Commit | Line | Data |
8b978dd5 |
1 | |
2 | package Class::MOP::Attribute; |
3 | |
4 | use strict; |
5 | use warnings; |
6 | |
ba38bf08 |
7 | use Class::MOP::Method::Accessor; |
8 | |
2eb717d5 |
9 | use Carp 'confess'; |
9b522fc4 |
10 | use Scalar::Util 'blessed', 'weaken'; |
2eb717d5 |
11 | |
4b18c1b3 |
12 | our $VERSION = '0.91'; |
d519662a |
13 | $VERSION = eval $VERSION; |
f0480c45 |
14 | our $AUTHORITY = 'cpan:STEVAN'; |
8b978dd5 |
15 | |
b1897d4d |
16 | use base 'Class::MOP::Object'; |
17 | |
727919c5 |
18 | # NOTE: (meta-circularity) |
1d68af04 |
19 | # This method will be replaced in the |
20 | # boostrap section of Class::MOP, by |
21 | # a new version which uses the |
727919c5 |
22 | # &Class::MOP::Class::construct_instance |
23 | # method to build an attribute meta-object |
24 | # which itself is described with attribute |
1d68af04 |
25 | # meta-objects. |
727919c5 |
26 | # - Ain't meta-circularity grand? :) |
8b978dd5 |
27 | sub new { |
649efb63 |
28 | my ( $class, @args ) = @_; |
29 | |
30 | unshift @args, "name" if @args % 2 == 1; |
31 | my %options = @args; |
32 | |
33 | my $name = $options{name}; |
1d68af04 |
34 | |
cbd9f942 |
35 | (defined $name && $name) |
8b978dd5 |
36 | || confess "You must provide a name for the attribute"; |
1d68af04 |
37 | |
38 | $options{init_arg} = $name |
5659d76e |
39 | if not exists $options{init_arg}; |
1d68af04 |
40 | if(exists $options{builder}){ |
41 | confess("builder must be a defined scalar value which is a method name") |
42 | if ref $options{builder} || !(defined $options{builder}); |
43 | confess("Setting both default and builder is not allowed.") |
44 | if exists $options{default}; |
8fe581e5 |
45 | } else { |
46 | (is_default_a_coderef(\%options)) |
47 | || confess("References are not allowed as default values, you must ". |
3c0a8087 |
48 | "wrap the default of '$name' in a CODE reference (ex: sub { [] } and not [])") |
8fe581e5 |
49 | if exists $options{default} && ref $options{default}; |
1d68af04 |
50 | } |
2e877f58 |
51 | if( $options{required} and not( defined($options{builder}) || defined($options{init_arg}) || exists $options{default} ) ) { |
52 | confess("A required attribute must have either 'init_arg', 'builder', or 'default'"); |
53 | } |
8683db0e |
54 | |
7813a0c5 |
55 | if(exists $options{trigger}){ |
56 | ( ref($options{trigger}) |
57 | ? (ref($options{trigger}) eq 'CODE') |
58 | :(defined $options{trigger} && length $options{trigger}) ) |
59 | || confess("Trigger must be a CODE ref or method name on attribute ($name)"); |
60 | } |
61 | |
cb75020f |
62 | $class->_new(\%options); |
4b698b1a |
63 | } |
64 | |
65 | sub _new { |
0bfc85b8 |
66 | my $class = shift; |
ec9e38e5 |
67 | |
68 | return Class::MOP::Class->initialize($class)->new_object(@_) |
812d58f9 |
69 | if $class ne __PACKAGE__; |
ec9e38e5 |
70 | |
0bfc85b8 |
71 | my $options = @_ == 1 ? $_[0] : {@_}; |
4b698b1a |
72 | |
8b978dd5 |
73 | bless { |
d9d99689 |
74 | 'name' => $options->{name}, |
75 | 'accessor' => $options->{accessor}, |
76 | 'reader' => $options->{reader}, |
77 | 'writer' => $options->{writer}, |
78 | 'predicate' => $options->{predicate}, |
79 | 'clearer' => $options->{clearer}, |
80 | 'builder' => $options->{builder}, |
81 | 'init_arg' => $options->{init_arg}, |
82 | 'default' => $options->{default}, |
83 | 'initializer' => $options->{initializer}, |
84 | 'definition_context' => $options->{definition_context}, |
7813a0c5 |
85 | 'trigger' => $options->{trigger}, |
1d68af04 |
86 | # keep a weakened link to the |
9ec169fe |
87 | # class we are associated with |
8683db0e |
88 | 'associated_class' => undef, |
1d68af04 |
89 | # and a list of the methods |
3545c727 |
90 | # associated with this attr |
8683db0e |
91 | 'associated_methods' => [], |
dc9d420c |
92 | # this let's us keep track of |
93 | # our order inside the associated |
94 | # class |
95 | 'insertion_order' => undef, |
0bfc85b8 |
96 | }, $class; |
8b978dd5 |
97 | } |
98 | |
7b31baf4 |
99 | # NOTE: |
1d68af04 |
100 | # this is a primative (and kludgy) clone operation |
16e960bd |
101 | # for now, it will be replaced in the Class::MOP |
1d68af04 |
102 | # bootstrap with a proper one, however we know |
5659d76e |
103 | # that this one will work fine for now. |
104 | sub clone { |
105 | my $self = shift; |
106 | my %options = @_; |
107 | (blessed($self)) |
108 | || confess "Can only clone an instance"; |
b3fa93c7 |
109 | return bless { %{$self}, %options } => ref($self); |
5659d76e |
110 | } |
111 | |
bd4e03f9 |
112 | sub initialize_instance_slot { |
f892c0f0 |
113 | my ($self, $meta_instance, $instance, $params) = @_; |
8683db0e |
114 | my $init_arg = $self->{'init_arg'}; |
115 | |
bd4e03f9 |
116 | # try to fetch the init arg from the %params ... |
8d2d4c67 |
117 | |
1d68af04 |
118 | # if nothing was in the %params, we can use the |
bd4e03f9 |
119 | # attribute's default value (if it has one) |
2e877f58 |
