Commit | Line | Data |
8b978dd5 |
1 | |
2 | package Class::MOP::Attribute; |
3 | |
4 | use strict; |
5 | use warnings; |
6 | |
ba38bf08 |
7 | use Class::MOP::Method::Accessor; |
8 | |
2eb717d5 |
9 | use Carp 'confess'; |
9b522fc4 |
10 | use Scalar::Util 'blessed', 'weaken'; |
2eb717d5 |
11 | |
eca95e04 |
12 | our $VERSION = '0.78'; |
d519662a |
13 | $VERSION = eval $VERSION; |
f0480c45 |
14 | our $AUTHORITY = 'cpan:STEVAN'; |
8b978dd5 |
15 | |
b1897d4d |
16 | use base 'Class::MOP::Object'; |
17 | |
727919c5 |
18 | # NOTE: (meta-circularity) |
1d68af04 |
19 | # This method will be replaced in the |
20 | # boostrap section of Class::MOP, by |
21 | # a new version which uses the |
727919c5 |
22 | # &Class::MOP::Class::construct_instance |
23 | # method to build an attribute meta-object |
24 | # which itself is described with attribute |
1d68af04 |
25 | # meta-objects. |
727919c5 |
26 | # - Ain't meta-circularity grand? :) |
8b978dd5 |
27 | sub new { |
649efb63 |
28 | my ( $class, @args ) = @_; |
29 | |
30 | unshift @args, "name" if @args % 2 == 1; |
31 | my %options = @args; |
32 | |
33 | my $name = $options{name}; |
1d68af04 |
34 | |
cbd9f942 |
35 | (defined $name && $name) |
8b978dd5 |
36 | || confess "You must provide a name for the attribute"; |
1d68af04 |
37 | |
38 | $options{init_arg} = $name |
5659d76e |
39 | if not exists $options{init_arg}; |
1d68af04 |
40 | if(exists $options{builder}){ |
41 | confess("builder must be a defined scalar value which is a method name") |
42 | if ref $options{builder} || !(defined $options{builder}); |
43 | confess("Setting both default and builder is not allowed.") |
44 | if exists $options{default}; |
8fe581e5 |
45 | } else { |
46 | (is_default_a_coderef(\%options)) |
47 | || confess("References are not allowed as default values, you must ". |
3c0a8087 |
48 | "wrap the default of '$name' in a CODE reference (ex: sub { [] } and not [])") |
8fe581e5 |
49 | if exists $options{default} && ref $options{default}; |
1d68af04 |
50 | } |
2e877f58 |
51 | if( $options{required} and not( defined($options{builder}) || defined($options{init_arg}) || exists $options{default} ) ) { |
52 | confess("A required attribute must have either 'init_arg', 'builder', or 'default'"); |
53 | } |
8683db0e |
54 | |
cb75020f |
55 | $class->_new(\%options); |
4b698b1a |
56 | } |
57 | |
58 | sub _new { |
0bfc85b8 |
59 | my $class = shift; |
60 | my $options = @_ == 1 ? $_[0] : {@_}; |
4b698b1a |
61 | |
8b978dd5 |
62 | bless { |
d9d99689 |
63 | 'name' => $options->{name}, |
64 | 'accessor' => $options->{accessor}, |
65 | 'reader' => $options->{reader}, |
66 | 'writer' => $options->{writer}, |
67 | 'predicate' => $options->{predicate}, |
68 | 'clearer' => $options->{clearer}, |
69 | 'builder' => $options->{builder}, |
70 | 'init_arg' => $options->{init_arg}, |
71 | 'default' => $options->{default}, |
72 | 'initializer' => $options->{initializer}, |
73 | 'definition_context' => $options->{definition_context}, |
1d68af04 |
74 | # keep a weakened link to the |
9ec169fe |
75 | # class we are associated with |
8683db0e |
76 | 'associated_class' => undef, |
1d68af04 |
77 | # and a list of the methods |
3545c727 |
78 | # associated with this attr |
8683db0e |
79 | 'associated_methods' => [], |
0bfc85b8 |
80 | }, $class; |
8b978dd5 |
81 | } |
82 | |
7b31baf4 |
83 | # NOTE: |
1d68af04 |
84 | # this is a primative (and kludgy) clone operation |
16e960bd |
85 | # for now, it will be replaced in the Class::MOP |
1d68af04 |
86 | # bootstrap with a proper one, however we know |
5659d76e |
87 | # that this one will work fine for now. |
88 | sub clone { |
89 | my $self = shift; |
90 | my %options = @_; |
91 | (blessed($self)) |
92 | || confess "Can only clone an instance"; |
b3fa93c7 |
93 | return bless { %{$self}, %options } => ref($self); |
5659d76e |
94 | } |
95 | |
bd4e03f9 |
96 | sub initialize_instance_slot { |
f892c0f0 |
97 | my ($self, $meta_instance, $instance, $params) = @_; |
8683db0e |
98 | my $init_arg = $self->{'init_arg'}; |
99 | |
bd4e03f9 |
100 | # try to fetch the init arg from the %params ... |
8d2d4c67 |
101 | |
1d68af04 |
102 | # if nothing was in the %params, we can use the |
bd4e03f9 |
103 | # attribute's default value (if it has one) |
2e877f58 |
104 | if(defined $init_arg and exists $params->{$init_arg}){ |
8ee74136 |
105 | $self->_set_initial_slot_value( |
106 | $meta_instance, |
0ab65f99 |
107 | $instance, |
0ab65f99 |
108 | $params->{$init_arg}, |
0ab65f99 |
109 | ); |
b7bdffc3 |
110 | } |
8683db0e |
111 | elsif (defined $self->{'default'}) { |
8ee74136 |
112 | $self->_set_initial_slot_value( |
113 | $meta_instance, |
