Moose::Role - The Moose Role


Moose documentation Contained in the Moose distribution.

Index


Code Index:

NAME

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Moose::Role - The Moose Role

VERSION

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version 2.0010

SYNOPSIS

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  package Eq;
  use Moose::Role; # automatically turns on strict and warnings

  requires 'equal';

  sub no_equal {
      my ($self, $other) = @_;
      !$self->equal($other);
  }

  # ... then in your classes

  package Currency;
  use Moose; # automatically turns on strict and warnings

  with 'Eq';

  sub equal {
      my ($self, $other) = @_;
      $self->as_float == $other->as_float;
  }

DESCRIPTION

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The concept of roles is documented in Moose::Manual::Roles. This document serves as API documentation.

EXPORTED FUNCTIONS

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Moose::Role currently supports all of the functions that Moose exports, but differs slightly in how some items are handled (see CAVEATS below for details).

Moose::Role also offers two role-specific keyword exports:

requires (@method_names)

Roles can require that certain methods are implemented by any class which does the role.

Note that attribute accessors also count as methods for the purposes of satisfying the requirements of a role.

excludes (@role_names)

Roles can exclude other roles, in effect saying "I can never be combined with these @role_names". This is a feature which should not be used lightly.

unimport

Moose::Role offers a way to remove the keywords it exports, through the unimport method. You simply have to say no Moose::Role at the bottom of your code for this to work.

METACLASS

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When you use Moose::Role, you can specify traits which will be applied to your role metaclass:

    use Moose::Role -traits => 'My::Trait';

This is very similar to the attribute traits feature. When you do this, your class's meta object will have the specified traits applied to it. See Metaclass and Trait Name Resolution in Moose for more details.

APPLYING ROLES

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In addition to being applied to a class using the 'with' syntax (see Moose::Manual::Roles) and using the Moose::Util 'apply_all_roles' method, roles may also be applied to an instance of a class using Moose::Util 'apply_all_roles' or the role's metaclass:

   MyApp::Test::SomeRole->meta->apply( $instance );

Doing this creates a new, mutable, anonymous subclass, applies the role to that, and reblesses. In a debugger, for example, you will see class names of the form Moose::Meta::Class::__ANON__::SERIAL::6 , which means that doing a 'ref' on your instance may not return what you expect. See Moose::Object for 'DOES'.

Additional params may be added to the new instance by providing 'rebless_params'. See Moose::Meta::Role::Application::ToInstance.

CAVEATS

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Role support has only a few caveats:

BUGS

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See BUGS in Moose for details on reporting bugs.

AUTHOR

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Stevan Little <stevan@iinteractive.com>

COPYRIGHT AND LICENSE

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Moose documentation Contained in the Moose distribution.

package Moose::Role;
BEGIN {
  $Moose::Role::AUTHORITY = 'cpan:STEVAN';
}
BEGIN {
  $Moose::Role::VERSION = '2.0010';
}
use strict;
use warnings;

use Scalar::Util 'blessed';
use Carp         'croak';

use Sub::Exporter;

use Moose       ();
use Moose::Util ();

use Moose::Exporter;
use Moose::Meta::Role;
use Moose::Util::TypeConstraints;

sub extends {
    croak "Roles do not support 'extends' (you can use 'with' to specialize a role)";
}

sub with {
    Moose::Util::apply_all_roles( shift, @_ );
}

sub requires {
    my $meta = shift;
    croak "Must specify at least one method" unless @_;
    $meta->add_required_methods(@_);
}

sub excludes {
    my $meta = shift;
    croak "Must specify at least one role" unless @_;
    $meta->add_excluded_roles(@_);
}

sub has {
    my $meta = shift;
    my $name = shift;
    croak 'Usage: has \'name\' => ( key => value, ... )' if @_ == 1;
    my %options = ( definition_context => Moose::Util::_caller_info(), @_ );
    my $attrs = ( ref($name) eq 'ARRAY' ) ? $name : [ ($name) ];
    $meta->add_attribute( $_, %options ) for @$attrs;
}

sub _add_method_modifier {
    my $type = shift;
    my $meta = shift;

    if ( ref($_[0]) eq 'Regexp' ) {
        croak "Roles do not currently support regex "
            . " references for $type method modifiers";
    }

    Moose::Util::add_method_modifier($meta, $type, \@_);
}

sub before { _add_method_modifier('before', @_) }

sub after  { _add_method_modifier('after',  @_) }

sub around { _add_method_modifier('around', @_) }

# see Moose.pm for discussion
sub super {
    return unless $Moose::SUPER_BODY;
    $Moose::SUPER_BODY->(@Moose::SUPER_ARGS);
}

sub override {
    my $meta = shift;
    my ( $name, $code ) = @_;
    $meta->add_override_method_modifier( $name, $code );
}

sub inner {
    croak "Roles cannot support 'inner'";
}

sub augment {
    croak "Roles cannot support 'augment'";
}

Moose::Exporter->setup_import_methods(
    with_meta => [
        qw( with requires excludes has before after around override )
    ],
    as_is => [
        qw( extends super inner augment ),
        \&Carp::confess,
        \&Scalar::Util::blessed,
    ],
);

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

    my $role = $args{for_class};

    unless ($role) {
        require Moose;
        Moose->throw_error("Cannot call init_meta without specifying a for_class");
    }

    my $metaclass = $args{metaclass} || "Moose::Meta::Role";
    my $meta_name = exists $args{meta_name} ? $args{meta_name} : 'meta';

    Moose->throw_error("The Metaclass $metaclass must be loaded. (Perhaps you forgot to 'use $metaclass'?)")
        unless Class::MOP::is_class_loaded($metaclass);

    Moose->throw_error("The Metaclass $metaclass must be a subclass of Moose::Meta::Role.")
        unless $metaclass->isa('Moose::Meta::Role');

    # make a subtype for each Moose role
    role_type $role unless find_type_constraint($role);

    my $meta;
    if ( $meta = Class::MOP::get_metaclass_by_name($role) ) {
        unless ( $meta->isa("Moose::Meta::Role") ) {
            my $error_message = "$role already has a metaclass, but it does not inherit $metaclass ($meta).";
            if ( $meta->isa('Moose::Meta::Class') ) {
                Moose->throw_error($error_message . ' You cannot make the same thing a role and a class. Remove either Moose or Moose::Role.');
            } else {
                Moose->throw_error($error_message);
            }
        }
    }
    else {
        $meta = $metaclass->initialize($role);
    }

    if (defined $meta_name) {
        # also check for inherited non moose 'meta' method?
        my $existing = $meta->get_method($meta_name);
        if ($existing && !$existing->isa('Class::MOP::Method::Meta')) {
            Carp::cluck "Moose::Role is overwriting an existing method named "
                      . "$meta_name in role $role with a method "
                      . "which returns the class's metaclass. If this is "
                      . "actually what you want, you should remove the "
                      . "existing method, otherwise, you should rename or "
                      . "disable this generated method using the "
                      . "'-meta_name' option to 'use Moose::Role'.";
        }
        $meta->_add_meta_method($meta_name);
    }

    return $meta;
}

1;

# ABSTRACT: The Moose Role




__END__