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
=over 4
-=item Arguments: $accessor_name, $related_class, $foreign_key_column?, $attr?
+=item Arguments: $accessor_name, $related_class, $foreign_key_column|$cond?, $attr?
+
+=back
+
+Creates a relationship where the calling class stores the foreign class's
+primary key in one (or more) of its columns. This relationship defaults to
+using C<$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
+
+=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::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
+ $obj->author( $new_author_obj ); # set author object
- My::DBIC::Schema::Book->belongs_to(publisher =>
+The above belongs_to relationship could also have been specified as,
-Creates a relationship where the calling class stores the foreign class's
-primary key in one (or more) of its columns. If C<$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.
+ 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
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
=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.$foreign_key_column>. This is useful for
+relations that are across multiple columns.
+
+=back
+
# in an Author class (where Author has_many Books)
My::DBIC::Schema::Author->has_many(books => 'My::DBIC::Schema::Book', 'author');
'foreign.author' => 'self.author',
});
-Creates a one-to-many relationship, where the corresponding elements of the
-foreign class store the calling class's primary key in one (or more) of its
-columns. You should pass the name of the column in the foreign class as the
-C<$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<$accessor_name()>. The second is
almost exactly the same as the accessor method but "_rs" is added to the end of
database-level cascade or restrict will take precedence over a
DBIx-Class-based cascading delete.
-See L<DBIx::Class::Relationship::Base> for documentation on relationship methods.
+If you copy an object in a class with a C<has_many> relationship, all
+the related objects will be copied as well. To turn this behaviour off,
+pass C<< cascade_copy => 0 >> in the C<$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?, $attr?
+
+=back
+
+Creates an optional one-to-one relationship with a class. This relationship
+defaults to using C<$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::DBIC::Schema::Author->might_have( pseudonym =>
+ 'My::DBIC::Schema::Pseudonym' );
my $pname = $obj->pseudonym; # to get the Pseudonym object
-Creates an optional one-to-one relationship with a class. This relationship
-defaults to using C<$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.
+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. 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
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
=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
+
To create a many_to_many relationship from Actor to Role:
My::DBIC::Schema::Actor->has_many( actor_roles =>
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
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
projects / dbsrgits/DBIx-Class.git / blobdiff