120 | if(defined $init_arg and exists $params->{$init_arg}){ |
8ee74136 |
121 | $self->_set_initial_slot_value( |
122 | $meta_instance, |
0ab65f99 |
123 | $instance, |
0ab65f99 |
124 | $params->{$init_arg}, |
0ab65f99 |
125 | ); |
b7bdffc3 |
126 | } |
8683db0e |
127 | elsif (defined $self->{'default'}) { |
8ee74136 |
128 | $self->_set_initial_slot_value( |
129 | $meta_instance, |
0ab65f99 |
130 | $instance, |
0ab65f99 |
131 | $self->default($instance), |
0ab65f99 |
132 | ); |
b7bdffc3 |
133 | } |
8683db0e |
134 | elsif (defined( my $builder = $self->{'builder'})) { |
b7bdffc3 |
135 | if ($builder = $instance->can($builder)) { |
8ee74136 |
136 | $self->_set_initial_slot_value( |
137 | $meta_instance, |
0ab65f99 |
138 | $instance, |
0ab65f99 |
139 | $instance->$builder, |
0ab65f99 |
140 | ); |
b7bdffc3 |
141 | } |
142 | else { |
b3fa93c7 |
143 | confess(ref($instance)." does not support builder method '". $self->{'builder'} ."' for attribute '" . $self->name . "'"); |
8fe581e5 |
144 | } |
1d68af04 |
145 | } |
bd4e03f9 |
146 | } |
147 | |
8ee74136 |
148 | sub _set_initial_slot_value { |
149 | my ($self, $meta_instance, $instance, $value) = @_; |
150 | |
151 | my $slot_name = $self->name; |
152 | |
7813a0c5 |
153 | unless($self->has_initializer){ |
154 | $meta_instance->set_slot_value($instance, $slot_name, $value); |
155 | $self->call_trigger($instance, $value); |
156 | return; |
157 | } |
8ee74136 |
158 | |
159 | my $callback = sub { |
160 | $meta_instance->set_slot_value($instance, $slot_name, $_[0]); |
161 | }; |
162 | |
163 | my $initializer = $self->initializer; |
164 | |
165 | # most things will just want to set a value, so make it first arg |
166 | $instance->$initializer($value, $callback, $self); |
7813a0c5 |
167 | $self->call_trigger($instance, $value); |
168 | return; |
8ee74136 |
169 | } |
170 | |
5659d76e |
171 | # NOTE: |
1d68af04 |
172 | # the next bunch of methods will get bootstrapped |
7b31baf4 |
173 | # away in the Class::MOP bootstrapping section |
174 | |
8683db0e |
175 | sub associated_class { $_[0]->{'associated_class'} } |
176 | sub associated_methods { $_[0]->{'associated_methods'} } |
177 | |
b3fa93c7 |
178 | sub has_accessor { defined($_[0]->{'accessor'}) } |
179 | sub has_reader { defined($_[0]->{'reader'}) } |
180 | sub has_writer { defined($_[0]->{'writer'}) } |
181 | sub has_predicate { defined($_[0]->{'predicate'}) } |
182 | sub has_clearer { defined($_[0]->{'clearer'}) } |
183 | sub has_builder { defined($_[0]->{'builder'}) } |
184 | sub has_init_arg { defined($_[0]->{'init_arg'}) } |
185 | sub has_default { defined($_[0]->{'default'}) } |
186 | sub has_initializer { defined($_[0]->{'initializer'}) } |
dc9d420c |
187 | sub has_insertion_order { defined($_[0]->{'insertion_order'}) } |
7813a0c5 |
188 | sub has_trigger { defined($_[0]->{'trigger'}) } |
8683db0e |
189 | |
d9d99689 |
190 | sub accessor { $_[0]->{'accessor'} } |
191 | sub reader { $_[0]->{'reader'} } |
192 | sub writer { $_[0]->{'writer'} } |
193 | sub predicate { $_[0]->{'predicate'} } |
194 | sub clearer { $_[0]->{'clearer'} } |
195 | sub builder { $_[0]->{'builder'} } |
196 | sub init_arg { $_[0]->{'init_arg'} } |
197 | sub initializer { $_[0]->{'initializer'} } |
198 | sub definition_context { $_[0]->{'definition_context'} } |
dc9d420c |
199 | sub insertion_order { $_[0]->{'insertion_order'} } |
943cbe2d |
200 | sub _set_insertion_order { $_[0]->{'insertion_order'} = $_[1] } |
7813a0c5 |
201 | sub trigger { $_[0]->{'trigger'} } |
202 | |
203 | sub call_trigger{ |
204 | my($self, $instance, $value) = @_; |
c50c603e |
205 | |
7813a0c5 |
206 | if(defined(my $trigger = $self->{trigger})){ |
207 | $instance->$trigger($value); |
208 | } |
209 | return; |
210 | } |
7b31baf4 |
211 | # end bootstrapped away method section. |
212 | # (all methods below here are kept intact) |
213 | |
9e517e01 |
214 | sub has_read_method { $_[0]->has_reader || $_[0]->has_accessor } |
215 | sub has_write_method { $_[0]->has_writer || $_[0]->has_accessor } |
216 | |
7813a0c5 |
217 | |
218 | |
d14f6cbe |
219 | sub get_read_method { |
220 | my $self = shift; |
221 | my $reader = $self->reader || $self->accessor; |
222 | # normal case ... |
223 | return $reader unless ref $reader; |
224 | # the HASH ref case |
225 | my ($name) = %$reader; |
226 | return $name; |
227 | } |
228 | |
229 | sub get_write_method { |
230 | my $self = shift; |
231 | my $writer = $self->writer || $self->accessor; |
232 | # normal case ... |
233 | return $writer unless ref $writer; |
234 | # the HASH ref case |
235 | my ($name) = %$writer; |
236 | return $name; |
237 | } |
b25109b1 |
238 | |
5da16d1b |
239 | sub get_read_method_ref { |
240 | my $self = shift; |
742fb371 |
241 | if ((my $reader = $self->get_read_method) && $self->associated_class) { |
5da16d1b |
242 | return $self->associated_class->get_method($reader); |
243 | } |
244 | else { |
def5c0b5 |
245 | my $code = sub { $self->get_value(@_) }; |
