Catalyst add methods to a DBI model - perl

Question

How would I add methods to my DBI model if I have 'Catalyst::Model::DBI' based model and I'd like a method to have something like $c->model('DBI')->my_method(); but $c->model('DBI') doesn't return a ref to my that object, rather I get back a DBI::db. I can get back the dbh and operate on that, but I have a bunch of utility methods that I'd prefer to add here.

Answer 1

I haven’t seen you code so I can’t know for sure what you’re doing but if you’re using Catalyst::Model::DBI you’re doing something wrong. The raw model does return the object, e.g.: MyApp::Model::DBI=HASH(0xdf7ba0)
It sounds like you might be trying to load DBI with the Adaptor stuff. Subclassing DBI is harder than you might think so I’d definitely shy away from that.
Minimal reproduction–
# Create a new test model with SQLite.
script/*create.pl model DBI DBI "dbi:SQLite::memory:"
# A test controller to go with it.
script/*create.pl controller DBI
# Change the index method to show your raw model–
sub index :Path Args(0) {
my ( $self, $c ) = #_;
$c->response->body( $c->model("DBI") );
}
Now you could try adding something to your model–
# lib/MyApp/Model/DBI.pm
sub add {
my $self = shift;
my #add = #_;
#add == 2 or die "2 is a terrible error message: 2";
return $self->dbh->selectrow_array("SELECT ? + ?", {}, #add);
}
And this to your controller–
# lib/MyApp/Controller/DBI.pm
sub add : Local Args(0) {
my ( $self, $c ) = #_;
$c->response->body( $c->model("DBI")->add( 2,2 ) );
}
Then visit localhost:3000/dbi/add. Continue to extend your model however you like.
Now, that the question is answered. You really, really, really should take the learning hit right now and get familiar with DBIx::Class or one of the other first class ORMs in Perl. Bare bones DBI is fine but you’re going to find 100 problems over time that DBIC has solved and it comes with a deep test suite, a long history, dozens of extensions, and a helpful community.

Answer 2

I am not using a direct DBI model myself, so I am not sure this works for you. I use the DBIC::Schema model
script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
create=static dbi:mysql:mydb dbusername dbpass
This creates a DB model in the Model dir that is merely a wrapper to the underlying DBIx::Class::Schema schema that is saved in lib/MyApp/Schema.pm and lib/MyApp/Schema/Result/
If I add a foo() subroutine to lib/MyApp/Model/DB.pm I can simply reference it like
$c->model('DB')->foo()
I thought the DBI model also created a wrapper model, $c->model('DBI')->dbh should return the raw DBI handle, $c->model('DBI') the catalyst model wrapper

Answer 3

The code below is an example of how I build my Models, I've written a tutorial on this at:
http://brainbuz.org/techinfo. I use DBIx::Simple as a convenience, you can easily skip it for raw dbi, and directly reference $self->dbh in your Model.
# Parent MODEL
package BoPeep::Model::BoPeep;
use strict;
use warnings;
use DBIx::Simple ;
use parent 'Catalyst::Model::DBI';
__PACKAGE__->config(
dsn => BoPeep->config->{dsn} ,
user => BoPeep->config->{user} ,
password => BoPeep->config->{password} ,
);
use Moose ; #use Moose immediately before calling
#on Moose to extend the object
has db=>(
is =>'ro',
isa=>'DBIx::Simple',
lazy_build=> 1,
# If we don't want to handle all dbis methods,
# specify those that we want.
# handles=> [qw/query flat /],
);
sub _build_db {
my $self = shift ;
return DBIx::Simple->connect($self->dbh);
} ;
# Child Model
package BoPeep::Model::BoPeep::Flock;
use Moose;
use BoPeep;
use namespace::autoclean;
extends 'BoPeep::Model::BoPeep';
sub List {
my $self = shift ;
my $db = $self->db ;
my #sheep = $db->query('SELECT * FROM flock')->flat ;
return #sheep ;
}
__PACKAGE__->meta->make_immutable( inline_constructor => 0 );
1;