22: Clean Architecture

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Clean Architecture Blog

Similar Architectures

• Hexagonal Architecture (Ports & Adapters)

• DCI

• BCE

They all have the same objective:

• The separation of concerns achieved by dividing the software into layers.

Each architecture produces a system with the following characteristics:

• Independent of Frameworks

• Testable

• Independent of the UI

• Independent of the database

• Independent of any external agency.

Entities

• Encapsulate enterprise-wide (or domain) Critical Business Rules.

• Can be an object with methods, or it can be a set of data structures and functions.

• Can be used by many different applications.

• Business Objects of the Application/Domain.

• Encapsulate the most general, high-level rules.

• Least likely to change when something external happens.

Use Cases

• Layer contains Application-specific business rules.

• Use cases orchestrate the flow of data to and from the entities, and direct those entities to use their Critical Business Rules to achieve the goals of the Use Case.

• We do NOT expect....

  • Changes in this layer to affect the Entities.

  • This layer to be affected by changes to externalities such as the database, the UI, or any of the common frameworks.

• Changes to the operation of the application will affect the use cases and software in this layer.

Interface Adapters

• A set of adapters that convert data from the format most convenient for the user cases and entities, to the format convenient for some external agency (database or web).

• Also in this layer is any adapter necessary to convert data from some external form (external service) to the internal form used by the use cases and entities.