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 | |
6f88e1d0 |
13 | our $VERSION = '1.01'; |
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}, |
76 | 'default' => $options->{default}, |
77 | 'initializer' => $options->{initializer}, |
78 | 'definition_context' => $options->{definition_context}, |
1d68af04 |
79 | # keep a weakened link to the |
9ec169fe |
80 | # class we are associated with |
8683db0e |
81 | 'associated_class' => undef, |
1d68af04 |
82 | # and a list of the methods |
3545c727 |
83 | # associated with this attr |
8683db0e |
84 | 'associated_methods' => [], |
dc9d420c |
85 | # this let's us keep track of |
86 | # our order inside the associated |
87 | # class |
88 | 'insertion_order' => undef, |
0bfc85b8 |
89 | }, $class; |
8b978dd5 |
90 | } |
91 | |
7b31baf4 |
92 | # NOTE: |
1d68af04 |
93 | # this is a primative (and kludgy) clone operation |
16e960bd |
94 | # for now, it will be replaced in the Class::MOP |
1d68af04 |
95 | # bootstrap with a proper one, however we know |
5659d76e |
96 | # that this one will work fine for now. |
97 | sub clone { |
98 | my $self = shift; |
99 | my %options = @_; |
100 | (blessed($self)) |
101 | || confess "Can only clone an instance"; |
b3fa93c7 |
102 | return bless { %{$self}, %options } => ref($self); |
5659d76e |
103 | } |
104 | |
bd4e03f9 |
105 | sub initialize_instance_slot { |
f892c0f0 |
106 | my ($self, $meta_instance, $instance, $params) = @_; |
8683db0e |
107 | my $init_arg = $self->{'init_arg'}; |
108 | |
bd4e03f9 |
109 | # try to fetch the init arg from the %params ... |
8d2d4c67 |
110 | |
1d68af04 |
111 | # if nothing was in the %params, we can use the |
bd4e03f9 |
112 | # attribute's default value (if it has one) |
2e877f58 |
113 | if(defined $init_arg and exists $params->{$init_arg}){ |
8ee74136 |
114 | $self->_set_initial_slot_value( |
115 | $meta_instance, |
0ab65f99 |
116 | $instance, |
0ab65f99 |
117 | $params->{$init_arg}, |
0ab65f99 |
118 | ); |
b7bdffc3 |
119 | } |
8683db0e |
120 | elsif (defined $self->{'default'}) { |
8ee74136 |
121 | $self->_set_initial_slot_value( |
122 | $meta_instance, |
0ab65f99 |
123 | $instance, |
0ab65f99 |
124 | $self->default($instance), |
0ab65f99 |
125 | ); |
b7bdffc3 |
126 | } |
8683db0e |
127 | elsif (defined( my $builder = $self->{'builder'})) { |
b7bdffc3 |
128 | if ($builder = $instance->can($builder)) { |
8ee74136 |
129 | $self->_set_initial_slot_value( |
130 | $meta_instance, |
0ab65f99 |
131 | $instance, |
0ab65f99 |
132 | $instance->$builder, |
0ab65f99 |
133 | ); |
b7bdffc3 |
134 | } |
135 | else { |
b3fa93c7 |
136 | confess(ref($instance)." does not support builder method '". $self->{'builder'} ."' for attribute '" . $self->name . "'"); |
8fe581e5 |
137 | } |
1d68af04 |
138 | } |
bd4e03f9 |
139 | } |
140 | |
8ee74136 |
141 | sub _set_initial_slot_value { |
142 | my ($self, $meta_instance, $instance, $value) = @_; |
143 | |
144 | my $slot_name = $self->name; |
145 | |
146 | return $meta_instance->set_slot_value($instance, $slot_name, $value) |
147 | unless $self->has_initializer; |
148 | |
149 | my $callback = sub { |
150 | $meta_instance->set_slot_value($instance, $slot_name, $_[0]); |
151 | }; |
152 | |
153 | my $initializer = $self->initializer; |
154 | |
155 | # most things will just want to set a value, so make it first arg |
156 | $instance->$initializer($value, $callback, $self); |
157 | } |
158 | |
8683db0e |
159 | sub associated_class { $_[0]->{'associated_class'} } |
160 | sub associated_methods { $_[0]->{'associated_methods'} } |
161 | |
d14f6cbe |
162 | sub get_read_method { |
163 | my $self = shift; |
164 | my $reader = $self->reader || $self->accessor; |
165 | # normal case ... |
166 | return $reader unless ref $reader; |
167 | # the HASH ref case |
168 | my ($name) = %$reader; |
169 | return $name; |
170 | } |
171 | |
172 | sub get_write_method { |
173 | my $self = shift; |
174 | my $writer = $self->writer || $self->accessor; |
175 | # normal case ... |
176 | return $writer unless ref $writer; |
177 | # the HASH ref case |
178 | my ($name) = %$writer; |
179 | return $name; |
180 | } |
b25109b1 |
181 | |
5da16d1b |
182 | sub get_read_method_ref { |
