=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'});
my $fred = $schema->resultset('Author')->find({ Name => 'Fred' });
my $fredsbooks = $schema->resultset('Book')->search({ Author => $fred->ID });
+
With a has_many relationship called "books" on Author (see below for details),
we can do this instead:
=head1 METHODS
-All helper methods take the following arguments:
+All helper methods are called similar to the following template:
- __PACKAGE__>$method_name('relname', 'Foreign::Class', $cond, $attrs);
+ __PACKAGE__->$method_name('relname', 'Foreign::Class', $cond, $attrs);
Both C<$cond> and C<$attrs> are optional. Pass C<undef> for C<$cond> if
you want to use the default value for it, but still want to set C<$attrs>.
-See L<DBIx::Class::Relationship::Base> for a list of valid attributes.
+See L<DBIx::Class::Relationship::Base> for documentation on the
+attrubutes that are allowed in the C<$attrs> argument.
+
=head2 belongs_to
=over 4
-=item Arguments: $accessor_name, $related_class, $foreign_key_column?, $attr?
+=item Arguments: $accessor_name, $related_class, $fk_column|\%cond|\@cond?, \%attr?
=back
- # in a Book class (where Author has many Books)
- My::DBIC::Schema::Book->belongs_to(author => 'My::DBIC::Schema::Author');
+Creates a relationship where the calling class stores the foreign
+class's primary key in one (or more) of its columns. This relationship
+defaults to using C<$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
+
+=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 referenced by the foreign key in
+this class.
+
+=item fk_column
- my $author_obj = $obj->author; # get author object
- $obj->author($new_author_obj); # set author object
+The column name on this class that contains the foreign key.
- My::DBIC::Schema::Book->belongs_to(publisher =>
+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
+
+
+ # in a Book class (where Author has many Books)
+ 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:
+ $book->get_column('author_id');
-Creates a relationship where the calling class stores the foreign class's
-primary key in one (or more) of its columns. If C<$cond> is a column name
-instead of a join condition hash, it is used as the name of the foreign key
-column in the calling class. If C<$cond> is not given, C<$accessor_name> is
-used as the column name.
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>
NOTE: If you are used to L<Class::DBI> relationships, this is the equivalent
of C<has_a>.
-See L<DBIx::Class::Relationship::Base> for documentation on relationship methods.
+See L<DBIx::Class::Relationship::Base> for documentation on relationship
+methods and valid relationship attributes.
=head2 has_many
=over 4
-=item Arguments: $accessor_name, $related_class, $foreign_key_column|$cond?, $attr?
+=item Arguments: $accessor_name, $related_class, $foreign_key_column|\%cond|\@cond?, \%attr?
+
+=back
+
+Creates a one-to-many relationship, where the corresponding elements
+of the foreign class store the calling class's primary key in one (or
+more) of its columns. This relationship defaults to using the end of
+this classes namespace as the foreign key in C<$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.
+
+=over
+
+=item accessor_name
+
+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. 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.$foreign_key_column> and
+the values are C<self.$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');
+ # assuming related class is storing our PK in "author_id"
+ My::DBIC::Schema::Author->has_many(
+ books =>
+ 'My::DBIC::Schema::Book',
+ 'author_id'
+ );
+
+ # OR (same result)
+ My::DBIC::Schema::Author->has_many(
+ books =>
+ 'My::DBIC::Schema::Book',
+ { 'foreign.author_id' => 'self.id' },
+ );
+
+ # OR (similar result, assuming related_class is storing our PK, in "author")
+ # (the "author" is guessed at from "Author" in the class namespace)
+ My::DBIC::Schema::Author->has_many(
+ books =>
+ 'My::DBIC::Schema::Book',
+ );
- 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;
- My::DBIC::Schema::Author->has_many( books => 'My::DBIC::Schema::Book', {
- 'foreign.author' => 'self.author',
- });
+ # create a new book for this author, the relation fields are auto-filled
+ $author->create_related('books', \%col_data);
+ # alternative method for the above
+ $author->add_to_books(\%col_data);
-Creates a one-to-many relationship, where the corresponding elements of the
-foreign class store the calling class's primary key in one (or more) of its
-columns. You should pass the name of the column in the foreign class as the
-C<$cond> argument, or specify a complete join condition.
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<$attr> hashref. However, any
+pass C<< cascade_delete => 0 >> in the C<attr> hashref. However, any
database-level cascade or restrict will take precedence over a
DBIx-Class-based cascading delete.
-See L<DBIx::Class::Relationship::Base> for documentation on relationship methods.
+If you copy an object in a class with a C<has_many> relationship, all
+the related objects will be copied as well. To turn this behaviour off,
+pass C<< cascade_copy => 0 >> in the C<$attr> hashref. The behaviour
+defaults to C<< cascade_copy => 1 >>.
