Further reading
Clean Architecture is a very complex subject, and one chapter is simply not enough to cover it. However, one of the most important concepts that Clean Architecture brings is the Dependency Rule. The Dependency Rule states that within a project, dependencies can only point inward.
To understand what the Dependency Rule is about, let's visualize the layer dependencies of our Restaurants app through a simplified version of concentric circles. Each concentric circle represents different areas of software with their corresponding layer dependencies (and libraries).
Figure 8.7 – The Dependency Rule with layers and components
This representation dictates that implementation details should be placed in outer circles (just as Compose is an implementation detail of the UI layer or Retrofit is an implementation detail for the Data layer), while business policies (Use Cases from the Domain layer) are placed within the inner circle.
The...
