Re: Repositories Global only or contextual?

On Tue, 2014-01-21 at 16:35 -0800, [email protected] wrote:
> Repository is not really a concept from your domain. That's an
> infrastructure concept [so that domain can make side effects ;)]

I beg to differ. According to Eric Evans in chapter 6 of the blue book:
«A REPOSITORY lifts a huge burden from the client, which can now talk to
a simple, intention-revealing interface, and aks for what it needs *in
terms of the model*. To support all this requires a lot of complex
technical infrastructure, but *the interface is simple and conceptually
connected to the domain model*.» (my emphasis).

The implementation of a repository is thus an infrastructure concern,
but the interface of the repository is in terms of the model. I think
leaving repositories alone in the infrastructure might disconnect the
language of the repository's interface from the one of your domain over
time. I therefor consider it a best practice to model the interface of
the required repositories in the domain, and implement those interfaces
in the infrastructure.

> Having said that, lazy load is another story. While you could use
> signature to implement lazy load. since you are using Java, your
> signature would not look too nice (in .NET you could leverage
> IQueryable from LINQ - which looks much better).

Lazy loading is an optimization mechanism that should only be used if
required. And if it's required, it should not be a part of the
repository's published signature, but rather an infrastructure concern
that is encapsulated and hidden from the calling client.


Thomas.



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