0ab65f99 |
114 | $instance, |
0ab65f99 |
115 | $self->default($instance), |
0ab65f99 |
116 | ); |
b7bdffc3 |
117 | } |
8683db0e |
118 | elsif (defined( my $builder = $self->{'builder'})) { |
b7bdffc3 |
119 | if ($builder = $instance->can($builder)) { |
8ee74136 |
120 | $self->_set_initial_slot_value( |
121 | $meta_instance, |
0ab65f99 |
122 | $instance, |
0ab65f99 |
123 | $instance->$builder, |
0ab65f99 |
124 | ); |
b7bdffc3 |
125 | } |
126 | else { |
b3fa93c7 |
127 | confess(ref($instance)." does not support builder method '". $self->{'builder'} ."' for attribute '" . $self->name . "'"); |
8fe581e5 |
128 | } |
1d68af04 |
129 | } |
bd4e03f9 |
130 | } |
131 | |
8ee74136 |
132 | sub _set_initial_slot_value { |
133 | my ($self, $meta_instance, $instance, $value) = @_; |
134 | |
135 | my $slot_name = $self->name; |
136 | |
137 | return $meta_instance->set_slot_value($instance, $slot_name, $value) |
138 | unless $self->has_initializer; |
139 | |
140 | my $callback = sub { |
141 | $meta_instance->set_slot_value($instance, $slot_name, $_[0]); |
142 | }; |
143 | |
144 | my $initializer = $self->initializer; |
145 | |
146 | # most things will just want to set a value, so make it first arg |
147 | $instance->$initializer($value, $callback, $self); |
148 | } |
149 | |
5659d76e |
150 | # NOTE: |
1d68af04 |
151 | # the next bunch of methods will get bootstrapped |
7b31baf4 |
152 | # away in the Class::MOP bootstrapping section |
153 | |
8683db0e |
154 | sub associated_class { $_[0]->{'associated_class'} } |
155 | sub associated_methods { $_[0]->{'associated_methods'} } |
156 | |
b3fa93c7 |
157 | sub has_accessor { defined($_[0]->{'accessor'}) } |
158 | sub has_reader { defined($_[0]->{'reader'}) } |
159 | sub has_writer { defined($_[0]->{'writer'}) } |
160 | sub has_predicate { defined($_[0]->{'predicate'}) } |
161 | sub has_clearer { defined($_[0]->{'clearer'}) } |
162 | sub has_builder { defined($_[0]->{'builder'}) } |
163 | sub has_init_arg { defined($_[0]->{'init_arg'}) } |
164 | sub has_default { defined($_[0]->{'default'}) } |
165 | sub has_initializer { defined($_[0]->{'initializer'}) } |
8683db0e |
166 | |
d9d99689 |
167 | sub accessor { $_[0]->{'accessor'} } |
168 | sub reader { $_[0]->{'reader'} } |
169 | sub writer { $_[0]->{'writer'} } |
170 | sub predicate { $_[0]->{'predicate'} } |
171 | sub clearer { $_[0]->{'clearer'} } |
172 | sub builder { $_[0]->{'builder'} } |
173 | sub init_arg { $_[0]->{'init_arg'} } |
174 | sub initializer { $_[0]->{'initializer'} } |
175 | sub definition_context { $_[0]->{'definition_context'} } |
c50c603e |
176 | |
7b31baf4 |
177 | # end bootstrapped away method section. |
178 | # (all methods below here are kept intact) |
179 | |
9e517e01 |
180 | sub has_read_method { $_[0]->has_reader || $_[0]->has_accessor } |
181 | sub has_write_method { $_[0]->has_writer || $_[0]->has_accessor } |
182 | |
d14f6cbe |
183 | sub get_read_method { |
184 | my $self = shift; |
185 | my $reader = $self->reader || $self->accessor; |
186 | # normal case ... |
187 | return $reader unless ref $reader; |
188 | # the HASH ref case |
189 | my ($name) = %$reader; |
190 | return $name; |
191 | } |
192 | |
193 | sub get_write_method { |
194 | my $self = shift; |
195 | my $writer = $self->writer || $self->accessor; |
196 | # normal case ... |
197 | return $writer unless ref $writer; |
198 | # the HASH ref case |
199 | my ($name) = %$writer; |
200 | return $name; |
201 | } |
b25109b1 |
202 | |
5da16d1b |
203 | sub get_read_method_ref { |
204 | my $self = shift; |
742fb371 |
205 | if ((my $reader = $self->get_read_method) && $self->associated_class) { |
5da16d1b |
206 | return $self->associated_class->get_method($reader); |
207 | } |
208 | else { |
def5c0b5 |
209 | my $code = sub { $self->get_value(@_) }; |
210 | if (my $class = $self->associated_class) { |
211 | return $class->method_metaclass->wrap( |
212 | $code, |
213 | package_name => $class->name, |
214 | name => '__ANON__' |
215 | ); |
216 | } |
217 | else { |
218 | return $code; |
219 | } |
5da16d1b |
220 | } |
221 | } |
222 | |
223 | sub get_write_method_ref { |
224 | my $self = shift; |
d14f6cbe |
225 | if ((my $writer = $self->get_write_method) && $self->associated_class) { |
742fb371 |
226 | return $self->associated_class->get_method($writer); |
5da16d1b |
227 | } |
228 | else { |
def5c0b5 |
229 | my $code = sub { $self->set_value(@_) }; |
230 | if (my $class = $self->associated_class) { |
231 | return $class->method_metaclass->wrap( |
232 | $code, |
233 | package_name => $class->name, |
234 | name => '__ANON__' |
235 | ); |
236 | } |
237 | else { |
