Clean Architecture with Repositories and Services

Question

I am implementing a Clean Architecture. I have four projects: Domain, Application, Infrastructure, and Presentation.

I have repository implementations defined in the Infrastructure. And I have the Repository Interfaces in the Domain.

I also have Services with a corresponding repository injected. For example, StudentService. I inject the StudentRepository into the StudentService. My question is, where do I put the interface IStudentService? Should it reside in the Domain along with the interface IStudenRepository? Or is it more proper to place it in the Application?

I currently have my IStudentService in the Application project. But my understanding is to have loose coupling and placing all Interfaces in the Domain project. Is my understanding correct?

Answer 1

It is generally a good practice to place interface definitions in the Domain layer of a Clean Architecture application. This is because the Domain layer represents the core business logic of the application, and interfaces are an important part of defining the contract for that logic. By placing interface definitions in the Domain layer, you can ensure that the Domain is decoupled from the implementation details in the other layers of the application.

For example, in your case, the IStudentRepository interface would be defined in the Domain layer because it represents the contract for how the StudentService can interact with the student data store. The IStudentService interface would also be defined in the Domain layer because it represents the contract for the business logic related to students.

By placing both of these interfaces in the Domain layer, you can ensure that the Domain is decoupled from the implementation details in the other layers of the application. This makes it easier to change the implementation of these interfaces without affecting the rest of the application.

In summary, it is generally a good practice to place interface definitions in the Domain layer of a Clean Architecture application in order to ensure loose coupling and separation of concerns.

Answer 2

To implement Clean Architecture follow the following steps:

Domain Project:

• Domain should have just entities such as "Student" Entity.

Application Project:

• Application should have interfaces and services and the implementation of services.

Infrastructure Project:

• Infrastructure should have the implementation of interfaces that are defined in the Application, and DbContext class.

The presentation should have the UI.