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'; |
a8344505 |
11 | use Try::Tiny; |
2eb717d5 |
12 | |
a9f48b4b |
13 | our $VERSION = '1.11'; |
d519662a |
14 | $VERSION = eval $VERSION; |
f0480c45 |
15 | our $AUTHORITY = 'cpan:STEVAN'; |
8b978dd5 |
16 | |
9b871d79 |
17 | use base 'Class::MOP::Object', 'Class::MOP::Mixin::AttributeCore'; |
b1897d4d |
18 | |
727919c5 |
19 | # NOTE: (meta-circularity) |
1d68af04 |
20 | # This method will be replaced in the |
21 | # boostrap section of Class::MOP, by |
22 | # a new version which uses the |
727919c5 |
23 | # &Class::MOP::Class::construct_instance |
24 | # method to build an attribute meta-object |
25 | # which itself is described with attribute |
1d68af04 |
26 | # meta-objects. |
727919c5 |
27 | # - Ain't meta-circularity grand? :) |
8b978dd5 |
28 | sub new { |
649efb63 |
29 | my ( $class, @args ) = @_; |
30 | |
31 | unshift @args, "name" if @args % 2 == 1; |
32 | my %options = @args; |
33 | |
34 | my $name = $options{name}; |
1d68af04 |
35 | |
d9330488 |
36 | (defined $name) |
8b978dd5 |
37 | || confess "You must provide a name for the attribute"; |
1d68af04 |
38 | |
39 | $options{init_arg} = $name |
5659d76e |
40 | if not exists $options{init_arg}; |
1d68af04 |
41 | if(exists $options{builder}){ |
42 | confess("builder must be a defined scalar value which is a method name") |
43 | if ref $options{builder} || !(defined $options{builder}); |
44 | confess("Setting both default and builder is not allowed.") |
45 | if exists $options{default}; |
8fe581e5 |
46 | } else { |
9b871d79 |
47 | ($class->is_default_a_coderef(\%options)) |
8fe581e5 |
48 | || confess("References are not allowed as default values, you must ". |
3c0a8087 |
49 | "wrap the default of '$name' in a CODE reference (ex: sub { [] } and not [])") |
8fe581e5 |
50 | if exists $options{default} && ref $options{default}; |
1d68af04 |
51 | } |
2e877f58 |
52 | if( $options{required} and not( defined($options{builder}) || defined($options{init_arg}) || exists $options{default} ) ) { |
53 | confess("A required attribute must have either 'init_arg', 'builder', or 'default'"); |
54 | } |
8683db0e |
55 | |
cb75020f |
56 | $class->_new(\%options); |
4b698b1a |
57 | } |
58 | |
59 | sub _new { |
0bfc85b8 |
60 | my $class = shift; |
ec9e38e5 |
61 | |
62 | return Class::MOP::Class->initialize($class)->new_object(@_) |
812d58f9 |
63 | if $class ne __PACKAGE__; |
ec9e38e5 |
64 | |
0bfc85b8 |
65 | my $options = @_ == 1 ? $_[0] : {@_}; |
4b698b1a |
66 | |
8b978dd5 |
67 | bless { |
d9d99689 |
68 | 'name' => $options->{name}, |
69 | 'accessor' => $options->{accessor}, |
70 | 'reader' => $options->{reader}, |
71 | 'writer' => $options->{writer}, |
72 | 'predicate' => $options->{predicate}, |
73 | 'clearer' => $options->{clearer}, |
74 | 'builder' => $options->{builder}, |
75 | 'init_arg' => $options->{init_arg}, |
8343d501 |
76 | exists $options->{default} |
77 | ? ('default' => $options->{default}) |
78 | : (), |
d9d99689 |
79 | 'initializer' => $options->{initializer}, |
80 | 'definition_context' => $options->{definition_context}, |
1d68af04 |
81 | # keep a weakened link to the |
9ec169fe |
82 | # class we are associated with |
8683db0e |
83 | 'associated_class' => undef, |
1d68af04 |
84 | # and a list of the methods |
3545c727 |
85 | # associated with this attr |
8683db0e |
86 | 'associated_methods' => [], |
dc9d420c |
87 | # this let's us keep track of |
88 | # our order inside the associated |
89 | # class |
90 | 'insertion_order' => undef, |
0bfc85b8 |
91 | }, $class; |
8b978dd5 |
92 | } |
93 | |
7b31baf4 |
94 | # NOTE: |
1d68af04 |
95 | # this is a primative (and kludgy) clone operation |
16e960bd |
96 | # for now, it will be replaced in the Class::MOP |
1d68af04 |
97 | # bootstrap with a proper one, however we know |
5659d76e |
98 | # that this one will work fine for now. |
99 | sub clone { |
100 | my $self = shift; |
101 | my %options = @_; |
102 | (blessed($self)) |
103 | || confess "Can only clone an instance"; |
b3fa93c7 |
104 | return bless { %{$self}, %options } => ref($self); |
5659d76e |
105 | } |
106 | |
bd4e03f9 |
107 | sub initialize_instance_slot { |
f892c0f0 |
108 | my ($self, $meta_instance, $instance, $params) = @_; |
8683db0e |
109 | my $init_arg = $self->{'init_arg'}; |
110 | |
bd4e03f9 |
111 | # try to fetch the init arg from the %params ... |
8d2d4c67 |
112 | |
1d68af04 |
113 | # if nothing was in the %params, we can use the |
bd4e03f9 |
114 | # attribute's default value (if it has one) |
2e877f58 |
115 | if(defined $init_arg and exists $params->{$init_arg}){ |
8ee74136 |
116 | $self->_set_initial_slot_value( |
117 | $meta_instance, |
0ab65f99 |
118 | $instance, |
0ab65f99 |
119 | $params->{$init_arg}, |
0ab65f99 |
120 | ); |
b7bdffc3 |
121 | } |
8343d501 |
