Class::...ritable(3)

✨ NAME ✨

Class::Data::Inheritable — inheritable, overridable class data. That's the whole vibe. This is the User Contributed Perl Documentation page for Class::Data::Inheritable(3), so get cozy bestie 💖

🌸 SYNOPSIS 🌸

Here's the setup, no cap:

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 literally here to create accessor/mutators to class data. Iykyk: if you want to store something about your class as a whole instead of about a single object, this is your moment. That data then gets inherited by your subclasses and can be overridden. ✨

For example:

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

This 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 overridden a method:

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

Now that Raygun has overridden Pere::Ubu, further changes by Pere::Ubu no longer affect 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.

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Okay bestie, that's the whole page 💖 This one's from the User Contributed Perl Documentation, and the footer source/version is perl v5.42.0, dated 2024-10-24. Slay. 🫶