible, and easy to evolve.
Through this chapter, you’ll gain tools to move beyond isolated pattern usage and toward composable, scalable design thinking grounded in real-world application needs.
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