122 | elsif (exists $self->{'default'}) { |
8ee74136 |
123 | $self->_set_initial_slot_value( |
124 | $meta_instance, |
0ab65f99 |
125 | $instance, |
0ab65f99 |
126 | $self->default($instance), |
0ab65f99 |
127 | ); |
b7bdffc3 |
128 | } |
8683db0e |
129 | elsif (defined( my $builder = $self->{'builder'})) { |
b7bdffc3 |
130 | if ($builder = $instance->can($builder)) { |
8ee74136 |
131 | $self->_set_initial_slot_value( |
132 | $meta_instance, |
0ab65f99 |
133 | $instance, |
0ab65f99 |
134 | $instance->$builder, |
0ab65f99 |
135 | ); |
b7bdffc3 |
136 | } |
137 | else { |
b3fa93c7 |
138 | confess(ref($instance)." does not support builder method '". $self->{'builder'} ."' for attribute '" . $self->name . "'"); |
8fe581e5 |
139 | } |
1d68af04 |
140 | } |
bd4e03f9 |
141 | } |
142 | |
8ee74136 |
143 | sub _set_initial_slot_value { |
144 | my ($self, $meta_instance, $instance, $value) = @_; |
145 | |
146 | my $slot_name = $self->name; |
147 | |
148 | return $meta_instance->set_slot_value($instance, $slot_name, $value) |
149 | unless $self->has_initializer; |
150 | |
151 | my $callback = sub { |
152 | $meta_instance->set_slot_value($instance, $slot_name, $_[0]); |
153 | }; |
154 | |
155 | my $initializer = $self->initializer; |
156 | |
157 | # most things will just want to set a value, so make it first arg |
158 | $instance->$initializer($value, $callback, $self); |
159 | } |
160 | |
d14f6cbe |
161 | sub get_read_method { |
162 | my $self = shift; |
163 | my $reader = $self->reader || $self->accessor; |
164 | # normal case ... |
165 | return $reader unless ref $reader; |
166 | # the HASH ref case |
167 | my ($name) = %$reader; |
168 | return $name; |
169 | } |
170 | |
171 | sub get_write_method { |
172 | my $self = shift; |
173 | my $writer = $self->writer || $self->accessor; |
174 | # normal case ... |
175 | return $writer unless ref $writer; |
176 | # the HASH ref case |
177 | my ($name) = %$writer; |
178 | return $name; |
179 | } |
b25109b1 |
180 | |
5da16d1b |
181 | sub get_read_method_ref { |
182 | my $self = shift; |
742fb371 |
183 | if ((my $reader = $self->get_read_method) && $self->associated_class) { |
5da16d1b |
184 | return $self->associated_class->get_method($reader); |
185 | } |
186 | else { |
def5c0b5 |
187 | my $code = sub { $self->get_value(@_) }; |
188 | if (my $class = $self->associated_class) { |
189 | return $class->method_metaclass->wrap( |
190 | $code, |
191 | package_name => $class->name, |
192 | name => '__ANON__' |
193 | ); |
194 | } |
195 | else { |
196 | return $code; |
197 | } |
5da16d1b |
198 | } |
199 | } |
200 | |
201 | sub get_write_method_ref { |
202 | my $self = shift; |
d14f6cbe |
203 | if ((my $writer = $self->get_write_method) && $self->associated_class) { |
742fb371 |
204 | return $self->associated_class->get_method($writer); |
5da16d1b |
205 | } |
206 | else { |
def5c0b5 |
207 | my $code = sub { $self->set_value(@_) }; |
208 | if (my $class = $self->associated_class) { |
209 | return $class->method_metaclass->wrap( |
210 | $code, |
211 | package_name => $class->name, |
212 | name => '__ANON__' |
213 | ); |
214 | } |
215 | else { |
216 | return $code; |
217 | } |
5da16d1b |
218 | } |
219 | } |
220 | |
c57c8b10 |
221 | # slots |
222 | |
223 | sub slots { (shift)->name } |
224 | |
1d68af04 |
225 | # class association |
727919c5 |
226 | |
9ec169fe |
227 | sub attach_to_class { |
228 | my ($self, $class) = @_; |
229 | (blessed($class) && $class->isa('Class::MOP::Class')) |
230 | || confess "You must pass a Class::MOP::Class instance (or a subclass)"; |
8683db0e |
231 | weaken($self->{'associated_class'} = $class); |
9ec169fe |
232 | } |
233 | |
234 | sub detach_from_class { |
235 | my $self = shift; |
8683db0e |
236 | $self->{'associated_class'} = undef; |
9ec169fe |
237 | } |
238 | |
1d68af04 |
239 | # method association |
3545c727 |
240 | |
241 | sub associate_method { |
242 | my ($self, $method) = @_; |
8683db0e |
243 | push @{$self->{'associated_methods'}} => $method; |
3545c727 |
244 | } |
245 | |
16e960bd |
246 | ## Slot management |
247 | |
ef91a0e2 |
248 | sub set_initial_value { |
249 | my ($self, $instance, $value) = @_; |
e76b01fb |
250 | $self->_set_initial_slot_value( |
b3fa93c7 |
251 | Class::MOP::Class->initialize(ref($instance))->get_meta_instance, |
8ee74136 |
252 | $instance, |
253 | $value |
254 | ); |
ef91a0e2 |
255 | } |
256 | |
7e5efe15 |
257 | sub set_value { shift->set_raw_value(@_) } |
7e5efe15 |
258 | |
259 | sub set_raw_value { |
5e5102f1 |
260 | my $self = shift; |
261 | my ($instance, $value) = @_; |
262 | |
263 | my $mi = Class::MOP::Class->initialize(ref($instance))->get_meta_instance; |
264 | return $mi->set_slot_value($instance, $self->name, $value); |
265 | } |
266 | |
267 | sub _inline_set_value { |
