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Class::MakeMethods::Emulator::Inheritable.3pm

NAME

Class::MakeMethods::Emulator::Inheritable - Emulate Class::Inheritable

SYNOPSIS

   package Stuff;
   use base qw(Class::MakeMethods::Emulator::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');
 
 

DESCRIPTION

This module is an adaptor that provides emulatation of Class::Data::Inheritable by invoking similiar functionality provided by Class::MakeMethods::ClassInherit.

The public interface provided by Class::MakeMethods::Emulator::Inheritable is identical to that of Class::Data::Inheritable.

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.

USAGE

As specified by Class::Data::Inheritable, clients should inherit from this module and then invoke the mk_classdata() method for each class method desired:

   Class->mk_classdata($data_accessor_name);
 
 

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.

   Class->mk_classdata($data_accessor_name, $initial_value);
 
 

You may also pass a second argument to initialize the 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(@_);
   }
 
 

COMPATIBILITY

Note that the internal implementation of Class::MakeMethods::ClassInherit does not match that of Class::Data::Inheritable. In particular, Class::Data::Inheritable installs new methods in subclasses when they first initialize their value, while

EXAMPLE

The example provided by Class::Data::Inheritable is equally applicable to this emulator.

   package Pere::Ubu;
   use base qw(Class::MakeMethods::Emulator::Inheritable);
   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 analgous 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');
 
 

SEE ALSO

See Class::MakeMethods for general information about this distribution.

See Class::MakeMethods::Emulator for more about this family of subclasses.

See Class::Data::Inheritable for documentation of the original module.

See perltootc for a discussion of class data in Perl.

See Class::MakeMethods::Standard::Inheritable and Class::MakeMethods::Template::ClassInherit for inheritable data methods.