Class::Data::InheritablUes(e3r)Contributed Perl DocumentCaltaisosn::Data::Inheritable(3)

NAME
       Class::Data::Inheritable - Inheritable, overridable class data

SYNOPSIS
         package Stuff;
         use base qw(Class::Data::Inheritable);

         # Set up DataFile as inheritable class data.
         Stuff->mkclassdata('DataFile');

         # Declare the location of the data file for this class.
         Stuff->DataFile('/etc/stuff/data');

         # Or, all in one shot:
         Stuff->mkclassdata(DataFile => '/etc/stuff/data');

DESCRIPTION
       Class::Data::Inheritable is for creating accessor/mutators to class
       data.  That is, if you want to store something about your class as a
       whole (instead of about a single object).  This data is then inherited
       by your subclasses and can be overriden.

       For example:

         Pere::Ubu->mkclassdata('Suitcase');

       will generate the method Suitcase() in the class Pere::Ubu.

       This new method can be used to get and set a piece of class data.

         Pere::Ubu->Suitcase('Red');
         $suitcase = Pere::Ubu->Suitcase;

       The interesting part happens when a class inherits from Pere::Ubu:

         package Raygun;
         use base qw(Pere::Ubu);

         # Raygun's suitcase is Red.
         $suitcase = Raygun->Suitcase;

       Raygun inherits its Suitcase class data from Pere::Ubu.

       Inheritance of class data works analogous to method inheritance.  As
       long as Raygun does not "override" its inherited class data (by using
       Suitcase() to set a new value) it will continue to use whatever is set
       in Pere::Ubu and inherit further changes:

         # Both Raygun's and Pere::Ubu's suitcases are now Blue
         Pere::Ubu->Suitcase('Blue');

       However, should Raygun decide to set its own Suitcase() it has now
       "overridden" Pere::Ubu and is on its own, just like if it had overriden
       a method:

         # Raygun has an orange suitcase, Pere::Ubu's is still Blue.
         Raygun->Suitcase('Orange');

       Now that Raygun has overridden Pere::Ubu futher changes by Pere::Ubu no
       longer effect Raygun.

         # Raygun still has an orange suitcase, but Pere::Ubu is using Samsonite.
         Pere::Ubu->Suitcase('Samsonite');

Methods       mmkkccllaassssddaattaa

         Class->mkclassdata($dataaccessorname);
         Class->mkclassdata($dataaccessorname => $value);

       This is a class method used to declare new class data accessors.  A new
       accessor will be created in the Class using the name from
       $dataaccessorname, and optionally initially setting it to the given
       value.

       To facilitate overriding, mkclassdata creates an alias to the
       accessor, fieldaccessor().  So Suitcase() would have an alias
       Suitcaseaccessor() that does the exact same thing as Suitcase().
       This is useful if you want to alter the behavior of a single accessor
       yet still get the benefits of inheritable class data.  For example.

         sub Suitcase {
             my($self) = shift;
             warn "Fashion tragedy" if @ and $[0] eq 'Plaid';

             $self->Suitcaseaccessor(@);
         }

AUTHOR       Original code by Damian Conway.

       Maintained by Michael G Schwern until September 2005.

       Now maintained by Tony Bowden.

BUGS and QUERIES
       Please direct all correspondence regarding this module to:
         bug-Class-Data-Inheritable@rt.cpan.org

COPYRIGHT and LICENSE
       Copyright (c) 2000-2005, Damian Conway and Michael G Schwern.  All
       Rights Reserved.

       This module is free software. It may be used, redistributed and/or
       modified under the terms of the Perl Artistic License (see
       http://www.perl.com/perl/misc/Artistic.html)

SEE ALSO
       perltootc has a very elaborate discussion of class data in Perl.



perl v5.8.8                       2006-09-20       Class::Data::Inheritable(3)