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 | $value |
254 | ); |
ef91a0e2 |
255 | } |
256 | |
7e5efe15 |
257 | sub set_value { shift->set_raw_value(@_) } |
258 | sub get_value { shift->get_raw_value(@_) } |
259 | |
260 | sub set_raw_value { |
1396f86b |
261 | my ($self, $instance, $value) = @_; |
16e960bd |
262 | |
b3fa93c7 |
263 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
264 | ->get_meta_instance |
265 | ->set_slot_value($instance, $self->name, $value); |
16e960bd |
266 | } |
267 | |
7e5efe15 |
268 | sub get_raw_value { |
1396f86b |
269 | my ($self, $instance) = @_; |
16e960bd |
270 | |
b3fa93c7 |
271 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
272 | ->get_meta_instance |
273 | ->get_slot_value($instance, $self->name); |
16e960bd |
274 | } |
275 | |
3545c727 |
276 | sub has_value { |
277 | my ($self, $instance) = @_; |
1d68af04 |
278 | |
b3fa93c7 |
279 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
280 | ->get_meta_instance |
281 | ->is_slot_initialized($instance, $self->name); |
3545c727 |
282 | } |
283 | |
284 | sub clear_value { |
285 | my ($self, $instance) = @_; |
1d68af04 |
286 | |
b3fa93c7 |
287 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
288 | ->get_meta_instance |
289 | ->deinitialize_slot($instance, $self->name); |
3545c727 |
290 | } |
291 | |
ba38bf08 |
292 | ## load em up ... |
c0cbf4d9 |
293 | |
ba38bf08 |
294 | sub accessor_metaclass { 'Class::MOP::Method::Accessor' } |
c0cbf4d9 |
295 | |
45a183fb |
296 | sub _process_accessors { |
c0cbf4d9 |
297 | my ($self, $type, $accessor, $generate_as_inline_methods) = @_; |
d9d99689 |
298 | |
299 | my $method_ctx; |
300 | |
301 | if ( my $ctx = $self->definition_context ) { |
302 | $method_ctx = { %$ctx }; |
303 | } |
304 | |
9b522fc4 |
305 | if (ref($accessor)) { |
306 | (ref($accessor) eq 'HASH') |
7d28758b |
307 | || confess "bad accessor/reader/writer/predicate/clearer format, must be a HASH ref"; |
4d47b77f |
308 | my ($name, $method) = %{$accessor}; |
4c105333 |
309 | $method = $self->accessor_metaclass->wrap( |
310 | $method, |
311 | package_name => $self->associated_class->name, |
312 | name => $name, |
d9d99689 |
313 | definition_context => $method_ctx, |
4c105333 |
314 | ); |
3545c727 |
315 | $self->associate_method($method); |
1d68af04 |
316 | return ($name, $method); |
2eb717d5 |
317 | } |
9ec169fe |
318 | else { |
1d68af04 |
319 | my $inline_me = ($generate_as_inline_methods && $self->associated_class->instance_metaclass->is_inlinable); |
ba38bf08 |
320 | my $method; |
a8344505 |
321 | try { |
d9d99689 |
322 | if ( $method_ctx ) { |
323 | my $desc = "accessor $accessor"; |
324 | if ( $accessor ne $self->name ) { |
325 | $desc .= " of attribute " . $self->name; |
326 | } |
327 | |
328 | $method_ctx->{description} = $desc; |
329 | } |
330 | |
ba38bf08 |
331 | $method = $self->accessor_metaclass->new( |
332 | attribute => $self, |
d90b42a6 |
333 | is_inline => $inline_me, |
ba38bf08 |
334 | accessor_type => $type, |
4c105333 |
335 | package_name => $self->associated_class->name, |
336 | name => $accessor, |
d9d99689 |
337 | definition_context => $method_ctx, |
1d68af04 |
338 | ); |
a8344505 |
339 | } |
340 | catch { |
341 | confess "Could not create the '$type' method for " . $self->name . " because : $_"; |
ba38bf08 |
342 | }; |
3545c727 |
343 | $self->associate_method($method); |
ba38bf08 |
344 | return ($accessor, $method); |
1d68af04 |
345 | } |
9ec169fe |
346 | } |
347 | |
348 | sub install_accessors { |
c0cbf4d9 |
349 | my $self = shift; |
350 | my $inline = shift; |