238 | return $code; |
239 | } |
5da16d1b |
240 | } |
241 | } |
242 | |
1d68af04 |
243 | sub is_default_a_coderef { |
4e55a580 |
244 | ('CODE' eq ref($_[0]->{'default'})) |
c0cbf4d9 |
245 | } |
246 | |
1d68af04 |
247 | sub default { |
c0cbf4d9 |
248 | my ($self, $instance) = @_; |
9363ea89 |
249 | if (defined $instance && $self->is_default_a_coderef) { |
1d68af04 |
250 | # if the default is a CODE ref, then |
727919c5 |
251 | # we pass in the instance and default |
1d68af04 |
252 | # can return a value based on that |
727919c5 |
253 | # instance. Somewhat crude, but works. |
8683db0e |
254 | return $self->{'default'}->($instance); |
1d68af04 |
255 | } |
8683db0e |
256 | $self->{'default'}; |
c50c603e |
257 | } |
8b978dd5 |
258 | |
c57c8b10 |
259 | # slots |
260 | |
261 | sub slots { (shift)->name } |
262 | |
1d68af04 |
263 | # class association |
727919c5 |
264 | |
9ec169fe |
265 | sub attach_to_class { |
266 | my ($self, $class) = @_; |
267 | (blessed($class) && $class->isa('Class::MOP::Class')) |
268 | || confess "You must pass a Class::MOP::Class instance (or a subclass)"; |
8683db0e |
269 | weaken($self->{'associated_class'} = $class); |
9ec169fe |
270 | } |
271 | |
272 | sub detach_from_class { |
273 | my $self = shift; |
8683db0e |
274 | $self->{'associated_class'} = undef; |
9ec169fe |
275 | } |
276 | |
1d68af04 |
277 | # method association |
3545c727 |
278 | |
279 | sub associate_method { |
280 | my ($self, $method) = @_; |
8683db0e |
281 | push @{$self->{'associated_methods'}} => $method; |
3545c727 |
282 | } |
283 | |
16e960bd |
284 | ## Slot management |
285 | |
ef91a0e2 |
286 | sub set_initial_value { |
287 | my ($self, $instance, $value) = @_; |
e76b01fb |
288 | $self->_set_initial_slot_value( |
b3fa93c7 |
289 | Class::MOP::Class->initialize(ref($instance))->get_meta_instance, |
8ee74136 |
290 | $instance, |
291 | $value |
292 | ); |
ef91a0e2 |
293 | } |
294 | |
16e960bd |
295 | sub set_value { |
1396f86b |
296 | my ($self, $instance, $value) = @_; |
16e960bd |
297 | |
b3fa93c7 |
298 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
299 | ->get_meta_instance |
300 | ->set_slot_value($instance, $self->name, $value); |
16e960bd |
301 | } |
302 | |
303 | sub get_value { |
1396f86b |
304 | my ($self, $instance) = @_; |
16e960bd |
305 | |
b3fa93c7 |
306 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
307 | ->get_meta_instance |
308 | ->get_slot_value($instance, $self->name); |
16e960bd |
309 | } |
310 | |
3545c727 |
311 | sub has_value { |
312 | my ($self, $instance) = @_; |
1d68af04 |
313 | |
b3fa93c7 |
314 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
315 | ->get_meta_instance |
316 | ->is_slot_initialized($instance, $self->name); |
3545c727 |
317 | } |
318 | |
319 | sub clear_value { |
320 | my ($self, $instance) = @_; |
1d68af04 |
321 | |
b3fa93c7 |
322 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
323 | ->get_meta_instance |
324 | ->deinitialize_slot($instance, $self->name); |
3545c727 |
325 | } |
326 | |
ba38bf08 |
327 | ## load em up ... |
c0cbf4d9 |
328 | |
ba38bf08 |
329 | sub accessor_metaclass { 'Class::MOP::Method::Accessor' } |
c0cbf4d9 |
330 | |
9ec169fe |
331 | sub process_accessors { |
c0cbf4d9 |
332 | my ($self, $type, $accessor, $generate_as_inline_methods) = @_; |
d9d99689 |
333 | |
334 | my $method_ctx; |
335 | |
336 | if ( my $ctx = $self->definition_context ) { |
337 | $method_ctx = { %$ctx }; |
338 | } |
339 | |
9b522fc4 |
340 | if (ref($accessor)) { |
341 | (ref($accessor) eq 'HASH') |
7d28758b |
342 | || confess "bad accessor/reader/writer/predicate/clearer format, must be a HASH ref"; |
4d47b77f |
343 | my ($name, $method) = %{$accessor}; |
4c105333 |
344 | $method = $self->accessor_metaclass->wrap( |
345 | $method, |
346 | package_name => $self->associated_class->name, |
347 | name => $name, |
d9d99689 |
348 | definition_context => $method_ctx, |
4c105333 |
349 | ); |
3545c727 |
350 | $self->associate_method($method); |
1d68af04 |
351 | return ($name, $method); |
2eb717d5 |
352 | } |
9ec169fe |
353 | else { |
1d68af04 |
354 | my $inline_me = ($generate_as_inline_methods && $self->associated_class->instance_metaclass->is_inlinable); |
ba38bf08 |
355 | my $method; |
356 | eval { |
d9d99689 |
357 | if ( $method_ctx ) { |
358 | my $desc = "accessor $accessor"; |
359 | if ( $accessor ne $self->name ) { |
360 | $desc .= " of attribute " . $self->name; |
361 | } |
362 | |
363 | $method_ctx->{description} = $desc; |
364 | } |
365 | |
ba38bf08 |
366 | $method = $self->accessor_metaclass->new( |
367 | attribute => $self, |
d90b42a6 |
368 | is_inline => $inline_me, |
ba38bf08 |