183 | my $self = shift; |
742fb371 |
184 | if ((my $reader = $self->get_read_method) && $self->associated_class) { |
5da16d1b |
185 | return $self->associated_class->get_method($reader); |
186 | } |
187 | else { |
def5c0b5 |
188 | my $code = sub { $self->get_value(@_) }; |
189 | if (my $class = $self->associated_class) { |
190 | return $class->method_metaclass->wrap( |
191 | $code, |
192 | package_name => $class->name, |
193 | name => '__ANON__' |
194 | ); |
195 | } |
196 | else { |
197 | return $code; |
198 | } |
5da16d1b |
199 | } |
200 | } |
201 | |
202 | sub get_write_method_ref { |
203 | my $self = shift; |
d14f6cbe |
204 | if ((my $writer = $self->get_write_method) && $self->associated_class) { |
742fb371 |
205 | return $self->associated_class->get_method($writer); |
5da16d1b |
206 | } |
207 | else { |
def5c0b5 |
208 | my $code = sub { $self->set_value(@_) }; |
209 | if (my $class = $self->associated_class) { |
210 | return $class->method_metaclass->wrap( |
211 | $code, |
212 | package_name => $class->name, |
213 | name => '__ANON__' |
214 | ); |
215 | } |
216 | else { |
217 | return $code; |
218 | } |
5da16d1b |
219 | } |
220 | } |
221 | |
c57c8b10 |
222 | # slots |
223 | |
224 | sub slots { (shift)->name } |
225 | |
1d68af04 |
226 | # class association |
727919c5 |
227 | |
9ec169fe |
228 | sub attach_to_class { |
229 | my ($self, $class) = @_; |
230 | (blessed($class) && $class->isa('Class::MOP::Class')) |
231 | || confess "You must pass a Class::MOP::Class instance (or a subclass)"; |
8683db0e |
232 | weaken($self->{'associated_class'} = $class); |
9ec169fe |
233 | } |
234 | |
235 | sub detach_from_class { |
236 | my $self = shift; |
8683db0e |
237 | $self->{'associated_class'} = undef; |
9ec169fe |
238 | } |
239 | |
1d68af04 |
240 | # method association |
3545c727 |
241 | |
242 | sub associate_method { |
243 | my ($self, $method) = @_; |
8683db0e |
244 | push @{$self->{'associated_methods'}} => $method; |
3545c727 |
245 | } |
246 | |
16e960bd |
247 | ## Slot management |
248 | |
ef91a0e2 |
249 | sub set_initial_value { |
250 | my ($self, $instance, $value) = @_; |
e76b01fb |
251 | $self->_set_initial_slot_value( |
b3fa93c7 |
252 | Class::MOP::Class->initialize(ref($instance))->get_meta_instance, |
8ee74136 |
253 | $instance, |
254 | $value |
255 | ); |
ef91a0e2 |
256 | } |
257 | |
7e5efe15 |
258 | sub set_value { shift->set_raw_value(@_) } |
259 | sub get_value { shift->get_raw_value(@_) } |
260 | |
261 | sub set_raw_value { |
1396f86b |
262 | my ($self, $instance, $value) = @_; |
16e960bd |
263 | |
b3fa93c7 |
264 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
265 | ->get_meta_instance |
266 | ->set_slot_value($instance, $self->name, $value); |
16e960bd |
267 | } |
268 | |
7e5efe15 |
269 | sub get_raw_value { |
1396f86b |
270 | my ($self, $instance) = @_; |
16e960bd |
271 | |
b3fa93c7 |
272 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
273 | ->get_meta_instance |
274 | ->get_slot_value($instance, $self->name); |
16e960bd |
275 | } |
276 | |
3545c727 |
277 | sub has_value { |
278 | my ($self, $instance) = @_; |
1d68af04 |
279 | |
b3fa93c7 |
280 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
281 | ->get_meta_instance |
282 | ->is_slot_initialized($instance, $self->name); |
3545c727 |
283 | } |
284 | |
285 | sub clear_value { |
286 | my ($self, $instance) = @_; |
1d68af04 |
287 | |
b3fa93c7 |
288 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
289 | ->get_meta_instance |
290 | ->deinitialize_slot($instance, $self->name); |
3545c727 |
291 | } |
292 | |
ba38bf08 |
293 | ## load em up ... |
c0cbf4d9 |
294 | |
ba38bf08 |
295 | sub accessor_metaclass { 'Class::MOP::Method::Accessor' } |
c0cbf4d9 |
296 | |
45a183fb |
297 | sub _process_accessors { |
c0cbf4d9 |
298 | my ($self, $type, $accessor, $generate_as_inline_methods) = @_; |
d9d99689 |
299 | |
300 | my $method_ctx; |
301 | |
302 | if ( my $ctx = $self->definition_context ) { |
303 | $method_ctx = { %$ctx }; |
304 | } |
305 | |
9b522fc4 |
306 | if (ref($accessor)) { |
307 | (ref($accessor) eq 'HASH') |
7d28758b |
308 | || confess "bad accessor/reader/writer/predicate/clearer format, must be a HASH ref"; |
4d47b77f |