351 | my $class = $self->associated_class; |
1d68af04 |
352 | |
9ec169fe |
353 | $class->add_method( |
45a183fb |
354 | $self->_process_accessors('accessor' => $self->accessor(), $inline) |
9ec169fe |
355 | ) if $self->has_accessor(); |
356 | |
1d68af04 |
357 | $class->add_method( |
45a183fb |
358 | $self->_process_accessors('reader' => $self->reader(), $inline) |
9ec169fe |
359 | ) if $self->has_reader(); |
360 | |
361 | $class->add_method( |
45a183fb |
362 | $self->_process_accessors('writer' => $self->writer(), $inline) |
9ec169fe |
363 | ) if $self->has_writer(); |
364 | |
365 | $class->add_method( |
45a183fb |
366 | $self->_process_accessors('predicate' => $self->predicate(), $inline) |
9ec169fe |
367 | ) if $self->has_predicate(); |
1d68af04 |
368 | |
7d28758b |
369 | $class->add_method( |
45a183fb |
370 | $self->_process_accessors('clearer' => $self->clearer(), $inline) |
7d28758b |
371 | ) if $self->has_clearer(); |
1d68af04 |
372 | |
9ec169fe |
373 | return; |
2eb717d5 |
374 | } |
375 | |
b51af7f9 |
376 | { |
377 | my $_remove_accessor = sub { |
378 | my ($accessor, $class) = @_; |
9b522fc4 |
379 | if (ref($accessor) && ref($accessor) eq 'HASH') { |
c50c603e |
380 | ($accessor) = keys %{$accessor}; |
1d68af04 |
381 | } |
382 | my $method = $class->get_method($accessor); |
383 | $class->remove_method($accessor) |
b3fa93c7 |
384 | if (ref($method) && $method->isa('Class::MOP::Method::Accessor')); |
b51af7f9 |
385 | }; |
1d68af04 |
386 | |
b51af7f9 |
387 | sub remove_accessors { |
9ec169fe |
388 | my $self = shift; |
2367814a |
389 | # TODO: |
1d68af04 |
390 | # we really need to make sure to remove from the |
391 | # associates methods here as well. But this is |
392 | # such a slimly used method, I am not worried |
2367814a |
393 | # about it right now. |
9ec169fe |
394 | $_remove_accessor->($self->accessor(), $self->associated_class()) if $self->has_accessor(); |
395 | $_remove_accessor->($self->reader(), $self->associated_class()) if $self->has_reader(); |
396 | $_remove_accessor->($self->writer(), $self->associated_class()) if $self->has_writer(); |
397 | $_remove_accessor->($self->predicate(), $self->associated_class()) if $self->has_predicate(); |
7d28758b |
398 | $_remove_accessor->($self->clearer(), $self->associated_class()) if $self->has_clearer(); |
1d68af04 |
399 | return; |
b51af7f9 |
400 | } |
401 | |
8b978dd5 |
402 | } |
403 | |
03a3092d |
404 | sub inline_get { |
405 | my $self = shift; |
406 | my ($instance) = @_; |
407 | |
408 | return $self->associated_class->get_meta_instance->inline_get_slot_value( |
409 | $instance, $self->name ); |
410 | } |
411 | |
412 | sub inline_set { |
413 | my $self = shift; |
414 | my ( $instance, $value ) = @_; |
415 | |
416 | return $self->associated_class->get_meta_instance->inline_set_slot_value( |
417 | $instance, $self->name, $value ); |
418 | } |
419 | |
420 | sub inline_has { |
421 | my $self = shift; |
422 | my ($instance) = @_; |
423 | |
424 | return |
425 | $self->associated_class->get_meta_instance |
426 | ->inline_is_slot_initialized( $instance, $self->name ); |
427 | } |
428 | |
429 | sub inline_clear { |
430 | my $self = shift; |
431 | my ($instance) = @_; |
432 | |
433 | return |
434 | $self->associated_class->get_meta_instance |
435 | ->inline_deinitialize_slot( $instance, $self->name ); |
436 | } |
437 | |
8b978dd5 |
438 | 1; |
439 | |
440 | __END__ |
441 | |
442 | =pod |
443 | |
1d68af04 |
444 | =head1 NAME |
8b978dd5 |
445 | |
446 | Class::MOP::Attribute - Attribute Meta Object |
447 | |