268 | my $self = shift; |
269 | return $self->_inline_instance_set(@_) . ';'; |
270 | } |
16e960bd |
271 | |
5e5102f1 |
272 | sub _inline_instance_set { |
273 | my $self = shift; |
274 | my ($instance, $value) = @_; |
275 | |
276 | my $mi = $self->associated_class->get_meta_instance; |
277 | return $mi->inline_set_slot_value($instance, $self->name, $value); |
16e960bd |
278 | } |
279 | |
5e5102f1 |
280 | sub get_value { shift->get_raw_value(@_) } |
281 | |
7e5efe15 |
282 | sub get_raw_value { |
5e5102f1 |
283 | my $self = shift; |
284 | my ($instance) = @_; |
16e960bd |
285 | |
5e5102f1 |
286 | my $mi = Class::MOP::Class->initialize(ref($instance))->get_meta_instance; |
287 | return $mi->get_slot_value($instance, $self->name); |
288 | } |
289 | |
290 | sub _inline_get_value { |
291 | my $self = shift; |
292 | return $self->_inline_instance_get(@_) . ';'; |
293 | } |
294 | |
295 | sub _inline_instance_get { |
296 | my $self = shift; |
297 | my ($instance) = @_; |
298 | |
299 | my $mi = $self->associated_class->get_meta_instance; |
300 | return $mi->inline_get_slot_value($instance, $self->name); |
16e960bd |
301 | } |
302 | |
3545c727 |
303 | sub has_value { |
5e5102f1 |
304 | my $self = shift; |
305 | my ($instance) = @_; |
1d68af04 |
306 | |
5e5102f1 |
307 | my $mi = Class::MOP::Class->initialize(ref($instance))->get_meta_instance; |
308 | return $mi->is_slot_initialized($instance, $self->name); |
309 | } |
310 | |
311 | sub _inline_has_value { |
312 | my $self = shift; |
313 | return $self->_inline_instance_has(@_) . ';'; |
314 | } |
315 | |
316 | sub _inline_instance_has { |
317 | my $self = shift; |
318 | my ($instance) = @_; |
319 | |
320 | my $mi = $self->associated_class->get_meta_instance; |
321 | return $mi->inline_is_slot_initialized($instance, $self->name); |
3545c727 |
322 | } |
323 | |
324 | sub clear_value { |
5e5102f1 |
325 | my $self = shift; |
326 | my ($instance) = @_; |
327 | |
328 | my $mi = Class::MOP::Class->initialize(ref($instance))->get_meta_instance; |
329 | return $mi->deinitialize_slot($instance, $self->name); |
330 | } |
1d68af04 |
331 | |
5e5102f1 |
332 | sub _inline_clear_value { |
333 | my $self = shift; |
334 | return $self->_inline_instance_clear(@_) . ';'; |
335 | } |
336 | |
337 | sub _inline_instance_clear { |
338 | my $self = shift; |
339 | my ($instance) = @_; |
340 | |
341 | my $mi = $self->associated_class->get_meta_instance; |
342 | return $mi->inline_deinitialize_slot($instance, $self->name); |
3545c727 |
343 | } |
344 | |
ba38bf08 |
345 | ## load em up ... |
c0cbf4d9 |
346 | |
ba38bf08 |
347 | sub accessor_metaclass { 'Class::MOP::Method::Accessor' } |
c0cbf4d9 |
348 | |
45a183fb |
349 | sub _process_accessors { |
c0cbf4d9 |
350 | my ($self, $type, $accessor, $generate_as_inline_methods) = @_; |
d9d99689 |
351 | |
352 | my $method_ctx; |
353 | |
354 | if ( my $ctx = $self->definition_context ) { |
355 | $method_ctx = { %$ctx }; |
356 | } |
357 | |
9b522fc4 |
358 | if (ref($accessor)) { |
359 | (ref($accessor) eq 'HASH') |
7d28758b |
360 | || confess "bad accessor/reader/writer/predicate/clearer format, must be a HASH ref"; |
4d47b77f |
361 | my ($name, $method) = %{$accessor}; |
4c105333 |
362 | $method = $self->accessor_metaclass->wrap( |
363 | $method, |
364 | package_name => $self->associated_class->name, |
365 | name => $name, |
d9d99689 |
366 | definition_context => $method_ctx, |
4c105333 |
367 | ); |
3545c727 |
368 | $self->associate_method($method); |
1d68af04 |
369 | return ($name, $method); |
2eb717d5 |
370 | } |
9ec169fe |
371 | else { |
1d68af04 |
372 | my $inline_me = ($generate_as_inline_methods && $self->associated_class->instance_metaclass->is_inlinable); |
ba38bf08 |
373 | my $method; |
a8344505 |
374 | try { |
d9d99689 |
375 | if ( $method_ctx ) { |
376 | my $desc = "accessor $accessor"; |
377 | if ( $accessor ne $self->name ) { |
378 | $desc .= " of attribute " . $self->name; |
379 | } |
380 | |
381 | $method_ctx->{description} = $desc; |
382 | } |
383 | |
ba38bf08 |
384 | $method = $self->accessor_metaclass->new( |
385 | attribute => $self, |
d90b42a6 |
386 | is_inline => $inline_me, |
ba38bf08 |
387 | accessor_type => $type, |
4c105333 |
388 | package_name => $self->associated_class->name, |
389 | name => $accessor, |
d9d99689 |
390 | definition_context => $method_ctx, |
1d68af04 |
391 | ); |
a8344505 |
392 | } |
393 | catch { |
394 | confess "Could not create the '$type' method for " . $self->name . " because : $_"; |
ba38bf08 |
395 | }; |
3545c727 |
396 | $self->associate_method($method); |
ba38bf08 |
397 | return ($accessor, $method); |
1d68af04 |
398 | } |
9ec169fe |
399 | } |
400 | |
401 | sub install_accessors { |
c0cbf4d9 |
402 | my $self = shift; |
403 | my $inline = shift; |
404 | my $class = $self->associated_class; |