246 | if (my $class = $self->associated_class) { |
247 | return $class->method_metaclass->wrap( |
248 | $code, |
249 | package_name => $class->name, |
250 | name => '__ANON__' |
251 | ); |
252 | } |
253 | else { |
254 | return $code; |
255 | } |
5da16d1b |
256 | } |
257 | } |
258 | |
259 | sub get_write_method_ref { |
260 | my $self = shift; |
d14f6cbe |
261 | if ((my $writer = $self->get_write_method) && $self->associated_class) { |
742fb371 |
262 | return $self->associated_class->get_method($writer); |
5da16d1b |
263 | } |
264 | else { |
def5c0b5 |
265 | my $code = sub { $self->set_value(@_) }; |
266 | if (my $class = $self->associated_class) { |
267 | return $class->method_metaclass->wrap( |
268 | $code, |
269 | package_name => $class->name, |
270 | name => '__ANON__' |
271 | ); |
272 | } |
273 | else { |
274 | return $code; |
275 | } |
5da16d1b |
276 | } |
277 | } |
278 | |
1d68af04 |
279 | sub is_default_a_coderef { |
ed337aad |
280 | my ($value) = $_[0]->{'default'}; |
281 | return unless ref($value); |
282 | return ref($value) eq 'CODE' || (blessed($value) && $value->isa('Class::MOP::Method')); |
c0cbf4d9 |
283 | } |
284 | |
1d68af04 |
285 | sub default { |
c0cbf4d9 |
286 | my ($self, $instance) = @_; |
9363ea89 |
287 | if (defined $instance && $self->is_default_a_coderef) { |
1d68af04 |
288 | # if the default is a CODE ref, then |
727919c5 |
289 | # we pass in the instance and default |
1d68af04 |
290 | # can return a value based on that |
727919c5 |
291 | # instance. Somewhat crude, but works. |
8683db0e |
292 | return $self->{'default'}->($instance); |
1d68af04 |
293 | } |
8683db0e |
294 | $self->{'default'}; |
c50c603e |
295 | } |
8b978dd5 |
296 | |
c57c8b10 |
297 | # slots |
298 | |
299 | sub slots { (shift)->name } |
300 | |
1d68af04 |
301 | # class association |
727919c5 |
302 | |
9ec169fe |
303 | sub attach_to_class { |
304 | my ($self, $class) = @_; |
305 | (blessed($class) && $class->isa('Class::MOP::Class')) |
306 | || confess "You must pass a Class::MOP::Class instance (or a subclass)"; |
8683db0e |
307 | weaken($self->{'associated_class'} = $class); |
9ec169fe |
308 | } |
309 | |
310 | sub detach_from_class { |
311 | my $self = shift; |
8683db0e |
312 | $self->{'associated_class'} = undef; |
9ec169fe |
313 | } |
314 | |
1d68af04 |
315 | # method association |
3545c727 |
316 | |
317 | sub associate_method { |
318 | my ($self, $method) = @_; |
8683db0e |
319 | push @{$self->{'associated_methods'}} => $method; |
3545c727 |
320 | } |
321 | |
16e960bd |
322 | ## Slot management |
323 | |
ef91a0e2 |
324 | sub set_initial_value { |
325 | my ($self, $instance, $value) = @_; |
e76b01fb |
326 | $self->_set_initial_slot_value( |
b3fa93c7 |
327 | Class::MOP::Class->initialize(ref($instance))->get_meta_instance, |
8ee74136 |
328 | $instance, |
329 | $value |
330 | ); |
7813a0c5 |
331 | return; |
ef91a0e2 |
332 | } |
333 | |
16e960bd |
334 | sub set_value { |
1396f86b |
335 | my ($self, $instance, $value) = @_; |
16e960bd |
336 | |
b3fa93c7 |
337 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
338 | ->get_meta_instance |
339 | ->set_slot_value($instance, $self->name, $value); |
7813a0c5 |
340 | $self->call_trigger($instance, $value); |
341 | return; |
16e960bd |
342 | } |
343 | |
344 | sub get_value { |
1396f86b |
345 | my ($self, $instance) = @_; |
16e960bd |
346 | |
b3fa93c7 |
347 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
348 | ->get_meta_instance |
349 | ->get_slot_value($instance, $self->name); |
16e960bd |
350 | } |
351 | |
3545c727 |
352 | sub has_value { |
353 | my ($self, $instance) = @_; |
1d68af04 |
354 | |
b3fa93c7 |
355 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
356 | ->get_meta_instance |
357 | ->is_slot_initialized($instance, $self->name); |
3545c727 |
358 | } |
359 | |
360 | sub clear_value { |
361 | my ($self, $instance) = @_; |
1d68af04 |
362 | |
b3fa93c7 |
363 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
364 | ->get_meta_instance |
365 | ->deinitialize_slot($instance, $self->name); |
7813a0c5 |
366 | $self->call_trigger($instance); |
367 | return; |
3545c727 |
368 | } |
369 | |
ba38bf08 |
370 | ## load em up ... |
c0cbf4d9 |
371 | |
ba38bf08 |
372 | sub accessor_metaclass { 'Class::MOP::Method::Accessor' } |
c0cbf4d9 |
373 | |
9ec169fe |
374 | sub process_accessors { |
c7e28c19 |
375 | Carp::cluck('The process_accessors method has been made private.' |
376 | . " The public version is deprecated and will be removed in a future release.\n"); |
e056bd42 |
377 | shift->_process_accessors(@_); |
45a183fb |
378 | } |
379 | |
380 | sub _process_accessors { |
c0cbf4d9 |
381 | my ($self, $type, $accessor, $generate_as_inline_methods) = @_; |
d9d99689 |
382 | |
383 | my $method_ctx; |
384 | |
385 | if ( my $ctx = $self->definition_context ) { |
386 | $method_ctx = { %$ctx }; |
387 | } |
388 | |
9b522fc4 |
389 | if (ref($accessor)) { |
390 | (ref($accessor) eq 'HASH') |
7d28758b |
