[Dbix-class] has_many relationships

[Aran Deltac]

On 5/1/06, Dan Horne <dan.horne at redbone.co.nz> wrote:
> Hi all
>
> I'm don't quite understand how to do joins in a "has many" context, and why
> it works differently from a "belongs_to" equivalent. Take, for example the
> music schema in Example.pod
> (http://search.cpan.org/~elliott/DBIx-Class-0.06002/lib/DBIx/Class/Manual/Ex
> ample.pod). The following query works (where CDs have many Tracks):
>
>   sub get_cd_by_track {
>     my $tracktitle = shift;
>     print "get_cd_by_track($tracktitle):\n";
>     my $rs = $schema->resultset('Cd')->search(
>       {
>         'tracks.title' => $tracktitle
>       },
>       {
>         join     => [qw/ tracks /],
>       }
>     );
>     my $cd = $rs->first;
>     print $cd->title . "\n\n";
>   }
>
> This all works, but if I try to add the track title to the query:
>
>     print $cd->tracks->title . "\n\n";

$cd->tracks() returns a resultset.  If you want to get at the title of
the tracks do something like this:

my $tracks_rs = $cd->tracks();
while (my $track = $tracks_rs->next()) {
  print( $track->title() . "\n" );
}

> I get:
>
>     Can't locate object method "title" via package "DBIx::Class::ResultSet"
>
> How do I also get the track title from the resultset?

A resultset by definition is a set, not a single record.  So,
retrieving a single field on a resultset is not a logical approach.

Aran

> Dan
>
>
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