1d68af04 |
405 | |
9ec169fe |
406 | $class->add_method( |
45a183fb |
407 | $self->_process_accessors('accessor' => $self->accessor(), $inline) |
9ec169fe |
408 | ) if $self->has_accessor(); |
409 | |
1d68af04 |
410 | $class->add_method( |
45a183fb |
411 | $self->_process_accessors('reader' => $self->reader(), $inline) |
9ec169fe |
412 | ) if $self->has_reader(); |
413 | |
414 | $class->add_method( |
45a183fb |
415 | $self->_process_accessors('writer' => $self->writer(), $inline) |
9ec169fe |
416 | ) if $self->has_writer(); |
417 | |
418 | $class->add_method( |
45a183fb |
419 | $self->_process_accessors('predicate' => $self->predicate(), $inline) |
9ec169fe |
420 | ) if $self->has_predicate(); |
1d68af04 |
421 | |
7d28758b |
422 | $class->add_method( |
45a183fb |
423 | $self->_process_accessors('clearer' => $self->clearer(), $inline) |
7d28758b |
424 | ) if $self->has_clearer(); |
1d68af04 |
425 | |
9ec169fe |
426 | return; |
2eb717d5 |
427 | } |
428 | |
b51af7f9 |
429 | { |
430 | my $_remove_accessor = sub { |
431 | my ($accessor, $class) = @_; |
9b522fc4 |
432 | if (ref($accessor) && ref($accessor) eq 'HASH') { |
c50c603e |
433 | ($accessor) = keys %{$accessor}; |
1d68af04 |
434 | } |
435 | my $method = $class->get_method($accessor); |
436 | $class->remove_method($accessor) |
b3fa93c7 |
437 | if (ref($method) && $method->isa('Class::MOP::Method::Accessor')); |
b51af7f9 |
438 | }; |
1d68af04 |
439 | |
b51af7f9 |
440 | sub remove_accessors { |
9ec169fe |
441 | my $self = shift; |
2367814a |
442 | # TODO: |
1d68af04 |
443 | # we really need to make sure to remove from the |
444 | # associates methods here as well. But this is |
445 | # such a slimly used method, I am not worried |
2367814a |
446 | # about it right now. |
9ec169fe |
447 | $_remove_accessor->($self->accessor(), $self->associated_class()) if $self->has_accessor(); |
448 | $_remove_accessor->($self->reader(), $self->associated_class()) if $self->has_reader(); |
449 | $_remove_accessor->($self->writer(), $self->associated_class()) if $self->has_writer(); |
450 | $_remove_accessor->($self->predicate(), $self->associated_class()) if $self->has_predicate(); |
7d28758b |
451 | $_remove_accessor->($self->clearer(), $self->associated_class()) if $self->has_clearer(); |
1d68af04 |
452 | return; |
b51af7f9 |
453 | } |
454 | |
8b978dd5 |
455 | } |
456 | |
457 | 1; |
458 | |
459 | __END__ |
460 | |
461 | =pod |
462 | |
1d68af04 |
463 | =head1 NAME |
8b978dd5 |
464 | |
465 | Class::MOP::Attribute - Attribute Meta Object |
466 | |
467 | =head1 SYNOPSIS |
1d68af04 |
468 | |
2e23f7dc |
469 | Class::MOP::Attribute->new( |
470 | foo => ( |
471 | accessor => 'foo', # dual purpose get/set accessor |
472 | predicate => 'has_foo', # predicate check for defined-ness |
473 | init_arg => '-foo', # class->new will look for a -foo key |
474 | default => 'BAR IS BAZ!' # if no -foo key is provided, use this |
475 | ) |
476 | ); |
477 | |
478 | Class::MOP::Attribute->new( |
479 | bar => ( |
480 | reader => 'bar', # getter |
481 | writer => 'set_bar', # setter |
482 | predicate => 'has_bar', # predicate check for defined-ness |
483 | init_arg => ':bar', # class->new will look for a :bar key |
484 | # no default value means it is undef |
485 | ) |
486 | ); |
8b978dd5 |
487 | |
488 | =head1 DESCRIPTION |
489 | |
2e23f7dc |
490 | The Attribute Protocol is almost entirely an invention of |
491 | C<Class::MOP>. Perl 5 does not have a consistent notion of |
492 | attributes. There are so many ways in which this is done, and very few |
493 | (if any) are easily discoverable by this module. |
552e3d24 |
494 | |
2e23f7dc |
495 | With that said, this module attempts to inject some order into this |
1d68af04 |
496 | chaos, by introducing a consistent API which can be used to create |
fe122940 |
497 | object attributes. |
552e3d24 |
498 | |
499 | =head1 METHODS |
500 | |
501 | =head2 Creation |
502 | |
503 | =over 4 |
504 | |
2e23f7dc |
505 | =item B<< Class::MOP::Attribute->new($name, ?%options) >> |
fe122940 |
506 | |
1d68af04 |
507 | An attribute must (at the very least), have a C<$name>. All other |
2e23f7dc |
508 | C<%options> are added as key-value pairs. |
fe122940 |
509 | |
2e23f7dc |
510 | =over 8 |
fe122940 |
511 | |
76187047 |
512 | =item * init_arg |
fe122940 |
513 | |
2e23f7dc |
514 | This is a string value representing the expected key in an |
515 | initialization hash. For instance, if we have an C<init_arg> value of |
516 | C<-foo>, then the following code will Just Work. |
fe122940 |
517 | |
d69fb6b3 |
518 | MyClass->meta->new_object( -foo => 'Hello There' ); |
fe122940 |
519 | |
2e23f7dc |
520 | If an init_arg is not assigned, it will automatically use the |
521 | attribute's name. If C<init_arg> is explicitly set to C<undef>, the |
