Commit | Line | Data |
231be3be |
1 | package Moose::Util::MetaRole; |
2 | |
3 | use strict; |
4 | use warnings; |
5 | |
6 | use List::MoreUtils qw( all ); |
7 | |
8 | sub apply_metaclass_roles { |
9 | my %options = @_; |
10 | |
11 | my $for = $options{for_class}; |
12 | |
13 | my $meta = _make_new_metaclass( $for, \%options ); |
14 | |
15 | for my $tor_class ( grep { $options{ $_ . '_roles' } } |
16 | qw( constructor_class destructor_class ) ) { |
17 | |
18 | my $class = _make_new_class( |
19 | $meta->$tor_class(), |
20 | $options{ $tor_class . '_roles' } |
21 | ); |
22 | |
23 | $meta->$tor_class($class); |
24 | } |
25 | |
26 | return $meta; |
27 | } |
28 | |
29 | sub _make_new_metaclass { |
30 | my $for = shift; |
31 | my $options = shift; |
32 | |
33 | return $for->meta() |
34 | unless grep { exists $options->{ $_ . '_roles' } } |
35 | qw( |
36 | metaclass |
37 | attribute_metaclass |
38 | method_metaclass |
39 | instance_metaclass |
40 | ); |
41 | |
42 | my $new_metaclass |
43 | = _make_new_class( ref $for->meta(), $options->{metaclass_roles} ); |
44 | |
45 | my $old_meta = $for->meta(); |
46 | |
72d15b83 |
47 | # This could get called for a Moose::Meta::Role as well as a Moose::Meta::Class |
231be3be |
48 | my %classes = map { |
49 | $_ => _make_new_class( $old_meta->$_(), $options->{ $_ . '_roles' } ) |
72d15b83 |
50 | } |
51 | grep { $old_meta->can($_) } |
52 | qw( |
231be3be |
53 | attribute_metaclass |
54 | method_metaclass |
55 | instance_metaclass |
56 | ); |
57 | |
58 | return $new_metaclass->reinitialize( $for, %classes ); |
59 | } |
60 | |
61 | sub apply_base_class_roles { |
62 | my %options = @_; |
63 | |
64 | my $for = $options{for_class}; |
65 | |
66 | my $meta = $for->meta(); |
67 | |
68 | my $new_base = _make_new_class( |
69 | $for, |
70 | $options{roles}, |
71 | [ $meta->superclasses() ], |
72 | ); |
73 | |
74 | $meta->superclasses($new_base) |
75 | if $new_base ne $meta->name(); |
76 | } |
77 | |
78 | sub _make_new_class { |
79 | my $existing_class = shift; |
80 | my $roles = shift; |
81 | my $superclasses = shift || [$existing_class]; |
82 | |
83 | return $existing_class unless $roles; |
84 | |
85 | my $meta = $existing_class->meta(); |
86 | |
87 | return $existing_class |
88 | if $meta->can('does_role') && all { $meta->does_role($_) } @{$roles}; |
89 | |
90 | return Moose::Meta::Class->create_anon_class( |
91 | superclasses => $superclasses, |
92 | roles => $roles, |
93 | cache => 1, |
94 | )->name(); |
95 | } |
96 | |
97 | 1; |
c59bc009 |
98 | |
99 | __END__ |
100 | |
101 | =head1 NAME |
102 | |
103 | Moose::Util::MetaRole - Apply roles to any metaclass, as well as the object base class |
104 | |
105 | =head1 SYNOPSIS |
106 | |
107 | package MyApp::Moose; |
108 | |
109 | use strict; |
110 | use warnings; |
111 | |
112 | use Moose (); |
113 | use Moose::Exporter; |
114 | use Moose::Util::Meta::Role; |
115 | |
116 | use MyApp::Role::Meta::Class; |
117 | use MyApp::Role::Meta::Method::Constructor; |
118 | use MyApp::Role::Object; |
119 | |
120 | Moose::Exporter->setup_import_methods( also => 'Moose' ); |
121 | |
122 | sub init_meta { |
123 | shift; |
124 | my %options = @_; |
125 | |
126 | Moose->init_meta(%options); |
127 | |
128 | Moose::Util::MetaRole::apply_metaclass_roles( |
129 | for_class => $options{for_class}, |
130 | metaclass_roles => ['MyApp::Role::Meta::Class'], |
131 | constructor_class_roles => ['MyApp::Role::Meta::Method::Constructor'], |
132 | ); |
133 | |
134 | Moose::Util::MetaRole::apply_base_class_roles( |
135 | for_class => $options{for_class}, |
136 | roles => ['MyApp::Role::Object'], |
137 | ); |
138 | |
139 | return $options{for_class}->meta(); |
140 | } |
141 | |
142 | =head1 DESCRIPTION |
143 | |
dd9a6d87 |
144 | B<The whole concept behind this module is still considered |
145 | experimental, and it could go away in the future!> |
146 | |