369 | accessor_type => $type, |
4c105333 |
370 | package_name => $self->associated_class->name, |
371 | name => $accessor, |
d9d99689 |
372 | definition_context => $method_ctx, |
1d68af04 |
373 | ); |
ba38bf08 |
374 | }; |
1d68af04 |
375 | confess "Could not create the '$type' method for " . $self->name . " because : $@" if $@; |
3545c727 |
376 | $self->associate_method($method); |
ba38bf08 |
377 | return ($accessor, $method); |
1d68af04 |
378 | } |
9ec169fe |
379 | } |
380 | |
381 | sub install_accessors { |
c0cbf4d9 |
382 | my $self = shift; |
383 | my $inline = shift; |
384 | my $class = $self->associated_class; |
1d68af04 |
385 | |
9ec169fe |
386 | $class->add_method( |
c0cbf4d9 |
387 | $self->process_accessors('accessor' => $self->accessor(), $inline) |
9ec169fe |
388 | ) if $self->has_accessor(); |
389 | |
1d68af04 |
390 | $class->add_method( |
c0cbf4d9 |
391 | $self->process_accessors('reader' => $self->reader(), $inline) |
9ec169fe |
392 | ) if $self->has_reader(); |
393 | |
394 | $class->add_method( |
c0cbf4d9 |
395 | $self->process_accessors('writer' => $self->writer(), $inline) |
9ec169fe |
396 | ) if $self->has_writer(); |
397 | |
398 | $class->add_method( |
c0cbf4d9 |
399 | $self->process_accessors('predicate' => $self->predicate(), $inline) |
9ec169fe |
400 | ) if $self->has_predicate(); |
1d68af04 |
401 | |
7d28758b |
402 | $class->add_method( |
403 | $self->process_accessors('clearer' => $self->clearer(), $inline) |
404 | ) if $self->has_clearer(); |
1d68af04 |
405 | |
9ec169fe |
406 | return; |
2eb717d5 |
407 | } |
408 | |
b51af7f9 |
409 | { |
410 | my $_remove_accessor = sub { |
411 | my ($accessor, $class) = @_; |
9b522fc4 |
412 | if (ref($accessor) && ref($accessor) eq 'HASH') { |
c50c603e |
413 | ($accessor) = keys %{$accessor}; |
1d68af04 |
414 | } |
415 | my $method = $class->get_method($accessor); |
416 | $class->remove_method($accessor) |
b3fa93c7 |
417 | if (ref($method) && $method->isa('Class::MOP::Method::Accessor')); |
b51af7f9 |
418 | }; |
1d68af04 |
419 | |
b51af7f9 |
420 | sub remove_accessors { |
9ec169fe |
421 | my $self = shift; |
2367814a |
422 | # TODO: |
1d68af04 |
423 | # we really need to make sure to remove from the |
424 | # associates methods here as well. But this is |
425 | # such a slimly used method, I am not worried |
2367814a |
426 | # about it right now. |
9ec169fe |
427 | $_remove_accessor->($self->accessor(), $self->associated_class()) if $self->has_accessor(); |
428 | $_remove_accessor->($self->reader(), $self->associated_class()) if $self->has_reader(); |
429 | $_remove_accessor->($self->writer(), $self->associated_class()) if $self->has_writer(); |
430 | $_remove_accessor->($self->predicate(), $self->associated_class()) if $self->has_predicate(); |
7d28758b |
431 | $_remove_accessor->($self->clearer(), $self->associated_class()) if $self->has_clearer(); |
1d68af04 |
432 | return; |
b51af7f9 |
433 | } |
434 | |
8b978dd5 |
435 | } |
436 | |
437 | 1; |
438 | |
439 | __END__ |
440 | |
441 | =pod |
442 | |
1d68af04 |
443 | =head1 NAME |
8b978dd5 |
444 | |
445 | Class::MOP::Attribute - Attribute Meta Object |
446 | |
447 | =head1 SYNOPSIS |
1d68af04 |
448 | |
2e23f7dc |
449 | Class::MOP::Attribute->new( |
450 | foo => ( |
451 | accessor => 'foo', # dual purpose get/set accessor |
452 | predicate => 'has_foo', # predicate check for defined-ness |
453 | init_arg => '-foo', # class->new will look for a -foo key |
454 | default => 'BAR IS BAZ!' # if no -foo key is provided, use this |
455 | ) |
456 | ); |
457 | |
458 | Class::MOP::Attribute->new( |
459 | bar => ( |
460 | reader => 'bar', # getter |
461 | writer => 'set_bar', # setter |
462 | predicate => 'has_bar', # predicate check for defined-ness |
463 | init_arg => ':bar', # class->new will look for a :bar key |
464 | # no default value means it is undef |
465 | ) |
466 | ); |
8b978dd5 |
467 | |
468 | =head1 DESCRIPTION |
469 | |
2e23f7dc |
470 | The Attribute Protocol is almost entirely an invention of |
471 | C<Class::MOP>. Perl 5 does not have a consistent notion of |
472 | attributes. There are so many ways in which this is done, and very few |
473 | (if any) are easily discoverable by this module. |
552e3d24 |
474 | |
2e23f7dc |
475 | With that said, this module attempts to inject some order into this |
1d68af04 |
476 | chaos, by introducing a consistent API which can be used to create |
fe122940 |
477 | object attributes. |
552e3d24 |
478 | |
479 | =head1 METHODS |
480 | |
481 | =head2 Creation |
482 | |
483 | =over 4 |
484 | |
2e23f7dc |
485 | =item B<< Class::MOP::Attribute->new($name, ?%options) >> |
fe122940 |
486 | |
1d68af04 |
