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 | |
b4bd10ec |
12 | our $VERSION = '0.77'; |
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 name { $_[0]->{'name'} } |
155 | |
156 | sub associated_class { $_[0]->{'associated_class'} } |
157 | sub associated_methods { $_[0]->{'associated_methods'} } |
158 | |
b3fa93c7 |
159 | sub has_accessor { defined($_[0]->{'accessor'}) } |
160 | sub has_reader { defined($_[0]->{'reader'}) } |
161 | sub has_writer { defined($_[0]->{'writer'}) } |
162 | sub has_predicate { defined($_[0]->{'predicate'}) } |
163 | sub has_clearer { defined($_[0]->{'clearer'}) } |
164 | sub has_builder { defined($_[0]->{'builder'}) } |
165 | sub has_init_arg { defined($_[0]->{'init_arg'}) } |
166 | sub has_default { defined($_[0]->{'default'}) } |
167 | sub has_initializer { defined($_[0]->{'initializer'}) } |
8683db0e |
168 | |
d9d99689 |
169 | sub accessor { $_[0]->{'accessor'} } |
170 | sub reader { $_[0]->{'reader'} } |
171 | sub writer { $_[0]->{'writer'} } |
172 | sub predicate { $_[0]->{'predicate'} } |
173 | sub clearer { $_[0]->{'clearer'} } |
174 | sub builder { $_[0]->{'builder'} } |
175 | sub init_arg { $_[0]->{'init_arg'} } |
176 | sub initializer { $_[0]->{'initializer'} } |
177 | sub definition_context { $_[0]->{'definition_context'} } |
c50c603e |
178 | |
7b31baf4 |
179 | # end bootstrapped away method section. |
180 | # (all methods below here are kept intact) |
181 | |
9e517e01 |
182 | sub has_read_method { $_[0]->has_reader || $_[0]->has_accessor } |
183 | sub has_write_method { $_[0]->has_writer || $_[0]->has_accessor } |
184 | |
d14f6cbe |
185 | sub get_read_method { |
186 | my $self = shift; |
187 | my $reader = $self->reader || $self->accessor; |
188 | # normal case ... |
189 | return $reader unless ref $reader; |
190 | # the HASH ref case |
191 | my ($name) = %$reader; |
192 | return $name; |
193 | } |
194 | |
195 | sub get_write_method { |
196 | my $self = shift; |
197 | my $writer = $self->writer || $self->accessor; |
198 | # normal case ... |
199 | return $writer unless ref $writer; |
200 | # the HASH ref case |
201 | my ($name) = %$writer; |
202 | return $name; |
203 | } |
b25109b1 |
204 | |
5da16d1b |
205 | sub get_read_method_ref { |
206 | my $self = shift; |
742fb371 |
207 | if ((my $reader = $self->get_read_method) && $self->associated_class) { |
5da16d1b |
208 | return $self->associated_class->get_method($reader); |
209 | } |
210 | else { |
def5c0b5 |
211 | my $code = sub { $self->get_value(@_) }; |
212 | if (my $class = $self->associated_class) { |
213 | return $class->method_metaclass->wrap( |
214 | $code, |
215 | package_name => $class->name, |
216 | name => '__ANON__' |
217 | ); |
218 | } |
219 | else { |
220 | return $code; |
221 | } |
5da16d1b |
222 | } |
223 | } |
224 | |
225 | sub get_write_method_ref { |
226 | my $self = shift; |
d14f6cbe |
227 | if ((my $writer = $self->get_write_method) && $self->associated_class) { |
742fb371 |
228 | return $self->associated_class->get_method($writer); |
5da16d1b |
229 | } |
230 | else { |
def5c0b5 |
231 | my $code = sub { $self->set_value(@_) }; |
232 | if (my $class = $self->associated_class) { |
233 | return $class->method_metaclass->wrap( |
234 | $code, |
235 | package_name => $class->name, |
236 | name => '__ANON__' |
237 | ); |
238 | } |
239 | else { |
240 | return $code; |
241 | } |
5da16d1b |
242 | } |
243 | } |
244 | |
1d68af04 |
245 | sub is_default_a_coderef { |
4e55a580 |
246 | ('CODE' eq ref($_[0]->{'default'})) |
c0cbf4d9 |
247 | } |
248 | |
1d68af04 |
249 | sub default { |
c0cbf4d9 |
250 | my ($self, $instance) = @_; |
9363ea89 |
251 | if (defined $instance && $self->is_default_a_coderef) { |
1d68af04 |
252 | # if the default is a CODE ref, then |
727919c5 |