448 | =head1 SYNOPSIS |
1d68af04 |
449 | |
2e23f7dc |
450 | Class::MOP::Attribute->new( |
451 | foo => ( |
452 | accessor => 'foo', # dual purpose get/set accessor |
453 | predicate => 'has_foo', # predicate check for defined-ness |
454 | init_arg => '-foo', # class->new will look for a -foo key |
455 | default => 'BAR IS BAZ!' # if no -foo key is provided, use this |
456 | ) |
457 | ); |
458 | |
459 | Class::MOP::Attribute->new( |
460 | bar => ( |
461 | reader => 'bar', # getter |
462 | writer => 'set_bar', # setter |
463 | predicate => 'has_bar', # predicate check for defined-ness |
464 | init_arg => ':bar', # class->new will look for a :bar key |
465 | # no default value means it is undef |
466 | ) |
467 | ); |
8b978dd5 |
468 | |
469 | =head1 DESCRIPTION |
470 | |
2e23f7dc |
471 | The Attribute Protocol is almost entirely an invention of |
472 | C<Class::MOP>. Perl 5 does not have a consistent notion of |
473 | attributes. There are so many ways in which this is done, and very few |
474 | (if any) are easily discoverable by this module. |
552e3d24 |
475 | |
2e23f7dc |
476 | With that said, this module attempts to inject some order into this |
1d68af04 |
477 | chaos, by introducing a consistent API which can be used to create |
fe122940 |
478 | object attributes. |
552e3d24 |
479 | |
480 | =head1 METHODS |
481 | |
482 | =head2 Creation |
483 | |
484 | =over 4 |
485 | |
2e23f7dc |
486 | =item B<< Class::MOP::Attribute->new($name, ?%options) >> |
fe122940 |
487 | |
1d68af04 |
488 | An attribute must (at the very least), have a C<$name>. All other |
2e23f7dc |
489 | C<%options> are added as key-value pairs. |
fe122940 |
490 | |
2e23f7dc |
491 | =over 8 |
fe122940 |
492 | |
76187047 |
493 | =item * init_arg |
fe122940 |
494 | |
2e23f7dc |
495 | This is a string value representing the expected key in an |
496 | initialization hash. For instance, if we have an C<init_arg> value of |
497 | C<-foo>, then the following code will Just Work. |
fe122940 |
498 | |
d69fb6b3 |
499 | MyClass->meta->new_object( -foo => 'Hello There' ); |
fe122940 |
500 | |
2e23f7dc |
501 | If an init_arg is not assigned, it will automatically use the |
502 | attribute's name. If C<init_arg> is explicitly set to C<undef>, the |
503 | attribute cannot be specified during initialization. |
7b31baf4 |
504 | |
76187047 |
505 | =item * builder |
1d68af04 |
506 | |
2e23f7dc |
507 | This provides the name of a method that will be called to initialize |
508 | the attribute. This method will be called on the object after it is |
509 | constructed. It is expected to return a valid value for the attribute. |
fe122940 |
510 | |
76187047 |
511 | =item * default |
4c4a6c41 |
512 | |
2e23f7dc |
513 | This can be used to provide an explicit default for initializing the |
514 | attribute. If the default you provide is a subroutine reference, then |
515 | this reference will be called I<as a method> on the object. |
4c4a6c41 |
516 | |
2e23f7dc |
517 | If the value is a simple scalar (string or number), then it can be |
518 | just passed as is. However, if you wish to initialize it with a HASH |
519 | or ARRAY ref, then you need to wrap that inside a subroutine |
520 | reference: |
fe122940 |
521 | |
2e23f7dc |
522 | Class::MOP::Attribute->new( |
523 | 'foo' => ( |
524 | default => sub { [] }, |
525 | ) |
526 | ); |
1d68af04 |
527 | |
528 | # or ... |
529 | |
2e23f7dc |
530 | Class::MOP::Attribute->new( |
531 | 'foo' => ( |
532 | default => sub { {} }, |
533 | ) |
534 | ); |
535 | |
536 | If you wish to initialize an attribute with a subroutine reference |