487 | An attribute must (at the very least), have a C<$name>. All other |
2e23f7dc |
488 | C<%options> are added as key-value pairs. |
fe122940 |
489 | |
2e23f7dc |
490 | =over 8 |
fe122940 |
491 | |
492 | =item I<init_arg> |
493 | |
2e23f7dc |
494 | This is a string value representing the expected key in an |
495 | initialization hash. For instance, if we have an C<init_arg> value of |
496 | C<-foo>, then the following code will Just Work. |
fe122940 |
497 | |
2e23f7dc |
498 | MyClass->meta->construct_instance( -foo => 'Hello There' ); |
fe122940 |
499 | |
2e23f7dc |
500 | If an init_arg is not assigned, it will automatically use the |
501 | attribute's name. If C<init_arg> is explicitly set to C<undef>, the |
502 | attribute cannot be specified during initialization. |
7b31baf4 |
503 | |
1d68af04 |
504 | =item I<builder> |
505 | |
2e23f7dc |
506 | This provides the name of a method that will be called to initialize |
507 | the attribute. This method will be called on the object after it is |
508 | constructed. It is expected to return a valid value for the attribute. |
fe122940 |
509 | |
4c4a6c41 |
510 | =item I<default> |
511 | |
2e23f7dc |
512 | This can be used to provide an explicit default for initializing the |
513 | attribute. If the default you provide is a subroutine reference, then |
514 | this reference will be called I<as a method> on the object. |
4c4a6c41 |
515 | |
2e23f7dc |
516 | If the value is a simple scalar (string or number), then it can be |
517 | just passed as is. However, if you wish to initialize it with a HASH |
518 | or ARRAY ref, then you need to wrap that inside a subroutine |
519 | reference: |
fe122940 |
520 | |
2e23f7dc |
521 | Class::MOP::Attribute->new( |
522 | 'foo' => ( |
523 | default => sub { [] }, |
524 | ) |
525 | ); |
1d68af04 |
526 | |
527 | # or ... |
528 | |
2e23f7dc |
529 | Class::MOP::Attribute->new( |
530 | 'foo' => ( |
531 | default => sub { {} }, |
532 | ) |
533 | ); |
534 | |
535 | If you wish to initialize an attribute with a subroutine reference |
536 | itself, then you need to wrap that in a subroutine as well: |
537 | |
538 | Class::MOP::Attribute->new( |
539 | 'foo' => ( |
540 | default => sub { |
541 | sub { print "Hello World" } |
542 | }, |
543 | ) |
544 | ); |
545 | |
546 | And lastly, if the value of your attribute is dependent upon some |
547 | other aspect of the instance structure, then you can take advantage of |
548 | the fact that when the C<default> value is called as a method: |
549 | |
550 | Class::MOP::Attribute->new( |
551 | 'object_identity' => ( |
552 | default => sub { Scalar::Util::refaddr( $_[0] ) }, |
553 | ) |
554 | ); |
555 | |
556 | Note that there is no guarantee that attributes are initialized in any |
557 | particular order, so you cannot rely on the value of some other |
558 | attribute when generating the default. |
fe122940 |
559 | |
0ef07b33 |
560 | =item I<initializer> |
561 | |
2e23f7dc |
562 | This option can be either a method name or a subroutine |
563 | reference. This method will be called when setting the attribute's |
564 | value in the constructor. Unlike C<default> and C<builder>, the |
565 | initializer is only called when a value is provided to the |
566 | constructor. The initializer allows you to munge this value during |
567 | object construction. |
568 | |
569 | The initializer is called as a method with three arguments. The first |
570 | is the value that was passed to the constructor. The second is a |
571 | subroutine reference that can be called to actually set the |
572 | attribute's value, and the last is the associated |
573 | C<Class::MOP::Attribute> object. |
574 | |
575 | This contrived example shows an initializer that sets the attribute to |
576 | twice the given value. |
577 | |
578 | Class::MOP::Attribute->new( |
579 | 'doubled' => ( |
580 | initializer => sub { |
581 | my ( $instance, $value, $set ) = @_; |
582 | $set->( $value * 2 ); |
583 | }, |
584 | ) |
585 | ); |
586 | |
587 | Since an initializer can be a method name, you can easily make |
0ef07b33 |
588 | attribute initialization use the writer: |
589 | |
2e23f7dc |
590 | Class::MOP::Attribute->new( |
591 | 'some_attr' => ( |
592 | writer => 'some_attr', |
593 | initializer => 'some_attr', |
594 | ) |
595 | ); |
0ef07b33 |
596 | |
2e23f7dc |
597 | Your writer will need to examine C<@_> and determine under which |
598 | context it is being called. |
127d39a7 |
599 | |
fe122940 |
600 | =back |
601 | |
2e23f7dc |
602 | The C<accessor>, C<reader>, C<writer>, C<predicate> and C<clearer> |
603 | options all accept the same parameters. You can provide the name of |
