=head1 SYNOPSIS
+ ## Creating relationships
MyDB::Schema::Actor->has_many('actorroles' => 'MyDB::Schema::ActorRole',
'actor');
MyDB::Schema::Role->has_many('actorroles' => 'MyDB::Schema::ActorRole',
MyDB::Schema::Role->many_to_many('actors' => 'actorroles', 'actor');
MyDB::Schema::Actor->many_to_many('roles' => 'actorroles', 'role');
+ ## Using relationships
$schema->resultset('Actor')->roles();
$schema->resultset('Role')->search_related('actors', { Name => 'Fred' });
$schema->resultset('ActorRole')->add_to_roles({ Name => 'Sherlock Holmes'});
=over 4
-=item Arguments: $accessor_name, $related_class, $fk_column|$cond?, $attr?
+=item Arguments: $accessor_name, $related_class, $fk_column|\%cond|\@cond?, \%attr?
=back
-Creates a relationship where the calling class stores the foreign class's
-primary key in one (or more) of its columns. This relationship defaults to
-using C<$accessor_name> as the foreign key in C<$related_class> to resolve the
-join, unless C<$fk_column> specifies the foreign key column in
-this class or C<$cond> specifies a reference to a join condition hash.
+Creates a relationship where the calling class stores the foreign
+class's primary key in one (or more) of its columns. This relationship
+defaults to using C<$accessor_name> as the column in this class
+to resolve the join against the primary key from C<$related_class>,
+unless C<$fk_column> specifies the foreign key column in this class or
+C<cond> specifies a reference to a join condition hash.
=over
# in a Book class (where Author has many Books)
- My::DBIC::Schema::Book->belongs_to( author => 'My::DBIC::Schema::Author' );
+ My::DBIC::Schema::Book->belongs_to(
+ author =>
+ 'My::DBIC::Schema::Author',
+ 'author_id'
+ );
+
+ # OR (same result)
+ My::DBIC::Schema::Book->belongs_to(
+ author =>
+ 'My::DBIC::Schema::Author',
+ { 'foreign.author_id' => 'self.author_id' }
+ );
+
+ # OR (similar result but uglier accessor name)
+ My::DBIC::Schema::Book->belongs_to(
+ author_id =>
+ 'My::DBIC::Schema::Author'
+ );
+
+ # Usage
+ my $author_obj = $book->author; # get author object
+ $book->author( $new_author_obj ); # set author object
+ $book->author_id(); # get the plain id
+
+ # To retrieve the plain id if you used the ugly version:
+ $book->get_column('author_id');
- my $author_obj = $obj->author; # get author object
- $obj->author( $new_author_obj ); # set author object
-
-The above belongs_to relationship could also have been specified as,
-
- My::DBIC::Schema::Book->belongs_to( author,
- 'My::DBIC::Schema::Author',
- { 'foreign.author' => 'self.author' } );
If the relationship is optional -- i.e. the column containing the foreign key
can be NULL -- then the belongs_to relationship does the right thing. Thus, in
operations work correctly. The modified declaration is shown below:
# in a Book class (where Author has_many Books)
- __PACKAGE__->belongs_to(author => 'My::DBIC::Schema::Author',
- 'author', {join_type => 'left'});
+ __PACKAGE__->belongs_to(
+ author =>
+ 'My::DBIC::Schema::Author',
+ 'author',
+ { join_type => 'left' }
+ );
Cascading deletes are off by default on a C<belongs_to>
=over 4
-=item Arguments: $accessor_name, $related_class, $foreign_key_column|$cond?, $attr?
+=item Arguments: $accessor_name, $related_class, $foreign_key_column|\%cond|\@cond?, \%attr?
=back
foreign class store the calling class's primary key in one (or more) of its
columns. This relationship defaults to using C<$accessor_name> as the foreign
key in C<$related_class> to resolve the join, unless C<$foreign_key_column>
-specifies the foreign key column in C<$related_class> or C<$cond> specifies a
+specifies the foreign key column in C<$related_class> or C<cond> specifies a
reference to a join condition hash.
=over
This argument is the name of the method you can call on a
L<DBIx::Class::Row> object to retrieve a resultset of the related
class restricted to the ones related to the row object. In list
-context it returns the row objects.
+context it returns the row objects. This is often called the
+C<relation(ship) name>.
-Use this accessor_name (relation name) in L<DBIx::Class::ResultSet/join>
+Use this accessor_name in L<DBIx::Class::ResultSet/join>
or L<DBIx::Class::ResultSet/prefetch> to join to the foreign table
indicated by this relationship.
