Moose::Role(3pm) User Contributed Perl Documentation Moose::Role(3pm)
NAME
Moose::Role - The Moose Role
VERSION
version 2.2200
SYNOPSIS
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);
DESCRIPTION
The concept of roles is documented in Moose::Manual::Roles. This
document serves as API documentation.
EXPORTED FUNCTIONS
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.
no Moose::Role
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
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.
All role metaclasses (note, not the role itself) extend
Moose::Meta::Role. You can test if a package is a role or not using
"is_role" in Moose::Util.
APPLYING ROLES
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
Role support has only a few caveats:
• Roles cannot use the "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.
BUGS
See "BUGS" in Moose for details on reporting bugs.
AUTHORS
• Stevan Little <stevan@cpan.org>
• Dave Rolsky <autarch@urth.org>
• Jesse Luehrs <doy@cpan.org>
• Shawn M Moore <sartak@cpan.org>
• יובל קוג'מן (Yuval Kogman) <nothingmuch@woobling.org>
• Karen Etheridge <ether@cpan.org>
• Florian Ragwitz <rafl@debian.org>
• Hans Dieter Pearcey <hdp@cpan.org>
• Chris Prather <chris@prather.org>
• 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::Role(3pm)
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