253 | # we pass in the instance and default |
1d68af04 |
254 | # can return a value based on that |
727919c5 |
255 | # instance. Somewhat crude, but works. |
8683db0e |
256 | return $self->{'default'}->($instance); |
1d68af04 |
257 | } |
8683db0e |
258 | $self->{'default'}; |
c50c603e |
259 | } |
8b978dd5 |
260 | |
c57c8b10 |
261 | # slots |
262 | |
263 | sub slots { (shift)->name } |
264 | |
1d68af04 |
265 | # class association |
727919c5 |
266 | |
9ec169fe |
267 | sub attach_to_class { |
268 | my ($self, $class) = @_; |
269 | (blessed($class) && $class->isa('Class::MOP::Class')) |
270 | || confess "You must pass a Class::MOP::Class instance (or a subclass)"; |
8683db0e |
271 | weaken($self->{'associated_class'} = $class); |
9ec169fe |
272 | } |
273 | |
274 | sub detach_from_class { |
275 | my $self = shift; |
8683db0e |
276 | $self->{'associated_class'} = undef; |
9ec169fe |
277 | } |
278 | |
1d68af04 |
279 | # method association |
3545c727 |
280 | |
281 | sub associate_method { |
282 | my ($self, $method) = @_; |
8683db0e |
283 | push @{$self->{'associated_methods'}} => $method; |
3545c727 |
284 | } |
285 | |
16e960bd |
286 | ## Slot management |
287 | |
ef91a0e2 |
288 | sub set_initial_value { |
289 | my ($self, $instance, $value) = @_; |
e76b01fb |
290 | $self->_set_initial_slot_value( |
b3fa93c7 |
291 | Class::MOP::Class->initialize(ref($instance))->get_meta_instance, |
8ee74136 |
292 | $instance, |
293 | $value |
294 | ); |
ef91a0e2 |
295 | } |
296 | |
16e960bd |
297 | sub set_value { |
1396f86b |
298 | my ($self, $instance, $value) = @_; |
16e960bd |
299 | |
b3fa93c7 |
300 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
301 | ->get_meta_instance |
302 | ->set_slot_value($instance, $self->name, $value); |
16e960bd |
303 | } |
304 | |
305 | sub get_value { |
1396f86b |
306 | my ($self, $instance) = @_; |
16e960bd |
307 | |
b3fa93c7 |
308 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
309 | ->get_meta_instance |
310 | ->get_slot_value($instance, $self->name); |
16e960bd |
311 | } |
312 | |
3545c727 |
313 | sub has_value { |
314 | my ($self, $instance) = @_; |
1d68af04 |
315 | |
b3fa93c7 |
316 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
317 | ->get_meta_instance |
318 | ->is_slot_initialized($instance, $self->name); |
3545c727 |
319 | } |
320 | |
321 | sub clear_value { |
322 | my ($self, $instance) = @_; |
1d68af04 |
323 | |
b3fa93c7 |
324 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
325 | ->get_meta_instance |
326 | ->deinitialize_slot($instance, $self->name); |
3545c727 |
327 | } |
328 | |
ba38bf08 |
329 | ## load em up ... |
c0cbf4d9 |
330 | |
ba38bf08 |
331 | sub accessor_metaclass { 'Class::MOP::Method::Accessor' } |
c0cbf4d9 |
332 | |
9ec169fe |
333 | sub process_accessors { |
c0cbf4d9 |
334 | my ($self, $type, $accessor, $generate_as_inline_methods) = @_; |
d9d99689 |
335 | |
336 | my $method_ctx; |
337 | |
338 | if ( my $ctx = $self->definition_context ) { |
339 | $method_ctx = { %$ctx }; |
340 | } |
341 | |
9b522fc4 |
342 | if (ref($accessor)) { |
343 | (ref($accessor) eq 'HASH') |
7d28758b |
344 | || confess "bad accessor/reader/writer/predicate/clearer format, must be a HASH ref"; |
4d47b77f |
345 | my ($name, $method) = %{$accessor}; |
4c105333 |
346 | $method = $self->accessor_metaclass->wrap( |
347 | $method, |
348 | package_name => $self->associated_class->name, |
349 | name => $name, |
d9d99689 |
350 | definition_context => $method_ctx, |
4c105333 |
351 | ); |
3545c727 |
352 | $self->associate_method($method); |
1d68af04 |
353 | return ($name, $method); |
2eb717d5 |
354 | } |
9ec169fe |
355 | else { |
1d68af04 |
356 | my $inline_me = ($generate_as_inline_methods && $self->associated_class->instance_metaclass->is_inlinable); |
