Commit | Line | Data |
231be3be |
1 | package Moose::Util::MetaRole; |
2 | |
3 | use strict; |
4 | use warnings; |
5 | |
6 | use List::MoreUtils qw( all ); |
7 | |
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8 | my @Classes = qw( constructor_class destructor_class error_class ); |
9 | |
231be3be |
10 | sub apply_metaclass_roles { |
11 | my %options = @_; |
12 | |
13 | my $for = $options{for_class}; |
14 | |
9eaf623d |
15 | my %old_classes |
16 | = map { $_ => $for->meta->$_ } grep { $for->meta->can($_) } @Classes; |
231be3be |
17 | |
8f05895e |
18 | my $meta = _make_new_metaclass( $for, \%options ); |
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19 | |
9eaf623d |
20 | for my $c ( grep { $meta->can($_) } @Classes ) { |
8f05895e |
21 | if ( $options{ $c . '_roles' } ) { |
22 | my $class = _make_new_class( |
23 | $meta->$c(), |
24 | $options{ $c . '_roles' } |
25 | ); |
231be3be |
26 | |
8f05895e |
27 | $meta->$c($class); |
28 | } |
29 | else { |
30 | $meta->$c( $old_classes{$c} ); |
31 | } |
231be3be |
32 | } |
33 | |
34 | return $meta; |
35 | } |
36 | |
37 | sub _make_new_metaclass { |
38 | my $for = shift; |
39 | my $options = shift; |
40 | |
41 | return $for->meta() |
42 | unless grep { exists $options->{ $_ . '_roles' } } |
43 | qw( |
44 | metaclass |
45 | attribute_metaclass |
46 | method_metaclass |
47 | instance_metaclass |
48 | ); |
49 | |
50 | my $new_metaclass |
51 | = _make_new_class( ref $for->meta(), $options->{metaclass_roles} ); |
52 | |
53 | my $old_meta = $for->meta(); |
54 | |
72d15b83 |
55 | # This could get called for a Moose::Meta::Role as well as a Moose::Meta::Class |
231be3be |
56 | my %classes = map { |
57 | $_ => _make_new_class( $old_meta->$_(), $options->{ $_ . '_roles' } ) |
72d15b83 |
58 | } |
59 | grep { $old_meta->can($_) } |
60 | qw( |
231be3be |
61 | attribute_metaclass |
62 | method_metaclass |
63 | instance_metaclass |
64 | ); |
65 | |
66 | return $new_metaclass->reinitialize( $for, %classes ); |
67 | } |
68 | |
69 | sub apply_base_class_roles { |
70 | my %options = @_; |
71 | |
72 | my $for = $options{for_class}; |
73 | |
74 | my $meta = $for->meta(); |
75 | |
76 | my $new_base = _make_new_class( |
77 | $for, |
78 | $options{roles}, |
79 | [ $meta->superclasses() ], |
80 | ); |
81 | |
82 | $meta->superclasses($new_base) |
83 | if $new_base ne $meta->name(); |
84 | } |
85 | |
86 | sub _make_new_class { |
87 | my $existing_class = shift; |
88 | my $roles = shift; |
89 | my $superclasses = shift || [$existing_class]; |
90 | |
91 | return $existing_class unless $roles; |
92 | |
8f05895e |
93 | my $meta = Class::MOP::Class->initialize($existing_class); |
231be3be |
94 | |
95 | return $existing_class |
96 | if $meta->can('does_role') && all { $meta->does_role($_) } @{$roles}; |
97 | |
98 | return Moose::Meta::Class->create_anon_class( |
99 | superclasses => $superclasses, |
100 | roles => $roles, |
101 | cache => 1, |
102 | )->name(); |
103 | } |
104 | |
105 | 1; |
c59bc009 |
106 | |
107 | __END__ |
108 | |
109 | =head1 NAME |
110 | |
111 | Moose::Util::MetaRole - Apply roles to any metaclass, as well as the object base class |
112 | |
113 | =head1 SYNOPSIS |
114 | |
115 | package MyApp::Moose; |
116 | |
117 | use strict; |
118 | use warnings; |
119 | |
120 | use Moose (); |
121 | use Moose::Exporter; |
122 | use Moose::Util::Meta::Role; |
123 | |
124 | use MyApp::Role::Meta::Class; |
125 | use MyApp::Role::Meta::Method::Constructor; |
126 | use MyApp::Role::Object; |
127 | |
128 | Moose::Exporter->setup_import_methods( also => 'Moose' ); |
129 | |
130 | sub init_meta { |
131 | shift; |
132 | my %options = @_; |
133 | |
134 | Moose->init_meta(%options); |
135 | |
136 | Moose::Util::MetaRole::apply_metaclass_roles( |
137 | for_class => $options{for_class}, |
138 | metaclass_roles => ['MyApp::Role::Meta::Class'], |
139 | constructor_class_roles => ['MyApp::Role::Meta::Method::Constructor'], |
140 | ); |
141 | |
142 | Moose::Util::MetaRole::apply_base_class_roles( |
143 | for_class => $options{for_class}, |
144 | roles => ['MyApp::Role::Object'], |
145 | ); |
146 | |
147 | return $options{for_class}->meta(); |
