NAME

Moose::Util::MetaRole - Apply roles to any metaclass, as well as the object base class

SYNOPSIS

  package MyApp::Moose;

  use Moose ();
  use Moose::Exporter;
  use Moose::Util::MetaRole;

  use MyApp::Role::Meta::Class;
  use MyApp::Role::Meta::Method::Constructor;
  use MyApp::Role::Object;

  Moose::Exporter->setup_import_methods( also => 'Moose' );

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

      Moose->init_meta(%args);

      Moose::Util::MetaRole::apply_metaroles(
          for             => $args{for_class},
          class_metaroles => {
              class => => ['MyApp::Role::Meta::Class'],
              constructor => ['MyApp::Role::Meta::Method::Constructor'],
          },
      );

      Moose::Util::MetaRole::apply_base_class_roles(
          for   => $args{for_class},
          roles => ['MyApp::Role::Object'],
      );

      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

It is very important that you only call this module's functions when your module is imported by the caller. The process of applying roles to the metaclass reinitializes the metaclass object, which wipes out any existing attributes already defined. However, as long as you do this when your module is imported, the caller should not have any attributes defined yet.

The easiest way to ensure that this happens is to use Moose::Exporter, 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:

• 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 or Moose::Meta::Role).

• 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

• 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

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.

AUTHOR

Dave Rolsky <autarch@urth.org>

COPYRIGHT AND LICENSE

Copyright 2009 by Infinity Interactive, Inc.

http://www.iinteractive.com

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