ba38bf08 |
357 | my $method; |
358 | eval { |
d9d99689 |
359 | if ( $method_ctx ) { |
360 | my $desc = "accessor $accessor"; |
361 | if ( $accessor ne $self->name ) { |
362 | $desc .= " of attribute " . $self->name; |
363 | } |
364 | |
365 | $method_ctx->{description} = $desc; |
366 | } |
367 | |
ba38bf08 |
368 | $method = $self->accessor_metaclass->new( |
369 | attribute => $self, |
d90b42a6 |
370 | is_inline => $inline_me, |
ba38bf08 |
371 | accessor_type => $type, |
4c105333 |
372 | package_name => $self->associated_class->name, |
373 | name => $accessor, |
d9d99689 |
374 | definition_context => $method_ctx, |
1d68af04 |
375 | ); |
ba38bf08 |
376 | }; |
1d68af04 |
377 | confess "Could not create the '$type' method for " . $self->name . " because : $@" if $@; |
3545c727 |
378 | $self->associate_method($method); |
ba38bf08 |
379 | return ($accessor, $method); |
1d68af04 |
380 | } |
9ec169fe |
381 | } |
382 | |
383 | sub install_accessors { |
c0cbf4d9 |
384 | my $self = shift; |
385 | my $inline = shift; |
386 | my $class = $self->associated_class; |
1d68af04 |
387 | |
9ec169fe |
388 | $class->add_method( |
c0cbf4d9 |
389 | $self->process_accessors('accessor' => $self->accessor(), $inline) |
9ec169fe |
390 | ) if $self->has_accessor(); |
391 | |
1d68af04 |
392 | $class->add_method( |
c0cbf4d9 |
393 | $self->process_accessors('reader' => $self->reader(), $inline) |
9ec169fe |
394 | ) if $self->has_reader(); |
395 | |
396 | $class->add_method( |
c0cbf4d9 |
397 | $self->process_accessors('writer' => $self->writer(), $inline) |
9ec169fe |
398 | ) if $self->has_writer(); |
399 | |
400 | $class->add_method( |
c0cbf4d9 |
401 | $self->process_accessors('predicate' => $self->predicate(), $inline) |
9ec169fe |
402 | ) if $self->has_predicate(); |
1d68af04 |
403 | |
7d28758b |
404 | $class->add_method( |
405 | $self->process_accessors('clearer' => $self->clearer(), $inline) |
406 | ) if $self->has_clearer(); |
1d68af04 |
407 | |
9ec169fe |
408 | return; |
2eb717d5 |
409 | } |
410 | |
b51af7f9 |
411 | { |
412 | my $_remove_accessor = sub { |
413 | my ($accessor, $class) = @_; |
9b522fc4 |
414 | if (ref($accessor) && ref($accessor) eq 'HASH') { |
c50c603e |
415 | ($accessor) = keys %{$accessor}; |
1d68af04 |
416 | } |
417 | my $method = $class->get_method($accessor); |
418 | $class->remove_method($accessor) |
b3fa93c7 |
419 | if (ref($method) && $method->isa('Class::MOP::Method::Accessor')); |
b51af7f9 |
420 | }; |
1d68af04 |
421 | |
b51af7f9 |
422 | sub remove_accessors { |
9ec169fe |
423 | my $self = shift; |
2367814a |
424 | # TODO: |
1d68af04 |
425 | # we really need to make sure to remove from the |
426 | # associates methods here as well. But this is |
427 | # such a slimly used method, I am not worried |
2367814a |
428 | # about it right now. |
9ec169fe |
429 | $_remove_accessor->($self->accessor(), $self->associated_class()) if $self->has_accessor(); |
430 | $_remove_accessor->($self->reader(), $self->associated_class()) if $self->has_reader(); |
431 | $_remove_accessor->($self->writer(), $self->associated_class()) if $self->has_writer(); |
432 | $_remove_accessor->($self->predicate(), $self->associated_class()) if $self->has_predicate(); |
7d28758b |
433 | $_remove_accessor->($self->clearer(), $self->associated_class()) if $self->has_clearer(); |
1d68af04 |
434 | return; |
b51af7f9 |
435 | } |
436 | |
8b978dd5 |
437 | } |
438 | |
439 | 1; |
440 | |
441 | __END__ |
442 | |
443 | =pod |
444 | |
1d68af04 |
445 | =head1 NAME |
8b978dd5 |
446 | |
447 | Class::MOP::Attribute - Attribute Meta Object |
448 | |
449 | =head1 SYNOPSIS |
1d68af04 |
450 | |
f91a23dd |
451 | Class::MOP::Attribute->new( foo => ( |
fe122940 |
452 | accessor => 'foo', # dual purpose get/set accessor |
1d68af04 |
