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231be3be |
1 | package Moose::Util::MetaRole; |
2 | |
3 | use strict; |
4 | use warnings; |
5 | |
df8260e9 |
6 | our $VERSION = '0.63'; |
ae18d5ec |
7 | $VERSION = eval $VERSION; |
8 | our $AUTHORITY = 'cpan:STEVAN'; |
9 | |
231be3be |
10 | use List::MoreUtils qw( all ); |
11 | |
8f05895e |
12 | my @Classes = qw( constructor_class destructor_class error_class ); |
13 | |
231be3be |
14 | sub apply_metaclass_roles { |
15 | my %options = @_; |
16 | |
17 | my $for = $options{for_class}; |
18 | |
9eaf623d |
19 | my %old_classes |
20 | = map { $_ => $for->meta->$_ } grep { $for->meta->can($_) } @Classes; |
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21 | |
8f05895e |
22 | my $meta = _make_new_metaclass( $for, \%options ); |
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23 | |
9eaf623d |
24 | for my $c ( grep { $meta->can($_) } @Classes ) { |
8f05895e |
25 | if ( $options{ $c . '_roles' } ) { |
26 | my $class = _make_new_class( |
27 | $meta->$c(), |
28 | $options{ $c . '_roles' } |
29 | ); |
231be3be |
30 | |
8f05895e |
31 | $meta->$c($class); |
32 | } |
33 | else { |
34 | $meta->$c( $old_classes{$c} ); |
35 | } |
231be3be |
36 | } |
37 | |
38 | return $meta; |
39 | } |
40 | |
41 | sub _make_new_metaclass { |
42 | my $for = shift; |
43 | my $options = shift; |
44 | |
45 | return $for->meta() |
46 | unless grep { exists $options->{ $_ . '_roles' } } |
47 | qw( |
48 | metaclass |
49 | attribute_metaclass |
50 | method_metaclass |
51 | instance_metaclass |
52 | ); |
53 | |
54 | my $new_metaclass |
55 | = _make_new_class( ref $for->meta(), $options->{metaclass_roles} ); |
56 | |
57 | my $old_meta = $for->meta(); |
58 | |
72d15b83 |
59 | # This could get called for a Moose::Meta::Role as well as a Moose::Meta::Class |
231be3be |
60 | my %classes = map { |
61 | $_ => _make_new_class( $old_meta->$_(), $options->{ $_ . '_roles' } ) |
72d15b83 |
62 | } |
63 | grep { $old_meta->can($_) } |
64 | qw( |
231be3be |
65 | attribute_metaclass |
66 | method_metaclass |
67 | instance_metaclass |
68 | ); |
69 | |
70 | return $new_metaclass->reinitialize( $for, %classes ); |
71 | } |
72 | |
73 | sub apply_base_class_roles { |
74 | my %options = @_; |
75 | |
76 | my $for = $options{for_class}; |
77 | |
78 | my $meta = $for->meta(); |
79 | |
80 | my $new_base = _make_new_class( |
81 | $for, |
82 | $options{roles}, |
83 | [ $meta->superclasses() ], |
84 | ); |
85 | |
86 | $meta->superclasses($new_base) |
87 | if $new_base ne $meta->name(); |
88 | } |
89 | |
90 | sub _make_new_class { |
91 | my $existing_class = shift; |
92 | my $roles = shift; |
93 | my $superclasses = shift || [$existing_class]; |
94 | |
95 | return $existing_class unless $roles; |
96 | |
8f05895e |
97 | my $meta = Class::MOP::Class->initialize($existing_class); |
231be3be |
98 | |
99 | return $existing_class |
100 | if $meta->can('does_role') && all { $meta->does_role($_) } @{$roles}; |
101 | |
102 | return Moose::Meta::Class->create_anon_class( |
103 | superclasses => $superclasses, |
104 | roles => $roles, |
105 | cache => 1, |
106 | )->name(); |
107 | } |
108 | |
109 | 1; |
c59bc009 |
110 | |
111 | __END__ |
112 | |
113 | =head1 NAME |
114 | |
115 | Moose::Util::MetaRole - Apply roles to any metaclass, as well as the object base class |
116 | |
117 | =head1 SYNOPSIS |
118 | |
119 | package MyApp::Moose; |
120 | |
121 | use strict; |
122 | use warnings; |
123 | |
124 | use Moose (); |
125 | use Moose::Exporter; |
126 | use Moose::Util::Meta::Role; |
127 | |
128 | use MyApp::Role::Meta::Class; |
129 | use MyApp::Role::Meta::Method::Constructor; |
130 | use MyApp::Role::Object; |
131 | |
132 | Moose::Exporter->setup_import_methods( also => 'Moose' ); |
133 | |
134 | sub init_meta { |
135 | shift; |
136 | my %options = @_; |
137 | |
138 | Moose->init_meta(%options); |
139 | |
140 | Moose::Util::MetaRole::apply_metaclass_roles( |
141 | for_class => $options{for_class}, |
142 | metaclass_roles => ['MyApp::Role::Meta::Class'], |
143 | constructor_class_roles => ['MyApp::Role::Meta::Method::Constructor'], |
144 | ); |
145 | |
146 | Moose::Util::MetaRole::apply_base_class_roles( |
147 | for_class => $options{for_class}, |
148 | roles => ['MyApp::Role::Object'], |
149 | ); |
150 | |
