Class::Data::Inheritable(3) User Contributed Perl Documentation Class::Data::Inheritable(3)

# [NAME](#NAME)

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

# [SYNOPSIS](#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](#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 overridden.

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 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 effect Raygun.

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

# [Methods](#Methods)

## [mk\_classdata](#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](#AUTHOR)

Original code by Damian Conway.

Maintained by Michael G Schwern until September 2005.

Now maintained by Tony Bowden.

# [BUGS and QUERIES](#BUGS_and_QUERIES)

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

# [COPYRIGHT and LICENSE](#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](#SEE_ALSO)

perltooc has a very elaborate discussion of class data in Perl.

2026-10-25 perl v5.44.0

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Document: Class::Data::Inheritable(3pm) from perl-class-data-inheritable 0.10-r7 (Chainguard OS)
Source: https://github.com/class-data-inheritable/class-data-inheritable