391 | || confess "bad accessor/reader/writer/predicate/clearer format, must be a HASH ref"; |
4d47b77f |
392 | my ($name, $method) = %{$accessor}; |
4c105333 |
393 | $method = $self->accessor_metaclass->wrap( |
394 | $method, |
395 | package_name => $self->associated_class->name, |
396 | name => $name, |
d9d99689 |
397 | definition_context => $method_ctx, |
4c105333 |
398 | ); |
3545c727 |
399 | $self->associate_method($method); |
1d68af04 |
400 | return ($name, $method); |
2eb717d5 |
401 | } |
9ec169fe |
402 | else { |
1d68af04 |
403 | my $inline_me = ($generate_as_inline_methods && $self->associated_class->instance_metaclass->is_inlinable); |
ba38bf08 |
404 | my $method; |
405 | eval { |
d9d99689 |
406 | if ( $method_ctx ) { |
407 | my $desc = "accessor $accessor"; |
408 | if ( $accessor ne $self->name ) { |
409 | $desc .= " of attribute " . $self->name; |
410 | } |
411 | |
412 | $method_ctx->{description} = $desc; |
413 | } |
414 | |
ba38bf08 |
415 | $method = $self->accessor_metaclass->new( |
416 | attribute => $self, |
d90b42a6 |
417 | is_inline => $inline_me, |
ba38bf08 |
418 | accessor_type => $type, |
4c105333 |
419 | package_name => $self->associated_class->name, |
420 | name => $accessor, |
d9d99689 |
421 | definition_context => $method_ctx, |
1d68af04 |
422 | ); |
ba38bf08 |
423 | }; |
1d68af04 |
424 | confess "Could not create the '$type' method for " . $self->name . " because : $@" if $@; |
3545c727 |
425 | $self->associate_method($method); |
ba38bf08 |
426 | return ($accessor, $method); |
1d68af04 |
427 | } |
9ec169fe |
428 | } |
429 | |
430 | sub install_accessors { |
c0cbf4d9 |
431 | my $self = shift; |
432 | my $inline = shift; |
433 | my $class = $self->associated_class; |
1d68af04 |
434 | |
9ec169fe |
435 | $class->add_method( |
45a183fb |
436 | $self->_process_accessors('accessor' => $self->accessor(), $inline) |
9ec169fe |
437 | ) if $self->has_accessor(); |
438 | |
1d68af04 |
439 | $class->add_method( |
45a183fb |
440 | $self->_process_accessors('reader' => $self->reader(), $inline) |
9ec169fe |
441 | ) if $self->has_reader(); |
442 | |
443 | $class->add_method( |
45a183fb |
444 | $self->_process_accessors('writer' => $self->writer(), $inline) |
9ec169fe |
445 | ) if $self->has_writer(); |
446 | |
447 | $class->add_method( |
45a183fb |
448 | $self->_process_accessors('predicate' => $self->predicate(), $inline) |
9ec169fe |
449 | ) if $self->has_predicate(); |
1d68af04 |
450 | |
7d28758b |
451 | $class->add_method( |
45a183fb |
452 | $self->_process_accessors('clearer' => $self->clearer(), $inline) |
7d28758b |
453 | ) if $self->has_clearer(); |
1d68af04 |
454 | |
9ec169fe |
455 | return; |
2eb717d5 |
456 | } |
457 | |
b51af7f9 |
458 | { |
459 | my $_remove_accessor = sub { |
460 | my ($accessor, $class) = @_; |
9b522fc4 |
461 | if (ref($accessor) && ref($accessor) eq 'HASH') { |
c50c603e |
462 | ($accessor) = keys %{$accessor}; |
1d68af04 |
463 | } |
464 | my $method = $class->get_method($accessor); |
465 | $class->remove_method($accessor) |
b3fa93c7 |
466 | if (ref($method) && $method->isa('Class::MOP::Method::Accessor')); |
b51af7f9 |
467 | }; |
1d68af04 |
468 | |
b51af7f9 |
469 | sub remove_accessors { |
9ec169fe |
470 | my $self = shift; |
2367814a |
471 | # TODO: |
1d68af04 |
472 | # we really need to make sure to remove from the |
473 | # associates methods here as well. But this is |
474 | # such a slimly used method, I am not worried |
2367814a |
475 | # about it right now. |
9ec169fe |
476 | $_remove_accessor->($self->accessor(), $self->associated_class()) if $self->has_accessor(); |
477 | $_remove_accessor->($self->reader(), $self->associated_class()) if $self->has_reader(); |
478 | $_remove_accessor->($self->writer(), $self->associated_class()) if $self->has_writer(); |
479 | $_remove_accessor->($self->predicate(), $self->associated_class()) if $self->has_predicate(); |
7d28758b |
480 | $_remove_accessor->($self->clearer(), $self->associated_class()) if $self->has_clearer(); |
1d68af04 |
481 | return; |
b51af7f9 |
482 | } |
483 | |
8b978dd5 |
484 | } |
485 | |
486 | 1; |
487 | |
488 | __END__ |
489 | |
490 | =pod |
491 | |
1d68af04 |
492 | =head1 NAME |
8b978dd5 |
493 | |
494 | Class::MOP::Attribute - Attribute Meta Object |
495 | |
496 | =head1 SYNOPSIS |
1d68af04 |
497 | |
2e23f7dc |
498 | Class::MOP::Attribute->new( |
499 | foo => ( |
500 | accessor => 'foo', # dual purpose get/set accessor |
501 | predicate => 'has_foo', # predicate check for defined-ness |
502 | init_arg => '-foo', # class->new will look for a -foo key |
503 | default => 'BAR IS BAZ!' # if no -foo key is provided, use this |
504 | ) |
505 | ); |
506 | |
507 | Class::MOP::Attribute->new( |
508 | bar => ( |
509 | reader => 'bar', # getter |
510 | writer => 'set_bar', # setter |
511 | predicate => 'has_bar', # predicate check for defined-ness |
512 | init_arg => ':bar', # class->new will look for a :bar key |