+
+See L<DBIx::Class::Relationship::Base> for documentation on relationship
+methods and valid relationship attributes.
=head2 might_have
=over 4
-=item Arguments: $accessor_name, $related_class, $join_condition?, $attr?
+=item Arguments: $accessor_name, $related_class, $foreign_key_column|\%cond|\@cond?, \%attr?
=back
- My::DBIC::Schema::Author->might_have(pseudonym =>
- 'My::DBIC::Schema::Pseudonym');
+Creates an optional one-to-one relationship with a class. This relationship
+defaults to using C<$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
+condition hash.
- my $pname = $obj->pseudonym; # to get the Pseudonym object
+=over
-Creates an optional one-to-one relationship with a class. This relationship
-defaults to using C<$accessor_name> as the foreign key in C<$related_class>
-to resolve the join, unless C<$join_condition> specifies a column in
-C<$related_class> or a join condition hash reference.
+=item accessor_name
+
+This argument is the name of the method you can call on a
+L<DBIx::Class::Row> object to retrieve the instance of the foreign
+class matching this relationship. This is often called the
+C<relation(ship) name>.
+
+Use this accessor_name in L<DBIx::Class::ResultSet/join>
+or L<DBIx::Class::ResultSet/prefetch> to join to the foreign table
+indicated by this relationship.
+
+=item related_class
+
+This is the class name of the table which contains a foreign key
+column containing PK values of this class.
+
+=item foreign_key_column
+
+The column name on the related class that contains the foreign key.
+
+OR
+
+=item cond
+
+A hashref where the keys are C<foreign.$column_on_related_table> and
+the values are C<self.$matching_column>. This is useful for
+relations that are across multiple columns.
+
+=back
+
+ # 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
hashref. Any database-level update or delete constraints will override
this behavior.
-See L<DBIx::Class::Relationship::Base> for more information.
+See L<DBIx::Class::Relationship::Base> for documentation on relationship
+methods and valid relationship attributes.
=head2 has_one
=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.
+
+=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
- my $isbn_obj = $obj->isbn; # to get the ISBN object
+This is the class name of the table which contains a foreign key
+column containing PK values of this class.
-Creates a one-to-one relationship with another class. This is just like
-C<might_have>, except the implication is that the other object is always
-present. The only difference between C<has_one> and C<might_have> is that
-C<has_one> uses an (ordinary) inner join, whereas C<might_have> uses a
-left join.
+=item foreign_key_column
+
+The column name on the related class that contains the foreign key.
+
+OR
+
+=item cond
+
+A hashref where the keys are C<foreign.$column_on_related_table> and
+the values are C<self.$matching_column>. This is useful for
+relations that are across multiple columns.
+
+=back
+
+ # 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
In the above example, each Book in the database is associated with exactly one
ISBN object.
-See L<DBIx::Class::Relationship::Base> for documentation on relationship methods.
+See L<DBIx::Class::Relationship::Base> for documentation on relationship
+methods and valid relationship attributes.
=head2 many_to_many
=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
+
+C<many_to_many> is not strictly a relationship in its own right. Instead, it is
+a bridge between two resultsets which provide the same kind of convenience
+accessors as true relationships provide. Although the accessor will return a
+resultset or collection of objects just like has_many does, you cannot call
+C<related_resultset> and similar methods which operate on true relationships.
+
+=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 rows matching this
+relationship.
+
+On a many_to_many, unlike other relationships, this cannot be used in
+L<DBIx::Class::ResultSet/search> to join tables. Use the relations
+bridged across instead.
+
+=item link_rel_name
+
+This is the accessor_name from the has_many relationship we are
+bridging from.
+
+=item foreign_rel_name
+
+This is the accessor_name of the belongs_to relationship in the link
+table that we are bridging across (which gives us the table we are
+bridging to).
=back
My::DBIC::Schema::Role->many_to_many( actors => 'actor_roles', 'actor' );
-Creates accessors bridging two relationships; not strictly a relationship in
-its own right, although the accessor will return a resultset or collection of
-objects just as a has_many would.
+To add a role for your actor, and fill in the year of the role in the
+actor_roles table:
+
+ $actor->add_to_roles($role, { year => 1995 });
In the above example, ActorRoles is the link table class, and Role is the
foreign class. The C<$link_rel_name> parameter is the name of the accessor for
relation names are then used in the many_to_many call.
In the above example, the Actor class will have 3 many_to_many accessor methods
-set: C<$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.
-See L<DBIx::Class::Relationship::Base> for documentation on relationship methods.
+See L<DBIx::Class::Relationship::Base> for documentation on relationship
+methods and valid relationship attributes.
=cut
=head1 AUTHORS
-Matt S. Trout <mst@shadowcatsystems.co.uk>
+see L<DBIx::Class>
=head1 LICENSE
projects / dbsrgits/DBIx-Class.git / blobdiff