=item cond
-A hashref where the keys are C<foreign.$column_on_related_table> and
-the values are C<self.$foreign_key_column>. This is useful for
+A hashref where the keys are C<foreign.$foreign_key_column> and
+the values are C<self.$matching_column>. This is useful for
relations that are across multiple columns.
+OR
+
+An arrayref containing an SQL::Abstract-like condition. For example a
+link table where two columns link back to the same table. This is an
+OR condition.
+
+ My::Schema::Item->has_many('rels', 'My::Schema::Relationships',
+ [ { 'foreign.LItemID' => 'self.ID' },
+ { 'foreign.RItemID' => 'self.ID'} ]);
=back
# in an Author class (where Author has_many Books)
- My::DBIC::Schema::Author->has_many(books => 'My::DBIC::Schema::Book', 'author');
+ My::DBIC::Schema::Author->has_many(
+ books =>
+ 'My::DBIC::Schema::Book',
+ 'author_id'
+ );
+
+ # OR (same result, assuming related_class is storing our PK)
+ My::DBIC::Schema::Author->has_many(
+ books =>
+ 'My::DBIC::Schema::Book',
+ );
+
+ # OR (same result)
+ My::DBIC::Schema::Author->has_many(
+ books =>
+ 'My::DBIC::Schema::Book',
+ { 'foreign.author_id' => 'self.id' },
+ );
+
- my $booklist = $obj->books;
- my $booklist = $obj->books({
+ # Usage
+ # resultset of Books belonging to author
+ my $booklist = $author->books;
+
+ # resultset of Books belonging to author, restricted by author name
+ my $booklist = $author->books({
name => { LIKE => '%macaroni%' },
{ prefetch => [qw/book/],
});
- my @book_objs = $obj->books;
- my $books_rs = $obj->books;
- ( $books_rs ) = $obj->books_rs;
- $obj->add_to_books(\%col_data);
+ # array of Book objects belonging to author
+ my @book_objs = $author->books;
-The above C<has_many> relationship could also have been specified with an
-explicit join condition:
+ # force resultset even in list context
+ my $books_rs = $author->books;
+ ( $books_rs ) = $obj->books_rs;
+
+ # create a new book for this author, the relation fields are auto-filled
+ $author->create_related('books', \%col_data);
+ # alternative method for the above
+ $author->add_to_books(\%col_data);
- My::DBIC::Schema::Author->has_many( books => 'My::DBIC::Schema::Book', {
- 'foreign.author' => 'self.author',
- });
Three methods are created when you create a has_many relationship. The first
method is the expected accessor method, C<$accessor_name()>. The second is
almost exactly the same as the accessor method but "_rs" is added to the end of
the method name. This method works just like the normal accessor, except that
-it returns a resultset no matter what, even in list context. The third method,
+it always returns a resultset, even in list context. The third method,
named C<< add_to_$relname >>, will also be added to your Row items; this
allows you to insert new related items, using the same mechanism as in
L<DBIx::Class::Relationship::Base/"create_related">.
If you delete an object in a class with a C<has_many> relationship, all
the related objects will be deleted as well. To turn this behaviour off,
-pass C<< cascade_delete => 0 >> in the C<$attr> hashref. However, any
+pass C<< cascade_delete => 0 >> in the C<attr> hashref. However, any
database-level cascade or restrict will take precedence over a
DBIx-Class-based cascading delete.
=over 4
-=item Arguments: $accessor_name, $related_class, $foreign_key_column|$cond?, $attr?
+=item Arguments: $accessor_name, $related_class, $foreign_key_column|\%cond|\@cond?, \%attr?
=back
Creates an optional one-to-one relationship with a class. This relationship
defaults to using C<$accessor_name> as the foreign key in C<$related_class> to
resolve the join, unless C<$foreign_key_column> specifies the foreign key
-column in C<$related_class> or C<$cond> specifies a reference to a join
+column in C<$related_class> or C<cond> specifies a reference to a join
condition hash.
=over
This argument is the name of the method you can call on a
L<DBIx::Class::Row> object to retrieve the instance of the foreign
-class matching this relationship.
+class matching this relationship. This is often called the
+C<relation(ship) name>.
-Use this accessor_name (relation name) in L<DBIx::Class::ResultSet/join>
+Use this accessor_name in L<DBIx::Class::ResultSet/join>
or L<DBIx::Class::ResultSet/prefetch> to join to the foreign table
indicated by this relationship.