453 | predicate => 'has_foo' # predicate check for defined-ness |
fe122940 |
454 | init_arg => '-foo', # class->new will look for a -foo key |
455 | default => 'BAR IS BAZ!' # if no -foo key is provided, use this |
8b978dd5 |
456 | )); |
1d68af04 |
457 | |
f91a23dd |
458 | Class::MOP::Attribute->new( bar => ( |
fe122940 |
459 | reader => 'bar', # getter |
1d68af04 |
460 | writer => 'set_bar', # setter |
461 | predicate => 'has_bar' # predicate check for defined-ness |
fe122940 |
462 | init_arg => ':bar', # class->new will look for a :bar key |
8b978dd5 |
463 | # no default value means it is undef |
464 | )); |
465 | |
466 | =head1 DESCRIPTION |
467 | |
fe122940 |
468 | The Attribute Protocol is almost entirely an invention of this module, |
1d68af04 |
469 | and is completely optional to this MOP. This is because Perl 5 does not |
470 | have consistent notion of what is an attribute of a class. There are |
471 | so many ways in which this is done, and very few (if any) are |
fe122940 |
472 | easily discoverable by this module. |
552e3d24 |
473 | |
1d68af04 |
474 | So, all that said, this module attempts to inject some order into this |
475 | chaos, by introducing a consistent API which can be used to create |
fe122940 |
476 | object attributes. |
552e3d24 |
477 | |
478 | =head1 METHODS |
479 | |
480 | =head2 Creation |
481 | |
482 | =over 4 |
483 | |
fe122940 |
484 | =item B<new ($name, ?%options)> |
485 | |
1d68af04 |
486 | An attribute must (at the very least), have a C<$name>. All other |
a2e85e6c |
487 | C<%options> are contained added as key-value pairs. Acceptable keys |
fe122940 |
488 | are as follows: |
489 | |
490 | =over 4 |
491 | |
492 | =item I<init_arg> |
493 | |
1d68af04 |
494 | This should be a string value representing the expected key in |
495 | an initialization hash. For instance, if we have an I<init_arg> |
fe122940 |
496 | value of C<-foo>, then the following code will Just Work. |
497 | |
498 | MyClass->meta->construct_instance(-foo => "Hello There"); |
499 | |
1d68af04 |
500 | In an init_arg is not assigned, it will automatically use the |
0ef07b33 |
501 | value of C<$name>. If an explicit C<undef> is given for an init_arg, |
502 | an attribute value can't be specified during initialization. |
7b31baf4 |
503 | |
1d68af04 |
504 | =item I<builder> |
505 | |
506 | The value of this key is the name of the method that will be |
507 | called to obtain the value used to initialize the attribute. |
508 | This should be a method in the class associated with the attribute, |
509 | not a method in the attribute class itself. |
fe122940 |
510 | |
4c4a6c41 |
511 | =item I<default> |
512 | |
513 | The value of this key is the default value which |
514 | C<Class::MOP::Class::construct_instance> will initialize the |
515 | attribute to. |
516 | |
fe122940 |
517 | B<NOTE:> |
1d68af04 |
518 | If the value is a simple scalar (string or number), then it can |
519 | be just passed as is. However, if you wish to initialize it with |
520 | a HASH or ARRAY ref, then you need to wrap that inside a CODE |
fe122940 |
521 | reference, like so: |
522 | |
523 | Class::MOP::Attribute->new('@foo' => ( |
524 | default => sub { [] }, |
525 | )); |
1d68af04 |
526 | |
527 | # or ... |
528 | |
fe122940 |
529 | Class::MOP::Attribute->new('%foo' => ( |
530 | default => sub { {} }, |
1d68af04 |
531 | )); |
fe122940 |
532 | |
1d68af04 |
533 | If you wish to initialize an attribute with a CODE reference |
fe122940 |
534 | itself, then you need to wrap that in a subroutine as well, like |
535 | so: |
1d68af04 |
536 | |
fe122940 |
537 | Class::MOP::Attribute->new('&foo' => ( |
538 | default => sub { sub { print "Hello World" } }, |
539 | )); |
540 | |
1d68af04 |
