DBIx::Class::Relationship::Base - Inter-table relationships
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.
__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.
JOIN
foreign
self
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:
Author
Book
author_id
{ '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"):
Edition
{ '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 ANDed conditions. To add an ORed condition, use an arrayref of hashrefs. See the SQL::Abstract documentation for more details.
AND
OR
In addition to standard result set attributes, the following attributes are also valid:
Explicitly specifies the type of join to use in the relationship. Any SQL join type is valid, e.g. LEFT or RIGHT. It will be placed in the SQL command immediately before JOIN.
LEFT
RIGHT
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
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), and filter (for when there is a single related object, but you also want the relationship accessor to double as a column accessor). For multi accessors, an add_to_* method is also created, which calls create_related for the relationship.
single
multi
filter
create_related
If you are using SQL::Translator to create SQL for you and you find that it is creating constraints where it shouldn't, or not creating them where it should, set this attribute to a true or false value to override the detection of when to create constraints.
Registers a relationship on the class. This is called internally by DBIx::Class::ResultSourceProxy to set up Accessors and Proxies.
$rs = $cd->related_resultset('artist');
Returns a DBIx::Class::ResultSet for the relationship named $relationship_name.
@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.
( $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.
$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.
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.
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.
create
new
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.
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.
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.
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.
$book->set_from_related('author', $author_obj); $book->author($author_obj); ## same thing
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.
This is called internally when you pass existing objects as values to "create" in DBIx::Class::ResultSet, or pass an object to a belongs_to acessor.
The columns are only set in the local copy of the object, call "update" to set them in the storage.
$book->update_from_related('author', $author_obj);
The same as "set_from_related", but the changes are immediately updated in storage.
$obj->delete_related('relname', $cond, $attrs);
Delete any related item subject to the given conditions.
Currently only available for has_many, many-to-many and 'multi' type relationships.
has_many
many-to-many
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.
$obj
$foreign_vals
$link_vals
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 $actor's previous roles with the two named
Replace all the related objects with the given reference to a list of objects. This does a delete on the link table resultset to remove the association between the current object and all related objects, then calls add_to_$rel repeatedly to link all the new objects.
delete
add_to_$rel
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.
Due to a mistake in the original implementation of this method, it will also accept a list of objects or hash references. This is deprecated and will be removed in a future version.
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.
Matt S. Trout <mst@shadowcatsystems.co.uk>
You may distribute this code under the same terms as Perl itself.
To install DBIx::Class, copy and paste the appropriate command in to your terminal.
cpanm
cpanm DBIx::Class
CPAN shell
perl -MCPAN -e shell install DBIx::Class
For more information on module installation, please visit the detailed CPAN module installation guide.