[Dbix-class] Encapsulate multiple steps for insertion

John Napiorkowski jjn1056 at yahoo.com
Thu Jan 11 16:44:46 GMT 2007

--- Tobias <list at funkreich.de> wrote:

> Hi everybody,
> I'm writing a forum application with DBIx::Class and
> Catalyst. Every post in a
> forum is stored using two tables (for performance
> reasons):
>   * posts - (DBIC class "Forum::Post")
>     contains basic data for every post
>     has_one relationship with Forum::PostText
>   * post_texts - (DBIC class "Forum::PostText")
>     contains just the texts
>     belongs_to Forum::Post
> I'm wondering what's the best way to encapsulate
> this because I don't want to
> make calls to several DBIx::Class classes everywhere
> I want to insert a new
> post (i.e. in Catalyst controllers). Should I just
> create a third class outside
> the Schema namespace which utilizes all neccessary
> DBIx::Class classes for
> inserting a new post to hide the underlying
> separation into two tables from
> the rest of the application? What I want is to call
> _ONE_ method in my
> Catalyst controllers to insert a new post into the
> database. The controller
> shouldn't worry if the data gets stored in one, two
> or ten tables.
> Maybe there's some sort of DBIx::Class magic to do
> this without having to
> add an extra layer myself?
> Thanks for any suggestions!
> --Tobias

I think there are two (or two and a half) ways of
dealing with this that I've seen kicked around are:

1) Add some methods to your DBIx::Class files.  For
example you can write a method called create_post that
would be attached to the post class that would insert
into both tables for you.

I've heard this method called the "ActiveRecord"
pattern, since you are combining your physical model
(the object that maps to a table) with a business
model (that encapsulates your business rules).

2) Create a custom Catalyst Model that offers methods
for your business rules and creates it's own DBIx
class objects as part of it's instantiation.

2.5) like 2) but instead of the object being a
catalyst model you make it a plain Perl object (or use
a OO framework like Moose) and then have a very simple
Catalyst model instantiate it for you.

I tend to do 1) because it's easy and makes it so that
your business rules are not just inside catalyst (you
can use them for CRONS, etc).  I would like 2.5 for
the same reason but I'm not sure about the best
approach.  I'm hoping someone with a better grasp of
MVC best practices eventually releases an example :) 
For example I can see if you really get Moose you
could create a business object rule that all your
business classes you and then you are sure of the way
it would work.  This is the generally the approach
that J2EE uses; they have a bean object that uses an
interface for this, I think.

I think 1) is okay for rules that work primarily on a
single table or on tables that are related.  But
ideally you should have a separate domain object for
each class of business rule, or at least that is what
I am gathering from my reading of the way MVC is
handled in other frameworks.  This way you get better
reusability and can compose your objects best.  I
think it would also fit into the work being done on
Reaction (although please don't quote me on this, I am
still reading and re-reading reaction source) because
if you have a business object with a defined interface
that would make it easier to hook it to the UI model
through Moose's reflection.  Sounds great, wish I know
how to make it work :)

Will be watching this thread with interest.


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