Moose::Role - The Moose Role |
Moose::Role - The Moose Role
version 2.1605
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; }
# ... and also
package Comparator; use Moose;
has compare_to => ( is => 'ro', does => 'Eq', handles => 'Eq', );
# ... which allows
my $currency1 = Currency->new(...); my $currency2 = Currency->new(...); Comparator->new(compare_to => $currency1)->equal($currency2);
The concept of roles is documented in the Moose::Manual::Roles manpage. This document serves as API documentation.
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:
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.
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.
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.
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 Moose/Metaclass and Trait Name Resolution for more
details.
All role metaclasses (note, not the role itself) extend the Moose::Meta::Role manpage. You can test if a package is a role or not using is_role in the Moose::Util manpage.
In addition to being applied to a class using the 'with' syntax (see the Moose::Manual::Roles manpage) and using the the Moose::Util manpage 'apply_all_roles' method, roles may also be applied to an instance of a class using the Moose::Util manpage '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 the Moose::Object manpage for
'DOES'.
Additional params may be added to the new instance by providing 'rebless_params'. See the Moose::Meta::Role::Application::ToInstance manpage.
Role support has only a few caveats:
extends
keyword; it will throw an exception for now.
The same is true of the augment
and inner
keywords (not sure those
really make sense for roles). All other Moose keywords will be deferred
so that they can be applied to the consuming class.
Role composition does its best to not be order-sensitive when it comes to
conflict resolution and requirements detection. However, it is order-sensitive
when it comes to method modifiers. All before/around/after modifiers are
included whenever a role is composed into a class, and then applied in the order
in which the roles are used. This also means that there is no conflict for
before/around/after modifiers.
In most cases, this will be a non-issue; however, it is something to keep in mind when using method modifiers in a role. You should never assume any ordering.
See Moose/BUGS for details on reporting bugs.
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.
Moose::Role - The Moose Role |