=back
- My::DBIC::Schema::Author->might_have( pseudonym =>
- 'My::DBIC::Schema::Pseudonym' );
-
- my $pname = $obj->pseudonym; # to get the Pseudonym object
-
-The above might_have relationship could have been specified as:
-
- My::DBIC::Schema::Author->might_have( pseudonym =>
- 'My::DBIC::Schema::Pseudonym',
- 'author' );
-
-Or even:
-
- My::DBIC::Schema::Author->might_have( pseudonym =>
- 'My::DBIC::Schema::Pseudonym',
- { 'foreign.author' => 'self.author' } );
+ # Author may have an entry in the pseudonym table
+ My::DBIC::Schema::Author->might_have(
+ pseudonym =>
+ 'My::DBIC::Schema::Pseudonym',
+ 'author_id',
+ );
+
+ # OR (same result, assuming the related_class stores our PK)
+ My::DBIC::Schema::Author->might_have(
+ pseudonym =>
+ 'My::DBIC::Schema::Pseudonym',
+ );
+
+ # OR (same result)
+ My::DBIC::Schema::Author->might_have(
+ pseudonym =>
+ 'My::DBIC::Schema::Pseudonym',
+ { 'foreign.author_id' => 'self.id' },
+ );
+
+ # Usage
+ my $pname = $author->pseudonym; # to get the Pseudonym object
If you update or delete an object in a class with a C<might_have>
relationship, the related object will be updated or deleted as well. To
=over 4
-=item Arguments: $accessor_name, $related_class_name, $join_condition?, $attr?
+=item Arguments: $accessor_name, $related_class, $foreign_key_column|\%cond|\@cond?, \%attr?
=back
- My::DBIC::Schema::Book->has_one(isbn => 'My::DBIC::Schema::ISBN');
+Creates a one-to-one relationship with a class. This relationship
+defaults to using C<$accessor_name> as the foreign key in C<$related_class> to
+resolve the join, unless C<$foreign_key_column> specifies the foreign key
+column in C<$related_class> or C<cond> specifies a reference to a join
+condition hash.
- my $isbn_obj = $obj->isbn; # to get the ISBN object
+=over
+
+=item accessor_name
+
+This argument is the name of the method you can call on a
+L<DBIx::Class::Row> object to retrieve the instance of the foreign
+class matching this relationship. This is often called the
+C<relation(ship) name>.
+
+Use this accessor_name in L<DBIx::Class::ResultSet/join>
+or L<DBIx::Class::ResultSet/prefetch> to join to the foreign table
+indicated by this relationship.
+
+=item related_class
+
+This is the class name of the table which contains a foreign key
+column containing PK values of this class.
+
+=item foreign_key_column
+
+The column name on the related class that contains the foreign key.
+
+OR
+
+=item cond
+
+A hashref where the keys are C<foreign.$column_on_related_table> and
+the values are C<self.$foreign_key_column>. This is useful for
+relations that are across multiple columns.
+
+=back
-Creates a one-to-one relationship with another class. This is just like
-C<might_have>, except the implication is that the other object is always
-present. The only difference between C<has_one> and C<might_have> is that
-C<has_one> uses an (ordinary) inner join, whereas C<might_have> uses a
-left join.
+ # Every book has exactly one ISBN
+ My::DBIC::Schema::Book->has_one(
+ isbn =>
+ 'My::DBIC::Schema::ISBN',
+ 'book_id',
+ );
+
+ # OR (same result, assuming related_class stores our PK)
+ My::DBIC::Schema::Book->has_one(
+ isbn =>
+ 'My::DBIC::Schema::ISBN',
+ );
+
+ # OR (same result)
+ My::DBIC::Schema::Book->has_one(
+ isbn =>
+ 'My::DBIC::Schema::ISBN',
+ { 'foreign.book_id' => 'self.id' },
+ );
+
+ # Usage
+ my $isbn_obj = $book->isbn; # to get the ISBN object
+
+Creates a one-to-one relationship with another class. This is just
+like C<might_have>, except the implication is that the other object is
+always present. The only difference between C<has_one> and
+C<might_have> is that C<has_one> uses an (ordinary) inner join,
+whereas C<might_have> defaults to a left join.
The has_one relationship should be used when a row in the table has exactly one
related row in another table. If the related row might not exist in the foreign
=over 4
-=item Arguments: $accessor_name, $link_rel_name, $foreign_rel_name, $attr?
+=item Arguments: $accessor_name, $link_rel_name, $foreign_rel_name, \%attr?
=back
relation names are then used in the many_to_many call.
In the above example, the Actor class will have 3 many_to_many accessor methods
-set: C<$roles>, C<$add_to_roles>, C<$set_roles>, and similarly named accessors
+set: C<roles>, C<add_to_roles>, C<set_roles>, and similarly named accessors
will be created for the Role class for the C<actors> many_to_many
relationship.
=head1 AUTHORS
-Matt S. Trout <mst@shadowcatsystems.co.uk>
+see L<DBIx::Class>
=head1 LICENSE
projects / dbsrgits/DBIx-Class.git / commitdiff