[Dbix-class] Where to define constants.

[Ian]

Bill
Yes, I have pondered the same question.

My current solution is to have a MooseX::Singleton class that defines 
all constants used in my database (and perhaps elsewhere in my 
application). e.g.

package MyApp::Constants;

use MooseX::Singleton;

has track_type_foo => (is => 'ro', default = 1);
has track_type_bar => (is => 'ro', default = 2);

----
Then, as per Moosex::Singeton I initialize it once at the start of my 
application.

MyApp::Constant->initialize;

----
Then I can use it throughout my application.

my $constant = MyApp::Constant->instance;

   sub foo_track_type_count {
     return shift->tracks( {
       track_type => $constant->track_type_foo,
       })->count;
   }

----
regards
Ian


On 23/04/2010 22:46, Bill Moseley wrote:
>
> My music DB has CDs and each CD has many tracks.
>
> In my CD source class I have helper methods.
>
>     sub total_track_count {
>          return shift->tracks->count;
>     }
>
>
> And for the sake of the example, I have a "track_type".
>
>     sub foo_track_type_count {
>          return shift->tracks( { track_type => 1 } )->count;
>     }
>
>     sub bar_track_type_count {
>         return shift->tracks( { track_type => { -in => [2,3] } } )->count;
>     }
>
>
> I'm finding I need to know the track_type IDs in other code -- for
> example, in validation code.  I don't want to hard-code the track_type
> ids all over the place.  My question is how do you manage constants like
> this?
>
> One option is to have a constants module, i.e. "use MyApp::Const
> 'track_types'" that my result source uses.  Then any other code that
> needs those constants also uses MyApp::Const.
>
> Another option would be to define the constants in the Track source.
>
>     sub bar_types { return [2,3] }
>
>
> then back in the Cd class:
>
>     sub bar_track_type_count {
>         my $self = shift;
>
>         my $bar_types = $self->result_source->schema->resultset( 'Track'
>     )->result_class->bar_types;
>
>         return $self->tracks( { track_type => { -in => $bar_types } }
>     )->count;
>     }
>
>
> How do you manage constants like this?
>
> BTW -- Can't I get the result class w/o building a resultset?  Something
> like $schema->source( 'Track') ?
>
>
>
>
>
> --
> Bill Moseley
> moseley at hank.org <mailto:moseley at hank.org>
>
>
>
> _______________________________________________
> List: http://lists.scsys.co.uk/cgi-bin/mailman/listinfo/dbix-class
> IRC: irc.perl.org#dbix-class
> SVN: http://dev.catalyst.perl.org/repos/bast/DBIx-Class/
> Searchable Archive: http://www.grokbase.com/group/dbix-class@lists.scsys.co.uk