309 | my ($name, $method) = %{$accessor}; |
4c105333 |
310 | $method = $self->accessor_metaclass->wrap( |
311 | $method, |
312 | package_name => $self->associated_class->name, |
313 | name => $name, |
d9d99689 |
314 | definition_context => $method_ctx, |
4c105333 |
315 | ); |
3545c727 |
316 | $self->associate_method($method); |
1d68af04 |
317 | return ($name, $method); |
2eb717d5 |
318 | } |
9ec169fe |
319 | else { |
1d68af04 |
320 | my $inline_me = ($generate_as_inline_methods && $self->associated_class->instance_metaclass->is_inlinable); |
ba38bf08 |
321 | my $method; |
a8344505 |
322 | try { |
d9d99689 |
323 | if ( $method_ctx ) { |
324 | my $desc = "accessor $accessor"; |
325 | if ( $accessor ne $self->name ) { |
326 | $desc .= " of attribute " . $self->name; |
327 | } |
328 | |
329 | $method_ctx->{description} = $desc; |
330 | } |
331 | |
ba38bf08 |
332 | $method = $self->accessor_metaclass->new( |
333 | attribute => $self, |
d90b42a6 |
334 | is_inline => $inline_me, |
ba38bf08 |
335 | accessor_type => $type, |
4c105333 |
336 | package_name => $self->associated_class->name, |
337 | name => $accessor, |
d9d99689 |
338 | definition_context => $method_ctx, |
1d68af04 |
339 | ); |
a8344505 |
340 | } |
341 | catch { |
342 | confess "Could not create the '$type' method for " . $self->name . " because : $_"; |
ba38bf08 |
343 | }; |
3545c727 |
344 | $self->associate_method($method); |
ba38bf08 |
345 | return ($accessor, $method); |
1d68af04 |
346 | } |
9ec169fe |
347 | } |
348 | |
349 | sub install_accessors { |
c0cbf4d9 |
350 | my $self = shift; |
351 | my $inline = shift; |
352 | my $class = $self->associated_class; |
1d68af04 |
353 | |
9ec169fe |
354 | $class->add_method( |
45a183fb |
355 | $self->_process_accessors('accessor' => $self->accessor(), $inline) |
9ec169fe |
356 | ) if $self->has_accessor(); |
357 | |
1d68af04 |
358 | $class->add_method( |
45a183fb |
359 | $self->_process_accessors('reader' => $self->reader(), $inline) |
9ec169fe |
360 | ) if $self->has_reader(); |
361 | |
362 | $class->add_method( |
45a183fb |
363 | $self->_process_accessors('writer' => $self->writer(), $inline) |
9ec169fe |
364 | ) if $self->has_writer(); |
365 | |
366 | $class->add_method( |
45a183fb |
367 | $self->_process_accessors('predicate' => $self->predicate(), $inline) |
9ec169fe |
368 | ) if $self->has_predicate(); |
1d68af04 |
369 | |
7d28758b |
370 | $class->add_method( |
45a183fb |
371 | $self->_process_accessors('clearer' => $self->clearer(), $inline) |
7d28758b |
372 | ) if $self->has_clearer(); |
1d68af04 |
373 | |
9ec169fe |
374 | return; |
2eb717d5 |
375 | } |
376 | |
b51af7f9 |
377 | { |
378 | my $_remove_accessor = sub { |
379 | my ($accessor, $class) = @_; |
9b522fc4 |
380 | if (ref($accessor) && ref($accessor) eq 'HASH') { |
c50c603e |
381 | ($accessor) = keys %{$accessor}; |
1d68af04 |
382 | } |
383 | my $method = $class->get_method($accessor); |
384 | $class->remove_method($accessor) |
b3fa93c7 |
385 | if (ref($method) && $method->isa('Class::MOP::Method::Accessor')); |
b51af7f9 |
386 | }; |
1d68af04 |
387 | |
b51af7f9 |
388 | sub remove_accessors { |
9ec169fe |
389 | my $self = shift; |
2367814a |
390 | # TODO: |
1d68af04 |
391 | # we really need to make sure to remove from the |
392 | # associates methods here as well. But this is |
393 | # such a slimly used method, I am not worried |
2367814a |
394 | # about it right now. |
9ec169fe |
395 | $_remove_accessor->($self->accessor(), $self->associated_class()) if $self->has_accessor(); |
396 | $_remove_accessor->($self->reader(), $self->associated_class()) if $self->has_reader(); |
397 | $_remove_accessor->($self->writer(), $self->associated_class()) if $self->has_writer(); |
398 | $_remove_accessor->($self->predicate(), $self->associated_class()) if $self->has_predicate(); |
7d28758b |
399 | $_remove_accessor->($self->clearer(), $self->associated_class()) if $self->has_clearer(); |
1d68af04 |
400 | return; |
b51af7f9 |
401 | } |
402 | |
8b978dd5 |
403 | } |
404 | |
405 | 1; |
406 | |
407 | __END__ |
408 | |
409 | =pod |
410 | |
1d68af04 |
411 | =head1 NAME |
8b978dd5 |
412 | |
413 | Class::MOP::Attribute - Attribute Meta Object |
414 | |
