# info > Moose::Util::MetaRole

## [Moose::Util::MetaRole](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AUtil%3A%3AMetaRole/markdown)(User Contributed Perl [DocumentMoose::Util](https://www.chedong.com/phpMan.php/perldoc/DocumentMoose%3A%3AUtil/markdown)::[MetaRole(3pm)](https://www.chedong.com/phpMan.php/man/MetaRole/3pm/markdown)

## NAME
       [Moose::Util::MetaRole](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AUtil%3A%3AMetaRole/markdown) - Apply roles to any metaclass, as well as the
       object base class

## VERSION
       version 2.2200

## SYNOPSIS
         package [MyApp::Moose](https://www.chedong.com/phpMan.php/perldoc/MyApp%3A%3AMoose/markdown);

         use Moose ();
         use [Moose::Exporter](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AExporter/markdown);
         use [Moose::Util::MetaRole](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AUtil%3A%3AMetaRole/markdown);

         use [MyApp::Role::Meta::Class](https://www.chedong.com/phpMan.php/perldoc/MyApp%3A%3ARole%3A%3AMeta%3A%3AClass/markdown);
         use [MyApp::Role::Meta::Method::Constructor](https://www.chedong.com/phpMan.php/perldoc/MyApp%3A%3ARole%3A%3AMeta%3A%3AMethod%3A%3AConstructor/markdown);
         use [MyApp::Role::Object](https://www.chedong.com/phpMan.php/perldoc/MyApp%3A%3ARole%3A%3AObject/markdown);

         [Moose::Exporter](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AExporter/markdown)->setup_import_methods( also => 'Moose' );

         sub init_meta {
             shift;
             my %args = @_;

             Moose->init_meta(%args);

             [Moose::Util::MetaRole::apply_metaroles](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AUtil%3A%3AMetaRole%3A%3Aapplymetaroles/markdown)(
                 for             => $args{for_class},
                 class_metaroles => {
                     class       => ['[MyApp::Role::Meta::Class](https://www.chedong.com/phpMan.php/perldoc/MyApp%3A%3ARole%3A%3AMeta%3A%3AClass/markdown)'],
                     constructor => ['[MyApp::Role::Meta::Method::Constructor](https://www.chedong.com/phpMan.php/perldoc/MyApp%3A%3ARole%3A%3AMeta%3A%3AMethod%3A%3AConstructor/markdown)'],
                 },
             );

             [Moose::Util::MetaRole::apply_base_class_roles](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AUtil%3A%3AMetaRole%3A%3Aapplybaseclassroles/markdown)(
                 for   => $args{for_class},
                 roles => ['[MyApp::Role::Object](https://www.chedong.com/phpMan.php/perldoc/MyApp%3A%3ARole%3A%3AObject/markdown)'],
             );

             return $args{for_class}->meta();
         }

## DESCRIPTION
       This utility module is designed to help authors of Moose extensions
       write extensions that are able to cooperate with other Moose
       extensions. To do this, you must write your extensions as roles, which
       can then be dynamically applied to the caller's metaclasses.

       This module makes sure to preserve any existing superclasses and roles
       already set for the meta objects, which means that any number of
       extensions can apply roles in any order.

## USAGE
       The easiest way to use this module is through [Moose::Exporter](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AExporter/markdown), which
       can generate the appropriate "init_meta" method for you, and make sure
       it is called when imported.

## FUNCTIONS
       This module provides two functions.

   apply_metaroles( ... )
       This function will apply roles to one or more metaclasses for the
       specified class. It will return a new metaclass object for the class or
       role passed in the "for" parameter.

       It accepts the following parameters:

       o   for => $name

           This specifies the class or for which to alter the meta classes.
           This can be a package name, or an appropriate meta-object (a
           [Moose::Meta::Class](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AMeta%3A%3AClass/markdown) or [Moose::Meta::Role](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AMeta%3A%3ARole/markdown)).

       o   class_metaroles => \%roles

           This is a hash reference specifying which metaroles will be applied
           to the class metaclass and its contained metaclasses and helper
           classes.

           Each key should in turn point to an array reference of role names.

           It accepts the following keys:

           class
           attribute
           method
           wrapped_method
           instance
           constructor
           destructor
           error
       o   role_metaroles => \%roles

           This is a hash reference specifying which metaroles will be applied
           to the role metaclass and its contained metaclasses and helper
           classes.

           It accepts the following keys:

           role
           attribute
           method
           required_method
           conflicting_method
           application_to_class
           application_to_role
           application_to_instance
           application_role_summation
           applied_attribute

   apply_base_class_roles( for => $class, roles => \@roles )
       This function will apply the specified roles to the object's base
       class.

## BUGS
       See "BUGS" in Moose for details on reporting bugs.

## AUTHORS
       o   Stevan Little <<stevan@cpan.org>>

       o   Dave Rolsky <<autarch@urth.org>>

       o   Jesse Luehrs <<doy@cpan.org>>

       o   Shawn M Moore <<sartak@cpan.org>>

       o    ' (Yuval Kogman) <<nothingmuch@woobling.org>>

       o   Karen Etheridge <<ether@cpan.org>>

       o   Florian Ragwitz <<rafl@debian.org>>

       o   Hans Dieter Pearcey <<hdp@cpan.org>>

       o   Chris Prather <<chris@prather.org>>

       o   Matt S Trout <<mstrout@cpan.org>>

## COPYRIGHT AND LICENSE
       This software is copyright (c) 2006 by Infinity Interactive, Inc.

       This is free software; you can redistribute it and/or modify it under
       the same terms as the Perl 5 programming language system itself.

perl v5.34.0                      2022-02-06        [Moose::Util](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AUtil/markdown)::[MetaRole(3pm)](https://www.chedong.com/phpMan.php/man/MetaRole/3pm/markdown)