5 use Scalar::Util 'blessed';
14 use Moose::Meta::Role;
15 use Moose::Util::TypeConstraints;
18 croak "Roles do not support 'extends' (you can use 'with' to specialize a role)";
22 Moose::Util::apply_all_roles( shift, @_ );
27 croak "Must specify at least one method" unless @_;
28 $meta->add_required_methods(@_);
33 croak "Must specify at least one role" unless @_;
34 $meta->add_excluded_roles(@_);
40 croak 'Usage: has \'name\' => ( key => value, ... )' if @_ == 1;
41 my %options = ( definition_context => Moose::Util::_caller_info(), @_ );
42 my $attrs = ( ref($name) eq 'ARRAY' ) ? $name : [ ($name) ];
43 $meta->add_attribute( $_, %options ) for @$attrs;
46 sub _add_method_modifier {
50 if ( ref($_[0]) eq 'Regexp' ) {
51 croak "Roles do not currently support regex "
52 . " references for $type method modifiers";
55 Moose::Util::add_method_modifier($meta, $type, \@_);
58 sub before { _add_method_modifier('before', @_) }
60 sub after { _add_method_modifier('after', @_) }
62 sub around { _add_method_modifier('around', @_) }
64 # see Moose.pm for discussion
66 return unless $Moose::SUPER_BODY;
67 $Moose::SUPER_BODY->(@Moose::SUPER_ARGS);
72 my ( $name, $code ) = @_;
73 $meta->add_override_method_modifier( $name, $code );
77 croak "Roles cannot support 'inner'";
81 croak "Roles cannot support 'augment'";
84 Moose::Exporter->setup_import_methods(
86 qw( with requires excludes has before after around override )
89 qw( extends super inner augment ),
91 \&Scalar::Util::blessed,
99 my $role = $args{for_class};
103 Moose->throw_error("Cannot call init_meta without specifying a for_class");
106 my $metaclass = $args{metaclass} || "Moose::Meta::Role";
107 my $meta_name = exists $args{meta_name} ? $args{meta_name} : 'meta';
109 Moose->throw_error("The Metaclass $metaclass must be a subclass of Moose::Meta::Role.")
110 unless $metaclass->isa('Moose::Meta::Role');
112 # make a subtype for each Moose role
113 role_type $role unless find_type_constraint($role);
116 if ( $meta = Class::MOP::get_metaclass_by_name($role) ) {
117 unless ( $meta->isa("Moose::Meta::Role") ) {
118 my $error_message = "$role already has a metaclass, but it does not inherit $metaclass ($meta).";
119 if ( $meta->isa('Moose::Meta::Class') ) {
120 Moose->throw_error($error_message . ' You cannot make the same thing a role and a class. Remove either Moose or Moose::Role.');
122 Moose->throw_error($error_message);
127 $meta = $metaclass->initialize($role);
130 if (defined $meta_name) {
131 # also check for inherited non moose 'meta' method?
132 my $existing = $meta->get_method($meta_name);
133 if ($existing && !$existing->isa('Class::MOP::Method::Meta')) {
134 Carp::cluck "Moose::Role is overwriting an existing method named "
135 . "$meta_name in role $role with a method "
136 . "which returns the class's metaclass. If this is "
137 . "actually what you want, you should remove the "
138 . "existing method, otherwise, you should rename or "
139 . "disable this generated method using the "
140 . "'-meta_name' option to 'use Moose::Role'.";
142 $meta->_add_meta_method($meta_name);
150 # ABSTRACT: The Moose Role
159 use Moose::Role; # automatically turns on strict and warnings
164 my ($self, $other) = @_;
165 !$self->equal($other);
168 # ... then in your classes
171 use Moose; # automatically turns on strict and warnings
176 my ($self, $other) = @_;
177 $self->as_float == $other->as_float;
182 The concept of roles is documented in L<Moose::Manual::Roles>. This document
183 serves as API documentation.
185 =head1 EXPORTED FUNCTIONS
187 Moose::Role currently supports all of the functions that L<Moose> exports, but
188 differs slightly in how some items are handled (see L</CAVEATS> below for
191 Moose::Role also offers two role-specific keyword exports:
195 =item B<requires (@method_names)>
197 Roles can require that certain methods are implemented by any class which
200 Note that attribute accessors also count as methods for the purposes
201 of satisfying the requirements of a role.
203 =item B<excludes (@role_names)>
205 Roles can C<exclude> other roles, in effect saying "I can never be combined
206 with these C<@role_names>". This is a feature which should not be used
213 Moose::Role offers a way to remove the keywords it exports, through the
214 C<unimport> method. You simply have to say C<no Moose::Role> at the bottom of
215 your code for this to work.
217 =head2 B<< Moose::Role->init_meta(for_class => $role, metaclass => $metaclass) >>
219 The C<init_meta> method sets up the metaclass object for the role
220 specified by C<for_class>. It also injects a a C<meta> accessor into
221 the role so you can get at this object.
223 The default metaclass is L<Moose::Meta::Role>. You can specify an
224 alternate metaclass with the C<metaclass> parameter.
228 When you use Moose::Role, you can specify which metaclass to use:
230 use Moose::Role -metaclass => 'My::Meta::Role';
232 You can also specify traits which will be applied to your role metaclass:
234 use Moose::Role -traits => 'My::Trait';
236 This is very similar to the attribute traits feature. When you do
237 this, your class's C<meta> object will have the specified traits
238 applied to it. See L<Moose/Metaclass and Trait Name Resolution> for more
241 =head1 APPLYING ROLES
243 In addition to being applied to a class using the 'with' syntax (see
244 L<Moose::Manual::Roles>) and using the L<Moose::Util> 'apply_all_roles'
245 method, roles may also be applied to an instance of a class using
246 L<Moose::Util> 'apply_all_roles' or the role's metaclass:
248 MyApp::Test::SomeRole->meta->apply( $instance );
250 Doing this creates a new, mutable, anonymous subclass, applies the role to that,
251 and reblesses. In a debugger, for example, you will see class names of the
252 form C< Class::MOP::Class::__ANON__::SERIAL::6 >, which means that doing a 'ref'
253 on your instance may not return what you expect. See L<Moose::Object> for 'DOES'.
255 Additional params may be added to the new instance by providing 'rebless_params'.
256 See L<Moose::Meta::Role::Application::ToInstance>.
260 Role support has only a few caveats:
266 Roles cannot use the C<extends> keyword; it will throw an exception for now.
267 The same is true of the C<augment> and C<inner> keywords (not sure those
268 really make sense for roles). All other Moose keywords will be I<deferred>
269 so that they can be applied to the consuming class.
273 Role composition does its best to B<not> be order-sensitive when it comes to
274 conflict resolution and requirements detection. However, it is order-sensitive
275 when it comes to method modifiers. All before/around/after modifiers are
276 included whenever a role is composed into a class, and then applied in the order
277 in which the roles are used. This also means that there is no conflict for
278 before/around/after modifiers.
280 In most cases, this will be a non-issue; however, it is something to keep in
281 mind when using method modifiers in a role. You should never assume any
288 See L<Moose/BUGS> for details on reporting bugs.