Clean architecture is a software design philosophy that separates the business logic of an application from its external dependencies. This makes the application more flexible, maintainable, and testable.
Clean architecture is often visualized as a set of concentric circles, with the business logic at the center and the external dependencies on the outside. The dependencies between the circles can only flow inwards, meaning that the inner circles are not aware of the outer circles.
The following are the four main layers of clean architecture:
Entities: These are the core data objects of the application. They are independent of any external framework or technology.
Use cases: These are the business logic of the application. They implement the core functionality of the application and interact with the entities.
Interface adapters: These adapters provide a layer of abstraction between the use cases and the external dependencies. They convert the data between the use cases and the external dependencies.
External interfaces: These are the interfaces to the external dependencies of the application, such as the database, web server, and third-party services.
The dependency rule of clean architecture states that source code dependencies should only point inwards. This means that the inner layers should not know anything about the outer layers. This makes the application more modular and easier to test.
Clean architecture has a number of benefits, including:
Flexibility: The application is less coupled to its external dependencies, making it easier to change or replace those dependencies.
Maintainability: The application is easier to understand and maintain because the business logic is separated from the external dependencies.
Testability: The application is easier to test because the business logic can be tested in isolation from the external dependencies.
Portability: The application is easier to port to different platforms because the business logic is independent of any specific technology.
Clean architecture is a powerful tool for designing maintainable and testable software. It is a good choice for applications that need to be flexible and adaptable to change.
Here are some examples of how clean architecture can be used:
A web application might use clean architecture to separate the business logic from the database, web server, and user interface.
A mobile application might use clean architecture to separate the business logic from the native platform APIs.
A microservices architecture might use clean architecture to separate the business logic from the messaging system and other microservices.
If you are interested in learning more about clean architecture, I recommend reading the book "Clean Architecture: A Craftsman's Guide to Software Structure and Design" by Robert C. Martin.
The following are some of the alternatives to clean architecture:
Hexagonal architecture: Hexagonal architecture is also known as ports and adapters architecture. It is similar to clean architecture, but it uses a more flexible approach to designing the interfaces. The interfaces are represented by ports, which can be implemented in different ways.
Onion architecture: Onion architecture is another alternative to clean architecture. It is a layered architecture where the inner layers contain the core business logic and the outer layers contain the external dependencies. The inner layers are independent of the outer layers, making the application more flexible and maintainable.
Microservices architecture: Microservices architecture is a decentralized architecture where the application is decomposed into a set of small, independent services. Each service is responsible for a specific task and communicates with the other services through well-defined APIs.
Event-driven architecture: Event-driven architecture is an architectural pattern where the components of an application communicate with each other by exchanging events. Events are triggered by user actions, external events, or other components of the application.
Domain-driven design (DDD): DDD is a software design approach that focuses on modeling the business logic of an application using a rich domain model. The domain model is a conceptual model of the real-world problem that the application solves.
The best alternative to clean architecture will depend on the specific needs of the application. For example, if the application needs to be highly scalable and performant, then a microservices architecture may be a good choice. If the application needs to be highly flexible and maintainable, then a hexagonal or onion architecture may be a good choice.
Here are some additional considerations for choosing an alternative to clean architecture:
Size and complexity of the application: Larger and more complex applications will require more sophisticated architectures.
Performance requirements: Applications that require high performance will need architectures that minimize dependencies and interactions between components.
Scalability requirements: Applications that need to be scalable will need architectures that allow for easy addition or removal of components.
Existing codebase: If the application is already under development, it may be important to choose an architecture that is compatible with the existing codebase.
Ultimately, the best way to choose an alternative to clean architecture is to carefully consider the specific needs of the application.