151 | return $options{for_class}->meta(); |
152 | } |
153 | |
154 | =head1 DESCRIPTION |
155 | |
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156 | B<The whole concept behind this module is still considered |
157 | experimental, and it could go away in the future!> |
158 | |
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159 | This utility module is designed to help authors of Moose extensions |
160 | write extensions that are able to cooperate with other Moose |
161 | extensions. To do this, you must write your extensions as roles, which |
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162 | can then be dynamically applied to the caller's metaclasses. |
c59bc009 |
163 | |
164 | This module makes sure to preserve any existing superclasses and roles |
165 | already set for the meta objects, which means that any number of |
166 | extensions can apply roles in any order. |
167 | |
168 | =head1 USAGE |
169 | |
170 | B<It is very important that you only call this module's functions when |
171 | your module is imported by the caller>. The process of applying roles |
172 | to the metaclass reinitializes the metaclass object, which wipes out |
173 | any existing attributes already defined. However, as long as you do |
174 | this when your module is imported, the caller should not have any |
175 | attributes defined yet. |
176 | |
177 | The easiest way to ensure that this happens is to use |
178 | L<Moose::Exporter> and provide an C<init_meta> method that will be |
179 | called when imported. |
180 | |
181 | =head1 FUNCTIONS |
182 | |
183 | This module provides two functions. |
184 | |
185 | =head2 apply_metaclass_roles( ... ) |
186 | |
187 | This function will apply roles to one or more metaclasses for the |
188 | specified class. It accepts the following parameters: |
189 | |
190 | =over 4 |
191 | |
192 | =item * for_class => $name |
193 | |
194 | This specifies the class for which to alter the meta classes. |
195 | |
196 | =item * metaclass_roles => \@roles |
197 | |
198 | =item * attribute_metaclass_roles => \@roles |
199 | |
200 | =item * method_metaclass_roles => \@roles |
201 | |
202 | =item * instance_metaclass_roles => \@roles |
203 | |
204 | =item * constructor_class_roles => \@roles |
205 | |
206 | =item * destructor_class_roles => \@roles |
207 | |
208 | These parameter all specify one or more roles to be applied to the |
209 | specified metaclass. You can pass any or all of these parameters at |
210 | once. |
211 | |
212 | =back |
213 | |
214 | =head2 apply_base_class_roles( for_class => $class, roles => \@roles ) |
215 | |
216 | This function will apply the specified roles to the object's base class. |
217 | |
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218 | =head1 PROBLEMS WITH METACLASS ROLES AND SUBCLASS |
219 | |
220 | Because of the way this module works, there is an ordering problem |
221 | which occurs in certain situations. This sequence of events causes an |
222 | error: |
223 | |
224 | =over 4 |
225 | |
226 | =item 1. |
227 | |
228 | There is a class (ClassA) which uses some extension(s) that apply |
229 | roles to the metaclass. |
230 | |
231 | =item 2. |
232 | |
233 | You have another class (ClassB) which wants to subclass ClassA and |
234 | apply some more extensions. |
235 | |
236 | =back |
237 | |
238 | Normally, the call to C<extends> will happen at run time, I<after> the |
239 | additional extensions are applied. This causes an error when we try to |
240 | make the metaclass for ClassB compatible with the metaclass for |
241 | ClassA. |
242 | |
243 | We hope to be able to fix this in the future. |
244 | |
245 | For now the workaround is for ClassB to make sure it extends ClassA |
246 | I<before> it loads extensions: |
247 | |
248 | package ClassB; |
249 | |
250 | use Moose; |
251 | |
252 | BEGIN { extends 'ClassA' } |
253 | |
254 | use MooseX::SomeExtension; |
255 | |
c59bc009 |
256 | =head1 AUTHOR |
257 | |
258 | Dave Rolsky E<lt>autarch@urth.orgE<gt> |
259 | |
260 | =head1 COPYRIGHT AND LICENSE |
261 | |
262 | Copyright 2008 by Infinity Interactive, Inc. |
263 | |
264 | L<http://www.iinteractive.com> |
265 | |
266 | This library is free software; you can redistribute it and/or modify |
267 | it under the same terms as Perl itself. |
268 | |
269 | =cut |