513 | # no default value means it is undef |
514 | ) |
515 | ); |
8b978dd5 |
516 | |
517 | =head1 DESCRIPTION |
518 | |
2e23f7dc |
519 | The Attribute Protocol is almost entirely an invention of |
520 | C<Class::MOP>. Perl 5 does not have a consistent notion of |
521 | attributes. There are so many ways in which this is done, and very few |
522 | (if any) are easily discoverable by this module. |
552e3d24 |
523 | |
2e23f7dc |
524 | With that said, this module attempts to inject some order into this |
1d68af04 |
525 | chaos, by introducing a consistent API which can be used to create |
fe122940 |
526 | object attributes. |
552e3d24 |
527 | |
528 | =head1 METHODS |
529 | |
530 | =head2 Creation |
531 | |
532 | =over 4 |
533 | |
2e23f7dc |
534 | =item B<< Class::MOP::Attribute->new($name, ?%options) >> |
fe122940 |
535 | |
1d68af04 |
536 | An attribute must (at the very least), have a C<$name>. All other |
2e23f7dc |
537 | C<%options> are added as key-value pairs. |
fe122940 |
538 | |
2e23f7dc |
539 | =over 8 |
fe122940 |
540 | |
76187047 |
541 | =item * init_arg |
fe122940 |
542 | |
2e23f7dc |
543 | This is a string value representing the expected key in an |
544 | initialization hash. For instance, if we have an C<init_arg> value of |
545 | C<-foo>, then the following code will Just Work. |
fe122940 |
546 | |
d69fb6b3 |
547 | MyClass->meta->new_object( -foo => 'Hello There' ); |
fe122940 |
548 | |
2e23f7dc |
549 | If an init_arg is not assigned, it will automatically use the |
550 | attribute's name. If C<init_arg> is explicitly set to C<undef>, the |
551 | attribute cannot be specified during initialization. |
7b31baf4 |
552 | |
76187047 |
553 | =item * builder |
1d68af04 |
554 | |
2e23f7dc |
555 | This provides the name of a method that will be called to initialize |
556 | the attribute. This method will be called on the object after it is |
557 | constructed. It is expected to return a valid value for the attribute. |
fe122940 |
558 | |
76187047 |
559 | =item * default |
4c4a6c41 |
560 | |
2e23f7dc |
561 | This can be used to provide an explicit default for initializing the |
562 | attribute. If the default you provide is a subroutine reference, then |
563 | this reference will be called I<as a method> on the object. |
4c4a6c41 |
564 | |
2e23f7dc |
565 | If the value is a simple scalar (string or number), then it can be |
566 | just passed as is. However, if you wish to initialize it with a HASH |
567 | or ARRAY ref, then you need to wrap that inside a subroutine |
568 | reference: |
fe122940 |
569 | |
2e23f7dc |
570 | Class::MOP::Attribute->new( |
571 | 'foo' => ( |
572 | default => sub { [] }, |
573 | ) |
574 | ); |
1d68af04 |
575 | |
576 | # or ... |
577 | |
2e23f7dc |
578 | Class::MOP::Attribute->new( |
579 | 'foo' => ( |
580 | default => sub { {} }, |
581 | ) |
582 | ); |
583 | |
584 | If you wish to initialize an attribute with a subroutine reference |
585 | itself, then you need to wrap that in a subroutine as well: |
586 | |
587 | Class::MOP::Attribute->new( |
588 | 'foo' => ( |
589 | default => sub { |
590 | sub { print "Hello World" } |
591 | }, |
592 | ) |
593 | ); |
594 | |
595 | And lastly, if the value of your attribute is dependent upon some |
596 | other aspect of the instance structure, then you can take advantage of |
597 | the fact that when the C<default> value is called as a method: |
598 | |
599 | Class::MOP::Attribute->new( |
600 | 'object_identity' => ( |
601 | default => sub { Scalar::Util::refaddr( $_[0] ) }, |
602 | ) |
603 | ); |
604 | |
605 | Note that there is no guarantee that attributes are initialized in any |
606 | particular order, so you cannot rely on the value of some other |
607 | attribute when generating the default. |
fe122940 |
608 | |
76187047 |
609 | =item * initializer |
0ef07b33 |
610 | |
2e23f7dc |
611 | This option can be either a method name or a subroutine |
612 | reference. This method will be called when setting the attribute's |
613 | value in the constructor. Unlike C<default> and C<builder>, the |
614 | initializer is only called when a value is provided to the |
615 | constructor. The initializer allows you to munge this value during |
616 | object construction. |
617 | |
618 | The initializer is called as a method with three arguments. The first |
619 | is the value that was passed to the constructor. The second is a |
620 | subroutine reference that can be called to actually set the |
621 | attribute's value, and the last is the associated |
622 | C<Class::MOP::Attribute> object. |
623 | |
624 | This contrived example shows an initializer that sets the attribute to |
625 | twice the given value. |
626 | |
627 | Class::MOP::Attribute->new( |
628 | 'doubled' => ( |
629 | initializer => sub { |
630 | my ( $instance, $value, $set ) = @_; |
631 | $set->( $value * 2 ); |
632 | }, |
633 | ) |
634 | ); |
635 | |
636 | Since an initializer can be a method name, you can easily make |
