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Dave Rolsky


MooseX::ClassAttribute - Declare class attributes Moose-style


    package My::Class;

    use Moose;
    use MooseX::ClassAttribute;

    class_has 'Cache' =>
        ( is      => 'rw',
          isa     => 'HashRef',
          default => sub { {} },


    no Moose;
    no MooseX::ClassAttribute;

    # then later ...

    My::Class->Cache()->{thing} = ...;


This module allows you to declare class attributes in exactly the same way as you declare object attributes, except using class_has() instead of has(). It is also possible to make these attributes immutable (and faster) just as you can with normal Moose attributes.

You can use any feature of Moose's attribute declarations, including overriding a parent's attributes, delegation (handles), and attribute metaclasses, and it should just work.

The accessors methods for class attribute may be called on the class directly, or on objects of that class. Passing a class attribute to the constructor will not set it.


This class exports one function when you use it, class_has(). This works exactly like Moose's has(), but it declares class attributes.

One little nit is that if you include no Moose in your class, you won't remove the class_has() function. To do that you must include no MooseX::ClassAttribute as well.

If you want to use this module to create class attributes in other classes, you can call the process_class_attribute() function like this:

  MooseX::ClassAttribute::process_class_attribute( $package, ... );

The first argument is the package which will have the class attribute, and the remaining arguments are the same as those passed to class_has().

Implementation and Immutability

Underneath the hood, this class creates one new class for each class which has class attributes and sets up delegating methods in the class for which you're creating class attributes. You don't need to worry about this too much, except when it comes to making a class immutable.

Since the class attributes are not really stored in your class, you need to make the containing class immutable as well as your own ...


This may change in the future!


Dave Rolsky, <autarch@urth.org>


Please report any bugs or feature requests to bug-moosex-classattribute@rt.cpan.org, or through the web interface at http://rt.cpan.org. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.


Copyright 2007 Dave Rolsky, All Rights Reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.