415 | =head1 SYNOPSIS |
1d68af04 |
416 | |
2e23f7dc |
417 | Class::MOP::Attribute->new( |
418 | foo => ( |
419 | accessor => 'foo', # dual purpose get/set accessor |
420 | predicate => 'has_foo', # predicate check for defined-ness |
421 | init_arg => '-foo', # class->new will look for a -foo key |
422 | default => 'BAR IS BAZ!' # if no -foo key is provided, use this |
423 | ) |
424 | ); |
425 | |
426 | Class::MOP::Attribute->new( |
427 | bar => ( |
428 | reader => 'bar', # getter |
429 | writer => 'set_bar', # setter |
430 | predicate => 'has_bar', # predicate check for defined-ness |
431 | init_arg => ':bar', # class->new will look for a :bar key |
432 | # no default value means it is undef |
433 | ) |
434 | ); |
8b978dd5 |
435 | |
436 | =head1 DESCRIPTION |
437 | |
2e23f7dc |
438 | The Attribute Protocol is almost entirely an invention of |
439 | C<Class::MOP>. Perl 5 does not have a consistent notion of |
440 | attributes. There are so many ways in which this is done, and very few |
441 | (if any) are easily discoverable by this module. |
552e3d24 |
442 | |
2e23f7dc |
443 | With that said, this module attempts to inject some order into this |
1d68af04 |
444 | chaos, by introducing a consistent API which can be used to create |
fe122940 |
445 | object attributes. |
552e3d24 |
446 | |
447 | =head1 METHODS |
448 | |
449 | =head2 Creation |
450 | |
451 | =over 4 |
452 | |
2e23f7dc |
453 | =item B<< Class::MOP::Attribute->new($name, ?%options) >> |
fe122940 |
454 | |
1d68af04 |
455 | An attribute must (at the very least), have a C<$name>. All other |
2e23f7dc |
456 | C<%options> are added as key-value pairs. |
fe122940 |
457 | |
2e23f7dc |
458 | =over 8 |
fe122940 |
459 | |
76187047 |
460 | =item * init_arg |
fe122940 |
461 | |
2e23f7dc |
462 | This is a string value representing the expected key in an |
463 | initialization hash. For instance, if we have an C<init_arg> value of |
464 | C<-foo>, then the following code will Just Work. |
fe122940 |
465 | |
d69fb6b3 |
466 | MyClass->meta->new_object( -foo => 'Hello There' ); |
fe122940 |
467 | |
2e23f7dc |
468 | If an init_arg is not assigned, it will automatically use the |
469 | attribute's name. If C<init_arg> is explicitly set to C<undef>, the |
470 | attribute cannot be specified during initialization. |
7b31baf4 |
471 | |
76187047 |
472 | =item * builder |
1d68af04 |
473 | |
2e23f7dc |
474 | This provides the name of a method that will be called to initialize |
475 | the attribute. This method will be called on the object after it is |
476 | constructed. It is expected to return a valid value for the attribute. |
fe122940 |
477 | |
76187047 |
478 | =item * default |
4c4a6c41 |
479 | |
2e23f7dc |
480 | This can be used to provide an explicit default for initializing the |
481 | attribute. If the default you provide is a subroutine reference, then |
482 | this reference will be called I<as a method> on the object. |
4c4a6c41 |
483 | |
2e23f7dc |
484 | If the value is a simple scalar (string or number), then it can be |
485 | just passed as is. However, if you wish to initialize it with a HASH |
486 | or ARRAY ref, then you need to wrap that inside a subroutine |
487 | reference: |
fe122940 |
488 | |
2e23f7dc |
489 | Class::MOP::Attribute->new( |
490 | 'foo' => ( |
491 | default => sub { [] }, |
492 | ) |
493 | ); |
1d68af04 |
494 | |
495 | # or ... |
496 | |
2e23f7dc |
497 | Class::MOP::Attribute->new( |
498 | 'foo' => ( |
499 | default => sub { {} }, |
500 | ) |
501 | ); |
502 | |
503 | If you wish to initialize an attribute with a subroutine reference |
504 | itself, then you need to wrap that in a subroutine as well: |
505 | |
506 | Class::MOP::Attribute->new( |
507 | 'foo' => ( |
508 | default => sub { |
509 | sub { print "Hello World" } |
510 | }, |
511 | ) |
512 | ); |
513 | |
514 | And lastly, if the value of your attribute is dependent upon some |
515 | other aspect of the instance structure, then you can take advantage of |
516 | the fact that when the C<default> value is called as a method: |
517 | |
518 | Class::MOP::Attribute->new( |
519 | 'object_identity' => ( |
520 | default => sub { Scalar::Util::refaddr( $_[0] ) }, |
521 | ) |