0ef07b33 |
637 | attribute initialization use the writer: |
638 | |
2e23f7dc |
639 | Class::MOP::Attribute->new( |
640 | 'some_attr' => ( |
641 | writer => 'some_attr', |
642 | initializer => 'some_attr', |
643 | ) |
644 | ); |
0ef07b33 |
645 | |
2e23f7dc |
646 | Your writer will need to examine C<@_> and determine under which |
647 | context it is being called. |
127d39a7 |
648 | |
fe122940 |
649 | =back |
650 | |
2e23f7dc |
651 | The C<accessor>, C<reader>, C<writer>, C<predicate> and C<clearer> |
652 | options all accept the same parameters. You can provide the name of |
653 | the method, in which case an appropriate default method will be |
654 | generated for you. Or instead you can also provide hash reference |
655 | containing exactly one key (the method name) and one value. The value |
656 | should be a subroutine reference, which will be installed as the |
657 | method itself. |
59e7697f |
658 | |
76187047 |
659 | =over 8 |
59e7697f |
660 | |
76187047 |
661 | =item * accessor |
59e7697f |
662 | |
2e23f7dc |
663 | An C<accessor> is a standard Perl-style read/write accessor. It will |
664 | return the value of the attribute, and if a value is passed as an |
665 | argument, it will assign that value to the attribute. |
fe122940 |
666 | |
2e23f7dc |
667 | Note that C<undef> is a legitimate value, so this will work: |
fe122940 |
668 | |
669 | $object->set_something(undef); |
670 | |
76187047 |
671 | =item * reader |
59e7697f |
672 | |
2e23f7dc |
673 | This is a basic read-only accessor. It returns the value of the |
674 | attribute. |
fe122940 |
675 | |
76187047 |
676 | =item * writer |
59e7697f |
677 | |
1d68af04 |
678 | This is a basic write accessor, it accepts a single argument, and |
2e23f7dc |
679 | assigns that value to the attribute. |
59e7697f |
680 | |
2e23f7dc |
681 | Note that C<undef> is a legitimate value, so this will work: |
59e7697f |
682 | |
2e23f7dc |
683 | $object->set_something(undef); |
fe122940 |
684 | |
76187047 |
685 | =item * predicate |
fe122940 |
686 | |
2e23f7dc |
687 | The predicate method returns a boolean indicating whether or not the |
688 | attribute has been explicitly set. |
07dca7e3 |
689 | |
2e23f7dc |
690 | Note that the predicate returns true even if the attribute was set to |
691 | a false value (C<0> or C<undef>). |
07dca7e3 |
692 | |
76187047 |
693 | =item * clearer |
7d28758b |
694 | |
2e23f7dc |
695 | This method will uninitialize the attribute. After an attribute is |
696 | cleared, its C<predicate> will return false. |
7d28758b |
697 | |
76187047 |
698 | =item * definition_context |
f8813817 |
699 | |
700 | Mostly, this exists as a hook for the benefit of Moose. |
701 | |
702 | This option should be a hash reference containing several keys which |
703 | will be used when inlining the attribute's accessors. The keys should |
704 | include C<line>, the line number where the attribute was created, and |
705 | either C<file> or C<description>. |
706 | |
707 | This information will ultimately be used when eval'ing inlined |
708 | accessor code so that error messages report a useful line and file |
709 | name. |
710 | |
59e7697f |
711 | =back |
552e3d24 |
712 | |
2e23f7dc |
713 | =item B<< $attr->clone(%options) >> |
bd4e03f9 |
714 | |
2e23f7dc |
715 | This clones the attribute. Any options you provide will override the |
716 | settings of the original attribute. You can change the name of the new |
717 | attribute by passing a C<name> key in C<%options>. |
127d39a7 |
718 | |
2e23f7dc |
719 | =back |
bd4e03f9 |
720 | |
2e23f7dc |
721 | =head2 Informational |
127d39a7 |
722 | |
2e23f7dc |
723 | These are all basic read-only accessors for the values passed into |
724 | the constructor. |
552e3d24 |
725 | |
2e23f7dc |
726 | =over 4 |
16e960bd |
727 | |
2e23f7dc |
728 | =item B<< $attr->name >> |
2367814a |
729 | |
76187047 |
730 | Returns the attribute's name. |
731 | |
2e23f7dc |
732 | =item B<< $attr->accessor >> |
2367814a |
733 | |
2e23f7dc |
734 | =item B<< $attr->reader >> |
16e960bd |
735 | |
2e23f7dc |
736 | =item B<< $attr->writer >> |
16e960bd |
737 | |
2e23f7dc |
738 | =item B<< $attr->predicate >> |
16e960bd |
739 | |
2e23f7dc |
740 | =item B<< $attr->clearer >> |
c0921932 |
741 | |
2e23f7dc |
742 | The C<accessor>, C<reader>, C<writer>, C<predicate>, and C<clearer> |
743 | methods all return exactly what was passed to the constructor, so it |
a6710c60 |
744 | can be either a string containing a method name, or a hash reference. |
c0921932 |
745 | |
2e23f7dc |
746 | =item B<< $attr->initializer >> |
16e960bd |
747 | |
a6710c60 |
748 | Returns the initializer as passed to the constructor, so this may be |
2e23f7dc |
749 | either a method name or a subroutine reference. |
16e960bd |
750 | |
2e23f7dc |
751 | =item B<< $attr->init_arg >> |
3545c727 |
752 | |
2e23f7dc |
753 | =item B<< $attr->is_default_a_coderef >> |
2367814a |
754 | |
2e23f7dc |
