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 | |
19042e4d |
12 | our $VERSION = '0.92'; |
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 | |
d9330488 |
35 | (defined $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 | |
3ac9bef6 |
55 | my $self = $class->_new(\%options); |
56 | $self->BUILD(); # Initializer in XS |
57 | return $self; |
4b698b1a |
58 | } |
59 | |
60 | sub _new { |
0bfc85b8 |
61 | my $class = shift; |
ec9e38e5 |
62 | |
63 | return Class::MOP::Class->initialize($class)->new_object(@_) |
812d58f9 |
64 | if $class ne __PACKAGE__; |
ec9e38e5 |
65 | |
0bfc85b8 |
66 | my $options = @_ == 1 ? $_[0] : {@_}; |
4b698b1a |
67 | |
8b978dd5 |
68 | bless { |
d9d99689 |
69 | 'name' => $options->{name}, |
70 | 'accessor' => $options->{accessor}, |
71 | 'reader' => $options->{reader}, |
72 | 'writer' => $options->{writer}, |
73 | 'predicate' => $options->{predicate}, |
74 | 'clearer' => $options->{clearer}, |
75 | 'builder' => $options->{builder}, |
76 | 'init_arg' => $options->{init_arg}, |
77 | 'default' => $options->{default}, |
78 | 'initializer' => $options->{initializer}, |
79 | 'definition_context' => $options->{definition_context}, |
1d68af04 |
80 | # keep a weakened link to the |
9ec169fe |
81 | # class we are associated with |
8683db0e |
82 | 'associated_class' => undef, |
1d68af04 |
83 | # and a list of the methods |
3545c727 |
84 | # associated with this attr |
8683db0e |
85 | 'associated_methods' => [], |
dc9d420c |
86 | # this let's us keep track of |
87 | # our order inside the associated |
88 | # class |
89 | 'insertion_order' => undef, |
0bfc85b8 |
90 | }, $class; |
8b978dd5 |
91 | } |
92 | |
7b31baf4 |
93 | # NOTE: |
1d68af04 |
94 | # this is a primative (and kludgy) clone operation |
16e960bd |
95 | # for now, it will be replaced in the Class::MOP |
1d68af04 |
96 | # bootstrap with a proper one, however we know |
5659d76e |
97 | # that this one will work fine for now. |
98 | sub clone { |
99 | my $self = shift; |
100 | my %options = @_; |
101 | (blessed($self)) |
102 | || confess "Can only clone an instance"; |
3ac9bef6 |
103 | my $cloned = bless { %{$self}, %options } => ref($self); |
104 | $cloned->BUILD(); |
105 | return $cloned; |
5659d76e |
106 | } |
107 | |
bd4e03f9 |
108 | sub initialize_instance_slot { |
f892c0f0 |
109 | my ($self, $meta_instance, $instance, $params) = @_; |
8683db0e |
110 | my $init_arg = $self->{'init_arg'}; |
111 | |
bd4e03f9 |
112 | # try to fetch the init arg from the %params ... |
8d2d4c67 |
113 | |
1d68af04 |
114 | # if nothing was in the %params, we can use the |
bd4e03f9 |
115 | # attribute's default value (if it has one) |
2e877f58 |
116 | if(defined $init_arg and exists $params->{$init_arg}){ |
8ee74136 |
117 | $self->_set_initial_slot_value( |
118 | $meta_instance, |
0ab65f99 |
119 | $instance, |
0ab65f99 |
120 | $params->{$init_arg}, |
0ab65f99 |
121 | ); |
b7bdffc3 |
122 | } |
8683db0e |
123 | elsif (defined $self->{'default'}) { |
8ee74136 |
124 | $self->_set_initial_slot_value( |
125 | $meta_instance, |
0ab65f99 |
126 | $instance, |
0ab65f99 |
127 | $self->default($instance), |
0ab65f99 |
128 | ); |
b7bdffc3 |
129 | } |
8683db0e |
130 | elsif (defined( my $builder = $self->{'builder'})) { |
b7bdffc3 |
131 | if ($builder = $instance->can($builder)) { |
8ee74136 |
132 | $self->_set_initial_slot_value( |
133 | $meta_instance, |
0ab65f99 |
134 | $instance, |
0ab65f99 |
135 | $instance->$builder, |
0ab65f99 |
136 | ); |
b7bdffc3 |
137 | } |
138 | else { |
b3fa93c7 |
139 | confess(ref($instance)." does not support builder method '". $self->{'builder'} ."' for attribute '" . $self->name . "'"); |
8fe581e5 |
140 | } |
1d68af04 |
141 | } |
bd4e03f9 |
142 | } |
143 | |
8ee74136 |
144 | sub _set_initial_slot_value { |
145 | my ($self, $meta_instance, $instance, $value) = @_; |
146 | |
147 | my $slot_name = $self->name; |
148 | |
149 | return $meta_instance->set_slot_value($instance, $slot_name, $value) |
150 | unless $self->has_initializer; |
151 | |
152 | my $callback = sub { |
153 | $meta_instance->set_slot_value($instance, $slot_name, $_[0]); |
154 | }; |
155 | |
156 | my $initializer = $self->initializer; |
157 | |
158 | # most things will just want to set a value, so make it first arg |
159 | $instance->$initializer($value, $callback, $self); |
160 | } |