522 | ); |
523 | |
524 | Note that there is no guarantee that attributes are initialized in any |
525 | particular order, so you cannot rely on the value of some other |
526 | attribute when generating the default. |
fe122940 |
527 | |
76187047 |
528 | =item * initializer |
0ef07b33 |
529 | |
2e23f7dc |
530 | This option can be either a method name or a subroutine |
531 | reference. This method will be called when setting the attribute's |
532 | value in the constructor. Unlike C<default> and C<builder>, the |
533 | initializer is only called when a value is provided to the |
534 | constructor. The initializer allows you to munge this value during |
535 | object construction. |
536 | |
537 | The initializer is called as a method with three arguments. The first |
538 | is the value that was passed to the constructor. The second is a |
539 | subroutine reference that can be called to actually set the |
540 | attribute's value, and the last is the associated |
541 | C<Class::MOP::Attribute> object. |
542 | |
543 | This contrived example shows an initializer that sets the attribute to |
544 | twice the given value. |
545 | |
546 | Class::MOP::Attribute->new( |
547 | 'doubled' => ( |
548 | initializer => sub { |
ea62c8ab |
549 | my ( $self, $value, $set, $attr ) = @_; |
2e23f7dc |
550 | $set->( $value * 2 ); |
551 | }, |
552 | ) |
553 | ); |
554 | |
555 | Since an initializer can be a method name, you can easily make |
0ef07b33 |
556 | attribute initialization use the writer: |
557 | |
2e23f7dc |
558 | Class::MOP::Attribute->new( |
559 | 'some_attr' => ( |
560 | writer => 'some_attr', |
561 | initializer => 'some_attr', |
562 | ) |
563 | ); |
0ef07b33 |
564 | |
2e23f7dc |
565 | Your writer will need to examine C<@_> and determine under which |
566 | context it is being called. |
127d39a7 |
567 | |
fe122940 |
568 | =back |
569 | |
2e23f7dc |
570 | The C<accessor>, C<reader>, C<writer>, C<predicate> and C<clearer> |
571 | options all accept the same parameters. You can provide the name of |
572 | the method, in which case an appropriate default method will be |
573 | generated for you. Or instead you can also provide hash reference |
574 | containing exactly one key (the method name) and one value. The value |
575 | should be a subroutine reference, which will be installed as the |
576 | method itself. |
59e7697f |
577 | |
76187047 |
578 | =over 8 |
59e7697f |
579 | |
76187047 |
580 | =item * accessor |
59e7697f |
581 | |
2e23f7dc |
582 | An C<accessor> is a standard Perl-style read/write accessor. It will |
583 | return the value of the attribute, and if a value is passed as an |
584 | argument, it will assign that value to the attribute. |
fe122940 |
585 | |
2e23f7dc |
586 | Note that C<undef> is a legitimate value, so this will work: |
fe122940 |
587 | |
588 | $object->set_something(undef); |
589 | |
76187047 |
590 | =item * reader |
59e7697f |
591 | |
2e23f7dc |
592 | This is a basic read-only accessor. It returns the value of the |
593 | attribute. |
fe122940 |
594 | |
76187047 |
595 | =item * writer |
59e7697f |
596 | |
1d68af04 |
597 | This is a basic write accessor, it accepts a single argument, and |
2e23f7dc |
598 | assigns that value to the attribute. |
59e7697f |
599 | |
2e23f7dc |
600 | Note that C<undef> is a legitimate value, so this will work: |
59e7697f |
601 | |
2e23f7dc |
602 | $object->set_something(undef); |
fe122940 |
603 | |
76187047 |
604 | =item * predicate |
fe122940 |
605 | |
2e23f7dc |
606 | The predicate method returns a boolean indicating whether or not the |
607 | attribute has been explicitly set. |
07dca7e3 |
608 | |
2e23f7dc |
609 | Note that the predicate returns true even if the attribute was set to |
610 | a false value (C<0> or C<undef>). |
07dca7e3 |
611 | |
76187047 |
612 | =item * clearer |
7d28758b |
613 | |
2e23f7dc |
614 | This method will uninitialize the attribute. After an attribute is |
615 | cleared, its C<predicate> will return false. |
7d28758b |
616 | |
76187047 |
617 | =item * definition_context |
f8813817 |
618 | |
619 | Mostly, this exists as a hook for the benefit of Moose. |
620 | |
621 | This option should be a hash reference containing several keys which |
