[Catalyst] Creating Good Adaptor or Bridge Models (WAS: Creating a thin Model)

[John Napiorkowski]

--- Jamie Neil <jamie at versado.net> wrote:

> Matt S Trout wrote:
> > If you get stuck, could you start a fresh thread,
> please? I think this one
> > has officially got confused now :)
> 
> Ok. Just for the record though, this seems to be
> working fine so far:
> 
> 
> package MySite::Model::Widget;
> 
> use strict;
> use warnings;
> use base qw/Catalyst::Model/;
> use MySite::Widget;
> 
> __PACKAGE__->config(
>      connect_info => [
>          'dbi:Pg:mysite', 'username',
>          'password', { AutoCommit => 1 },
>      ],
> );
> 
> sub new {
>      my ( $class, $c, $args ) = @_;
>      return MySite::Widget->new(
>          Catalyst::Utils::merge_hashes( $args,
> $class->config ) );
> }
> 
> 1;

[CUT]

Hey,

Maybe we could summarize the best practice lessons
from this thread?  If so I'll be happy to put them on
the wiki someplace suitable.

So we are saying it's better to override new instead
of COMPONENT and that it's okay to return your class
directly in new and not have to create an accessor and
then use AUTOLOAD to dispatch method calls?

So when you just want to make the object available via
$c->model(...)->method you can do (in the catalist
model):

sub new {
  my ($class, $c, $args) = @_;

  return ExternalModule->new(
    Catalyst::Utils::merge_hashes( $args,
$class->config )
  );
}

But if you are adapting and/or altering the method
calls it would be better to:

__PACKAGE__->mk_accessors(qw/some_object/);

sub new {
  my ($class, $c, $args) = @_;
  my $self = $class->NEXT::new($c, $args);

  $self->some_object(Someobject->new(
    Catalyst::Utils::merge_hashes( $args,
$class->config )

  return $self;
}

sub adapted_method
{
  my $result = shift->some_object->internal_method;
  ## Do something to $result
  return $result;
}

The reason I ask is because there have been several
ways of doing this very basic type of thing floating
around CPAN and I'm sure I'm not the only one
confused.

Maybe we could try to generate a concise list of cases
and then try to work out a best practices example for
each?  I'm sure that would be a good thing for a wiki
entry or even as part of the POD docs.

--john

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