Are functionally connected to each other in a live application through Dependency Inversion-i.e.May also never know anything about layers which are adjacent to it.May never know anything about layers which surround (are outside of) it, just as Uncle Bob states.Layers in a Clean Architecture application: This is a great place to start, but I'd like to elaborate on it further.
That includes, functions, classes, variables, or any other named software entity."
In particular, the name of something declared in an outer circle must not be mentioned by the code in an inner circle. Nothing in an inner circle can know anything at all about something in an outer circle. This rule says that source code dependencies can only point inwards. "The overriding rule that makes this architecture work is The Dependency Rule. The principle that makes the architecture come together is called the Dependency Rule, as Uncle Bob describes: External agency independence: the business rules of the architecture are isolated and know nothing about the outside world.Ĭlean Architecture may be visualized as a series of concentric circles, each representing a different layer of the application.Database independence: the architecture is decoupled from the underlying data store.UI independence: the architecture can be unplugged from the user interface.Testable: the architecture is easy to write unit tests against.Framework independence: the architecture is decoupled from third party frameworks.In this article, Uncle Bob emphasizes five qualities which all of the predecessor architectures and Clean Architecture possess: It evolved over time from several other architectures including Hexagonal Architecture, Ports and Adapters, and Onion Architecture. Clean ArchitectureĬlean Architecture is a formal architecture which is relatively "modern" in that it is less than ten years old. Finally, I introduce Command Query Responsibility Segregation (CQRS), and describe how it complements and enhances Clean DDD solutions to create software systems that are elegant, robust, scalable, and testable.Īs before, here is the link to the demo application. Next, I discuss how Domain-Driven Design fits into this picture, and how DDD concepts dovetail nicely into Clean Architecture, producing a methodology called Clean DDD. In this blog entry I give a primer on Clean Architecture, which is a modern, scalable formal software architecture which is appropriate for modern web applications.