622 | will be used when inlining the attribute's accessors. The keys should |
623 | include C<line>, the line number where the attribute was created, and |
624 | either C<file> or C<description>. |
625 | |
626 | This information will ultimately be used when eval'ing inlined |
627 | accessor code so that error messages report a useful line and file |
628 | name. |
629 | |
59e7697f |
630 | =back |
552e3d24 |
631 | |
2e23f7dc |
632 | =item B<< $attr->clone(%options) >> |
bd4e03f9 |
633 | |
2e23f7dc |
634 | This clones the attribute. Any options you provide will override the |
635 | settings of the original attribute. You can change the name of the new |
636 | attribute by passing a C<name> key in C<%options>. |
127d39a7 |
637 | |
2e23f7dc |
638 | =back |
bd4e03f9 |
639 | |
2e23f7dc |
640 | =head2 Informational |
127d39a7 |
641 | |
2e23f7dc |
642 | These are all basic read-only accessors for the values passed into |
643 | the constructor. |
552e3d24 |
644 | |
2e23f7dc |
645 | =over 4 |
16e960bd |
646 | |
2e23f7dc |
647 | =item B<< $attr->name >> |
2367814a |
648 | |
76187047 |
649 | Returns the attribute's name. |
650 | |
2e23f7dc |
651 | =item B<< $attr->accessor >> |
2367814a |
652 | |
2e23f7dc |
653 | =item B<< $attr->reader >> |
16e960bd |
654 | |
2e23f7dc |
655 | =item B<< $attr->writer >> |
16e960bd |
656 | |
2e23f7dc |
657 | =item B<< $attr->predicate >> |
16e960bd |
658 | |
2e23f7dc |
659 | =item B<< $attr->clearer >> |
c0921932 |
660 | |
2e23f7dc |
661 | The C<accessor>, C<reader>, C<writer>, C<predicate>, and C<clearer> |
662 | methods all return exactly what was passed to the constructor, so it |
a6710c60 |
663 | can be either a string containing a method name, or a hash reference. |
c0921932 |
664 | |
2e23f7dc |
665 | =item B<< $attr->initializer >> |
16e960bd |
666 | |
a6710c60 |
667 | Returns the initializer as passed to the constructor, so this may be |
2e23f7dc |
668 | either a method name or a subroutine reference. |
16e960bd |
669 | |
2e23f7dc |
670 | =item B<< $attr->init_arg >> |
3545c727 |
671 | |
2e23f7dc |
672 | =item B<< $attr->is_default_a_coderef >> |
2367814a |
673 | |
2e23f7dc |
674 | =item B<< $attr->default($instance) >> |
3545c727 |
675 | |
2e23f7dc |
676 | The C<$instance> argument is optional. If you don't pass it, the |
677 | return value for this method is exactly what was passed to the |
678 | constructor, either a simple scalar or a subroutine reference. |
2367814a |
679 | |
2e23f7dc |
680 | If you I<do> pass an C<$instance> and the default is a subroutine |
681 | reference, then the reference is called as a method on the |
682 | C<$instance> and the generated value is returned. |
16e960bd |
683 | |
2e23f7dc |
684 | =item B<< $attr->slots >> |
552e3d24 |
685 | |
2e23f7dc |
686 | Return a list of slots required by the attribute. This is usually just |
687 | one, the name of the attribute. |
fe122940 |
688 | |
2e23f7dc |
689 | A slot is the name of the hash key used to store the attribute in an |
690 | object instance. |
552e3d24 |
691 | |
2e23f7dc |
692 | =item B<< $attr->get_read_method >> |
552e3d24 |
693 | |
2e23f7dc |
694 | =item B<< $attr->get_write_method >> |
552e3d24 |
695 | |
2e23f7dc |
696 | Returns the name of a method suitable for reading or writing the value |
697 | of the attribute in the associated class. |
552e3d24 |
698 | |
2e23f7dc |
699 | If an attribute is read- or write-only, then these methods can return |
700 | C<undef> as appropriate. |
552e3d24 |
701 | |
2e23f7dc |
702 | =item B<< $attr->has_read_method >> |
c50c603e |
703 | |
2e23f7dc |
704 | =item B<< $attr->has_write_method >> |
7d28758b |
705 | |
2e23f7dc |
706 | This returns a boolean indicating whether the attribute has a I<named> |
707 | read or write method. |
0ab65f99 |
708 | |
2e23f7dc |
709 | =item B<< $attr->get_read_method_ref >> |
552e3d24 |
710 | |
2e23f7dc |
711 | =item B<< $attr->get_write_method_ref >> |
495af518 |
712 | |
2e23f7dc |
713 | Returns the subroutine reference of a method suitable for reading or |
714 | writing the attribute's value in the associated class. These methods |
715 | always return a subroutine reference, regardless of whether or not the |
