my $fred = $schema->resultset('Author')->find({ Name => 'Fred' });
my $fredsbooks = $schema->resultset('Book')->search({ Author => $fred->ID });
+
With a has_many relationship called "books" on Author (see below for details),
we can do this instead:
Both C<$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 a list of valid attributes and valid
+relationship attributes.
=head2 belongs_to
- # in a Book class (where Author has many Books)
- My::DBIC::Schema::Book->belongs_to(author => 'My::DBIC::Schema::Author');
- my $author_obj = $obj->author;
- $obj->author($new_author_obj);
+=over 4
+
+=item Arguments: $accessor_name, $related_class, $foreign_key_column|$cond?, $attr?
+
+=back
Creates a relationship where the calling class stores the foreign class's
-primary key in one (or more) of its columns. If $cond is a column name
-instead of a join condition hash, that is used as the name of the column
-holding the foreign key. If $cond is not given, the relname is used as
-the column name.
+primary key in one (or more) of its columns. This relationship defaults to
+using C<$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 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.
+
+Use this accessor_name (relation 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 foreign_key_column
+
+The column name on this class that contains the foreign key.
+
+OR
-Cascading deletes are off per default on a C<belongs_to> relationship, to turn
-them on, pass C<< cascade_delete => 1 >> in the $attr hashref.
+=item cond
+
+A hashref where the keys are C<foreign.$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' );
+
+ my $author_obj = $obj->author; # get author object
+ $obj->author( $new_author_obj ); # set author object
+
+The above belongs_to relationship could also have been specified as,
+
+ My::DBIC::Schema::Book->belongs_to( author,
+ 'My::DBIC::Schema::Author',
+ { 'foreign.author' => 'self.author' } );
+
+If the relationship is optional -- i.e. the column containing the foreign key
+can be NULL -- then the belongs_to relationship does the right thing. Thus, in
+the example above C<$obj-E<gt>author> would return C<undef>. However in this
+case you would probably want to set the C<join_type> attribute so that a C<LEFT
+JOIN> is done, which makes complex resultsets involving C<join> or C<prefetch>
+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'});
+
+
+Cascading deletes are off by default on a C<belongs_to>
+relationship. To turn them on, pass C<< cascade_delete => 1 >>
+in the $attr hashref.
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 and valid relationship attributes.
+
=head2 has_many
- # in an Author class (where Author has many Books)
+=over 4
+
+=item Arguments: $accessor_name, $related_class, $foreign_key_column|$cond?, $attr?
+
+=back
+
+Creates a one-to-many relationship, where the corresponding elements of the
+foreign class store the calling class's primary key in one (or more) of its
+columns. This relationship defaults to using C<$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 a resultset of the related
+class restricted to the ones related to the row object. In list
+context it returns the row objects.
+
+Use this accessor_name (relation 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
+
+ # in an Author class (where Author has_many Books)
My::DBIC::Schema::Author->has_many(books => 'My::DBIC::Schema::Book', 'author');
+
my $booklist = $obj->books;
my $booklist = $obj->books({
name => { LIKE => '%macaroni%' },
$obj->add_to_books(\%col_data);
-Creates a one-to-many relationship, where the corresponding elements of the
-foreign class store the calling class's primary key in one (or more) of its
-columns. You should pass the name of the column in the foreign class as the
-$cond argument, or specify a complete join condition.
+The above C<has_many> relationship could also have been specified with an
+explicit join condition:
+
+ 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. 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, 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
+method is the expected accessor method, C<$accessor_name()>. The second is
+almost exactly the same as the accessor method but "_rs" is added to the end of
+the method name. This method works just like the normal accessor, except that
+it returns a resultset no matter what, even in list context. The third method,
+named C<< add_to_$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. However, any database-level
-cascade or restrict will take precedence. To turn this behavior off, pass
-C<< cascade_delete => 0 >> in the $attr hashref.
+the related objects will be deleted as well. To turn this behaviour off,
+pass C<< cascade_delete => 0 >> in the C<$attr> hashref. However, any
+database-level cascade or restrict will take precedence over a
+DBIx-Class-based cascading delete.
+
+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
- My::DBIC::Schema::Author->might_have(pseudonym =>
- 'My::DBIC::Schema::Pseudonyms');
+=over 4
+
+=item Arguments: $accessor_name, $related_class, $foreign_key_column|$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
+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.
+
+Use this accessor_name (relation 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
+
+ My::DBIC::Schema::Author->might_have( pseudonym =>
+ 'My::DBIC::Schema::Pseudonym' );
+
my $pname = $obj->pseudonym; # to get the Pseudonym object
-Creates an optional one-to-one relationship with a class, where the foreign
-class stores our primary key in one of its columns. Defaults to the primary
-key of the foreign class unless $cond specifies a column or join condition.
+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' } );
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.
-Any database-level update or delete constraints will override this behaviour.
-To turn off this behavior, add C<< cascade_delete => 0 >> to the $attr hashref.
+relationship, the related object will be updated or deleted as well. To
+turn off this behavior, add C<< cascade_delete => 0 >> to the C<$attr>
+hashref. Any database-level update or delete constraints will override
+this behavior.
