[Dbix-class] Prefetch, DBIC, Relationships

[Amiri Barksdale]

Hi folks.

I was chatting with ribasushi on irc today about the way to get
relationships with
$schema->source($source)->relationships/relationship_info, so I can
create a series of statements like this:

    list_prefetch_allows    =>  [ 
        'cds', { cds => [qw/cd_to_producer tags tracks/] },
    ],  

or like this:

    list_prefetch_allows    =>  [
        'cd_to_producer', { cd_to_producer => [qw//] },
        'tags', { tags => [qw//] },
        'tracks', { tracks => [qw//] },
    ],  

For a Catalyst::Helper::Controller I am writing. Now, I am not sure how
to implement ribasushi's advice, so I am posting the code here to
solicit feedback. It seems clumsy to me, and like ribasushi said,
I am sure I am doing it wrong, but I don't know how else to do it.

In a loop through $schema->sources, I do this:

  for my $source ($schema->sources) {
      my @list_prefetch_allows =
_return_has_many_list($schema->source($source)->_relationships);

      @list_prefetch_allows = map {
          my $ref = $_;
          qq|'$ref->[0]', { |
          . $ref->[0]
          . qq| => [qw/|
          . join (' ', map { $_->[0] }
_return_has_many_list($schema->source($ref->[1])->_relationships))
          . qq|/] },\n\t\t|;
      } @list_prefetch_allows;

The subroutine _return_has_many_list is this:

sub _return_has_many_list {
    my ($relationships) = @_;
    return grep { $relationships->{$_->[0]}->{attrs}->{accessor} =~
/multi/ } map { [$_, $relationships->{$_}->{source} ] } sort keys
%$relationships;
}

All feedback welcome!

Amiri