716 | attribute is read- or write-only. |
717 | |
eeff7496 |
718 | =item B<< $attr->insertion_order >> |
719 | |
720 | If this attribute has been inserted into a class, this returns a zero |
721 | based index regarding the order of insertion. |
722 | |
2e23f7dc |
723 | =back |
fe122940 |
724 | |
2e23f7dc |
725 | =head2 Informational predicates |
92d2abfa |
726 | |
2e23f7dc |
727 | These are all basic predicate methods for the values passed into C<new>. |
552e3d24 |
728 | |
2e23f7dc |
729 | =over 4 |
c57c8b10 |
730 | |
2e23f7dc |
731 | =item B<< $attr->has_accessor >> |
c57c8b10 |
732 | |
2e23f7dc |
733 | =item B<< $attr->has_reader >> |
b25109b1 |
734 | |
2e23f7dc |
735 | =item B<< $attr->has_writer >> |
b25109b1 |
736 | |
2e23f7dc |
737 | =item B<< $attr->has_predicate >> |
5da16d1b |
738 | |
2e23f7dc |
739 | =item B<< $attr->has_clearer >> |
5da16d1b |
740 | |
2e23f7dc |
741 | =item B<< $attr->has_initializer >> |
5da16d1b |
742 | |
2e23f7dc |
743 | =item B<< $attr->has_init_arg >> |
5da16d1b |
744 | |
2e23f7dc |
745 | This will be I<false> if the C<init_arg> was set to C<undef>. |
b25109b1 |
746 | |
2e23f7dc |
747 | =item B<< $attr->has_default >> |
9e517e01 |
748 | |
2e23f7dc |
749 | This will be I<false> if the C<default> was set to C<undef>, since |
750 | C<undef> is the default C<default> anyway. |
9e517e01 |
751 | |
2e23f7dc |
752 | =item B<< $attr->has_builder >> |
9e517e01 |
753 | |
eeff7496 |
754 | =item B<< $attr->has_insertion_order >> |
755 | |
756 | This will be I<false> if this attribute has not be inserted into a class |
757 | |
552e3d24 |
758 | =back |
759 | |
2e23f7dc |
760 | =head2 Value management |
552e3d24 |
761 | |
a6710c60 |
762 | These methods are basically "back doors" to the instance, and can be |
2e23f7dc |
763 | used to bypass the regular accessors, but still stay within the MOP. |
764 | |
765 | These methods are not for general use, and should only be used if you |
766 | really know what you are doing. |
fe122940 |
767 | |
552e3d24 |
768 | =over 4 |
769 | |
2e23f7dc |
770 | =item B<< $attr->initialize_instance_slot($meta_instance, $instance, $params) >> |
771 | |
772 | This method is used internally to initialize the attribute's slot in |
773 | the object C<$instance>. |
774 | |
775 | The C<$params> is a hash reference of the values passed to the object |
776 | constructor. |
777 | |
778 | It's unlikely that you'll need to call this method yourself. |
552e3d24 |
779 | |
2e23f7dc |
780 | =item B<< $attr->set_value($instance, $value) >> |
552e3d24 |
781 | |
2e23f7dc |
782 | Sets the value without going through the accessor. Note that this |
783 | works even with read-only attributes. |
552e3d24 |
784 | |
7e5efe15 |
785 | =item B<< $attr->set_raw_value($instance, $value) >> |
786 | |
787 | Sets the value with no side effects such as a trigger. |
788 | |
789 | This doesn't actually apply to Class::MOP attributes, only to subclasses. |
790 | |
2e23f7dc |
791 | =item B<< $attr->set_initial_value($instance, $value) >> |
c50c603e |
792 | |
2e23f7dc |
793 | Sets the value without going through the accessor. This method is only |
794 | called when the instance is first being initialized. |
7d28758b |
795 | |
2e23f7dc |
796 | =item B<< $attr->get_value($instance) >> |
0ab65f99 |
797 | |
2e23f7dc |
798 | Returns the value without going through the accessor. Note that this |
799 | works even with write-only accessors. |
552e3d24 |
800 | |
25b3fdad |
801 | =item B<< $attr->get_raw_value($instance) >> |
7e5efe15 |
802 | |
803 | Returns the value without any side effects such as lazy attributes. |
804 | |
805 | Doesn't actually apply to Class::MOP attributes, only to subclasses. |
806 | |
2e23f7dc |
807 | =item B<< $attr->has_value($instance) >> |
552e3d24 |
808 | |
2e23f7dc |
809 | Return a boolean indicating whether the attribute has been set in |
810 | C<$instance>. This how the default C<predicate> method works. |
811 | |
812 | =item B<< $attr->clear_value($instance) >> |
813 | |
814 | This will clear the attribute's value in C<$instance>. This is what |
815 | the default C<clearer> calls. |
816 | |
817 | Note that this works even if the attribute does not have any |