755 | =item B<< $attr->default($instance) >> |
3545c727 |
756 | |
2e23f7dc |
757 | The C<$instance> argument is optional. If you don't pass it, the |
758 | return value for this method is exactly what was passed to the |
759 | constructor, either a simple scalar or a subroutine reference. |
2367814a |
760 | |
2e23f7dc |
761 | If you I<do> pass an C<$instance> and the default is a subroutine |
762 | reference, then the reference is called as a method on the |
763 | C<$instance> and the generated value is returned. |
16e960bd |
764 | |
2e23f7dc |
765 | =item B<< $attr->slots >> |
552e3d24 |
766 | |
2e23f7dc |
767 | Return a list of slots required by the attribute. This is usually just |
768 | one, the name of the attribute. |
fe122940 |
769 | |
2e23f7dc |
770 | A slot is the name of the hash key used to store the attribute in an |
771 | object instance. |
552e3d24 |
772 | |
2e23f7dc |
773 | =item B<< $attr->get_read_method >> |
552e3d24 |
774 | |
2e23f7dc |
775 | =item B<< $attr->get_write_method >> |
552e3d24 |
776 | |
2e23f7dc |
777 | Returns the name of a method suitable for reading or writing the value |
778 | of the attribute in the associated class. |
552e3d24 |
779 | |
2e23f7dc |
780 | If an attribute is read- or write-only, then these methods can return |
781 | C<undef> as appropriate. |
552e3d24 |
782 | |
2e23f7dc |
783 | =item B<< $attr->has_read_method >> |
c50c603e |
784 | |
2e23f7dc |
785 | =item B<< $attr->has_write_method >> |
7d28758b |
786 | |
2e23f7dc |
787 | This returns a boolean indicating whether the attribute has a I<named> |
788 | read or write method. |
0ab65f99 |
789 | |
2e23f7dc |
790 | =item B<< $attr->get_read_method_ref >> |
552e3d24 |
791 | |
2e23f7dc |
792 | =item B<< $attr->get_write_method_ref >> |
495af518 |
793 | |
2e23f7dc |
794 | Returns the subroutine reference of a method suitable for reading or |
795 | writing the attribute's value in the associated class. These methods |
796 | always return a subroutine reference, regardless of whether or not the |
797 | attribute is read- or write-only. |
798 | |
eeff7496 |
799 | =item B<< $attr->insertion_order >> |
800 | |
801 | If this attribute has been inserted into a class, this returns a zero |
802 | based index regarding the order of insertion. |
803 | |
2e23f7dc |
804 | =back |
fe122940 |
805 | |
2e23f7dc |
806 | =head2 Informational predicates |
92d2abfa |
807 | |
2e23f7dc |
808 | These are all basic predicate methods for the values passed into C<new>. |
552e3d24 |
809 | |
2e23f7dc |
810 | =over 4 |
c57c8b10 |
811 | |
2e23f7dc |
812 | =item B<< $attr->has_accessor >> |
c57c8b10 |
813 | |
2e23f7dc |
814 | =item B<< $attr->has_reader >> |
b25109b1 |
815 | |
2e23f7dc |
816 | =item B<< $attr->has_writer >> |
b25109b1 |
817 | |
2e23f7dc |
818 | =item B<< $attr->has_predicate >> |
5da16d1b |
819 | |
2e23f7dc |
820 | =item B<< $attr->has_clearer >> |
5da16d1b |
821 | |
2e23f7dc |
822 | =item B<< $attr->has_initializer >> |
5da16d1b |
823 | |
2e23f7dc |
824 | =item B<< $attr->has_init_arg >> |
5da16d1b |
825 | |
2e23f7dc |
826 | This will be I<false> if the C<init_arg> was set to C<undef>. |
b25109b1 |
827 | |
2e23f7dc |
828 | =item B<< $attr->has_default >> |
9e517e01 |
829 | |
2e23f7dc |
830 | This will be I<false> if the C<default> was set to C<undef>, since |
831 | C<undef> is the default C<default> anyway. |
9e517e01 |
832 | |
2e23f7dc |
833 | =item B<< $attr->has_builder >> |
9e517e01 |
834 | |
eeff7496 |
835 | =item B<< $attr->has_insertion_order >> |
836 | |
837 | This will be I<false> if this attribute has not be inserted into a class |
838 | |
552e3d24 |
839 | =back |
840 | |
2e23f7dc |
841 | =head2 Value management |
552e3d24 |
842 | |
a6710c60 |
843 | These methods are basically "back doors" to the instance, and can be |
2e23f7dc |
844 | used to bypass the regular accessors, but still stay within the MOP. |
845 | |
846 | These methods are not for general use, and should only be used if you |
847 | really know what you are doing. |
fe122940 |
848 | |
552e3d24 |
849 | =over 4 |
850 | |
2e23f7dc |
851 | =item B<< $attr->initialize_instance_slot($meta_instance, $instance, $params) >> |
852 | |
853 | This method is used internally to initialize the attribute's slot in |
854 | the object C<$instance>. |
855 | |
856 | The C<$params> is a hash reference of the values passed to the object |
857 | constructor. |
858 | |
859 | It's unlikely that you'll need to call this method yourself. |
552e3d24 |
860 | |
2e23f7dc |
861 | =item B<< $attr->set_value($instance, $value) >> |
552e3d24 |
862 | |
2e23f7dc |
863 | Sets the value without going through the accessor. Note that this |
864 | works even with read-only attributes. |
552e3d24 |
865 | |
2e23f7dc |
866 | =item B<< $attr->set_initial_value($instance, $value) >> |
c50c603e |
867 | |
2e23f7dc |
868 | Sets the value without going through the accessor. This method is only |
869 | called when the instance is first being initialized. |
