[Catalyst] Mason + DBI + Catalyst?

[Marcello Romani]

Octavian Râsnita ha scritto:
>> On Tue, May 26, 2009 at 01:37:40AM +0200, Daniel Carrera wrote:
>>> >Being able to chain resultsets makes it much much easier than using
>>> >straight SQL, and you write less code.  If you have a query you've
>>> >constructed called $query, and lets say you now only want active 
>>> records
>>> >you can do $query = $query->search({ active => 1 });  In this way you
>>> >can filter many things incrementally.
>>>
>>> But is that efficient? It looks like you are getting MySQL to return the
>>> entire data set and then making Perl filter it. That can't be efficient.
> 
> Here it is a short code example that might appear in a controller:
> 
> sub author : Local {
>  my ($self, $c) = @_;
> 
> #Variables you might get after the user submits a form:
> 
>  my $name = $c->req->params->{name};
>  my $country = $c->req->params->{country};
> 
> #Search the database for all fiction authors:
> 
>  my $authors = $c->model("DB::Authors")->search({
>    style => 'fiction',
>  });
> 
> #Until this point DBIC doesn't touch the database.
> 
> #Add filters based on what the user searched using the form:
> 
>  $authors = $authors->search({name => {-like => "%$name%"}) if $name;
> 
>  $authors = $authors->search({country => $country}) if $country;
> 
> #Until this point, DBIC also didn't touch the database.
> 
> #Add the $authors object to the stash, to be able to print it in a 
> template:
>  $c->stash->{authors} = $authors;
> 
> #Until here, DBIC didn't touch the database
> }
> 
> #And the subroutine ended.
> 
> And then you can print some things using a Template-Toolkit template 
> (authors.tt):
> 
> [% IF some_variable = 1 %]
>  [% FOREACH author = authors.next %]
>    Name: [% author.name %]
>    Country: [% author.country %]
>    Localized birthday month: [% 
> author.birthday.set_locale('fr').month_name %]
> 
>    The books of this author:
>    [% FOREACH book = author.books %]
>      [% book.title %] - [% book.editor %]
>    [% END %]
>  [% END %]
> [% END %]
> 
> 
> And at this point, DBIC still doesn't touch the database if the variable 
> "some_variable" is not equal to 1 so the code below the IF line 
> shouldn't be executed.
> 
> But if the variable is 1, only at this point DBIC executes the necessary 
> queries and get the data. And you have seen that due to the relations 
> that were created in the DBIC result classes, it would be very simple to 
> access not only data about the authors, but about his books or data that 
> can be found in other related tables, without needing to define a new 
> query.
> 
> I wrote this code in Outlook Express and it might have bugs because I 
> didn't test it, but I hope it helps to make an idea about what DBIC can do.
> 
> Octavian
> 
> 
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> 

I think this example is very interesting and should end up into the wiki 
somewhere!

I think it can be a good selling point for DBIC, but I've not seen it 
explained so well until now (but I admit I've not looked up the docs in 
a while...)

Thank you.

-- 
Marcello Romani