161 | |
9e517e01 |
162 | sub has_read_method { $_[0]->has_reader || $_[0]->has_accessor } |
163 | sub has_write_method { $_[0]->has_writer || $_[0]->has_accessor } |
164 | |
d14f6cbe |
165 | sub get_read_method { |
166 | my $self = shift; |
167 | my $reader = $self->reader || $self->accessor; |
168 | # normal case ... |
169 | return $reader unless ref $reader; |
170 | # the HASH ref case |
171 | my ($name) = %$reader; |
172 | return $name; |
173 | } |
174 | |
175 | sub get_write_method { |
176 | my $self = shift; |
177 | my $writer = $self->writer || $self->accessor; |
178 | # normal case ... |
179 | return $writer unless ref $writer; |
180 | # the HASH ref case |
181 | my ($name) = %$writer; |
182 | return $name; |
183 | } |
b25109b1 |
184 | |
5da16d1b |
185 | sub get_read_method_ref { |
186 | my $self = shift; |
742fb371 |
187 | if ((my $reader = $self->get_read_method) && $self->associated_class) { |
5da16d1b |
188 | return $self->associated_class->get_method($reader); |
189 | } |
190 | else { |
def5c0b5 |
191 | my $code = sub { $self->get_value(@_) }; |
192 | if (my $class = $self->associated_class) { |
193 | return $class->method_metaclass->wrap( |
194 | $code, |
195 | package_name => $class->name, |
196 | name => '__ANON__' |
197 | ); |
198 | } |
199 | else { |
200 | return $code; |
201 | } |
5da16d1b |
202 | } |
203 | } |
204 | |
205 | sub get_write_method_ref { |
206 | my $self = shift; |
d14f6cbe |
207 | if ((my $writer = $self->get_write_method) && $self->associated_class) { |
742fb371 |
208 | return $self->associated_class->get_method($writer); |
5da16d1b |
209 | } |
210 | else { |
def5c0b5 |
211 | my $code = sub { $self->set_value(@_) }; |
212 | if (my $class = $self->associated_class) { |
213 | return $class->method_metaclass->wrap( |
214 | $code, |
215 | package_name => $class->name, |
216 | name => '__ANON__' |
217 | ); |
218 | } |
219 | else { |
220 | return $code; |
221 | } |
5da16d1b |
222 | } |
223 | } |
224 | |
1d68af04 |
225 | sub is_default_a_coderef { |
ed337aad |
226 | my ($value) = $_[0]->{'default'}; |
227 | return unless ref($value); |
228 | return ref($value) eq 'CODE' || (blessed($value) && $value->isa('Class::MOP::Method')); |
c0cbf4d9 |
229 | } |
230 | |
1d68af04 |
231 | sub default { |
c0cbf4d9 |
232 | my ($self, $instance) = @_; |
9363ea89 |
233 | if (defined $instance && $self->is_default_a_coderef) { |
1d68af04 |
234 | # if the default is a CODE ref, then |
727919c5 |
235 | # we pass in the instance and default |
1d68af04 |
236 | # can return a value based on that |
727919c5 |
237 | # instance. Somewhat crude, but works. |
8683db0e |
238 | return $self->{'default'}->($instance); |
1d68af04 |
239 | } |
8683db0e |
240 | $self->{'default'}; |
c50c603e |
241 | } |
8b978dd5 |
242 | |
c57c8b10 |
243 | # slots |
244 | |
245 | sub slots { (shift)->name } |
246 | |
1d68af04 |
247 | # class association |
727919c5 |
248 | |
9ec169fe |
249 | sub attach_to_class { |
250 | my ($self, $class) = @_; |
251 | (blessed($class) && $class->isa('Class::MOP::Class')) |
252 | || confess "You must pass a Class::MOP::Class instance (or a subclass)"; |
8683db0e |
253 | weaken($self->{'associated_class'} = $class); |
9ec169fe |
254 | } |
255 | |
256 | sub detach_from_class { |
257 | my $self = shift; |
8683db0e |
258 | $self->{'associated_class'} = undef; |
9ec169fe |
259 | } |
260 | |
1d68af04 |
261 | # method association |
3545c727 |
262 | |
263 | sub associate_method { |
264 | my ($self, $method) = @_; |
8683db0e |
265 | push @{$self->{'associated_methods'}} => $method; |
3545c727 |
266 | } |
267 | |
16e960bd |
268 | ## Slot management |
269 | |
ef91a0e2 |
270 | sub set_initial_value { |
271 | my ($self, $instance, $value) = @_; |
e76b01fb |
272 | $self->_set_initial_slot_value( |
b3fa93c7 |
273 | Class::MOP::Class->initialize(ref($instance))->get_meta_instance, |
8ee74136 |
274 | $instance, |
275 | $value |
276 | ); |
ef91a0e2 |
277 | } |
278 | |
16e960bd |
279 | sub set_value { |
1396f86b |
280 | my ($self, $instance, $value) = @_; |
16e960bd |
281 | |
b3fa93c7 |
282 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
283 | ->get_meta_instance |
284 | ->set_slot_value($instance, $self->name, $value); |
16e960bd |
285 | } |
286 | |
287 | sub get_value { |
1396f86b |
288 | my ($self, $instance) = @_; |
16e960bd |