537 | itself, then you need to wrap that in a subroutine as well: |
538 | |
539 | Class::MOP::Attribute->new( |
540 | 'foo' => ( |
541 | default => sub { |
542 | sub { print "Hello World" } |
543 | }, |
544 | ) |
545 | ); |
546 | |
547 | And lastly, if the value of your attribute is dependent upon some |
548 | other aspect of the instance structure, then you can take advantage of |
549 | the fact that when the C<default> value is called as a method: |
550 | |
551 | Class::MOP::Attribute->new( |
552 | 'object_identity' => ( |
553 | default => sub { Scalar::Util::refaddr( $_[0] ) }, |
554 | ) |
555 | ); |
556 | |
557 | Note that there is no guarantee that attributes are initialized in any |
558 | particular order, so you cannot rely on the value of some other |
559 | attribute when generating the default. |
fe122940 |
560 | |
76187047 |
561 | =item * initializer |
0ef07b33 |
562 | |
2e23f7dc |
563 | This option can be either a method name or a subroutine |
564 | reference. This method will be called when setting the attribute's |
565 | value in the constructor. Unlike C<default> and C<builder>, the |
566 | initializer is only called when a value is provided to the |
567 | constructor. The initializer allows you to munge this value during |
568 | object construction. |
569 | |
570 | The initializer is called as a method with three arguments. The first |
571 | is the value that was passed to the constructor. The second is a |
572 | subroutine reference that can be called to actually set the |
573 | attribute's value, and the last is the associated |
574 | C<Class::MOP::Attribute> object. |
575 | |
576 | This contrived example shows an initializer that sets the attribute to |
577 | twice the given value. |
578 | |
579 | Class::MOP::Attribute->new( |
580 | 'doubled' => ( |
581 | initializer => sub { |
ea62c8ab |
582 | my ( $self, $value, $set, $attr ) = @_; |
2e23f7dc |
583 | $set->( $value * 2 ); |
584 | }, |
585 | ) |
586 | ); |
587 | |
588 | Since an initializer can be a method name, you can easily make |
0ef07b33 |
589 | attribute initialization use the writer: |
590 | |
2e23f7dc |
591 | Class::MOP::Attribute->new( |
592 | 'some_attr' => ( |
593 | writer => 'some_attr', |
594 | initializer => 'some_attr', |
595 | ) |
596 | ); |
0ef07b33 |
597 | |
2e23f7dc |
598 | Your writer will need to examine C<@_> and determine under which |
599 | context it is being called. |
127d39a7 |
600 | |
fe122940 |
601 | =back |
602 | |
2e23f7dc |
603 | The C<accessor>, C<reader>, C<writer>, C<predicate> and C<clearer> |
604 | options all accept the same parameters. You can provide the name of |
605 | the method, in which case an appropriate default method will be |
606 | generated for you. Or instead you can also provide hash reference |
607 | containing exactly one key (the method name) and one value. The value |
608 | should be a subroutine reference, which will be installed as the |
609 | method itself. |
59e7697f |
610 | |
76187047 |
611 | =over 8 |
59e7697f |
612 | |
76187047 |
613 | =item * accessor |
59e7697f |
614 | |
2e23f7dc |
615 | An C<accessor> is a standard Perl-style read/write accessor. It will |
616 | return the value of the attribute, and if a value is passed as an |
617 | argument, it will assign that value to the attribute. |
fe122940 |
618 | |
2e23f7dc |
619 | Note that C<undef> is a legitimate value, so this will work: |
fe122940 |
620 | |
621 | $object->set_something(undef); |
622 | |
76187047 |
623 | =item * reader |
59e7697f |
624 | |
2e23f7dc |