+
+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?
+
+=back
+
My::DBIC::Schema::Book->has_one(isbn => 'My::DBIC::Schema::ISBN');
- my $isbn_obj = $obj->isbn;
+
+ my $isbn_obj = $obj->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
C<has_one> uses an (ordinary) inner join, whereas C<might_have> uses 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
+table, use the L<DBIx::Class::Relationship/might_have> relationship.
+
+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 and valid relationship attributes.
=head2 many_to_many
=over 4
-=item Arguments: $accessor_name, $link_rel_name, $foreign_rel_name
+=item Arguments: $accessor_name, $link_rel_name, $foreign_rel_name, $attr?
=back
- My::DBIC::Schema::Actor->has_many( actor_roles =>
- 'My::DBIC::Schema::ActorRoles',
- 'actor' );
- My::DBIC::Schema::ActorRoles->belongs_to( role =>
- 'My::DBIC::Schema::Role' );
- My::DBIC::Schema::ActorRoles->belongs_to( actor =>
- 'My::DBIC::Schema::Actor' );
-
- My::DBIC::Schema::Actor->many_to_many( roles => 'actor_roles',
- 'role' );
-
-Creates a 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.
+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.
-To use many_to_many, existing relationships from the original table to the link
-table, and from the link table to the end table must already exist, these
-relation names are then used in the many_to_many call.
-
-=head3 Created accessors
+=over
-=head4 $rel
+=item accessor_name
-=over 4
+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.
-=item Arguments: $vals?, $attrs
+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.
-=back
+=item link_rel_name
- my $role_rs = $actor->roles;
+This is the accessor_name from the has_many relationship we are
+bridging from.
- my $role1 = $actor->roles({ name => 'role1' })->first;
+=item foreign_rel_name
-Returns a resultset for the foreign table on the right side of the
-many-to-many relationship. (e.g., in the above example, a CD's
-producers). Takes the same arguments as L<DBIx::Class::ResultSet/"search">.
+This is the accessor_name of the belongs_to relationship in the link
+table that we are bridging across (which gives us the table we are
+bridging to).
-=head4 add_to_$rel
+=back
-=over 4
+To create a many_to_many relationship from Actor to Role:
-=item Arguments: ($foreign_vals | $obj), $link_vals?
+ My::DBIC::Schema::Actor->has_many( actor_roles =>
+ 'My::DBIC::Schema::ActorRoles',
+ 'actor' );
+ My::DBIC::Schema::ActorRoles->belongs_to( role =>
+ 'My::DBIC::Schema::Role' );
+ My::DBIC::Schema::ActorRoles->belongs_to( actor =>
+ 'My::DBIC::Schema::Actor' );
-=back
+ My::DBIC::Schema::Actor->many_to_many( roles => 'actor_roles',
+ 'role' );
- my $role = $schema->resultset('Role')->find(1);
- $actor->add_to_roles($role);
- # creates a My::DBIC::Schema::ActorRoles linking table row object
+And, for the reverse relationship, from Role to Actor:
- $actor->add_to_roles({ name => 'lead' }, { salary => 15_000_000 });
- # creates a new My::DBIC::Schema::Role row object and the linking table
- # object with an extra column in the link
+ My::DBIC::Schema::Role->has_many( actor_roles =>
+ 'My::DBIC::Schema::ActorRoles',
+ 'role' );
-Adds a linking table object for C<$obj> or C<$foreign_vals>. If the first
-argument is a hash reference, the related object is created first with the
-column values in the hash. If an object reference is given, just the linking
-table object is created. In either case, any additional column values for the
-linking table object can be specified in C<$link_vals>.
+ My::DBIC::Schema::Role->many_to_many( actors => 'actor_roles', 'actor' );
-=head4 remove_from_$rel
+To add a role for your actor, and fill in the year of the role in the
+actor_roles table:
-=over 4
+ $actor->add_to_roles($role, { year => 1995 });
-=item Arguments: $obj
+In the above example, ActorRoles is the link table class, and Role is the
+foreign class. The C<$link_rel_name> parameter is the name of the accessor for
+the has_many relationship from this table to the link table, and the
+C<$foreign_rel_name> parameter is the accessor for the belongs_to relationship
+from the link table to the foreign table.
-=back
+To use many_to_many, existing relationships from the original table to the link
+table, and from the link table to the end table must already exist, these
+relation names are then used in the many_to_many call.
- my $role = $schema->resultset('Role')->find(1);
- $actor->remove_from_roles($role);
- # removes $role's My::DBIC::Schema::ActorRoles linking table row object
+In the above example, the Actor class will have 3 many_to_many accessor methods
+set: C<$roles>, C<$add_to_roles>, C<$set_roles>, and similarly named accessors
+will be created for the Role class for the C<actors> many_to_many
+relationship.
-Removes the link between the current object and the related object. Note that
-the related object itself won't be deleted unless you call ->delete() on
-it. This method just removes the link between the two objects.
+See L<DBIx::Class::Relationship::Base> for documentation on relationship
+methods and valid relationship attributes.
=cut
projects / dbsrgits/DBIx-Class.git / blobdiff