604 | the method, in which case an appropriate default method will be |
605 | generated for you. Or instead you can also provide hash reference |
606 | containing exactly one key (the method name) and one value. The value |
607 | should be a subroutine reference, which will be installed as the |
608 | method itself. |
59e7697f |
609 | |
610 | =over 4 |
611 | |
612 | =item I<accessor> |
613 | |
2e23f7dc |
614 | An C<accessor> is a standard Perl-style read/write accessor. It will |
615 | return the value of the attribute, and if a value is passed as an |
616 | argument, it will assign that value to the attribute. |
fe122940 |
617 | |
2e23f7dc |
618 | Note that C<undef> is a legitimate value, so this will work: |
fe122940 |
619 | |
620 | $object->set_something(undef); |
621 | |
59e7697f |
622 | =item I<reader> |
623 | |
2e23f7dc |
624 | This is a basic read-only accessor. It returns the value of the |
625 | attribute. |
fe122940 |
626 | |
59e7697f |
627 | =item I<writer> |
628 | |
1d68af04 |
629 | This is a basic write accessor, it accepts a single argument, and |
2e23f7dc |
630 | assigns that value to the attribute. |
59e7697f |
631 | |
2e23f7dc |
632 | Note that C<undef> is a legitimate value, so this will work: |
59e7697f |
633 | |
2e23f7dc |
634 | $object->set_something(undef); |
fe122940 |
635 | |
636 | =item I<predicate> |
637 | |
2e23f7dc |
638 | The predicate method returns a boolean indicating whether or not the |
639 | attribute has been explicitly set. |
07dca7e3 |
640 | |
2e23f7dc |
641 | Note that the predicate returns true even if the attribute was set to |
642 | a false value (C<0> or C<undef>). |
07dca7e3 |
643 | |
7d28758b |
644 | =item I<clearer> |
645 | |
2e23f7dc |
646 | This method will uninitialize the attribute. After an attribute is |
647 | cleared, its C<predicate> will return false. |
7d28758b |
648 | |
59e7697f |
649 | =back |
552e3d24 |
650 | |
2e23f7dc |
651 | =item B<< $attr->clone(%options) >> |
bd4e03f9 |
652 | |
2e23f7dc |
653 | This clones the attribute. Any options you provide will override the |
654 | settings of the original attribute. You can change the name of the new |
655 | attribute by passing a C<name> key in C<%options>. |
127d39a7 |
656 | |
2e23f7dc |
657 | =back |
bd4e03f9 |
658 | |
2e23f7dc |
659 | =head2 Informational |
127d39a7 |
660 | |
2e23f7dc |
661 | These are all basic read-only accessors for the values passed into |
662 | the constructor. |
552e3d24 |
663 | |
2e23f7dc |
664 | =over 4 |
16e960bd |
665 | |
2e23f7dc |
666 | =item B<< $attr->name >> |
2367814a |
667 | |
2e23f7dc |
668 | =item B<< $attr->accessor >> |
2367814a |
669 | |
2e23f7dc |
670 | =item B<< $attr->reader >> |
16e960bd |
671 | |
2e23f7dc |
672 | =item B<< $attr->writer >> |
16e960bd |
673 | |
2e23f7dc |
674 | =item B<< $attr->predicate >> |
16e960bd |
675 | |
2e23f7dc |
676 | =item B<< $attr->clearer >> |
c0921932 |
677 | |
2e23f7dc |
678 | The C<accessor>, C<reader>, C<writer>, C<predicate>, and C<clearer> |
679 | methods all return exactly what was passed to the constructor, so it |
680 | can be either a string containing a method name, or a hash refrence. |
c0921932 |
681 | |
2e23f7dc |
682 | =item B<< $attr->initializer >> |
16e960bd |
683 | |
2e23f7dc |
684 | Returns the intializer as passed to the constructor, so this may be |
685 | either a method name or a subroutine reference. |
16e960bd |
686 | |
2e23f7dc |
687 | =item B<< $attr->init_arg >> |
3545c727 |
688 | |
2e23f7dc |
689 | =item B<< $attr->is_default_a_coderef >> |
2367814a |
690 | |
2e23f7dc |
691 | =item B<< $attr->default($instance) >> |
3545c727 |
692 | |
2e23f7dc |
693 | The C<$instance> argument is optional. If you don't pass it, the |
694 | return value for this method is exactly what was passed to the |
695 | constructor, either a simple scalar or a subroutine reference. |
2367814a |
696 | |
2e23f7dc |
697 | If you I<do> pass an C<$instance> and the default is a subroutine |
698 | reference, then the reference is called as a method on the |
699 | C<$instance> and the generated value is returned. |
16e960bd |
700 | |
2e23f7dc |
701 | =item B<< $attr->slots >> |
552e3d24 |
702 | |
2e23f7dc |
703 | Return a list of slots required by the attribute. This is usually just |
704 | one, the name of the attribute. |
fe122940 |
705 | |
2e23f7dc |
706 | A slot is the name of the hash key used to store the attribute in an |
707 | object instance. |
552e3d24 |
708 | |
2e23f7dc |
709 | =item B<< $attr->get_read_method >> |
552e3d24 |
710 | |
2e23f7dc |
711 | =item B<< $attr->get_write_method >> |
552e3d24 |
712 | |
2e23f7dc |
