[Catalyst] The model -is- where your business logic lives.

[Anthony Gardner]

I've gone about it this way, and although the business logic is not within Catalyst, somehow, what I've done doesn't feel right.

In myapp_server.pl I've had to add a few paths to @INC
use lib "/home/anthony/devel/lib";
use lib "/home/anthony/devel/lib/Test"

For my business layout I have ...

~/devel/lib/Test/TestSchema.pm
~/devel/lib/Test/TestSchema/UserProfile.pm
~/devel/lib/Test/Model/UserProfile.pm (see snippet two)
~/devel/lib/Test/Model/Base.pm (see snippet three)

Then I have for Catalyst

~/dev/websites/MyApp/lib/MyApp/Model/UserProfile.pm (see snippet one)

########### (snippet one)

package MyApp::Model::UserProfile;

use strict;
use base 'Catalyst::Model::DBIC::Schema';

use Test::Model::UserProfile;

__PACKAGE__->config(
    schema_class => 'Test::TroveSchema',
    connect_info => [
        'dbi:SQLite:db/test.db',
        '',
        '',

    ],
);

sub new {
  my $class = shift;
  my $c = shift;
  my $args = shift;

  my $merged_args = Catalyst::Utils::merge_hashes( $args, $class->config() );
  return Test::Model::UserProfile->new( $merged_args );

}

######################## (snippet two)


package Test::Model::UserProfile;

use strict;

use base 'Test::Model::Base';

<methods>

################## (snippet three)

package Test::Model::Base;

use base 'Class::Accessor';

use Carp;

use Test::TroveSchema;


__PACKAGE__->mk_accessors(qw|schema|);

sub new {
  my $class = shift;
  my $self = $class->next::method(@_);

  croak "->connect_info must be defined" unless( $self->{connect_info} );

  $self->{schema} = Test::TroveSchema->connect( @{ $self->{connect_info} } );

  $self
}

sub find {
  my $self = shift;
  my $id = shift;

  my $calling_pkg = (caller(0))[0];
  $calling_pkg =~ s|(.*)::(.*)$|$2|;

  return $self->{'schema'}->resultset($calling_pkg)->find($id);
}

Now, what seems wrong to me is that I've had to write new() methods and also, for example, a find() method which is in Test::Model::Base. This doesn't seem right to me.I would've thought I would have all of DBIC's utils available to me without having to recall them.

Can anyone offer pointers?

Many thanks

-Ants

Matt S Trout <dbix-class at trout.me.uk> wrote: On Thu, Sep 27, 2007 at 11:51:26AM +0100, Ian Docherty wrote:
> In a previous thread, Matt S Trout said.
> 
> >The model -is- where your business logic lives.
> >
> >The real question is whether your ORM should be directly in the model or
> >not, but that's a whole different thread.
> 
> Based on this I have the following simple code.
> 
> ####
> package MyApp::Model::DBIC;
> 
> use strict;
> use base qw(Catalyst::Model::DBIC::Schema);
> 
> ####
> package MyApp::Schema::Demo;
> 
> use base qw(DBIx::Class);
> 
> __PACKAGE__->load_components(qw(PK::Auto Core));
> __PACKAGE__->table('demo');
> __PACKAGE__->add_columns(qw(id name state));
> __PACKAGE__->set_primary_key('id');
> 
> 
> ####
> package MyApp::Model::DBIC::Demo;

Put this code in MyApp::Schema::Demo.

I often call it e.g. MyApp::DataStore or MyApp::Domain to remind me that
it's the business layer and the DBIC-ness is merely incidental.
 
> sub do_some_business_logic_stuff {
>    my ($self) = @_;
> 
>    if () {
>        $self->state('pending');
>        $self->update;
>    }
> }   
> 
> 
> #### somewhere in my application
> 
> $demo = $c->model('DBIC::Demo')->find($index);
> $demo->do_some_business_logic_stuff;
> 
> -------------
> 
> Is this a standard/typical/best-practice way to do this sort of thing? 
> 
> It seems to me that if I want to use the business logic in an external 
> application (cronjob) then I am having to use the MyApp::Model::DBIC::Demo 
> namespace as decreed by Catalyst (not that this is a big issue).

Having moved the logic out of MyApp::Model:: this ceases to be an issue.

Don't confuse class -names- with the nature of classes. MyApp::Model:: is
*adapters* that make a model available to MyApp, not where your domain model
logic itself should live.

I usually these days have MyApp::Web for the catalyst app instead of MyApp so
I can deploy things like MyApp::DataStore from a separate dir tree.

-- 
      Matt S Trout       Need help with your Catalyst or DBIx::Class project?
   Technical Director                    http://www.shadowcat.co.uk/catalyst/
 Shadowcat Systems Ltd.  Want a managed development or deployment platform?
http://chainsawblues.vox.com/            http://www.shadowcat.co.uk/servers/

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