UI layer dependency in DDD

Question

My current project is organized in this way:

• Domain Layer -> Domain objects and Repository Interfaces
• Infrastructure -> Repository implementation
• Application Layer -> Services in a MVVM pattern
• Presentation -> Accessing only Service Layer and working with ViewModels

I´m using an IoC Container (SimpleInjector). My Services receives an IRepository in the constructor like:

public CustomerService : ServiceBase
{
   public CustomerService(ICustomerRepository repository, IUnitOfWork<CustomerContext> uow)
   {
     ...
   }
}

My question is:

To inject a Repository in the Service, my Presentation Layer should reference the Domain Layer. It´s ok to add this reference? Shouldn't my presentation layer have reference only to the Infrastructure and the Application layer?

Answer 1

Yes, that's OK.

You need a reference to all components from the composition root (which usually resides in the presentation layer).

I understand it feels a bit strange at first, but you need to differentiate between a DLL-dependency and a hard class dependency. It's OK if your presentation layer depends on DLL's, it's not OK when a view depends on a SQL-repository (as an example).

I have written a blog post about this with some more information:

http://www.kenneth-truyers.net/2013/05/12/the-n-layer-myth-and-basic-dependency-injection/