713 | Returns the name of a method suitable for reading or writing the value |
714 | of the attribute in the associated class. |
552e3d24 |
715 | |
2e23f7dc |
716 | If an attribute is read- or write-only, then these methods can return |
717 | C<undef> as appropriate. |
552e3d24 |
718 | |
2e23f7dc |
719 | =item B<< $attr->has_read_method >> |
c50c603e |
720 | |
2e23f7dc |
721 | =item B<< $attr->has_write_method >> |
7d28758b |
722 | |
2e23f7dc |
723 | This returns a boolean indicating whether the attribute has a I<named> |
724 | read or write method. |
0ab65f99 |
725 | |
2e23f7dc |
726 | =item B<< $attr->get_read_method_ref >> |
552e3d24 |
727 | |
2e23f7dc |
728 | =item B<< $attr->get_write_method_ref >> |
495af518 |
729 | |
2e23f7dc |
730 | Returns the subroutine reference of a method suitable for reading or |
731 | writing the attribute's value in the associated class. These methods |
732 | always return a subroutine reference, regardless of whether or not the |
733 | attribute is read- or write-only. |
734 | |
735 | =back |
fe122940 |
736 | |
2e23f7dc |
737 | =head2 Informational predicates |
92d2abfa |
738 | |
2e23f7dc |
739 | These are all basic predicate methods for the values passed into C<new>. |
552e3d24 |
740 | |
2e23f7dc |
741 | =over 4 |
c57c8b10 |
742 | |
2e23f7dc |
743 | =item B<< $attr->has_accessor >> |
c57c8b10 |
744 | |
2e23f7dc |
745 | =item B<< $attr->has_reader >> |
b25109b1 |
746 | |
2e23f7dc |
747 | =item B<< $attr->has_writer >> |
b25109b1 |
748 | |
2e23f7dc |
749 | =item B<< $attr->has_predicate >> |
5da16d1b |
750 | |
2e23f7dc |
751 | =item B<< $attr->has_clearer >> |
5da16d1b |
752 | |
2e23f7dc |
753 | =item B<< $attr->has_initializer >> |
5da16d1b |
754 | |
2e23f7dc |
755 | =item B<< $attr->has_init_arg >> |
5da16d1b |
756 | |
2e23f7dc |
757 | This will be I<false> if the C<init_arg> was set to C<undef>. |
b25109b1 |
758 | |
2e23f7dc |
759 | =item B<< $attr->has_default >> |
9e517e01 |
760 | |
2e23f7dc |
761 | This will be I<false> if the C<default> was set to C<undef>, since |
762 | C<undef> is the default C<default> anyway. |
9e517e01 |
763 | |
2e23f7dc |
764 | =item B<< $attr->has_builder >> |
9e517e01 |
765 | |
552e3d24 |
766 | =back |
767 | |
2e23f7dc |
768 | =head2 Value management |
552e3d24 |
769 | |
2e23f7dc |
770 | These methods are basically "backdoors" to the instance, and can be |
771 | used to bypass the regular accessors, but still stay within the MOP. |
772 | |
773 | These methods are not for general use, and should only be used if you |
774 | really know what you are doing. |
fe122940 |
775 | |
552e3d24 |
776 | =over 4 |
777 | |
2e23f7dc |
778 | =item B<< $attr->initialize_instance_slot($meta_instance, $instance, $params) >> |
779 | |
780 | This method is used internally to initialize the attribute's slot in |
781 | the object C<$instance>. |
782 | |
783 | The C<$params> is a hash reference of the values passed to the object |
784 | constructor. |
785 | |
786 | It's unlikely that you'll need to call this method yourself. |
552e3d24 |
787 | |
2e23f7dc |
788 | =item B<< $attr->set_value($instance, $value) >> |
552e3d24 |
789 | |
2e23f7dc |
790 | Sets the value without going through the accessor. Note that this |
791 | works even with read-only attributes. |
552e3d24 |
792 | |
2e23f7dc |
793 | =item B<< $attr->set_initial_value($instance, $value) >> |
c50c603e |
794 | |
2e23f7dc |
795 | Sets the value without going through the accessor. This method is only |
796 | called when the instance is first being initialized. |
7d28758b |
797 | |
2e23f7dc |
798 | =item B<< $attr->get_value($instance) >> |
0ab65f99 |
799 | |
2e23f7dc |
800 | Returns the value without going through the accessor. Note that this |
801 | works even with write-only accessors. |
552e3d24 |
802 | |
2e23f7dc |
803 | =item B<< $attr->has_value($instance) >> |
552e3d24 |
804 | |
2e23f7dc |
805 | Return a boolean indicating whether the attribute has been set in |
806 | C<$instance>. This how the default C<predicate> method works. |
807 | |
808 | =item B<< $attr->clear_value($instance) >> |
809 | |
810 | This will clear the attribute's value in C<$instance>. This is what |
811 | the default C<clearer> calls. |
812 | |
813 | Note that this works even if the attribute does not have any |
814 | associated read, write or clear methods. |
bf731086 |
815 | |
552e3d24 |
816 | =back |
817 | |
9ec169fe |
818 | =head2 Class association |
819 | |
1d68af04 |
820 | These methods allow you to manage the attributes association with |
821 | the class that contains it. These methods should not be used |
2367814a |
