Appendix: Extended Composition with 3 or More Patterns

While this document primarily focuses on combinations of two design patterns, in practice it is not uncommon to find larger compositions where multiple patterns are layered to solve complex design needs.

This appendix presents several representative examples of three or more design patterns working together, along with a visual map to help understand the structural evolution and relationship between them.

✅ Purpose and Overview

• Combinations of three or more patterns often emerge as natural extensions of two-pattern compositions.
• Each pattern in the chain plays an independent yet complementary role.
• This section helps provide a bird’s-eye view of pattern expansion paths, building on the main chapter’s examples.

✅ Pattern Relationship Graph

The following diagram illustrates the common evolution paths from one pattern to another.
Each arrow (→) indicates that a higher-level pattern can naturally build upon the preceding one.

✅ Representative Pattern Stacks

Composition	Description
Strategy → Template Method → Command → Memento	A layered structure where dynamic behaviors (Strategy) are wrapped in a shared process flow (Template Method), transformed into executable commands (Command), and tracked with undo/redo capabilities (Memento)
Proxy → Strategy → Memento	A middleware layer combining access control (Proxy), dynamic execution paths (Strategy), and state preservation (Memento)
State → Mediator → Observer	A decoupled architecture where behavior changes with state (State), coordinated through a central mediator (Mediator), and observed via a publish-subscribe mechanism (Observer)
Facade → Iterator → Command	A streamlined interface (Facade) backed by internal iteration (Iterator) and encapsulated executable operations (Command)

✅ How to Use This Section

• This appendix offers a structural summary of extended compositions, rather than deep-dive implementation examples.
• While all detailed pages in this document focus on two-pattern combinations, these diagrams provide structural context for how larger patterns evolve.
• In real-world applications, three-pattern compositions often grow organically from a two-pattern base, once further flexibility or scalability is needed.

✅ Summary

• Multi-pattern structures involving three or more patterns are best understood as extensions of two-pattern compositions.
• This document is structured to equip readers with the foundational understanding of two-pattern usage, from which these larger structures can emerge.
• The diagram in this appendix serves as a visual reference for identifying natural paths of pattern expansion.