package Class::DBI::Relationship; use strict; use warnings; use base 'Class::Accessor::Fast'; __PACKAGE__->mk_accessors(qw/name class accessor foreign_class args/); sub set_up { my $proto = shift; my $self = $proto->_init(@_); $self->_set_up_class_data; $self->_add_triggers; $self->_add_methods; $self; } sub _init { my $proto = shift; my $name = shift; my ($class, $accessor, $foreign_class, $args) = $proto->remap_arguments(@_); $class->clear_object_index; return $proto->new( { name => $name, class => $class, foreign_class => $foreign_class, accessor => $accessor, args => $args, } ); } sub remap_arguments { my $self = shift; return @_; } sub _set_up_class_data { my $self = shift; $self->class->_extend_meta($self->name => $self->accessor => $self); } sub triggers { () } sub _add_triggers { my $self = shift; # need to treat as list in case there are multiples for the same point. my @triggers = $self->triggers or return; while (my ($point, $subref) = (splice @triggers, 0, 2)) { $self->class->add_trigger($point => $subref); } } sub methods { () } sub _add_methods { my $self = shift; my %methods = $self->methods or return; my $class = $self->class; no strict 'refs'; foreach my $method (keys %methods) { *{"$class\::$method"} = $methods{$method}; } } 1; __END__ =head1 NAME Class::DBI::Relationship - base class for Relationships =head1 DESCRIPTION A Class::DBI class represents a database table. But merely being able to represent single tables isn't really that useful - databases are all about relationships. So, Class::DBI provides a variety of Relationship models to represent common database occurences (HasA, HasMany and MightHave), and provides a way to add others. =head1 SUBCLASSING Relationships should inherit from Class::DBI::Relationship, and provide a variety of methods to represent the relationship. For examples of how these are used see Class::DBI::Relationship::HasA, Class::DBI::Relationship::HasMany and Class::DBI::Relationship::MightHave. =head2 remap_arguments sub remap_arguments { my $self = shift; # process @_; return ($class, accessor, $foreign_class, $args) } Subclasses should define a 'remap_arguments' method that takes the arguments with which your relationship method will be called, and transforms them into the structure that the Relationship modules requires. If this method is not provided, then it is assumed that your method will be called with these 3 arguments in this order. This should return a list of 4 items: =over 4 =item class The Class::DBI subclass to which this relationship applies. This will be passed in to you from the caller who actually set up the relationship, and is available for you to call methods on whilst performing this mapping. You should almost never need to change this. This usually an entire application base class (or Class::DBI itself), but could be a single class wishing to override a default relationship. =item accessor The method in the class which will provide access to the results of the relationship. =item foreign_class The class for the table with which the class has a relationship. =item args Any additional args that your relationship requires. It is recommended that you use this as a hashref to store any extra information your relationship needs rather than adding extra accessors, as this information will all be stored in the 'meta_info'. =back =head2 triggers sub triggers { return ( before_create => sub { ... }, after_create => sub { ... }, ); } Subclasses may define a 'triggers' method that returns a list of triggers that the relationship needs. This method can be omitted if there are no triggers to be set up. =head2 methods sub methods { return ( method1 => sub { ... }, method2 => sub { ... }, ); } Subclasses may define a 'methods' method that returns a list of methods to facilitate the relationship that should be created in the calling Class::DBI class. This method can be omitted if there are no methods to be set up. =cut