7d28758b |
870 | |
2e23f7dc |
871 | =item B<< $attr->get_value($instance) >> |
0ab65f99 |
872 | |
2e23f7dc |
873 | Returns the value without going through the accessor. Note that this |
874 | works even with write-only accessors. |
552e3d24 |
875 | |
2e23f7dc |
876 | =item B<< $attr->has_value($instance) >> |
552e3d24 |
877 | |
2e23f7dc |
878 | Return a boolean indicating whether the attribute has been set in |
879 | C<$instance>. This how the default C<predicate> method works. |
880 | |
881 | =item B<< $attr->clear_value($instance) >> |
882 | |
883 | This will clear the attribute's value in C<$instance>. This is what |
884 | the default C<clearer> calls. |
885 | |
886 | Note that this works even if the attribute does not have any |
887 | associated read, write or clear methods. |
bf731086 |
888 | |
552e3d24 |
889 | =back |
890 | |
9ec169fe |
891 | =head2 Class association |
892 | |
1d68af04 |
893 | These methods allow you to manage the attributes association with |
894 | the class that contains it. These methods should not be used |
2367814a |
895 | lightly, nor are they very magical, they are mostly used internally |
896 | and by metaclass instances. |
897 | |
9ec169fe |
898 | =over 4 |
899 | |
2e23f7dc |
900 | =item B<< $attr->associated_class >> |
901 | |
902 | This returns the C<Class::MOP::Class> with which this attribute is |
903 | associated, if any. |
904 | |
905 | =item B<< $attr->attach_to_class($metaclass) >> |
9ec169fe |
906 | |
2e23f7dc |
907 | This method stores a weakened reference to the C<$metaclass> object |
908 | internally. |
2367814a |
909 | |
2e23f7dc |
910 | This method does not remove the attribute from its old class, |
911 | nor does it create any accessors in the new class. |
9ec169fe |
912 | |
2e23f7dc |
913 | It is probably best to use the L<Class::MOP::Class> C<add_attribute> |
914 | method instead. |
2367814a |
915 | |
2e23f7dc |
916 | =item B<< $attr->detach_from_class >> |
9ec169fe |
917 | |
2e23f7dc |
918 | This method removes the associate metaclass object from the attribute |
919 | it has one. |
920 | |
921 | This method does not remove the attribute itself from the class, or |
922 | remove its accessors. |
923 | |
924 | It is probably best to use the L<Class::MOP::Class> |
925 | C<remove_attribute> method instead. |
2367814a |
926 | |
9ec169fe |
927 | =back |
928 | |
552e3d24 |
929 | =head2 Attribute Accessor generation |
930 | |
931 | =over 4 |
932 | |
2e23f7dc |
933 | =item B<< $attr->accessor_metaclass >> |
ba38bf08 |
934 | |
2e23f7dc |
935 | Accessor methods are generated using an accessor metaclass. By |
936 | default, this is L<Class::MOP::Method::Accessor>. This method returns |
2367814a |
937 | the name of the accessor metaclass that this attribute uses. |
938 | |
2e23f7dc |
939 | =item B<< $attr->associate_method($method) >> |
2367814a |
940 | |
2e23f7dc |
941 | This associates a L<Class::MOP::Method> object with the |
942 | attribute. Typically, this is called internally when an attribute |
943 | generates its accessors. |
3545c727 |
944 | |
2e23f7dc |
945 | =item B<< $attr->associated_methods >> |
3545c727 |
946 | |
2e23f7dc |
947 | This returns the list of methods which have been associated with the |
948 | attribute. |
2367814a |
949 | |
2e23f7dc |
950 | =item B<< $attr->install_accessors >> |
2eb717d5 |
951 | |
2e23f7dc |
952 | This method generates and installs code the attributes various |
953 | accessors. It is typically called from the L<Class::MOP::Class> |
954 | C<add_attribute> method. |
2eb717d5 |
955 | |
2e23f7dc |
956 | =item B<< $attr->remove_accessors >> |
2eb717d5 |
957 | |
2e23f7dc |
958 | This method removes all of the accessors associated with the |
959 | attribute. |
2eb717d5 |
960 | |
2e23f7dc |
961 | This does not currently remove methods from the list returned by |
962 | C<associated_methods>. |
2367814a |
963 | |
2eb717d5 |
964 | =back |
965 | |
966 | =head2 Introspection |
967 | |
968 | =over 4 |
552e3d24 |
969 | |
45b4c423 |
970 | =item B<< Class::MOP::Attribute->meta >> |
552e3d24 |
971 | |
2e23f7dc |
972 | This will return a L<Class::MOP::Class> instance for this class. |
fe122940 |
973 | |
2e23f7dc |
974 | It should also be noted that L<Class::MOP> will actually bootstrap |
975 | this module by installing a number of attribute meta-objects into its |
976 | metaclass. |
fe122940 |
977 | |
552e3d24 |
978 | =back |
979 | |
1a09d9cc |
980 | =head1 AUTHORS |
8b978dd5 |
981 | |
a2e85e6c |
982 | Stevan Little E<lt>stevan@iinteractive.comE<gt> |
8b978dd5 |
983 | |
984 | =head1 COPYRIGHT AND LICENSE |
985 | |
070bb6c9 |
986 | Copyright 2006-2009 by Infinity Interactive, Inc. |
8b978dd5 |
987 | |
988 | L<http://www.iinteractive.com> |
989 | |
990 | This library is free software; you can redistribute it and/or modify |
1d68af04 |
991 | it under the same terms as Perl itself. |
8b978dd5 |
992 | |
16e960bd |
993 | =cut |
994 | |
7d28758b |
995 | |