c59bc009 |
147 | This utility module is designed to help authors of Moose extensions |
148 | write extensions that are able to cooperate with other Moose |
149 | extensions. To do this, you must write your extensions as roles, which |
150 | can then be dynamically applyied to the caller's metaclasses. |
151 | |
152 | This module makes sure to preserve any existing superclasses and roles |
153 | already set for the meta objects, which means that any number of |
154 | extensions can apply roles in any order. |
155 | |
156 | =head1 USAGE |
157 | |
158 | B<It is very important that you only call this module's functions when |
159 | your module is imported by the caller>. The process of applying roles |
160 | to the metaclass reinitializes the metaclass object, which wipes out |
161 | any existing attributes already defined. However, as long as you do |
162 | this when your module is imported, the caller should not have any |
163 | attributes defined yet. |
164 | |
165 | The easiest way to ensure that this happens is to use |
166 | L<Moose::Exporter> and provide an C<init_meta> method that will be |
167 | called when imported. |
168 | |
169 | =head1 FUNCTIONS |
170 | |
171 | This module provides two functions. |
172 | |
173 | =head2 apply_metaclass_roles( ... ) |
174 | |
175 | This function will apply roles to one or more metaclasses for the |
176 | specified class. It accepts the following parameters: |
177 | |
178 | =over 4 |
179 | |
180 | =item * for_class => $name |
181 | |
182 | This specifies the class for which to alter the meta classes. |
183 | |
184 | =item * metaclass_roles => \@roles |
185 | |
186 | =item * attribute_metaclass_roles => \@roles |
187 | |
188 | =item * method_metaclass_roles => \@roles |
189 | |
190 | =item * instance_metaclass_roles => \@roles |
191 | |
192 | =item * constructor_class_roles => \@roles |
193 | |
194 | =item * destructor_class_roles => \@roles |
195 | |
196 | These parameter all specify one or more roles to be applied to the |
197 | specified metaclass. You can pass any or all of these parameters at |
198 | once. |
199 | |
200 | =back |
201 | |
202 | =head2 apply_base_class_roles( for_class => $class, roles => \@roles ) |
203 | |
204 | This function will apply the specified roles to the object's base class. |
205 | |
eaeacdd6 |
206 | =head1 PROBLEMS WITH METACLASS ROLES AND SUBCLASS |
207 | |
208 | Because of the way this module works, there is an ordering problem |
209 | which occurs in certain situations. This sequence of events causes an |
210 | error: |
211 | |
212 | =over 4 |
213 | |
214 | =item 1. |
215 | |
216 | There is a class (ClassA) which uses some extension(s) that apply |
217 | roles to the metaclass. |
218 | |
219 | =item 2. |
220 | |
221 | You have another class (ClassB) which wants to subclass ClassA and |
222 | apply some more extensions. |
223 | |
224 | =back |
225 | |
226 | Normally, the call to C<extends> will happen at run time, I<after> the |
227 | additional extensions are applied. This causes an error when we try to |
228 | make the metaclass for ClassB compatible with the metaclass for |
229 | ClassA. |
230 | |
231 | We hope to be able to fix this in the future. |
232 | |
233 | For now the workaround is for ClassB to make sure it extends ClassA |
234 | I<before> it loads extensions: |
235 | |
236 | package ClassB; |
237 | |
238 | use Moose; |
239 | |
240 | BEGIN { extends 'ClassA' } |
241 | |
242 | use MooseX::SomeExtension; |
243 | |
c59bc009 |
244 | =head1 AUTHOR |
245 | |
246 | Dave Rolsky E<lt>autarch@urth.orgE<gt> |
247 | |
248 | =head1 COPYRIGHT AND LICENSE |
249 | |
250 | Copyright 2008 by Infinity Interactive, Inc. |
251 | |
252 | L<http://www.iinteractive.com> |
253 | |
254 | This library is free software; you can redistribute it and/or modify |
255 | it under the same terms as Perl itself. |
256 | |
257 | =cut |