625 | This is a basic read-only accessor. It returns the value of the |
626 | attribute. |
fe122940 |
627 | |
76187047 |
628 | =item * writer |
59e7697f |
629 | |
1d68af04 |
630 | This is a basic write accessor, it accepts a single argument, and |
2e23f7dc |
631 | assigns that value to the attribute. |
59e7697f |
632 | |
2e23f7dc |
633 | Note that C<undef> is a legitimate value, so this will work: |
59e7697f |
634 | |
2e23f7dc |
635 | $object->set_something(undef); |
fe122940 |
636 | |
76187047 |
637 | =item * predicate |
fe122940 |
638 | |
2e23f7dc |
639 | The predicate method returns a boolean indicating whether or not the |
640 | attribute has been explicitly set. |
07dca7e3 |
641 | |
2e23f7dc |
642 | Note that the predicate returns true even if the attribute was set to |
643 | a false value (C<0> or C<undef>). |
07dca7e3 |
644 | |
76187047 |
645 | =item * clearer |
7d28758b |
646 | |
2e23f7dc |
647 | This method will uninitialize the attribute. After an attribute is |
648 | cleared, its C<predicate> will return false. |
7d28758b |
649 | |
76187047 |
650 | =item * definition_context |
f8813817 |
651 | |
652 | Mostly, this exists as a hook for the benefit of Moose. |
653 | |
654 | This option should be a hash reference containing several keys which |
655 | will be used when inlining the attribute's accessors. The keys should |
656 | include C<line>, the line number where the attribute was created, and |
657 | either C<file> or C<description>. |
658 | |
659 | This information will ultimately be used when eval'ing inlined |
660 | accessor code so that error messages report a useful line and file |
661 | name. |
662 | |
59e7697f |
663 | =back |
552e3d24 |
664 | |
2e23f7dc |
665 | =item B<< $attr->clone(%options) >> |
bd4e03f9 |
666 | |
2e23f7dc |
667 | This clones the attribute. Any options you provide will override the |
668 | settings of the original attribute. You can change the name of the new |
669 | attribute by passing a C<name> key in C<%options>. |
127d39a7 |
670 | |
2e23f7dc |
671 | =back |
bd4e03f9 |
672 | |
2e23f7dc |
673 | =head2 Informational |
127d39a7 |
674 | |
2e23f7dc |
675 | These are all basic read-only accessors for the values passed into |
676 | the constructor. |
552e3d24 |
677 | |
2e23f7dc |
678 | =over 4 |
16e960bd |
679 | |
2e23f7dc |
680 | =item B<< $attr->name >> |
2367814a |
681 | |
76187047 |
682 | Returns the attribute's name. |
683 | |
2e23f7dc |
684 | =item B<< $attr->accessor >> |
2367814a |
685 | |
2e23f7dc |
686 | =item B<< $attr->reader >> |
16e960bd |
687 | |
2e23f7dc |
688 | =item B<< $attr->writer >> |
16e960bd |
689 | |
2e23f7dc |
690 | =item B<< $attr->predicate >> |
16e960bd |
691 | |
2e23f7dc |
692 | =item B<< $attr->clearer >> |
c0921932 |
693 | |
2e23f7dc |
694 | The C<accessor>, C<reader>, C<writer>, C<predicate>, and C<clearer> |
695 | methods all return exactly what was passed to the constructor, so it |
a6710c60 |
696 | can be either a string containing a method name, or a hash reference. |
c0921932 |
697 | |
2e23f7dc |
698 | =item B<< $attr->initializer >> |
16e960bd |
699 | |
a6710c60 |
700 | Returns the initializer as passed to the constructor, so this may be |
2e23f7dc |
701 | either a method name or a subroutine reference. |
16e960bd |
702 | |
2e23f7dc |
703 | =item B<< $attr->init_arg >> |
3545c727 |
704 | |
2e23f7dc |
705 | =item B<< $attr->is_default_a_coderef >> |
2367814a |
706 | |
2e23f7dc |
707 | =item B<< $attr->default($instance) >> |
3545c727 |
708 | |
2e23f7dc |
709 | The C<$instance> argument is optional. If you don't pass it, the |