522 | attribute cannot be specified during initialization. |
7b31baf4 |
523 | |
76187047 |
524 | =item * builder |
1d68af04 |
525 | |
2e23f7dc |
526 | This provides the name of a method that will be called to initialize |
527 | the attribute. This method will be called on the object after it is |
528 | constructed. It is expected to return a valid value for the attribute. |
fe122940 |
529 | |
76187047 |
530 | =item * default |
4c4a6c41 |
531 | |
2e23f7dc |
532 | This can be used to provide an explicit default for initializing the |
533 | attribute. If the default you provide is a subroutine reference, then |
534 | this reference will be called I<as a method> on the object. |
4c4a6c41 |
535 | |
2e23f7dc |
536 | If the value is a simple scalar (string or number), then it can be |
537 | just passed as is. However, if you wish to initialize it with a HASH |
538 | or ARRAY ref, then you need to wrap that inside a subroutine |
539 | reference: |
fe122940 |
540 | |
2e23f7dc |
541 | Class::MOP::Attribute->new( |
542 | 'foo' => ( |
543 | default => sub { [] }, |
544 | ) |
545 | ); |
1d68af04 |
546 | |
547 | # or ... |
548 | |
2e23f7dc |
549 | Class::MOP::Attribute->new( |
550 | 'foo' => ( |
551 | default => sub { {} }, |
552 | ) |
553 | ); |
554 | |
555 | If you wish to initialize an attribute with a subroutine reference |
556 | itself, then you need to wrap that in a subroutine as well: |
557 | |
558 | Class::MOP::Attribute->new( |
559 | 'foo' => ( |
560 | default => sub { |
561 | sub { print "Hello World" } |
562 | }, |
563 | ) |
564 | ); |
565 | |
566 | And lastly, if the value of your attribute is dependent upon some |
567 | other aspect of the instance structure, then you can take advantage of |
568 | the fact that when the C<default> value is called as a method: |
569 | |
570 | Class::MOP::Attribute->new( |
571 | 'object_identity' => ( |
572 | default => sub { Scalar::Util::refaddr( $_[0] ) }, |
573 | ) |
574 | ); |
575 | |
576 | Note that there is no guarantee that attributes are initialized in any |
577 | particular order, so you cannot rely on the value of some other |
578 | attribute when generating the default. |
fe122940 |
579 | |
76187047 |
580 | =item * initializer |
0ef07b33 |
581 | |
2e23f7dc |
582 | This option can be either a method name or a subroutine |
583 | reference. This method will be called when setting the attribute's |
584 | value in the constructor. Unlike C<default> and C<builder>, the |
585 | initializer is only called when a value is provided to the |
586 | constructor. The initializer allows you to munge this value during |
587 | object construction. |
588 | |
589 | The initializer is called as a method with three arguments. The first |
590 | is the value that was passed to the constructor. The second is a |
591 | subroutine reference that can be called to actually set the |
592 | attribute's value, and the last is the associated |
593 | C<Class::MOP::Attribute> object. |
594 | |
595 | This contrived example shows an initializer that sets the attribute to |
596 | twice the given value. |
597 | |
598 | Class::MOP::Attribute->new( |
599 | 'doubled' => ( |
600 | initializer => sub { |
ea62c8ab |
601 | my ( $self, $value, $set, $attr ) = @_; |
2e23f7dc |
602 | $set->( $value * 2 ); |
603 | }, |
604 | ) |
605 | ); |
606 | |
607 | Since an initializer can be a method name, you can easily make |
0ef07b33 |
608 | attribute initialization use the writer: |
609 | |
2e23f7dc |
610 | Class::MOP::Attribute->new( |
611 | 'some_attr' => ( |
612 | writer => 'some_attr', |
613 | initializer => 'some_attr', |
614 | ) |
615 | ); |
0ef07b33 |
616 | |
2e23f7dc |
617 | Your writer will need to examine C<@_> and determine under which |
618 | context it is being called. |
127d39a7 |
619 | |
fe122940 |
620 | =back |
621 | |
2e23f7dc |
622 | The C<accessor>, C<reader>, C<writer>, C<predicate> and C<clearer> |
623 | options all accept the same parameters. You can provide the name of |
624 | the method, in which case an appropriate default method will be |
625 | generated for you. Or instead you can also provide hash reference |
626 | containing exactly one key (the method name) and one value. The value |
627 | should be a subroutine reference, which will be installed as the |
628 | method itself. |
59e7697f |
629 | |
76187047 |
630 | =over 8 |
59e7697f |
631 | |
76187047 |
632 | =item * accessor |
59e7697f |
633 | |
2e23f7dc |
634 | An C<accessor> is a standard Perl-style read/write accessor. It will |
635 | return the value of the attribute, and if a value is passed as an |
636 | argument, it will assign that value to the attribute. |
fe122940 |
637 | |
2e23f7dc |
638 | Note that C<undef> is a legitimate value, so this will work: |
fe122940 |
639 | |
