NAME
   DBIx::Class::DeleteAction - Define delete triggers

SYNOPSIS
    # Actor DBIC class
    package Your::Schema::Actor;
    use strict;
    use warnings;

    use base 'DBIx::Class';

    __PACKAGE__->load_components("DeleteAction","PK","Core");

    __PACKAGE__->table("actor");
    __PACKAGE__->add_columns(qw/id name/);
    __PACKAGE__->set_primary_key('id');

    __PACKAGE__->has_many(
       'actorroles' => 'MyDB::Schema::ActorRole',
       { 'foreign.actor' => 'self.id' },
       { delete_action => 'delete' }
    );

    # Actor Role DBIC class
    package Your::Schema::ActorRole;
    use strict;
    use warnings;

    use base 'DBIx::Class';

    __PACKAGE__->load_components("DeleteAction","PK","Core");

    __PACKAGE__->table("actor_role");
    __PACKAGE__->add_columns(qw/id name actor production/);
    __PACKAGE__->set_primary_key('id');

    __PACKAGE__->belongs_to(
       'actor' => 'MyDB::Schema::Actor',
       { 'foreign.id' => 'self.actor' },
       { delete_action =>
           sub {
               my ($self,$params) = @_;
               # Do something special
           }
       }
    );

    __PACKAGE__->belongs_to(
       'production' => 'MyDB::Schema::Production',
       { 'foreign.id' => 'self.production' },
       { delete_action => 'deny' }
    );

    # Somewhere else
    $schema->txn_do(sub {
       $actor->delete();
    });
    # Deletes all related actorroles only if they don't have a production
    # Finally deletes the actor itself (Always use transactions!!!)

    $schema->txn_do(sub {
       $actor_role->delete();
    });
    # Calls custom subroutine on actor
    # Denies deletion if a production is related

DESCRIPTION
   With this DBIx::Class component you can specify actions that should be
   triggered on a row delete. A delete action is specified by adding the
   'delete_action' key to the optional attribute HASH reference when
   specifing a new relation (see DBIx::Class::Relationship).

   The following delete actions are supported:

   *   null

       Set all columns in related rows pointing to this record to NULL.
       Only works on 'has_many' relationships.

   *   delete OR cascade

       Delete all related records one by one. This can trigger further
       delete actions.

   *   deleteall

       Delete all related records in a single step. This does not trigger
       further delete actions.

       Only works on 'has_many' relationships.

   *   deny

       Deny deletion if this record is being referenced from other rows.

   *   CODE reference

       Executes the code referece on delete. The current DBIx::Class::Row
       object and the name of the relation are passed to the code
       reference.

   *   STRING

       Execute a method with the given name. The method will be called on
       the current DBIx::Class::Row object and will be passed the name of
       the relation.

   *   ignore

       Do nothing

 Custom delete handlers
   If you set the "delete_action" to execute a method or a code reference
   the method will be called with the following parameters:

   *   $self

       The DBIx::Class::Row object the delete action has been called upon.

   *   HASHREF

       A hashref of named parameters

       *   relationship

           The name of the relationship that is currently being processed.

       *   related

           The related object(s) for the given object and relationship.

           Depending on the type of the relationship this can either be a
           DBIx::Class::Row or a DBIx::Class::ResultSet object.

       *   seen

           An arraryref with object identifiers which have already been
           processed. If you want to call another delete method from your
           code you MUST pass on this variable so that we can ensure that
           each object/row is handled only once.

       *   Extra values

           Any other values that you pass to 'delete'.

 delete
    $object->delete();
    OR
    $object->delete(HASHREF);

   This method overdrives the DBIx::Class::Row delete method. You can add
   arbitrary data as HASHREF which will be passed to your custom delete
   handles.

   Make sure that you ALWAYS call "delete" always inside a TRANSACTION
   block.

   If you call another "delete" from within a custom delete handler always
   pass on the "seen" parameter.

EXAMPLE
 Tree example
   This example shows a very simple tree schema, where each node points to
   its parent node. Once you delete an item from the tree, all child nodes
   will be appended to the parent node of the deleted node.

    package MyApp::Treenode;
    use strict;
    use warnings;

    use parent qw(DBIx::Class);

    __PACKAGE__->load_components(
      "+DBIx::Class::DeleteAction",
      "PK",
      "Core",
    );

    __PACKAGE__->table("treenode");
    __PACKAGE__->add_columns(qw/id name parent/);
    __PACKAGE__->set_primary_key("id");

    # Do not delete parent node
    __PACKAGE__->might_have(
       'parent' => 'MyApp::Treenode',
       { "foreign.id" => "self.parent" },
       { delete_action => 'ignore' },
    );

    # Update all child nodes
    __PACKAGE__->has_many(
       'children' => 'MyApp::Treenode',
       { "foreign.parent" => "self.id" },
       { delete_action => sub {
           my ($self,$params) = @_;
           $params->{related}->update({
               parent  => $self->get_column('parent'),
           });
       } },
    );

 Debugging
   Use "DBIC_TRACE=1" or set "__PACKAGE__-"storage->debug(1);> to see what
   is exactly going on.

CAVEATS
   Note that the "delete" method in DBIx::Class::ResultSet will not run
   DeleteAction triggers. See "delete_all" if you need triggers to run.

   Any database-level cascade, restrict or trigger will be performed AFTER
   DBIx-Class-DeleteAction based triggers.

   Always use transactions, or else you might end up with inconsistent
   data.

SUPPORT
   Please report any bugs or feature requests to
   [email protected], or through the web interface at
   <http://rt.cpan.org/Public/Bug/Report.html?Queue=DBIx::Class::DeleteActi
   on>. I will be notified, and then you'll automatically be notified of
   progress on your report as I make changes.

AUTHOR
       Maroš Kollár
       CPAN ID: MAROS
       maros [at] k-1.com
       L<http://www.revdev.at>

ACKNOWLEDGEMENTS
   This module was written for Revdev <http://www.revdev.at>, a nice litte
   software company I run with Koki and Domm
   (<http://search.cpan.org/~domm/>).

COPYRIGHT
   DBIx::Class::DeleteAction is Copyright (c) 2008-9 Maroš Kollár -
   <http://www.revdev.at>

   This program is free software; you can redistribute it and/or modify it
   under the same terms as Perl itself.

   The full text of the license can be found in the LICENSE file included
   with this module.

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