289 | |
b3fa93c7 |
290 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
291 | ->get_meta_instance |
292 | ->get_slot_value($instance, $self->name); |
16e960bd |
293 | } |
294 | |
3545c727 |
295 | sub has_value { |
296 | my ($self, $instance) = @_; |
1d68af04 |
297 | |
b3fa93c7 |
298 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
299 | ->get_meta_instance |
300 | ->is_slot_initialized($instance, $self->name); |
3545c727 |
301 | } |
302 | |
303 | sub clear_value { |
304 | my ($self, $instance) = @_; |
1d68af04 |
305 | |
b3fa93c7 |
306 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
307 | ->get_meta_instance |
308 | ->deinitialize_slot($instance, $self->name); |
3545c727 |
309 | } |
310 | |
ba38bf08 |
311 | ## load em up ... |
c0cbf4d9 |
312 | |
ba38bf08 |
313 | sub accessor_metaclass { 'Class::MOP::Method::Accessor' } |
c0cbf4d9 |
314 | |
45a183fb |
315 | sub _process_accessors { |
c0cbf4d9 |
316 | my ($self, $type, $accessor, $generate_as_inline_methods) = @_; |
d9d99689 |
317 | |
318 | my $method_ctx; |
319 | |
320 | if ( my $ctx = $self->definition_context ) { |
321 | $method_ctx = { %$ctx }; |
322 | } |
323 | |
ace00b18 |
324 | my $metaclass = $self->associated_class; |
325 | |
9b522fc4 |
326 | if (ref($accessor)) { |
327 | (ref($accessor) eq 'HASH') |
7d28758b |
328 | || confess "bad accessor/reader/writer/predicate/clearer format, must be a HASH ref"; |
4d47b77f |
329 | my ($name, $method) = %{$accessor}; |
ace00b18 |
330 | |
4c105333 |
331 | $method = $self->accessor_metaclass->wrap( |
ace00b18 |
332 | body => $method, |
333 | associated_metaclass => $metaclass, |
334 | package_name => $metaclass->name, |
335 | name => $name, |
336 | definition_context => $method_ctx, |
4c105333 |
337 | ); |
3545c727 |
338 | $self->associate_method($method); |
1d68af04 |
339 | return ($name, $method); |
2eb717d5 |
340 | } |
9ec169fe |
341 | else { |
ba38bf08 |
342 | my $method; |
343 | eval { |
d9d99689 |
344 | if ( $method_ctx ) { |
345 | my $desc = "accessor $accessor"; |
346 | if ( $accessor ne $self->name ) { |
347 | $desc .= " of attribute " . $self->name; |
348 | } |
349 | |
350 | $method_ctx->{description} = $desc; |
351 | } |
352 | |
ba38bf08 |
353 | $method = $self->accessor_metaclass->new( |
ace00b18 |
354 | attribute => $self, |
355 | accessor_type => $type, |
356 | associated_metaclass => $metaclass, |
357 | package_name => $metaclass->name, |
358 | name => $accessor, |
359 | definition_context => $method_ctx, |
ddd16947 |
360 | is_inline => $metaclass->instance_metaclass->is_inlinable, |
1d68af04 |
361 | ); |
ba38bf08 |
362 | }; |
1d68af04 |
363 | confess "Could not create the '$type' method for " . $self->name . " because : $@" if $@; |
3545c727 |
364 | $self->associate_method($method); |
ba38bf08 |
365 | return ($accessor, $method); |
1d68af04 |
366 | } |
9ec169fe |
367 | } |
368 | |
369 | sub install_accessors { |
c0cbf4d9 |
370 | my $self = shift; |
371 | my $inline = shift; |
372 | my $class = $self->associated_class; |
1d68af04 |
373 | |
9ec169fe |
374 | $class->add_method( |
45a183fb |
375 | $self->_process_accessors('accessor' => $self->accessor(), $inline) |
9ec169fe |
376 | ) if $self->has_accessor(); |
377 | |
1d68af04 |
378 | $class->add_method( |
45a183fb |
379 | $self->_process_accessors('reader' => $self->reader(), $inline) |
9ec169fe |
380 | ) if $self->has_reader(); |
381 | |
382 | $class->add_method( |
45a183fb |
383 | $self->_process_accessors('writer' => $self->writer(), $inline) |
9ec169fe |
384 | ) if $self->has_writer(); |
385 | |
386 | $class->add_method( |
45a183fb |
387 | $self->_process_accessors('predicate' => $self->predicate(), $inline) |
9ec169fe |
388 | ) if $self->has_predicate(); |
1d68af04 |
389 | |
7d28758b |
390 | $class->add_method( |
45a183fb |
391 | $self->_process_accessors('clearer' => $self->clearer(), $inline) |
7d28758b |
392 | ) if $self->has_clearer(); |
1d68af04 |
393 | |
9ec169fe |
394 | return; |
2eb717d5 |
395 | } |
396 | |
b51af7f9 |
397 | { |
398 | my $_remove_accessor = sub { |
399 | my ($accessor, $class) = @_; |
9b522fc4 |
400 | if (ref($accessor) && ref($accessor) eq 'HASH') { |
c50c603e |
401 | ($accessor) = keys %{$accessor}; |
1d68af04 |
402 | } |
403 | my $method = $class->get_method($accessor); |
404 | $class->remove_method($accessor) |
b3fa93c7 |
