How do I get values from a reference table in DBIx :: Class?
In my application, I have 2 tables, books and tags and a table of links book_tags. The link table also contains the number of times a book has been tagged with that particular tag. I can add a tag by doing
$book->add_tag($tag, { tag_count => 10 });
However, when I extract the tags for the book
@tags = $book->tags();
it does not return values from the reference table.
Is there a way to get values from the link table without doing it manually?
Since you have a named join table book_tags
, you will need to create a relationship many_to_many
from the table books
to the relationship of has_many
the table itself books
. The relationship has_many
should retrieve the id
tags associated with the book from the table book_tags
. You may need to add relationships similar to:
In Your::App::Schema::Result::Book
:
__PACKAGE__->has_many( book_tags => 'Your::App::Schema::Result::BookTag', 'book_id' );
__PACKAGE__->many_to_many( tags => 'book_tags', 'tag' );
In Your::App::Schema::Result::BookTag
:
__PACKAGE__->belongs_to( tag => 'Your::App::Schema::Result::Tag', 'tag_id' );
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You can proxy
properties through relationships like this:
Schema::Tag->has_many('book_tags' => 'Schema::BookTag',
undef, {
proxy => [ 'tag_count' ],
}
);
Then you can access the 'tag_count' like this:
my $tag_rs = $book->tags;
for( my $tag = $tag_rs->next ){
print $tag->tag_count;
}
More information can be found in the relationship docs .
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Thank! I've already done this part and it works.
My tables look like this:
BOOK:
book_id book_title [other fields]
TAG:
tag_id tag_name [other fields]
BOOK_TAG:
book_id tag_id tag_count
So I have a relationship between tags and books with many to many with an additional tag_count attribute that is stored in the link table.
I can add a tag to a book by doing
$book->add_to_tags($tag, { tag_count => 10 } );
which populates the tag_count field in the BOOK_TAG table.
But when I do
$book->tags();
it doesn't automatically retrieve the tag_count field from the BOOK_TAG. I can write
$tag = $schema->resultset('BookTag')->find( { book_id=>$book->book_id, tag=>$tag->tag_id });
$tag_count = $tag->tag_count();
I am trying to figure out if there is an easier way to get an extra attribute from a link table.