640 | $object->set_something(undef); |
641 | |
76187047 |
642 | =item * reader |
59e7697f |
643 | |
2e23f7dc |
644 | This is a basic read-only accessor. It returns the value of the |
645 | attribute. |
fe122940 |
646 | |
76187047 |
647 | =item * writer |
59e7697f |
648 | |
1d68af04 |
649 | This is a basic write accessor, it accepts a single argument, and |
2e23f7dc |
650 | assigns that value to the attribute. |
59e7697f |
651 | |
2e23f7dc |
652 | Note that C<undef> is a legitimate value, so this will work: |
59e7697f |
653 | |
2e23f7dc |
654 | $object->set_something(undef); |
fe122940 |
655 | |
76187047 |
656 | =item * predicate |
fe122940 |
657 | |
2e23f7dc |
658 | The predicate method returns a boolean indicating whether or not the |
659 | attribute has been explicitly set. |
07dca7e3 |
660 | |
2e23f7dc |
661 | Note that the predicate returns true even if the attribute was set to |
662 | a false value (C<0> or C<undef>). |
07dca7e3 |
663 | |
76187047 |
664 | =item * clearer |
7d28758b |
665 | |
2e23f7dc |
666 | This method will uninitialize the attribute. After an attribute is |
667 | cleared, its C<predicate> will return false. |
7d28758b |
668 | |
76187047 |
669 | =item * definition_context |
f8813817 |
670 | |
671 | Mostly, this exists as a hook for the benefit of Moose. |
672 | |
673 | This option should be a hash reference containing several keys which |
674 | will be used when inlining the attribute's accessors. The keys should |
675 | include C<line>, the line number where the attribute was created, and |
676 | either C<file> or C<description>. |
677 | |
678 | This information will ultimately be used when eval'ing inlined |
679 | accessor code so that error messages report a useful line and file |
680 | name. |
681 | |
59e7697f |
682 | =back |
552e3d24 |
683 | |
2e23f7dc |
684 | =item B<< $attr->clone(%options) >> |
bd4e03f9 |
685 | |
2e23f7dc |
686 | This clones the attribute. Any options you provide will override the |
687 | settings of the original attribute. You can change the name of the new |
688 | attribute by passing a C<name> key in C<%options>. |
127d39a7 |
689 | |
2e23f7dc |
690 | =back |
bd4e03f9 |
691 | |
2e23f7dc |
692 | =head2 Informational |
127d39a7 |
693 | |
2e23f7dc |
694 | These are all basic read-only accessors for the values passed into |
695 | the constructor. |
552e3d24 |
696 | |
2e23f7dc |
697 | =over 4 |
16e960bd |
698 | |
2e23f7dc |
699 | =item B<< $attr->name >> |
2367814a |
700 | |
76187047 |
701 | Returns the attribute's name. |
702 | |
2e23f7dc |
703 | =item B<< $attr->accessor >> |
2367814a |
704 | |
2e23f7dc |
705 | =item B<< $attr->reader >> |
16e960bd |
706 | |
2e23f7dc |
707 | =item B<< $attr->writer >> |
16e960bd |
708 | |
2e23f7dc |
709 | =item B<< $attr->predicate >> |
16e960bd |
710 | |
2e23f7dc |
711 | =item B<< $attr->clearer >> |
c0921932 |
712 | |
2e23f7dc |
713 | The C<accessor>, C<reader>, C<writer>, C<predicate>, and C<clearer> |
714 | methods all return exactly what was passed to the constructor, so it |
a6710c60 |
715 | can be either a string containing a method name, or a hash reference. |
c0921932 |
716 | |
2e23f7dc |
717 | =item B<< $attr->initializer >> |
16e960bd |
718 | |
a6710c60 |
719 | Returns the initializer as passed to the constructor, so this may be |
2e23f7dc |
720 | either a method name or a subroutine reference. |
16e960bd |
721 | |
2e23f7dc |
722 | =item B<< $attr->init_arg >> |
3545c727 |
723 | |
2e23f7dc |
724 | =item B<< $attr->is_default_a_coderef >> |
2367814a |
725 | |
2e23f7dc |
726 | =item B<< $attr->default($instance) >> |
3545c727 |
727 | |
2e23f7dc |
728 | The C<$instance> argument is optional. If you don't pass it, the |
729 | return value for this method is exactly what was passed to the |
730 | constructor, either a simple scalar or a subroutine reference. |
2367814a |
731 | |
2e23f7dc |
732 | If you I<do> pass an C<$instance> and the default is a subroutine |
733 | reference, then the reference is called as a method on the |
734 | C<$instance> and the generated value is returned. |
16e960bd |
735 | |
2e23f7dc |
736 | =item B<< $attr->slots >> |
552e3d24 |
737 | |
2e23f7dc |
738 | Return a list of slots required by the attribute. This is usually just |
739 | one, the name of the attribute. |
fe122940 |
740 | |
2e23f7dc |
741 | A slot is the name of the hash key used to store the attribute in an |
742 | object instance. |
552e3d24 |
743 | |
2e23f7dc |
744 | =item B<< $attr->get_read_method >> |
552e3d24 |
745 | |
2e23f7dc |
746 | =item B<< $attr->get_write_method >> |
552e3d24 |
747 | |
2e23f7dc |
748 | Returns the name of a method suitable for reading or writing the value |
749 | of the attribute in the associated class. |
552e3d24 |
750 | |
2e23f7dc |
751 | If an attribute is read- or write-only, then these methods can return |
