NAME

       Alzabo::Runtime::ForeignKey - Foreign key objects

SYNOPSIS

         $fk->register_insert( $value_for_column );
         $fk->register_update( $new_value_for_column );
         $fk->register_delete( $row_being_deleted );

DESCRIPTION

       Objects in this class maintain referential integrity.  This is really only useful when
       your RDBMS can't do this itself (like MySQL without InnoDB).

INHERITS FROM

       "Alzabo::ForeignKey"

       Note: all relevant documentation from the superclass has been merged into this document.

METHODS

   table_from
   table_to
       Returns the relevant "Alzabo::Runtime::Table" object.

   columns_from
   columns_to
       Returns the relevant "Alzabo::Runtime::Column" object(s) for the property as an array.

   cardinality
       Returns a two element array containing the two portions of the cardinality of the
       relationship.  Each portion will be either '1' or 'n'.

   from_is_dependent
   to_is_dependent
       Returns a boolean value indicating whether there is a dependency from one table to the
       other.

   is_one_to_one
   is_one_to_many
   is_many_to_one
       Returns a boolean value indicating what kind of relationship the object represents.

   is_same_relationship_as ($fk)
       Given a foreign key object, this returns true if the two objects represent the same
       relationship.  However, the two objects may represent the same relationship from different
       table's points of view.

   register_insert ($new_value)
       This method takes the proposed column value for a new row and makes sure that it is valid
       based on relationship that this object represents.

       Throws: "Alzabo::Exception::ReferentialIntegrity"

   register_update ($new_value)
       This method takes the proposed new value for a column and makes sure that it is valid
       based on relationship that this object represents.

       Throws: "Alzabo::Exception::ReferentialIntegrity"

   register_delete ("Alzabo::Runtime::Row" object)
       Allows the foreign key to delete rows dependent on the row being deleted.  Note, this can
       lead to a chain reaction of cascading deletions.  You have been warned.

       Throws: "Alzabo::Exception::ReferentialIntegrity"

   id
       Returns a string uniquely identifying the foreign key.

   comment
       Returns the comment associated with the foreign key object, if any.

AUTHOR

       Dave Rolsky, <autarch@urth.org>