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Class::Data::Inheritable(3) User Contributed Perl Documentation Class::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->mk_classdata('DataFile'); # Declare the location of the data file for this class. Stuff->DataFile('/etc/stuff/data'); # Or, all in one shot: Stuff->mk_classdata(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->mk_classdata('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. $suitcase = Raygun->Suitcase; Raygun inherits its Suitcase class data from Pere::Ubu. Inheritance of class data works analogous to method inheritance. As long as Raygun does not "override" its inherited class data (by using Suitcase() to set a new value) it will continue to use whatever is set in Pere::Ubu and inherit further changes: # Both Raygun's and Pere::Ubu's suitcases are now Blue Pere::Ubu->Suitcase('Blue'); However, should Raygun decide to set its own Suitcase() it has now "overridden" Pere::Ubu and is on its own, just like if it had overriden a method: # Raygun has an orange suitcase, Pere::Ubu's is still Blue. Raygun->Suitcase('Orange'); Now that Raygun has overridden Pere::Ubu futher changes by Pere::Ubu no longer effect Raygun. # Raygun still has an orange suitcase, but Pere::Ubu is using Samsonite. Pere::Ubu->Suitcase('Samsonite'); Methods mk_classdata Class->mk_classdata($data_accessor_name); Class->mk_classdata($data_accessor_name => $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 $data_accessor_name, and optionally initially setting it to the given value. To facilitate overriding, mk_classdata creates an alias to the accessor, _field_accessor(). So Suitcase() would have an alias _Suitcase_accessor() that does the exact same thing as Suitcase(). This is useful if you want to alter the behavior of a single accessor yet still get the benefits of inheritable class data. For example. sub Suitcase { my($self) = shift; warn "Fashion tragedy" if @_ and $_[0] eq 'Plaid'; $self->_Suitcase_accessor(@_); } 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 same terms as Perl itself. SEE ALSO
perltooc has a very elaborate discussion of class data in Perl. perl v5.18.2 2008-01-25 Class::Data::Inheritable(3)