752 | C<undef> as appropriate. |
552e3d24 |
753 | |
2e23f7dc |
754 | =item B<< $attr->has_read_method >> |
c50c603e |
755 | |
2e23f7dc |
756 | =item B<< $attr->has_write_method >> |
7d28758b |
757 | |
2e23f7dc |
758 | This returns a boolean indicating whether the attribute has a I<named> |
759 | read or write method. |
0ab65f99 |
760 | |
2e23f7dc |
761 | =item B<< $attr->get_read_method_ref >> |
552e3d24 |
762 | |
2e23f7dc |
763 | =item B<< $attr->get_write_method_ref >> |
495af518 |
764 | |
2e23f7dc |
765 | Returns the subroutine reference of a method suitable for reading or |
766 | writing the attribute's value in the associated class. These methods |
767 | always return a subroutine reference, regardless of whether or not the |
768 | attribute is read- or write-only. |
769 | |
eeff7496 |
770 | =item B<< $attr->insertion_order >> |
771 | |
772 | If this attribute has been inserted into a class, this returns a zero |
773 | based index regarding the order of insertion. |
774 | |
2e23f7dc |
775 | =back |
fe122940 |
776 | |
2e23f7dc |
777 | =head2 Informational predicates |
92d2abfa |
778 | |
2e23f7dc |
779 | These are all basic predicate methods for the values passed into C<new>. |
552e3d24 |
780 | |
2e23f7dc |
781 | =over 4 |
c57c8b10 |
782 | |
2e23f7dc |
783 | =item B<< $attr->has_accessor >> |
c57c8b10 |
784 | |
2e23f7dc |
785 | =item B<< $attr->has_reader >> |
b25109b1 |
786 | |
2e23f7dc |
787 | =item B<< $attr->has_writer >> |
b25109b1 |
788 | |
2e23f7dc |
789 | =item B<< $attr->has_predicate >> |
5da16d1b |
790 | |
2e23f7dc |
791 | =item B<< $attr->has_clearer >> |
5da16d1b |
792 | |
2e23f7dc |
793 | =item B<< $attr->has_initializer >> |
5da16d1b |
794 | |
2e23f7dc |
795 | =item B<< $attr->has_init_arg >> |
5da16d1b |
796 | |
2e23f7dc |
797 | This will be I<false> if the C<init_arg> was set to C<undef>. |
b25109b1 |
798 | |
2e23f7dc |
799 | =item B<< $attr->has_default >> |
9e517e01 |
800 | |
2e23f7dc |
801 | This will be I<false> if the C<default> was set to C<undef>, since |
802 | C<undef> is the default C<default> anyway. |
9e517e01 |
803 | |
2e23f7dc |
804 | =item B<< $attr->has_builder >> |
9e517e01 |
805 | |
eeff7496 |
806 | =item B<< $attr->has_insertion_order >> |
807 | |
808 | This will be I<false> if this attribute has not be inserted into a class |
809 | |
552e3d24 |
810 | =back |
811 | |
2e23f7dc |
812 | =head2 Value management |
552e3d24 |
813 | |
a6710c60 |
814 | These methods are basically "back doors" to the instance, and can be |
2e23f7dc |
815 | used to bypass the regular accessors, but still stay within the MOP. |
816 | |
817 | These methods are not for general use, and should only be used if you |
818 | really know what you are doing. |
fe122940 |
819 | |
552e3d24 |
820 | =over 4 |
821 | |
2e23f7dc |
822 | =item B<< $attr->initialize_instance_slot($meta_instance, $instance, $params) >> |
823 | |
824 | This method is used internally to initialize the attribute's slot in |
825 | the object C<$instance>. |
826 | |
827 | The C<$params> is a hash reference of the values passed to the object |
828 | constructor. |
829 | |
830 | It's unlikely that you'll need to call this method yourself. |
552e3d24 |
831 | |
2e23f7dc |
832 | =item B<< $attr->set_value($instance, $value) >> |
552e3d24 |
833 | |
2e23f7dc |
834 | Sets the value without going through the accessor. Note that this |
835 | works even with read-only attributes. |
552e3d24 |
836 | |
7e5efe15 |
837 | =item B<< $attr->set_raw_value($instance, $value) >> |
838 | |
839 | Sets the value with no side effects such as a trigger. |
840 | |
841 | This doesn't actually apply to Class::MOP attributes, only to subclasses. |
842 | |
2e23f7dc |
843 | =item B<< $attr->set_initial_value($instance, $value) >> |
c50c603e |
844 | |
2e23f7dc |
845 | Sets the value without going through the accessor. This method is only |
846 | called when the instance is first being initialized. |
7d28758b |
847 | |
2e23f7dc |
848 | =item B<< $attr->get_value($instance) >> |
0ab65f99 |
849 | |
2e23f7dc |
850 | Returns the value without going through the accessor. Note that this |
851 | works even with write-only accessors. |
552e3d24 |
852 | |
25b3fdad |
853 | =item B<< $attr->get_raw_value($instance) >> |
7e5efe15 |
854 | |
855 | Returns the value without any side effects such as lazy attributes. |
856 | |
857 | Doesn't actually apply to Class::MOP attributes, only to subclasses. |
858 | |
2e23f7dc |
859 | =item B<< $attr->has_value($instance) >> |
552e3d24 |
860 | |
2e23f7dc |
861 | Return a boolean indicating whether the attribute has been set in |
862 | C<$instance>. This how the default C<predicate> method works. |
863 | |
864 | =item B<< $attr->clear_value($instance) >> |
865 | |
