Comments on: Repositories don’t have save methods

By: Rohland

Rohland — Mon, 26 Oct 2009 07:33:20 +0000

Richard, in many cases you need to explicitly force an update as part of a larger unit of work. I am not sure if I prefer the SubmitChanges approach as implemented with LINQ to SQL.

For example, I don’t enjoy having to pass the data context to each repository. Obviously, you could implement some kind of IOC container so you don’t deal with the binding explicitly but when I have tried this in the past I have run into some weird runtime issues. Case in point – the LoadWith option in LINQ to SQL just doesn’t really work if you implement this kind of pattern because the options need to be set before the context is first utilised. This causes a headache in terms of lifetime management of the data context.

I have been using LLBLGEN for the past 6 months or so and have really been impressed with the library. Granted, my repositories have a “Save” method, but I am not sure if this is such a big issue.

By: Matt Freeman

Matt Freeman — Sat, 24 Oct 2009 06:38:28 +0000

I think I agree, although I have no yet adopted this approach myself, it should be a simple refactor. Infact my save method is pretty dumb since when the UOW is commited any dirty entities are flushed via nhibernate.

By: Richard

Richard — Fri, 23 Oct 2009 21:48:26 +0000

Mike: save is a frequently used term but so is login. Unless your domain is a document editor or security gateway, both are application concepts, not part of the domain model.

By: Richard

Richard — Fri, 23 Oct 2009 21:44:17 +0000

Rohland and Mathias: Add is just add, you only call it the first time an entity is made persistent. Updates to existing objects are handled via the unit of work; it keeps track of all loaded entities and at the end it looks for any that changed and saves them.

Both NHibernate’s ISession and Linq-to-SQL’s DataContext implement this pattern.

By: Mathias

Mathias — Fri, 23 Oct 2009 21:26:07 +0000

+1 to Rohland’s question! Is your Add an “Add or Replace”, and if not, how do you handle updates?

By: Mike

Mike — Fri, 23 Oct 2009 14:20:31 +0000

I agree mostly but sometimes “Save” is part of the ubiquitous language everyone agrees to.

By: Rohland

Rohland — Fri, 23 Oct 2009 08:57:06 +0000

Hi Richard,

Just interested, how would you implement the update mechanism in this case?

Cheers,
Rohland

By: Reflective Perspective - Chris Alcock » The Morning Brew #461

Reflective Perspective - Chris Alcock » The Morning Brew #461 — Fri, 23 Oct 2009 07:37:53 +0000

[...] Repositories don’t have save methods – Richard Dingwall argues that a correct DDD style repository does not have a save method, and should instead have a collection like interface, meaning Add is more appropriate [...]