[Catalyst] Catalyst::Model::DBIC::Schema or not?

[John Napiorkowski]

----- Original Message ----
From: Jason Gottshall <jgottshall at capwiz.com>
To: The elegant MVC web framework <catalyst at lists.rawmode.org>
Sent: Friday, April 27, 2007 12:54:39 PM
Subject: RE: [Catalyst] Catalyst::Model::DBIC::Schema or not?

Brian Kirkbride wrote:
> Jason Gottshall wrote:
> > Brian Kirkbride wrote:
> > > I usually have an architecture like this:
> > >
> > > Client -> Controller -> Model -> ORM -> Database
> > >
> > > The ORM is usually just vanilla (as you suggested), the Database 
> > > enforces simple 
> > > data constraints (foreign keys, etc) and the Model makes 
> > > sure that the complex 
> > > business logic constraints are met.  Some things are simply not 
> > > enforceable by a 
> > > stored procedure - this might involve validation of image files
for 
> > > example. 
> > > The beauty of Catalyst is that it's up to you how to 
> > > handle separation of 
> > > concerns and Catalyst is helpful no matter how you do.
> > 
> > Thanks, Brian. This is the exact structure I'm considering. So my 
> > question is this: If all the ORM interaction happens at the 
> > Model level, 
> > and DBIC isn't being treated as a "model" itself, is there 
> > any reason to 
> > use Catalyst::Model::DBIC::Schema to establish the db connections? I

> > guess my gut tells me "no", but I want to make sure I'm not missing 
> > something here.
> 
> No problem.  As I said in my earlier reply, I don't have DBIC 
> models in my 
> catalyst app because it encourages me to put ORM-related code 
> where it belongs, 
> in the Business Logic model(s).

Just a follow-up to this month-old thread: 

I tried eliminating Catalyst::Model::DBIC::Schema in favor of having my
true business Models do all the interfacing with DBIC. No problem with
those Models, but I did discover an unintended consequence:
Catalyst::Plugin::<whatever>::DBIC stuff stopped working! 

It was specifically the storage components for Authentication and
Session that choked. I couldn't figure out how to give either of them
the connection info they needed; they both expect to be configured with
the name of a schema/table class that is then used, via
C::M::DBIC::Schema, to get a resultset.

So I'm trying out a compromise. I've set up the appropriate
C::M::DBIC::Schema model, but don't intend to use it directly from
controllers or views. Instead, I've provided all my db-interactive
models with a schema()method; if the model is being used under Catalyst,
they get at the schema object via the already-connected Catalyst DBIC
model (thanks to ACCEPT_CONTEXT); otherwise, a new connection is
composed and returned. I had to do a little more refactoring so that
both C::M::DBIC::Schema and the independent models have access to the
same connection logic, but it seems to be working. Meanwhile, the Auth
and Session plugins are working again, and I should be able to use other
DBIC-dependent plugins without problem.

Now it's just a matter of resisting the temptation, as Brian mentioned,
of accessing DBIC directly outside of models. I'm pretty sure I have the
will power, so I just have to worry about indoctrinating the rest of the
programmers in my office. Wish me luck...

Jason

I hesitate to mention this because it's not my project but Mango has taken an approach that
seems similar to what you mentioned (and others have mentioned a few times in other recent
and older threats) by having DBIC based business model classes that are linked into the Model
via a base Provider class.  You can see:

http://svn.mangoframework.com/CPAN/Mango/trunk/lib/Mango/Catalyst/Model/

to check this out.  Seems like a clean and sane approach.  You can always have a model subclassing
C::M::DBIC::Schema in there for rapid prototyping or compatibility with plugins that expect to find it.

Peace,
John


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