Should the Domain Layer ever use the IRepositories it defines?

Tue, 06/16/2009 - 17:40 — SpartanDeveloper

Domain Layer
        class Member
                string UserName
        interface IMemberRepository

Let's say you want functionality to check if a UserName is in the database already. This logic would have to use a concrete implementation of the IMemberRepository, eg MemberRepositoryNHibernate.

My question is, where and how should this logic be implemented?

The Web Layer?

I think this is wrong because the functionality might be applicable across multiple UI layers.

In a "Service" in the Domain Layer?

If this method is used, how does the service retrieve the concrete implementation of IMemberRepository? Does it retrieve the repository from the IoC container, or should the repository be passed to the service's constructor? Any thoughts on this would be appreciated.

In the Entity itself?

I don't know...is it semantically wrong for the Member class to know about and utilize the IMemberRepository interface?

Here's the context in which I'm asking this question. I would like to have a separate IoC layer so that I could 1. switch containers easily and 2. eliminate references to the Peristence layer from my Web layer.

This IoC layer needs a reference to the Domain Layer, because it needs to know about the interfaces defined in the Domain Layer.

But now the Domain Layer can't use the IoC layer, that would be a circular dependancy. So that got me wondering about how proper that was anyway.

My current understanding is that since the Domain layer can't ask the container for a repository itself, it'll have to be passed in by the Web layer, which requests either the repository or the service from the container.

Much thanks to anyone who is willing to help straighten out my confusion.

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Thu, 12/24/2009 - 06:05 — Dasing29

Love Quotes

I recently read that love is entirely a matter of chemistry. That must be why my wife treats me like toxic waste. David Bissonnette I've been in love with the same woman for forty-one years. If my wife finds out, she'll kill me. Henry Youngman It's better to have loved and lost than to do forty pounds of laundry a week. Laurence J. Peter If love is blind, why is lingerie so popular? Unknown If love is the answer, could you rephrase the question? Lily Tomlin Love is the delightful interval between meeting a beautiful girl and discovering that she looks like a haddock. John Barrymore Love is an irresistible desire to be irresistibly desired. Robert Frost A kiss can be a comma, a question mark or an exclamation point. That's basic spelling that every woman ought to know. Mistinguette Absence -- that common cure of love.

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Sun, 07/19/2009 - 10:08 — Allard

Layer calling the Repository interface

Hi,

First some context: any application I develop has four mayor layers: UI, Application, Domain and infrastructure. The application layer is responsible for the "orchestration" of domain layer calls. The domain layer of course contains the actual operations and state as expressed by the ubiquitous language.

Since the application layer is responsible for orchestrating calls to the domain objects, it will first have to obtain a reference to them. The only way to do that is by calling the Repository implementation (through the interface, of course).

That's the way I do it in projects, and I find it useful. I hope it helps you too.

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Should the Domain Layer ever use the IRepositories it defines?