405 | if (ref($method) && $method->isa('Class::MOP::Method::Accessor')); |
b51af7f9 |
406 | }; |
1d68af04 |
407 | |
b51af7f9 |
408 | sub remove_accessors { |
9ec169fe |
409 | my $self = shift; |
2367814a |
410 | # TODO: |
1d68af04 |
411 | # we really need to make sure to remove from the |
412 | # associates methods here as well. But this is |
413 | # such a slimly used method, I am not worried |
2367814a |
414 | # about it right now. |
9ec169fe |
415 | $_remove_accessor->($self->accessor(), $self->associated_class()) if $self->has_accessor(); |
416 | $_remove_accessor->($self->reader(), $self->associated_class()) if $self->has_reader(); |
417 | $_remove_accessor->($self->writer(), $self->associated_class()) if $self->has_writer(); |
418 | $_remove_accessor->($self->predicate(), $self->associated_class()) if $self->has_predicate(); |
7d28758b |
419 | $_remove_accessor->($self->clearer(), $self->associated_class()) if $self->has_clearer(); |
1d68af04 |
420 | return; |
b51af7f9 |
421 | } |
422 | |
8b978dd5 |
423 | } |
424 | |
425 | 1; |
426 | |
427 | __END__ |
428 | |
429 | =pod |
430 | |
1d68af04 |
431 | =head1 NAME |
8b978dd5 |
432 | |
433 | Class::MOP::Attribute - Attribute Meta Object |
434 | |
435 | =head1 SYNOPSIS |
1d68af04 |
436 | |
2e23f7dc |
437 | Class::MOP::Attribute->new( |
438 | foo => ( |
439 | accessor => 'foo', # dual purpose get/set accessor |
440 | predicate => 'has_foo', # predicate check for defined-ness |
441 | init_arg => '-foo', # class->new will look for a -foo key |
442 | default => 'BAR IS BAZ!' # if no -foo key is provided, use this |
443 | ) |
444 | ); |
445 | |
446 | Class::MOP::Attribute->new( |
447 | bar => ( |
448 | reader => 'bar', # getter |
449 | writer => 'set_bar', # setter |
450 | predicate => 'has_bar', # predicate check for defined-ness |
451 | init_arg => ':bar', # class->new will look for a :bar key |
452 | # no default value means it is undef |
453 | ) |
454 | ); |
8b978dd5 |
455 | |
456 | =head1 DESCRIPTION |
457 | |
2e23f7dc |
458 | The Attribute Protocol is almost entirely an invention of |
459 | C<Class::MOP>. Perl 5 does not have a consistent notion of |
460 | attributes. There are so many ways in which this is done, and very few |
461 | (if any) are easily discoverable by this module. |
552e3d24 |
462 | |
2e23f7dc |
463 | With that said, this module attempts to inject some order into this |
1d68af04 |
464 | chaos, by introducing a consistent API which can be used to create |
fe122940 |
465 | object attributes. |
552e3d24 |
466 | |
467 | =head1 METHODS |
468 | |
469 | =head2 Creation |
470 | |
471 | =over 4 |
472 | |
2e23f7dc |
473 | =item B<< Class::MOP::Attribute->new($name, ?%options) >> |
fe122940 |
474 | |
1d68af04 |
475 | An attribute must (at the very least), have a C<$name>. All other |
2e23f7dc |
476 | C<%options> are added as key-value pairs. |
fe122940 |
477 | |
2e23f7dc |
478 | =over 8 |
fe122940 |
479 | |
76187047 |
480 | =item * init_arg |
fe122940 |
481 | |
2e23f7dc |
482 | This is a string value representing the expected key in an |
483 | initialization hash. For instance, if we have an C<init_arg> value of |
484 | C<-foo>, then the following code will Just Work. |
fe122940 |
485 | |
d69fb6b3 |
486 | MyClass->meta->new_object( -foo => 'Hello There' ); |
fe122940 |
487 | |
2e23f7dc |
488 | If an init_arg is not assigned, it will automatically use the |
489 | attribute's name. If C<init_arg> is explicitly set to C<undef>, the |
490 | attribute cannot be specified during initialization. |
7b31baf4 |
491 | |
76187047 |
492 | =item * builder |
1d68af04 |
493 | |
2e23f7dc |
494 | This provides the name of a method that will be called to initialize |
495 | the attribute. This method will be called on the object after it is |
496 | constructed. It is expected to return a valid value for the attribute. |
fe122940 |
497 | |
76187047 |
498 | =item * default |
4c4a6c41 |
499 | |
2e23f7dc |
500 | This can be used to provide an explicit default for initializing the |
501 | attribute. If the default you provide is a subroutine reference, then |
502 | this reference will be called I<as a method> on the object. |
4c4a6c41 |
503 | |
2e23f7dc |
504 | If the value is a simple scalar (string or number), then it can be |
505 | just passed as is. However, if you wish to initialize it with a HASH |
