Clean Architecture Principles

This skill provides language-agnostic Clean Architecture principles for designing maintainable, testable software systems.

When to Use This Skill

• •Designing new feature architecture
• •Reviewing layer boundaries and dependencies
• •Evaluating dependency injection approaches
• •Making decisions about abstraction placement

Core Concepts

Clean Architecture aims to create systems where:

• •Business rules are independent of frameworks
• •UI, database, and external services are interchangeable
• •The system is testable without external dependencies

Quick Reference

Layer Structure (Inside → Outside)

1. •Domain Layer - Business rules, entities, value objects (no dependencies)
2. •Application Layer - Use cases, application services, ports
3. •Presentation Layer - UI, controllers, view models
4. •Infrastructure Layer - Frameworks, databases, external APIs

Dependency Rule

Dependencies point inward only. Outer layers depend on inner layers, never the reverse.

Infrastructure → Presentation → Application → Domain
     ↑               ↑              ↑           ↑
   (outer)                                   (inner)

Key Principles

1. •Dependency Inversion: Depend on abstractions, not concretions
2. •Interface Segregation: Small, focused interfaces
3. •Single Responsibility: Each layer has one reason to change

Resources

Read these in order for comprehensive understanding:

1. •resources/dependency-inversion.md - Dependency Inversion Principle
2. •resources/layer-separation.md - Layer responsibilities and boundaries
3. •resources/reference-rules.md - Abstract reference rules for any language

Integration with Other Skills

• •good-test-principles: Testability through proper layer separation
• •code-review-guideline: Architecture compliance checking
• •For language-specific implementation, see app-level skills