NAME
DBIx::Class::Relationship::Base - Inter-table relationships
SYNOPSIS
DESCRIPTION
This class provides methods to describe the relationships between the tables in your database model. These are the "bare bones" relationships methods, for predefined ones, look in DBIx::Class::Relationship.
METHODS
add_relationship
__PACKAGE__->add_relationship('relname', 'Foreign::Class', $cond, $attrs);
The condition needs to be an SQL::Abstract-style representation of the join between the tables. When resolving the condition for use in a JOIN
, keys using the pseudo-table foreign
are resolved to mean "the Table on the other side of the relationship", and values using the pseudo-table self
are resolved to mean "the Table this class is representing". Other restrictions, such as by value, sub-select and other tables, may also be used. Please check your database for JOIN
parameter support.
For example, if you're creating a relationship from Author
to Book
, where the Book
table has a column author_id
containing the ID of the Author
row:
{ 'foreign.author_id' => 'self.id' }
will result in the JOIN
clause
author me JOIN book book ON book.author_id = me.id
For multi-column foreign keys, you will need to specify a foreign
-to-self
mapping for each column in the key. For example, if you're creating a relationship from Book
to Edition
, where the Edition
table refers to a publisher and a type (e.g. "paperback"):
{
'foreign.publisher_id' => 'self.publisher_id',
'foreign.type_id' => 'self.type_id',
}
This will result in the JOIN
clause:
book me JOIN edition edition ON edition.publisher_id = me.publisher_id
AND edition.type_id = me.type_id
Each key-value pair provided in a hashref will be used as AND
ed conditions. To add an OR
ed condition, use an arrayref of hashrefs. See the SQL::Abstract documentation for more details.
In addition to standard result set attributes, the following attributes are also valid:
- join_type
-
Explicitly specifies the type of join to use in the relationship. Any SQL join type is valid, e.g.
LEFT
orRIGHT
. It will be placed in the SQL command immediately beforeJOIN
. - proxy
-
An arrayref containing a list of accessors in the foreign class to create in the main class. If, for example, you do the following:
MyDB::Schema::CD->might_have(liner_notes => 'MyDB::Schema::LinerNotes', undef, { proxy => [ qw/notes/ ], });
Then, assuming MyDB::Schema::LinerNotes has an accessor named notes, you can do:
my $cd = MyDB::Schema::CD->find(1); $cd->notes('Notes go here'); # set notes -- LinerNotes object is # created if it doesn't exist
- accessor
-
Specifies the type of accessor that should be created for the relationship. Valid values are
single
(for when there is only a single related object),multi
(when there can be many), andfilter
(for when there is a single related object, but you also want the relationship accessor to double as a column accessor). Formulti
accessors, an add_to_* method is also created, which callscreate_related
for the relationship.
register_relationship
Registers a relationship on the class. This is called internally by DBIx::Class::ResultSourceProxy to set up Accessors and Proxies.
related_resultset
$rs = $cd->related_resultset('artist');
Returns a DBIx::Class::ResultSet for the relationship named $relationship_name.
search_related
@objects = $rs->search_related('relname', $cond, $attrs);
$objects_rs = $rs->search_related('relname', $cond, $attrs);
Run a search on a related resultset. The search will be restricted to the item or items represented by the DBIx::Class::ResultSet it was called upon. This method can be called on a ResultSet, a Row or a ResultSource class.
search_related_rs
( $objects_rs ) = $rs->search_related_rs('relname', $cond, $attrs);
This method works exactly the same as search_related, except that it garauntees a restultset, even in list context.
count_related
$obj->count_related('relname', $cond, $attrs);
Returns the count of all the items in the related resultset, restricted by the current item or where conditions. Can be called on a "ResultSet" in DBIx::Class::Manual::Glossary or a "Row" in DBIx::Class::Manual::Glossary object.
new_related
my $new_obj = $obj->new_related('relname', \%col_data);
Create a new item of the related foreign class. If called on a Row object, it will magically set any foreign key columns of the new object to the related primary key columns of the source object for you. The newly created item will not be saved into your storage until you call "insert" in DBIx::Class::Row on it.
create_related
my $new_obj = $obj->create_related('relname', \%col_data);
Creates a new item, similarly to new_related, and also inserts the item's data into your storage medium. See the distinction between create
and new
in DBIx::Class::ResultSet for details.
find_related
my $found_item = $obj->find_related('relname', @pri_vals | \%pri_vals);
Attempt to find a related object using its primary key or unique constraints. See "find" in DBIx::Class::ResultSet for details.
find_or_new_related
my $new_obj = $obj->find_or_new_related('relname', \%col_data);
Find an item of a related class. If none exists, instantiate a new item of the related class. The object will not be saved into your storage until you call "insert" in DBIx::Class::Row on it.
find_or_create_related
my $new_obj = $obj->find_or_create_related('relname', \%col_data);
Find or create an item of a related class. See "find_or_create" in DBIx::Class::ResultSet for details.
update_or_create_related
my $updated_item = $obj->update_or_create_related('relname', \%col_data, \%attrs?);
Update or create an item of a related class. See "update_or_create" in DBIx::Class::ResultSet for details.
set_from_related
$book->set_from_related('author', $author_obj);
Set column values on the current object, using related values from the given related object. This is used to associate previously separate objects, for example, to set the correct author for a book, find the Author object, then call set_from_related on the book.
The columns are only set in the local copy of the object, call "update" to set them in the storage.
update_from_related
$book->update_from_related('author', $author_obj);
The same as "set_from_related", but the changes are immediately updated in storage.
delete_related
$obj->delete_related('relname', $cond, $attrs);
Delete any related item subject to the given conditions.
add_to_$rel
Currently only available for has_many
, many-to-many
and 'multi' type relationships.
my $role = $schema->resultset('Role')->find(1);
$actor->add_to_roles($role);
# creates a My::DBIC::Schema::ActorRoles linking table row object
$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
Adds a linking table object for $obj
or $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 $link_vals
.
set_$rel
Currently only available for many-to-many
relationships.
my $actor = $schema->resultset('Actor')->find(1);
my @roles = $schema->resultset('Role')->search({ role =>
{ '-in' -> ['Fred', 'Barney'] } } );
$actor->set_roles(@roles);
# Replaces all of $actors previous roles with the two named
Replace all the related objects with the given list of objects. This does a delete
on the link table resultset to remove the association between the current object and all related objects, then calls add_to_$rel
repeatedly to link all the new objects.
Note that this means that this method will not delete any objects in the table on the right side of the relation, merely that it will delete the link between them.
remove_from_$rel
Currently only available for many-to-many
relationships.
my $role = $schema->resultset('Role')->find(1);
$actor->remove_from_roles($role);
# removes $role's My::DBIC::Schema::ActorRoles linking table row object
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.
AUTHORS
Matt S. Trout <mst@shadowcatsystems.co.uk>
LICENSE
You may distribute this code under the same terms as Perl itself.