541 | And lastly, if the value of your attribute is dependent upon |
542 | some other aspect of the instance structure, then you can take |
543 | advantage of the fact that when the I<default> value is a CODE |
127d39a7 |
544 | reference, it is passed the (as yet unfinished) instance structure |
fe122940 |
545 | as it's only argument. So you can do things like this: |
546 | |
547 | Class::MOP::Attribute->new('$object_identity' => ( |
548 | default => sub { Scalar::Util::refaddr($_[0]) }, |
549 | )); |
550 | |
1d68af04 |
551 | This last feature is fairly limited as there is no gurantee of |
552 | the order of attribute initializations, so you cannot perform |
553 | any kind of dependent initializations. However, if this is |
554 | something you need, you could subclass B<Class::MOP::Class> and |
555 | this class to acheive it. However, this is currently left as |
fe122940 |
556 | an exercise to the reader :). |
557 | |
0ef07b33 |
558 | =item I<initializer> |
559 | |
560 | This may be a method name (referring to a method on the class with this |
561 | attribute) or a CODE ref. The initializer is used to set the attribute value |
562 | on an instance when the attribute is set during instance initialization. When |
563 | called, it is passed the instance (as the invocant), the value to set, a |
564 | slot-setting CODE ref, and the attribute meta-instance. The slot-setting code |
565 | is provided to make it easy to set the (possibly altered) value on the instance |
566 | without going through several more method calls. |
567 | |
0ef07b33 |
568 | This contrived example shows an initializer that sets the attribute to twice |
569 | the given value. |
570 | |
571 | Class::MOP::Attribute->new('$doubled' => ( |
572 | initializer => sub { |
573 | my ($instance, $value, $set) = @_; |
574 | $set->($value * 2); |
575 | }, |
576 | )); |
577 | |
578 | As method names can be given as initializers, one can easily make |
579 | attribute initialization use the writer: |
580 | |
581 | Class::MOP::Attribute->new('$some_attr' => ( |
582 | writer => 'some_attr', |
583 | initializer => 'some_attr', |
584 | )); |
585 | |
127d39a7 |
586 | Your writer will simply need to examine it's C<@_> and determine under |
587 | which context it is being called. |
588 | |
fe122940 |
589 | =back |
590 | |
7d28758b |
591 | The I<accessor>, I<reader>, I<writer>, I<predicate> and I<clearer> keys can |
592 | contain either; the name of the method and an appropriate default one will be |
593 | generated for you, B<or> a HASH ref containing exactly one key (which will be |
594 | used as the name of the method) and one value, which should contain a CODE |
595 | reference which will be installed as the method itself. |
59e7697f |
596 | |
597 | =over 4 |
598 | |
599 | =item I<accessor> |
600 | |
1d68af04 |
601 | The I<accessor> is a standard perl-style read/write accessor. It will |
602 | return the value of the attribute, and if a value is passed as an argument, |
fe122940 |
603 | it will assign that value to the attribute. |
604 | |
605 | B<NOTE:> |
1d68af04 |
606 | This method will properly handle the following code, by assigning an |
fe122940 |
607 | C<undef> value to the attribute. |
608 | |
609 | $object->set_something(undef); |
610 | |
59e7697f |
611 | =item I<reader> |
612 | |
1d68af04 |
613 | This is a basic read-only accessor, it will just return the value of |
fe122940 |
614 | the attribute. |
615 | |
59e7697f |
616 | =item I<writer> |
617 | |
1d68af04 |
618 | This is a basic write accessor, it accepts a single argument, and |
619 | assigns that value to the attribute. This method does not intentially |
620 | return a value, however perl will return the result of the last |
621 | expression in the subroutine, which returns in this returning the |