710 | return value for this method is exactly what was passed to the |
711 | constructor, either a simple scalar or a subroutine reference. |
2367814a |
712 | |
2e23f7dc |
713 | If you I<do> pass an C<$instance> and the default is a subroutine |
714 | reference, then the reference is called as a method on the |
715 | C<$instance> and the generated value is returned. |
16e960bd |
716 | |
2e23f7dc |
717 | =item B<< $attr->slots >> |
552e3d24 |
718 | |
2e23f7dc |
719 | Return a list of slots required by the attribute. This is usually just |
720 | one, the name of the attribute. |
fe122940 |
721 | |
2e23f7dc |
722 | A slot is the name of the hash key used to store the attribute in an |
723 | object instance. |
552e3d24 |
724 | |
2e23f7dc |
725 | =item B<< $attr->get_read_method >> |
552e3d24 |
726 | |
2e23f7dc |
727 | =item B<< $attr->get_write_method >> |
552e3d24 |
728 | |
2e23f7dc |
729 | Returns the name of a method suitable for reading or writing the value |
730 | of the attribute in the associated class. |
552e3d24 |
731 | |
2e23f7dc |
732 | If an attribute is read- or write-only, then these methods can return |
733 | C<undef> as appropriate. |
552e3d24 |
734 | |
2e23f7dc |
735 | =item B<< $attr->has_read_method >> |
c50c603e |
736 | |
2e23f7dc |
737 | =item B<< $attr->has_write_method >> |
7d28758b |
738 | |
2e23f7dc |
739 | This returns a boolean indicating whether the attribute has a I<named> |
740 | read or write method. |
0ab65f99 |
741 | |
2e23f7dc |
742 | =item B<< $attr->get_read_method_ref >> |
552e3d24 |
743 | |
2e23f7dc |
744 | =item B<< $attr->get_write_method_ref >> |
495af518 |
745 | |
2e23f7dc |
746 | Returns the subroutine reference of a method suitable for reading or |
747 | writing the attribute's value in the associated class. These methods |
748 | always return a subroutine reference, regardless of whether or not the |
749 | attribute is read- or write-only. |
750 | |
eeff7496 |
751 | =item B<< $attr->insertion_order >> |
752 | |
753 | If this attribute has been inserted into a class, this returns a zero |
754 | based index regarding the order of insertion. |
755 | |
2e23f7dc |
756 | =back |
fe122940 |
757 | |
2e23f7dc |
758 | =head2 Informational predicates |
92d2abfa |
759 | |
2e23f7dc |
760 | These are all basic predicate methods for the values passed into C<new>. |
552e3d24 |
761 | |
2e23f7dc |
762 | =over 4 |
c57c8b10 |
763 | |
2e23f7dc |
764 | =item B<< $attr->has_accessor >> |
c57c8b10 |
765 | |
2e23f7dc |
766 | =item B<< $attr->has_reader >> |
b25109b1 |
767 | |
2e23f7dc |
768 | =item B<< $attr->has_writer >> |
b25109b1 |
769 | |
2e23f7dc |
770 | =item B<< $attr->has_predicate >> |
5da16d1b |
771 | |
2e23f7dc |
772 | =item B<< $attr->has_clearer >> |
5da16d1b |
773 | |
2e23f7dc |
774 | =item B<< $attr->has_initializer >> |
5da16d1b |
775 | |
2e23f7dc |
776 | =item B<< $attr->has_init_arg >> |
5da16d1b |
777 | |
2e23f7dc |
778 | This will be I<false> if the C<init_arg> was set to C<undef>. |
b25109b1 |
779 | |
2e23f7dc |
780 | =item B<< $attr->has_default >> |
9e517e01 |
781 | |
2e23f7dc |
782 | This will be I<false> if the C<default> was set to C<undef>, since |
783 | C<undef> is the default C<default> anyway. |
9e517e01 |
784 | |
2e23f7dc |
785 | =item B<< $attr->has_builder >> |
9e517e01 |
786 | |
eeff7496 |
787 | =item B<< $attr->has_insertion_order >> |
788 | |
789 | This will be I<false> if this attribute has not be inserted into a class |
790 | |
552e3d24 |
791 | =back |
792 | |
2e23f7dc |
793 | =head2 Value management |
552e3d24 |