866 | This will clear the attribute's value in C<$instance>. This is what |
867 | the default C<clearer> calls. |
868 | |
869 | Note that this works even if the attribute does not have any |
870 | associated read, write or clear methods. |
bf731086 |
871 | |
552e3d24 |
872 | =back |
873 | |
9ec169fe |
874 | =head2 Class association |
875 | |
1d68af04 |
876 | These methods allow you to manage the attributes association with |
877 | the class that contains it. These methods should not be used |
2367814a |
878 | lightly, nor are they very magical, they are mostly used internally |
879 | and by metaclass instances. |
880 | |
9ec169fe |
881 | =over 4 |
882 | |
2e23f7dc |
883 | =item B<< $attr->associated_class >> |
884 | |
885 | This returns the C<Class::MOP::Class> with which this attribute is |
886 | associated, if any. |
887 | |
888 | =item B<< $attr->attach_to_class($metaclass) >> |
9ec169fe |
889 | |
2e23f7dc |
890 | This method stores a weakened reference to the C<$metaclass> object |
891 | internally. |
2367814a |
892 | |
2e23f7dc |
893 | This method does not remove the attribute from its old class, |
894 | nor does it create any accessors in the new class. |
9ec169fe |
895 | |
2e23f7dc |
896 | It is probably best to use the L<Class::MOP::Class> C<add_attribute> |
897 | method instead. |
2367814a |
898 | |
2e23f7dc |
899 | =item B<< $attr->detach_from_class >> |
9ec169fe |
900 | |
2e23f7dc |
901 | This method removes the associate metaclass object from the attribute |
902 | it has one. |
903 | |
904 | This method does not remove the attribute itself from the class, or |
905 | remove its accessors. |
906 | |
907 | It is probably best to use the L<Class::MOP::Class> |
908 | C<remove_attribute> method instead. |
2367814a |
909 | |
9ec169fe |
910 | =back |
911 | |
552e3d24 |
912 | =head2 Attribute Accessor generation |
913 | |
914 | =over 4 |
915 | |
2e23f7dc |
916 | =item B<< $attr->accessor_metaclass >> |
ba38bf08 |
917 | |
2e23f7dc |
918 | Accessor methods are generated using an accessor metaclass. By |
919 | default, this is L<Class::MOP::Method::Accessor>. This method returns |
2367814a |
920 | the name of the accessor metaclass that this attribute uses. |
921 | |
2e23f7dc |
922 | =item B<< $attr->associate_method($method) >> |
2367814a |
923 | |
2e23f7dc |
924 | This associates a L<Class::MOP::Method> object with the |
925 | attribute. Typically, this is called internally when an attribute |
926 | generates its accessors. |
3545c727 |
927 | |
2e23f7dc |
928 | =item B<< $attr->associated_methods >> |
3545c727 |
929 | |
2e23f7dc |
930 | This returns the list of methods which have been associated with the |
931 | attribute. |
2367814a |
932 | |
2e23f7dc |
933 | =item B<< $attr->install_accessors >> |
2eb717d5 |
934 | |
2e23f7dc |
935 | This method generates and installs code the attributes various |
936 | accessors. It is typically called from the L<Class::MOP::Class> |
937 | C<add_attribute> method. |
2eb717d5 |
938 | |
2e23f7dc |
939 | =item B<< $attr->remove_accessors >> |
2eb717d5 |
940 | |
2e23f7dc |
941 | This method removes all of the accessors associated with the |
942 | attribute. |
2eb717d5 |
943 | |
2e23f7dc |
944 | This does not currently remove methods from the list returned by |
945 | C<associated_methods>. |
2367814a |
946 | |
03a3092d |
947 | =item B<< $attr->inline_get >> |
948 | |
949 | =item B<< $attr->inline_set >> |
950 | |
951 | =item B<< $attr->inline_has >> |
952 | |
953 | =item B<< $attr->inline_clear >> |
954 | |
955 | These methods return a code snippet suitable for inlining the relevant |
956 | operation. They expect strings containing variable names to be used in the |
957 | inlining, like C<'$self'> or C<'$_[1]'>. |
958 | |
2eb717d5 |
959 | =back |
960 | |
961 | =head2 Introspection |
962 | |
963 | =over 4 |
552e3d24 |
964 | |
45b4c423 |
965 | =item B<< Class::MOP::Attribute->meta >> |
552e3d24 |
966 | |
2e23f7dc |
967 | This will return a L<Class::MOP::Class> instance for this class. |
fe122940 |
968 | |
2e23f7dc |
969 | It should also be noted that L<Class::MOP> will actually bootstrap |
970 | this module by installing a number of attribute meta-objects into its |
971 | metaclass. |
fe122940 |
972 | |
552e3d24 |
973 | =back |
974 | |
1a09d9cc |
975 | =head1 AUTHORS |
8b978dd5 |
976 | |
a2e85e6c |
977 | Stevan Little E<lt>stevan@iinteractive.comE<gt> |
8b978dd5 |
978 | |
979 | =head1 COPYRIGHT AND LICENSE |
980 | |
3e2c8600 |
981 | Copyright 2006-2010 by Infinity Interactive, Inc. |
8b978dd5 |
982 | |
983 | L<http://www.iinteractive.com> |
984 | |
985 | This library is free software; you can redistribute it and/or modify |
1d68af04 |
986 | it under the same terms as Perl itself. |
8b978dd5 |
987 | |
16e960bd |
988 | =cut |
989 | |
7d28758b |
990 | |