506 | or ARRAY ref, then you need to wrap that inside a subroutine |
507 | reference: |
fe122940 |
508 | |
2e23f7dc |
509 | Class::MOP::Attribute->new( |
510 | 'foo' => ( |
511 | default => sub { [] }, |
512 | ) |
513 | ); |
1d68af04 |
514 | |
515 | # or ... |
516 | |
2e23f7dc |
517 | Class::MOP::Attribute->new( |
518 | 'foo' => ( |
519 | default => sub { {} }, |
520 | ) |
521 | ); |
522 | |
523 | If you wish to initialize an attribute with a subroutine reference |
524 | itself, then you need to wrap that in a subroutine as well: |
525 | |
526 | Class::MOP::Attribute->new( |
527 | 'foo' => ( |
528 | default => sub { |
529 | sub { print "Hello World" } |
530 | }, |
531 | ) |
532 | ); |
533 | |
534 | And lastly, if the value of your attribute is dependent upon some |
535 | other aspect of the instance structure, then you can take advantage of |
536 | the fact that when the C<default> value is called as a method: |
537 | |
538 | Class::MOP::Attribute->new( |
539 | 'object_identity' => ( |
540 | default => sub { Scalar::Util::refaddr( $_[0] ) }, |
541 | ) |
542 | ); |
543 | |
544 | Note that there is no guarantee that attributes are initialized in any |
545 | particular order, so you cannot rely on the value of some other |
546 | attribute when generating the default. |
fe122940 |
547 | |
76187047 |
548 | =item * initializer |
0ef07b33 |
549 | |
2e23f7dc |
550 | This option can be either a method name or a subroutine |
551 | reference. This method will be called when setting the attribute's |
552 | value in the constructor. Unlike C<default> and C<builder>, the |
553 | initializer is only called when a value is provided to the |
554 | constructor. The initializer allows you to munge this value during |
555 | object construction. |
556 | |
557 | The initializer is called as a method with three arguments. The first |
558 | is the value that was passed to the constructor. The second is a |
559 | subroutine reference that can be called to actually set the |
560 | attribute's value, and the last is the associated |
561 | C<Class::MOP::Attribute> object. |
562 | |
563 | This contrived example shows an initializer that sets the attribute to |
564 | twice the given value. |
565 | |
566 | Class::MOP::Attribute->new( |
567 | 'doubled' => ( |
568 | initializer => sub { |
569 | my ( $instance, $value, $set ) = @_; |
570 | $set->( $value * 2 ); |
571 | }, |
572 | ) |
573 | ); |
574 | |
575 | Since an initializer can be a method name, you can easily make |
0ef07b33 |
576 | attribute initialization use the writer: |
577 | |
2e23f7dc |
578 | Class::MOP::Attribute->new( |
579 | 'some_attr' => ( |
580 | writer => 'some_attr', |
581 | initializer => 'some_attr', |
582 | ) |
583 | ); |
0ef07b33 |
584 | |
2e23f7dc |
585 | Your writer will need to examine C<@_> and determine under which |
586 | context it is being called. |
127d39a7 |
587 | |
fe122940 |
588 | =back |
589 | |
2e23f7dc |
590 | The C<accessor>, C<reader>, C<writer>, C<predicate> and C<clearer> |
591 | options all accept the same parameters. You can provide the name of |
592 | the method, in which case an appropriate default method will be |
593 | generated for you. Or instead you can also provide hash reference |
594 | containing exactly one key (the method name) and one value. The value |
595 | should be a subroutine reference, which will be installed as the |
596 | method itself. |
59e7697f |
597 | |
76187047 |
598 | =over 8 |
59e7697f |
599 | |
76187047 |
600 | =item * accessor |
59e7697f |
601 | |
2e23f7dc |
602 | An C<accessor> is a standard Perl-style read/write accessor. It will |
603 | return the value of the attribute, and if a value is passed as an |
604 | argument, it will assign that value to the attribute. |
fe122940 |
605 | |
2e23f7dc |
606 | Note that C<undef> is a legitimate value, so this will work: |
fe122940 |
607 | |
608 | $object->set_something(undef); |
609 | |
76187047 |
610 | =item * reader |
59e7697f |
611 | |
2e23f7dc |
612 | This is a basic read-only accessor. It returns the value of the |
613 | attribute. |
fe122940 |
614 | |
76187047 |
615 | =item * writer |
59e7697f |
616 | |
1d68af04 |
617 | This is a basic write accessor, it accepts a single argument, and |
2e23f7dc |
618 | assigns that value to the attribute. |
59e7697f |
619 | |
2e23f7dc |
