Understanding Clean Architecture

Goals of Clean Architecture

Clean architecture aims to create software that is easy to understand, maintain, and test. It emphasizes separation of concerns and the creation of well-defined boundaries between different parts of the application parts. This separation allows for easier testing of individual components.

Benefits of Clean Architecture

• ➤ Framework Independence: Can be used with ASP.NET (Core), Java, Python, etc., without relying on any specific software library or proprietary codebase.
• ➤ Testability: Can be used with ASP.NET (Core), Java, Python, etc., without relying on any specific software library or proprietary codebase.
• ➤ UI Independence: Logic is kept out of the UI, making it easy to switch technologies, e.g., from Angular to React or Blazor.
• ➤ Database Independence: Cleanly separates data-access concerns, facilitating changes from SQL Server to CosmosDB.
• ➤ Independence from External Systems: Core is completely isolated from the outside world, ensuring longevity and ease of updates.
• ➤ Loose Coupling: Promotes loose coupling between components and layers, enhancing maintainability and scalability.

Clean Architecture: The Big Picture

• 1. Business Logic and Application Model at the Center: Ensures crucial aspects of the software are independent and well-defined.
• 2. Inverted Dependency: Business logic does not depend on data access or infrastructure concerns; instead, infrastructure depends on the Application Core.
• 3. Definite Abstractions in Application Core: Defines clear abstractions (interfaces) representing essential contracts.
• 4. Implementation in the Infrastructure Layer: Concrete implementations are in the Infrastructure layer, handling data access, external services, etc.
• 5. Inward Flow of Dependencies: All dependencies flow inward towards the Application Core, ensuring strict separation of concerns.

Layers in Clean Architecture

• ➤ Domain Layer: Core of the architecture, implementing business logic with no dependencies on other layers.
• ➤ Application Layer: Middle layer, managing data between domain and presentation/infrastructure layers.
• ➤ Infrastructure Layer: Contains classes for accessing external resources like file systems, web services, and databases.
• ➤ Presentation Layer: UI code, using ASP.NET Core for building interfaces.

Domain Driven Design (DDD)

Domain-Driven Design (DDD) is a set of principles and patterns for designing software that focuses on the core domain and its logic. DDD emphasizes collaboration between technical and domain experts to iteratively refine a conceptual model that addresses complex business requirements. The key concepts of DDD include:

• Entities:	Objects with a distinct identity that run through different states in the system.
• Value Objects:	Immutable objects that represent a descriptive aspect of the domain with no conceptual identity.
• Aggregates:	A cluster of domain objects that are treated as a single unit for data changes.
• Repositories:	Mechanisms for encapsulating storage, retrieval, and search behavior, imitating a collection of objects.

Testing in Clean Architecture

Testing in Clean Architecture involves testing each layer independently to ensure that all components work correctly and interact properly with one another. This is a very crucial step and significantly reduces complexity.

1. ➤ Mocking: Creating objects that simulate the behavior of real objects. In this case, you can mock your database repositories without the actual implementation.
2. ➤ Dependency Injection: Passing dependencies (such as repositories) into your use cases or services to make them easier to perform unit testing.
3. ➤ Isolation: Ensuring that each test is independent and does not rely on the state or data of other tests.

Implementing Clean Architecture

• 1. Configuration of Domain Layer: Define entities, enums, exceptions, interfaces, and types.
• 2. Configuration of Application Layer: Write business logic and service interfaces, maintaining loose coupling.
• 3. Configuration of Infrastructure Layer: Implement data access and external resource interactions based on Core interfaces.
• 4. Configuration of Presentation Layer: 4. Configuration of Presentation Layer:

Principles to Follow

1. Separation of Concerns:	Avoid mixing different code responsibilities in the same method/class/project.
2. Single Responsibility:	Each module/component should have only one reason to change.
3. Don’t Repeat Yourself (DRY):	Avoid duplicated code or logic.
4. Inverted Dependencies:	High-level policies should not depend on low-level details; use dependency injection to promote loose coupling.

Conclusion

Clean Architecture provides a robust foundation for building microservices using .NET Core Web API. By adhering to principles of separation of concerns and dependency inversion, developers can create scalable, maintainable, and testable applications. Embracing Clean Architecture ensures a solid foundation for the ever-changing demands of modern software development.

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