148 | } |
149 | |
150 | =head1 DESCRIPTION |
151 | |
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152 | B<The whole concept behind this module is still considered |
153 | experimental, and it could go away in the future!> |
154 | |
c59bc009 |
155 | This utility module is designed to help authors of Moose extensions |
156 | write extensions that are able to cooperate with other Moose |
157 | extensions. To do this, you must write your extensions as roles, which |
158 | can then be dynamically applyied to the caller's metaclasses. |
159 | |
160 | This module makes sure to preserve any existing superclasses and roles |
161 | already set for the meta objects, which means that any number of |
162 | extensions can apply roles in any order. |
163 | |
164 | =head1 USAGE |
165 | |
166 | B<It is very important that you only call this module's functions when |
167 | your module is imported by the caller>. The process of applying roles |
168 | to the metaclass reinitializes the metaclass object, which wipes out |
169 | any existing attributes already defined. However, as long as you do |
170 | this when your module is imported, the caller should not have any |
171 | attributes defined yet. |
172 | |
173 | The easiest way to ensure that this happens is to use |
174 | L<Moose::Exporter> and provide an C<init_meta> method that will be |
175 | called when imported. |
176 | |
177 | =head1 FUNCTIONS |
178 | |
179 | This module provides two functions. |
180 | |
181 | =head2 apply_metaclass_roles( ... ) |
182 | |
183 | This function will apply roles to one or more metaclasses for the |
184 | specified class. It accepts the following parameters: |
185 | |
186 | =over 4 |
187 | |
188 | =item * for_class => $name |
189 | |
190 | This specifies the class for which to alter the meta classes. |
191 | |
192 | =item * metaclass_roles => \@roles |
193 | |
194 | =item * attribute_metaclass_roles => \@roles |
195 | |
196 | =item * method_metaclass_roles => \@roles |
197 | |
198 | =item * instance_metaclass_roles => \@roles |
199 | |
200 | =item * constructor_class_roles => \@roles |
201 | |
202 | =item * destructor_class_roles => \@roles |
203 | |
204 | These parameter all specify one or more roles to be applied to the |
205 | specified metaclass. You can pass any or all of these parameters at |
206 | once. |
207 | |
208 | =back |
209 | |
210 | =head2 apply_base_class_roles( for_class => $class, roles => \@roles ) |
211 | |
212 | This function will apply the specified roles to the object's base class. |
213 | |
eaeacdd6 |
214 | =head1 PROBLEMS WITH METACLASS ROLES AND SUBCLASS |
215 | |
216 | Because of the way this module works, there is an ordering problem |
217 | which occurs in certain situations. This sequence of events causes an |
218 | error: |
219 | |
220 | =over 4 |
221 | |
222 | =item 1. |
223 | |
224 | There is a class (ClassA) which uses some extension(s) that apply |
225 | roles to the metaclass. |
226 | |
227 | =item 2. |
228 | |
229 | You have another class (ClassB) which wants to subclass ClassA and |
230 | apply some more extensions. |
231 | |
232 | =back |
233 | |
234 | Normally, the call to C<extends> will happen at run time, I<after> the |
235 | additional extensions are applied. This causes an error when we try to |
236 | make the metaclass for ClassB compatible with the metaclass for |
237 | ClassA. |
238 | |
239 | We hope to be able to fix this in the future. |
240 | |
241 | For now the workaround is for ClassB to make sure it extends ClassA |
242 | I<before> it loads extensions: |
243 | |
244 | package ClassB; |
245 | |
246 | use Moose; |
247 | |
248 | BEGIN { extends 'ClassA' } |
249 | |
250 | use MooseX::SomeExtension; |
251 | |
c59bc009 |
252 | =head1 AUTHOR |
253 | |
254 | Dave Rolsky E<lt>autarch@urth.orgE<gt> |
255 | |
256 | =head1 COPYRIGHT AND LICENSE |
257 | |
258 | Copyright 2008 by Infinity Interactive, Inc. |
259 | |
260 | L<http://www.iinteractive.com> |
261 | |
262 | This library is free software; you can redistribute it and/or modify |
263 | it under the same terms as Perl itself. |
264 | |
265 | =cut |