622 | same value that it was passed. |
59e7697f |
623 | |
fe122940 |
624 | B<NOTE:> |
1d68af04 |
625 | This method will properly handle the following code, by assigning an |
fe122940 |
626 | C<undef> value to the attribute. |
59e7697f |
627 | |
fe122940 |
628 | $object->set_something(); |
629 | |
630 | =item I<predicate> |
631 | |
07dca7e3 |
632 | This is a basic test to see if any value has been set for the |
633 | attribute. It will return true (C<1>) if the attribute has been set |
634 | to any value (even C<undef>), and false (C<0>) otherwise. |
635 | |
636 | B<NOTE:> |
637 | The predicate will return true even when you set an attribute's |
638 | value to C<undef>. This behaviour has changed as of version 0.43. In |
639 | older versions, the predicate (erroneously) checked for attribute |
640 | value definedness, instead of presence as it is now. |
641 | |
642 | If you really want to get rid of the value, you have to define and |
643 | use a I<clearer> (see below). |
644 | |
7d28758b |
645 | =item I<clearer> |
646 | |
647 | This is the a method that will uninitialize the attr, reverting lazy values |
648 | back to their "unfulfilled" state. |
649 | |
59e7697f |
650 | =back |
552e3d24 |
651 | |
bd4e03f9 |
652 | =item B<clone (%options)> |
653 | |
127d39a7 |
654 | This will return a clone of the attribute instance, allowing the overriding |
655 | of various attributes through the C<%options> supplied. |
656 | |
bd4e03f9 |
657 | =item B<initialize_instance_slot ($instance, $params)> |
658 | |
127d39a7 |
659 | This method is used internally to initialize the approriate slot for this |
660 | attribute in a given C<$instance>, the C<$params> passed are those that were |
661 | passed to the constructor. |
662 | |
1d68af04 |
663 | =back |
552e3d24 |
664 | |
16e960bd |
665 | =head2 Value management |
666 | |
1d68af04 |
667 | These methods are basically "backdoors" to the instance, which can be used |
668 | to bypass the regular accessors, but still stay within the context of the MOP. |
2367814a |
669 | |
1d68af04 |
670 | These methods are not for general use, and should only be used if you really |
2367814a |
671 | know what you are doing. |
672 | |
16e960bd |
673 | =over 4 |
674 | |
3545c727 |
675 | =item B<set_value ($instance, $value)> |
16e960bd |
676 | |
677 | Set the value without going through the accessor. Note that this may be done to |
678 | even attributes with just read only accessors. |
679 | |
c0921932 |
680 | =item B<set_initial_value ($instance, $value)> |
681 | |
682 | This method sets the value without going through the accessor -- but it is only |
683 | called when the instance data is first initialized. |
684 | |
3545c727 |
685 | =item B<get_value ($instance)> |
16e960bd |
686 | |
687 | Return the value without going through the accessor. Note that this may be done |
688 | even to attributes with just write only accessors. |
689 | |
3545c727 |
690 | =item B<has_value ($instance)> |
691 | |
92d2abfa |
692 | Return a boolean indicating if the item in the C<$instance> has a value in it. |
2367814a |
693 | This is basically what the default C<predicate> method calls. |
694 | |
3545c727 |
695 | =item B<clear_value ($instance)> |
696 | |
2367814a |
697 | This will clear the value in the C<$instance>. This is basically what the default |
1d68af04 |
698 | C<clearer> would call. Note that this may be done even if the attirbute does not |
2367814a |
699 | have any associated read, write or clear methods. |
700 | |
16e960bd |
701 | =back |
702 | |
552e3d24 |
703 | =head2 Informational |
704 | |
1d68af04 |
705 | These are all basic read-only value accessors for the values |
fe122940 |
706 | passed into C<new>. I think they are pretty much self-explanitory. |
707 | |