620 | Note that C<undef> is a legitimate value, so this will work: |
59e7697f |
621 | |
2e23f7dc |
622 | $object->set_something(undef); |
fe122940 |
623 | |
76187047 |
624 | =item * predicate |
fe122940 |
625 | |
2e23f7dc |
626 | The predicate method returns a boolean indicating whether or not the |
627 | attribute has been explicitly set. |
07dca7e3 |
628 | |
2e23f7dc |
629 | Note that the predicate returns true even if the attribute was set to |
630 | a false value (C<0> or C<undef>). |
07dca7e3 |
631 | |
76187047 |
632 | =item * clearer |
7d28758b |
633 | |
2e23f7dc |
634 | This method will uninitialize the attribute. After an attribute is |
635 | cleared, its C<predicate> will return false. |
7d28758b |
636 | |
76187047 |
637 | =item * definition_context |
f8813817 |
638 | |
639 | Mostly, this exists as a hook for the benefit of Moose. |
640 | |
641 | This option should be a hash reference containing several keys which |
642 | will be used when inlining the attribute's accessors. The keys should |
643 | include C<line>, the line number where the attribute was created, and |
644 | either C<file> or C<description>. |
645 | |
646 | This information will ultimately be used when eval'ing inlined |
647 | accessor code so that error messages report a useful line and file |
648 | name. |
649 | |
59e7697f |
650 | =back |
552e3d24 |
651 | |
2e23f7dc |
652 | =item B<< $attr->clone(%options) >> |
bd4e03f9 |
653 | |
2e23f7dc |
654 | This clones the attribute. Any options you provide will override the |
655 | settings of the original attribute. You can change the name of the new |
656 | attribute by passing a C<name> key in C<%options>. |
127d39a7 |
657 | |
2e23f7dc |
658 | =back |
bd4e03f9 |
659 | |
2e23f7dc |
660 | =head2 Informational |
127d39a7 |
661 | |
2e23f7dc |
662 | These are all basic read-only accessors for the values passed into |
663 | the constructor. |
552e3d24 |
664 | |
2e23f7dc |
665 | =over 4 |
16e960bd |
666 | |
2e23f7dc |
667 | =item B<< $attr->name >> |
2367814a |
668 | |
76187047 |
669 | Returns the attribute's name. |
670 | |
2e23f7dc |
671 | =item B<< $attr->accessor >> |
2367814a |
672 | |
2e23f7dc |
673 | =item B<< $attr->reader >> |
16e960bd |
674 | |
2e23f7dc |
675 | =item B<< $attr->writer >> |
16e960bd |
676 | |
2e23f7dc |
677 | =item B<< $attr->predicate >> |
16e960bd |
678 | |
2e23f7dc |
679 | =item B<< $attr->clearer >> |
c0921932 |
680 | |
2e23f7dc |
681 | The C<accessor>, C<reader>, C<writer>, C<predicate>, and C<clearer> |
682 | methods all return exactly what was passed to the constructor, so it |
a6710c60 |
683 | can be either a string containing a method name, or a hash reference. |
c0921932 |
684 | |
2e23f7dc |
685 | =item B<< $attr->initializer >> |
16e960bd |
686 | |
a6710c60 |
687 | Returns the initializer as passed to the constructor, so this may be |
2e23f7dc |
688 | either a method name or a subroutine reference. |
16e960bd |
689 | |
2e23f7dc |
690 | =item B<< $attr->init_arg >> |
3545c727 |
691 | |
2e23f7dc |
692 | =item B<< $attr->is_default_a_coderef >> |
2367814a |
693 | |
2e23f7dc |
694 | =item B<< $attr->default($instance) >> |
3545c727 |
695 | |
2e23f7dc |
696 | The C<$instance> argument is optional. If you don't pass it, the |
697 | return value for this method is exactly what was passed to the |
698 | constructor, either a simple scalar or a subroutine reference. |
2367814a |
699 | |
2e23f7dc |
700 | If you I<do> pass an C<$instance> and the default is a subroutine |
701 | reference, then the reference is called as a method on the |
702 | C<$instance> and the generated value is returned. |
16e960bd |
703 | |
2e23f7dc |
704 | =item B<< $attr->slots >> |
552e3d24 |
705 | |
2e23f7dc |
706 | Return a list of slots required by the attribute. This is usually just |
707 | one, the name of the attribute. |
fe122940 |
708 | |
2e23f7dc |
709 | A slot is the name of the hash key used to store the attribute in an |
710 | object instance. |
552e3d24 |
711 | |
2e23f7dc |
712 | =item B<< $attr->get_read_method >> |
552e3d24 |
713 | |
2e23f7dc |
714 | =item B<< $attr->get_write_method >> |
552e3d24 |
715 | |
2e23f7dc |
716 | Returns the name of a method suitable for reading or writing the value |
717 | of the attribute in the associated class. |
552e3d24 |
718 | |
2e23f7dc |