818 | associated read, write or clear methods. |
bf731086 |
819 | |
552e3d24 |
820 | =back |
821 | |
9ec169fe |
822 | =head2 Class association |
823 | |
1d68af04 |
824 | These methods allow you to manage the attributes association with |
825 | the class that contains it. These methods should not be used |
2367814a |
826 | lightly, nor are they very magical, they are mostly used internally |
827 | and by metaclass instances. |
828 | |
9ec169fe |
829 | =over 4 |
830 | |
2e23f7dc |
831 | =item B<< $attr->associated_class >> |
832 | |
833 | This returns the C<Class::MOP::Class> with which this attribute is |
834 | associated, if any. |
835 | |
836 | =item B<< $attr->attach_to_class($metaclass) >> |
9ec169fe |
837 | |
2e23f7dc |
838 | This method stores a weakened reference to the C<$metaclass> object |
839 | internally. |
2367814a |
840 | |
2e23f7dc |
841 | This method does not remove the attribute from its old class, |
842 | nor does it create any accessors in the new class. |
9ec169fe |
843 | |
2e23f7dc |
844 | It is probably best to use the L<Class::MOP::Class> C<add_attribute> |
845 | method instead. |
2367814a |
846 | |
2e23f7dc |
847 | =item B<< $attr->detach_from_class >> |
9ec169fe |
848 | |
2e23f7dc |
849 | This method removes the associate metaclass object from the attribute |
850 | it has one. |
851 | |
852 | This method does not remove the attribute itself from the class, or |
853 | remove its accessors. |
854 | |
855 | It is probably best to use the L<Class::MOP::Class> |
856 | C<remove_attribute> method instead. |
2367814a |
857 | |
9ec169fe |
858 | =back |
859 | |
552e3d24 |
860 | =head2 Attribute Accessor generation |
861 | |
862 | =over 4 |
863 | |
2e23f7dc |
864 | =item B<< $attr->accessor_metaclass >> |
ba38bf08 |
865 | |
2e23f7dc |
866 | Accessor methods are generated using an accessor metaclass. By |
867 | default, this is L<Class::MOP::Method::Accessor>. This method returns |
2367814a |
868 | the name of the accessor metaclass that this attribute uses. |
869 | |
2e23f7dc |
870 | =item B<< $attr->associate_method($method) >> |
2367814a |
871 | |
2e23f7dc |
872 | This associates a L<Class::MOP::Method> object with the |
873 | attribute. Typically, this is called internally when an attribute |
874 | generates its accessors. |
3545c727 |
875 | |
2e23f7dc |
876 | =item B<< $attr->associated_methods >> |
3545c727 |
877 | |
2e23f7dc |
878 | This returns the list of methods which have been associated with the |
879 | attribute. |
2367814a |
880 | |
2e23f7dc |
881 | =item B<< $attr->install_accessors >> |
2eb717d5 |
882 | |
2e23f7dc |
883 | This method generates and installs code the attributes various |
884 | accessors. It is typically called from the L<Class::MOP::Class> |
885 | C<add_attribute> method. |
2eb717d5 |
886 | |
2e23f7dc |
887 | =item B<< $attr->remove_accessors >> |
2eb717d5 |
888 | |
2e23f7dc |
889 | This method removes all of the accessors associated with the |
890 | attribute. |
2eb717d5 |
891 | |
2e23f7dc |
892 | This does not currently remove methods from the list returned by |
893 | C<associated_methods>. |
2367814a |
894 | |
2eb717d5 |
895 | =back |
896 | |
897 | =head2 Introspection |
898 | |
899 | =over 4 |
552e3d24 |
900 | |
45b4c423 |
901 | =item B<< Class::MOP::Attribute->meta >> |
552e3d24 |
902 | |
2e23f7dc |
903 | This will return a L<Class::MOP::Class> instance for this class. |
fe122940 |
904 | |
2e23f7dc |
905 | It should also be noted that L<Class::MOP> will actually bootstrap |
906 | this module by installing a number of attribute meta-objects into its |
907 | metaclass. |
fe122940 |
908 | |
552e3d24 |
909 | =back |
910 | |
1a09d9cc |
911 | =head1 AUTHORS |
8b978dd5 |
912 | |
a2e85e6c |
913 | Stevan Little E<lt>stevan@iinteractive.comE<gt> |
8b978dd5 |
914 | |
915 | =head1 COPYRIGHT AND LICENSE |
916 | |
3e2c8600 |
917 | Copyright 2006-2010 by Infinity Interactive, Inc. |
8b978dd5 |
918 | |
919 | L<http://www.iinteractive.com> |
920 | |
921 | This library is free software; you can redistribute it and/or modify |
1d68af04 |
922 | it under the same terms as Perl itself. |
8b978dd5 |
923 | |
16e960bd |
924 | =cut |
925 | |
7d28758b |
926 | |