822 | lightly, nor are they very magical, they are mostly used internally |
823 | and by metaclass instances. |
824 | |
9ec169fe |
825 | =over 4 |
826 | |
2e23f7dc |
827 | =item B<< $attr->associated_class >> |
828 | |
829 | This returns the C<Class::MOP::Class> with which this attribute is |
830 | associated, if any. |
831 | |
832 | =item B<< $attr->attach_to_class($metaclass) >> |
9ec169fe |
833 | |
2e23f7dc |
834 | This method stores a weakened reference to the C<$metaclass> object |
835 | internally. |
2367814a |
836 | |
2e23f7dc |
837 | This method does not remove the attribute from its old class, |
838 | nor does it create any accessors in the new class. |
9ec169fe |
839 | |
2e23f7dc |
840 | It is probably best to use the L<Class::MOP::Class> C<add_attribute> |
841 | method instead. |
2367814a |
842 | |
2e23f7dc |
843 | =item B<< $attr->detach_from_class >> |
9ec169fe |
844 | |
2e23f7dc |
845 | This method removes the associate metaclass object from the attribute |
846 | it has one. |
847 | |
848 | This method does not remove the attribute itself from the class, or |
849 | remove its accessors. |
850 | |
851 | It is probably best to use the L<Class::MOP::Class> |
852 | C<remove_attribute> method instead. |
2367814a |
853 | |
9ec169fe |
854 | =back |
855 | |
552e3d24 |
856 | =head2 Attribute Accessor generation |
857 | |
858 | =over 4 |
859 | |
2e23f7dc |
860 | =item B<< $attr->accessor_metaclass >> |
ba38bf08 |
861 | |
2e23f7dc |
862 | Accessor methods are generated using an accessor metaclass. By |
863 | default, this is L<Class::MOP::Method::Accessor>. This method returns |
2367814a |
864 | the name of the accessor metaclass that this attribute uses. |
865 | |
2e23f7dc |
866 | =item B<< $attr->associate_method($method) >> |
2367814a |
867 | |
2e23f7dc |
868 | This associates a L<Class::MOP::Method> object with the |
869 | attribute. Typically, this is called internally when an attribute |
870 | generates its accessors. |
3545c727 |
871 | |
2e23f7dc |
872 | =item B<< $attr->associated_methods >> |
3545c727 |
873 | |
2e23f7dc |
874 | This returns the list of methods which have been associated with the |
875 | attribute. |
2367814a |
876 | |
2e23f7dc |
877 | =item B<< $attr->install_accessors >> |
2eb717d5 |
878 | |
2e23f7dc |
879 | This method generates and installs code the attributes various |
880 | accessors. It is typically called from the L<Class::MOP::Class> |
881 | C<add_attribute> method. |
2eb717d5 |
882 | |
2e23f7dc |
883 | This method will call C<< $attr->process_accessors >> for each of the |
884 | possible method types (accessor, reader, writer & predicate). |
9ec169fe |
885 | |
2e23f7dc |
886 | =item B<< $attr->process_accessors($type, $value) >> |
9ec169fe |
887 | |
2e23f7dc |
888 | This method takes a C<$type> (accessor, reader, writer or predicate), and |
9ec169fe |
889 | a C<$value> (the value passed into the constructor for each of the |
2e23f7dc |
890 | different types). |
891 | |
892 | It will then either generate the method itself (using the |
893 | C<generate_*_method> methods listed below) or it will use the custom |
894 | method passed through the constructor. |
895 | |
896 | This method is mostly intended for internal use from the C<< |
897 | $attr->install_accessors >> method. |
9ec169fe |
898 | |
2e23f7dc |
899 | =item B<< $attr->remove_accessors >> |
2eb717d5 |
900 | |
2e23f7dc |
901 | This method removes all of the accessors associated with the |
902 | attribute. |
2eb717d5 |
903 | |
2e23f7dc |
904 | This does not currently remove methods from the list returned by |
905 | C<associated_methods>. |
2367814a |
906 | |
2eb717d5 |
907 | =back |
908 | |
909 | =head2 Introspection |
910 | |
911 | =over 4 |
552e3d24 |
912 | |
2e23f7dc |
913 | =item B<< $attr->meta >> |
552e3d24 |
914 | |
2e23f7dc |
915 | This will return a L<Class::MOP::Class> instance for this class. |
fe122940 |
916 | |
2e23f7dc |
917 | It should also be noted that L<Class::MOP> will actually bootstrap |
918 | this module by installing a number of attribute meta-objects into its |
919 | metaclass. |
fe122940 |
920 | |
552e3d24 |
921 | =back |
922 | |
1a09d9cc |
923 | =head1 AUTHORS |
8b978dd5 |
924 | |
a2e85e6c |
925 | Stevan Little E<lt>stevan@iinteractive.comE<gt> |
8b978dd5 |
926 | |
927 | =head1 COPYRIGHT AND LICENSE |
928 | |
070bb6c9 |
929 | Copyright 2006-2009 by Infinity Interactive, Inc. |
8b978dd5 |
930 | |
931 | L<http://www.iinteractive.com> |
932 | |
933 | This library is free software; you can redistribute it and/or modify |
1d68af04 |
934 | it under the same terms as Perl itself. |
8b978dd5 |
935 | |
16e960bd |
936 | =cut |
937 | |
7d28758b |
938 | |