719 | If an attribute is read- or write-only, then these methods can return |
720 | C<undef> as appropriate. |
552e3d24 |
721 | |
2e23f7dc |
722 | =item B<< $attr->has_read_method >> |
c50c603e |
723 | |
2e23f7dc |
724 | =item B<< $attr->has_write_method >> |
7d28758b |
725 | |
2e23f7dc |
726 | This returns a boolean indicating whether the attribute has a I<named> |
727 | read or write method. |
0ab65f99 |
728 | |
2e23f7dc |
729 | =item B<< $attr->get_read_method_ref >> |
552e3d24 |
730 | |
2e23f7dc |
731 | =item B<< $attr->get_write_method_ref >> |
495af518 |
732 | |
2e23f7dc |
733 | Returns the subroutine reference of a method suitable for reading or |
734 | writing the attribute's value in the associated class. These methods |
735 | always return a subroutine reference, regardless of whether or not the |
736 | attribute is read- or write-only. |
737 | |
eeff7496 |
738 | =item B<< $attr->insertion_order >> |
739 | |
740 | If this attribute has been inserted into a class, this returns a zero |
741 | based index regarding the order of insertion. |
742 | |
2e23f7dc |
743 | =back |
fe122940 |
744 | |
2e23f7dc |
745 | =head2 Informational predicates |
92d2abfa |
746 | |
2e23f7dc |
747 | These are all basic predicate methods for the values passed into C<new>. |
552e3d24 |
748 | |
2e23f7dc |
749 | =over 4 |
c57c8b10 |
750 | |
2e23f7dc |
751 | =item B<< $attr->has_accessor >> |
c57c8b10 |
752 | |
2e23f7dc |
753 | =item B<< $attr->has_reader >> |
b25109b1 |
754 | |
2e23f7dc |
755 | =item B<< $attr->has_writer >> |
b25109b1 |
756 | |
2e23f7dc |
757 | =item B<< $attr->has_predicate >> |
5da16d1b |
758 | |
2e23f7dc |
759 | =item B<< $attr->has_clearer >> |
5da16d1b |
760 | |
2e23f7dc |
761 | =item B<< $attr->has_initializer >> |
5da16d1b |
762 | |
2e23f7dc |
763 | =item B<< $attr->has_init_arg >> |
5da16d1b |
764 | |
2e23f7dc |
765 | This will be I<false> if the C<init_arg> was set to C<undef>. |
b25109b1 |
766 | |
2e23f7dc |
767 | =item B<< $attr->has_default >> |
9e517e01 |
768 | |
2e23f7dc |
769 | This will be I<false> if the C<default> was set to C<undef>, since |
770 | C<undef> is the default C<default> anyway. |
9e517e01 |
771 | |
2e23f7dc |
772 | =item B<< $attr->has_builder >> |
9e517e01 |
773 | |
eeff7496 |
774 | =item B<< $attr->has_insertion_order >> |
775 | |
776 | This will be I<false> if this attribute has not be inserted into a class |
777 | |
552e3d24 |
778 | =back |
779 | |
2e23f7dc |
780 | =head2 Value management |
552e3d24 |
781 | |
a6710c60 |
782 | These methods are basically "back doors" to the instance, and can be |
2e23f7dc |
783 | used to bypass the regular accessors, but still stay within the MOP. |
784 | |
785 | These methods are not for general use, and should only be used if you |
786 | really know what you are doing. |
fe122940 |
787 | |
552e3d24 |
788 | =over 4 |
789 | |
2e23f7dc |
790 | =item B<< $attr->initialize_instance_slot($meta_instance, $instance, $params) >> |
791 | |
792 | This method is used internally to initialize the attribute's slot in |
793 | the object C<$instance>. |
794 | |
795 | The C<$params> is a hash reference of the values passed to the object |
796 | constructor. |
797 | |
798 | It's unlikely that you'll need to call this method yourself. |
552e3d24 |
799 | |
2e23f7dc |
800 | =item B<< $attr->set_value($instance, $value) >> |
552e3d24 |
801 | |
2e23f7dc |
802 | Sets the value without going through the accessor. Note that this |
803 | works even with read-only attributes. |
552e3d24 |
804 | |
2e23f7dc |
805 | =item B<< $attr->set_initial_value($instance, $value) >> |
c50c603e |
806 | |
2e23f7dc |
807 | Sets the value without going through the accessor. This method is only |
808 | called when the instance is first being initialized. |
7d28758b |
809 | |
2e23f7dc |
810 | =item B<< $attr->get_value($instance) >> |
0ab65f99 |
811 | |
2e23f7dc |
812 | Returns the value without going through the accessor. Note that this |
813 | works even with write-only accessors. |
552e3d24 |
814 | |
2e23f7dc |
815 | =item B<< $attr->has_value($instance) >> |
552e3d24 |
816 | |
2e23f7dc |
817 | Return a boolean indicating whether the attribute has been set in |
818 | C<$instance>. This how the default C<predicate> method works. |
819 | |
820 | =item B<< $attr->clear_value($instance) >> |
821 | |
822 | This will clear the attribute's value in C<$instance>. This is what |
