NAME¶
Moose::Role - The Moose Role
VERSION¶
version 2.0603
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.
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.
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¶
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.
AUTHOR¶
Moose is maintained by the Moose Cabal, along with the help of many
contributors. See "CABAL" in Moose and "CONTRIBUTORS" in
Moose for details.
COPYRIGHT AND LICENSE¶
This software is copyright (c) 2012 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.