794 | |
a6710c60 |
795 | These methods are basically "back doors" to the instance, and can be |
2e23f7dc |
796 | used to bypass the regular accessors, but still stay within the MOP. |
797 | |
798 | These methods are not for general use, and should only be used if you |
799 | really know what you are doing. |
fe122940 |
800 | |
552e3d24 |
801 | =over 4 |
802 | |
2e23f7dc |
803 | =item B<< $attr->initialize_instance_slot($meta_instance, $instance, $params) >> |
804 | |
805 | This method is used internally to initialize the attribute's slot in |
806 | the object C<$instance>. |
807 | |
808 | The C<$params> is a hash reference of the values passed to the object |
809 | constructor. |
810 | |
811 | It's unlikely that you'll need to call this method yourself. |
552e3d24 |
812 | |
2e23f7dc |
813 | =item B<< $attr->set_value($instance, $value) >> |
552e3d24 |
814 | |
2e23f7dc |
815 | Sets the value without going through the accessor. Note that this |
816 | works even with read-only attributes. |
552e3d24 |
817 | |
7e5efe15 |
818 | =item B<< $attr->set_raw_value($instance, $value) >> |
819 | |
820 | Sets the value with no side effects such as a trigger. |
821 | |
822 | This doesn't actually apply to Class::MOP attributes, only to subclasses. |
823 | |
2e23f7dc |
824 | =item B<< $attr->set_initial_value($instance, $value) >> |
c50c603e |
825 | |
2e23f7dc |
826 | Sets the value without going through the accessor. This method is only |
827 | called when the instance is first being initialized. |
7d28758b |
828 | |
2e23f7dc |
829 | =item B<< $attr->get_value($instance) >> |
0ab65f99 |
830 | |
2e23f7dc |
831 | Returns the value without going through the accessor. Note that this |
832 | works even with write-only accessors. |
552e3d24 |
833 | |
25b3fdad |
834 | =item B<< $attr->get_raw_value($instance) >> |
7e5efe15 |
835 | |
836 | Returns the value without any side effects such as lazy attributes. |
837 | |
838 | Doesn't actually apply to Class::MOP attributes, only to subclasses. |
839 | |
2e23f7dc |
840 | =item B<< $attr->has_value($instance) >> |
552e3d24 |
841 | |
2e23f7dc |
842 | Return a boolean indicating whether the attribute has been set in |
843 | C<$instance>. This how the default C<predicate> method works. |
844 | |
845 | =item B<< $attr->clear_value($instance) >> |
846 | |
847 | This will clear the attribute's value in C<$instance>. This is what |
848 | the default C<clearer> calls. |
849 | |
850 | Note that this works even if the attribute does not have any |
851 | associated read, write or clear methods. |
bf731086 |
852 | |
552e3d24 |
853 | =back |
854 | |
9ec169fe |
855 | =head2 Class association |
856 | |
1d68af04 |
857 | These methods allow you to manage the attributes association with |
858 | the class that contains it. These methods should not be used |
2367814a |
859 | lightly, nor are they very magical, they are mostly used internally |
860 | and by metaclass instances. |
861 | |
9ec169fe |
862 | =over 4 |
863 | |
2e23f7dc |
864 | =item B<< $attr->associated_class >> |
865 | |
866 | This returns the C<Class::MOP::Class> with which this attribute is |
867 | associated, if any. |
868 | |
869 | =item B<< $attr->attach_to_class($metaclass) >> |
9ec169fe |
870 | |
2e23f7dc |
871 | This method stores a weakened reference to the C<$metaclass> object |
872 | internally. |
2367814a |
873 | |
2e23f7dc |
874 | This method does not remove the attribute from its old class, |
875 | nor does it create any accessors in the new class. |
9ec169fe |
876 | |
2e23f7dc |