823 | the default C<clearer> calls. |
824 | |
825 | Note that this works even if the attribute does not have any |
826 | associated read, write or clear methods. |
bf731086 |
827 | |
552e3d24 |
828 | =back |
829 | |
9ec169fe |
830 | =head2 Class association |
831 | |
1d68af04 |
832 | These methods allow you to manage the attributes association with |
833 | the class that contains it. These methods should not be used |
2367814a |
834 | lightly, nor are they very magical, they are mostly used internally |
835 | and by metaclass instances. |
836 | |
9ec169fe |
837 | =over 4 |
838 | |
2e23f7dc |
839 | =item B<< $attr->associated_class >> |
840 | |
841 | This returns the C<Class::MOP::Class> with which this attribute is |
842 | associated, if any. |
843 | |
844 | =item B<< $attr->attach_to_class($metaclass) >> |
9ec169fe |
845 | |
2e23f7dc |
846 | This method stores a weakened reference to the C<$metaclass> object |
847 | internally. |
2367814a |
848 | |
2e23f7dc |
849 | This method does not remove the attribute from its old class, |
850 | nor does it create any accessors in the new class. |
9ec169fe |
851 | |
2e23f7dc |
852 | It is probably best to use the L<Class::MOP::Class> C<add_attribute> |
853 | method instead. |
2367814a |
854 | |
2e23f7dc |
855 | =item B<< $attr->detach_from_class >> |
9ec169fe |
856 | |
2e23f7dc |
857 | This method removes the associate metaclass object from the attribute |
858 | it has one. |
859 | |
860 | This method does not remove the attribute itself from the class, or |
861 | remove its accessors. |
862 | |
863 | It is probably best to use the L<Class::MOP::Class> |
864 | C<remove_attribute> method instead. |
2367814a |
865 | |
9ec169fe |
866 | =back |
867 | |
552e3d24 |
868 | =head2 Attribute Accessor generation |
869 | |
870 | =over 4 |
871 | |
2e23f7dc |
872 | =item B<< $attr->accessor_metaclass >> |
ba38bf08 |
873 | |
2e23f7dc |
874 | Accessor methods are generated using an accessor metaclass. By |
875 | default, this is L<Class::MOP::Method::Accessor>. This method returns |
2367814a |
876 | the name of the accessor metaclass that this attribute uses. |
877 | |
2e23f7dc |
878 | =item B<< $attr->associate_method($method) >> |
2367814a |
879 | |
2e23f7dc |
880 | This associates a L<Class::MOP::Method> object with the |
881 | attribute. Typically, this is called internally when an attribute |
882 | generates its accessors. |
3545c727 |
883 | |
2e23f7dc |
884 | =item B<< $attr->associated_methods >> |
3545c727 |
885 | |
2e23f7dc |
886 | This returns the list of methods which have been associated with the |
887 | attribute. |
2367814a |
888 | |
2e23f7dc |
889 | =item B<< $attr->install_accessors >> |
2eb717d5 |
890 | |
2e23f7dc |
891 | This method generates and installs code the attributes various |
892 | accessors. It is typically called from the L<Class::MOP::Class> |
893 | C<add_attribute> method. |
2eb717d5 |
894 | |
2e23f7dc |
895 | =item B<< $attr->remove_accessors >> |
2eb717d5 |
896 | |
2e23f7dc |
897 | This method removes all of the accessors associated with the |
898 | attribute. |
2eb717d5 |
899 | |
2e23f7dc |
900 | This does not currently remove methods from the list returned by |
901 | C<associated_methods>. |
2367814a |
902 | |
2eb717d5 |
903 | =back |
904 | |
905 | =head2 Introspection |
906 | |
907 | =over 4 |
552e3d24 |
908 | |
45b4c423 |
909 | =item B<< Class::MOP::Attribute->meta >> |
552e3d24 |
910 | |
2e23f7dc |
911 | This will return a L<Class::MOP::Class> instance for this class. |
fe122940 |
912 | |
2e23f7dc |
913 | It should also be noted that L<Class::MOP> will actually bootstrap |
914 | this module by installing a number of attribute meta-objects into its |
915 | metaclass. |
fe122940 |
916 | |
552e3d24 |
917 | =back |
918 | |
1a09d9cc |
919 | =head1 AUTHORS |
8b978dd5 |
920 | |
a2e85e6c |
921 | Stevan Little E<lt>stevan@iinteractive.comE<gt> |
8b978dd5 |
922 | |
923 | =head1 COPYRIGHT AND LICENSE |
924 | |
070bb6c9 |
925 | Copyright 2006-2009 by Infinity Interactive, Inc. |
8b978dd5 |
926 | |
927 | L<http://www.iinteractive.com> |
928 | |
929 | This library is free software; you can redistribute it and/or modify |
1d68af04 |
930 | it under the same terms as Perl itself. |
8b978dd5 |
931 | |
16e960bd |
932 | =cut |
933 | |
7d28758b |
934 | |