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Class::DBI::Relationship(3pm) User Contributed Perl Documentation Class::DBI::Relationship(3pm)


Class::DBI::Relationship - base class for Relationships


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.


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.


        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:

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.

The method in the class which will provide access to the results of the relationship.
The class for the table with which the class has a relationship.
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'.


        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.


        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.

2022-03-28 perl v5.34.0