877 | It is probably best to use the L<Class::MOP::Class> C<add_attribute> |
878 | method instead. |
2367814a |
879 | |
2e23f7dc |
880 | =item B<< $attr->detach_from_class >> |
9ec169fe |
881 | |
2e23f7dc |
882 | This method removes the associate metaclass object from the attribute |
883 | it has one. |
884 | |
885 | This method does not remove the attribute itself from the class, or |
886 | remove its accessors. |
887 | |
888 | It is probably best to use the L<Class::MOP::Class> |
889 | C<remove_attribute> method instead. |
2367814a |
890 | |
9ec169fe |
891 | =back |
892 | |
552e3d24 |
893 | =head2 Attribute Accessor generation |
894 | |
895 | =over 4 |
896 | |
2e23f7dc |
897 | =item B<< $attr->accessor_metaclass >> |
ba38bf08 |
898 | |
2e23f7dc |
899 | Accessor methods are generated using an accessor metaclass. By |
900 | default, this is L<Class::MOP::Method::Accessor>. This method returns |
2367814a |
901 | the name of the accessor metaclass that this attribute uses. |
902 | |
2e23f7dc |
903 | =item B<< $attr->associate_method($method) >> |
2367814a |
904 | |
2e23f7dc |
905 | This associates a L<Class::MOP::Method> object with the |
906 | attribute. Typically, this is called internally when an attribute |
907 | generates its accessors. |
3545c727 |
908 | |
2e23f7dc |
909 | =item B<< $attr->associated_methods >> |
3545c727 |
910 | |
2e23f7dc |
911 | This returns the list of methods which have been associated with the |
912 | attribute. |
2367814a |
913 | |
2e23f7dc |
914 | =item B<< $attr->install_accessors >> |
2eb717d5 |
915 | |
2e23f7dc |
916 | This method generates and installs code the attributes various |
917 | accessors. It is typically called from the L<Class::MOP::Class> |
918 | C<add_attribute> method. |
2eb717d5 |
919 | |
2e23f7dc |
920 | =item B<< $attr->remove_accessors >> |
2eb717d5 |
921 | |
2e23f7dc |
922 | This method removes all of the accessors associated with the |
923 | attribute. |
2eb717d5 |
924 | |
2e23f7dc |
925 | This does not currently remove methods from the list returned by |
926 | C<associated_methods>. |
2367814a |
927 | |
03a3092d |
928 | =item B<< $attr->inline_get >> |
929 | |
930 | =item B<< $attr->inline_set >> |
931 | |
932 | =item B<< $attr->inline_has >> |
933 | |
934 | =item B<< $attr->inline_clear >> |
935 | |
936 | These methods return a code snippet suitable for inlining the relevant |
937 | operation. They expect strings containing variable names to be used in the |
938 | inlining, like C<'$self'> or C<'$_[1]'>. |
939 | |
2eb717d5 |
940 | =back |
941 | |
942 | =head2 Introspection |
943 | |
944 | =over 4 |
552e3d24 |
945 | |
45b4c423 |
946 | =item B<< Class::MOP::Attribute->meta >> |
552e3d24 |
947 | |
2e23f7dc |
948 | This will return a L<Class::MOP::Class> instance for this class. |
fe122940 |
949 | |
2e23f7dc |
950 | It should also be noted that L<Class::MOP> will actually bootstrap |
951 | this module by installing a number of attribute meta-objects into its |
952 | metaclass. |
fe122940 |
953 | |
552e3d24 |
954 | =back |
955 | |
1a09d9cc |
956 | =head1 AUTHORS |
8b978dd5 |
957 | |
a2e85e6c |
958 | Stevan Little E<lt>stevan@iinteractive.comE<gt> |
8b978dd5 |
959 | |
960 | =head1 COPYRIGHT AND LICENSE |
961 | |
3e2c8600 |
962 | Copyright 2006-2010 by Infinity Interactive, Inc. |
8b978dd5 |
963 | |
964 | L<http://www.iinteractive.com> |
965 | |
966 | This library is free software; you can redistribute it and/or modify |
1d68af04 |
967 | it under the same terms as Perl itself. |
8b978dd5 |
968 | |
16e960bd |
969 | =cut |
970 | |
7d28758b |
971 | |