552e3d24 |
708 | =over 4 |
709 | |
710 | =item B<name> |
711 | |
712 | =item B<accessor> |
713 | |
714 | =item B<reader> |
715 | |
716 | =item B<writer> |
717 | |
c50c603e |
718 | =item B<predicate> |
719 | |
7d28758b |
720 | =item B<clearer> |
721 | |
0ab65f99 |
722 | =item B<initializer> |
723 | |
552e3d24 |
724 | =item B<init_arg> |
725 | |
495af518 |
726 | =item B<is_default_a_coderef> |
727 | |
fe122940 |
728 | =item B<default (?$instance)> |
729 | |
92d2abfa |
730 | Return the default value for the attribute. |
731 | |
732 | If you pass in an C<$instance> argument to this accessor and the |
733 | I<default> is a CODE reference, then the CODE reference will be |
734 | executed with the C<$instance> as its argument. |
552e3d24 |
735 | |
c57c8b10 |
736 | =item B<slots> |
737 | |
92d2abfa |
738 | Return a list of slots required by the attribute. This is usually |
c57c8b10 |
739 | just one, which is the name of the attribute. |
740 | |
b25109b1 |
741 | =item B<get_read_method> |
742 | |
743 | =item B<get_write_method> |
744 | |
5da16d1b |
745 | Return the name of a method name suitable for reading / writing the value |
746 | of the attribute in the associated class. Suitable for use whether |
747 | C<reader> and C<writer> or C<accessor> was used. |
748 | |
749 | =item B<get_read_method_ref> |
750 | |
751 | =item B<get_write_method_ref> |
752 | |
753 | Return the CODE reference of a method suitable for reading / writing the |
754 | value of the attribute in the associated class. Suitable for use whether |
755 | C<reader> and C<writer> or C<accessor> was specified or not. |
756 | |
127d39a7 |
757 | NOTE: If no reader/writer/accessor was specified, this will use the |
5da16d1b |
758 | attribute get_value/set_value methods, which can be very inefficient. |
b25109b1 |
759 | |
9e517e01 |
760 | =item B<has_read_method> |
761 | |
762 | =item B<has_write_method> |
763 | |
764 | Return whether a method exists suitable for reading / writing the value |
765 | of the attribute in the associated class. Suitable for use whether |
766 | C<reader> and C<writer> or C<accessor> was used. |
767 | |
552e3d24 |
768 | =back |
769 | |
770 | =head2 Informational predicates |
771 | |
a2e85e6c |
772 | These are all basic predicate methods for the values passed into C<new>. |
fe122940 |
773 | |
552e3d24 |
774 | =over 4 |
775 | |
776 | =item B<has_accessor> |
777 | |
552e3d24 |
778 | =item B<has_reader> |
779 | |
552e3d24 |
780 | =item B<has_writer> |
781 | |
c50c603e |
782 | =item B<has_predicate> |
783 | |
7d28758b |
784 | =item B<has_clearer> |
785 | |
0ab65f99 |
786 | =item B<has_initializer> |
787 | |
552e3d24 |
788 | =item B<has_init_arg> |
789 | |
552e3d24 |
790 | =item B<has_default> |
791 | |
bf731086 |
792 | =item B<has_builder> |
793 | |
552e3d24 |
794 | =back |
795 | |
9ec169fe |
796 | =head2 Class association |
797 | |
1d68af04 |
798 | These methods allow you to manage the attributes association with |
799 | the class that contains it. These methods should not be used |
2367814a |
800 | lightly, nor are they very magical, they are mostly used internally |
801 | and by metaclass instances. |
802 | |
9ec169fe |
803 | =over 4 |
804 | |
805 | =item B<associated_class> |
806 | |
2367814a |
807 | This returns the metaclass this attribute is associated with. |
808 | |
9ec169fe |
809 | =item B<attach_to_class ($class)> |
810 | |
1d68af04 |
811 | This will store a weaken reference to C<$class> internally. You should |
2367814a |
812 | note that just changing the class assocation will not remove the attribute |
813 | from it's old class, and initialize it (and it's accessors) in the new |
814 | C<$class>. It is up to you to do this manually. |
815 | |
9ec169fe |
816 | =item B<detach_from_class> |
817 | |
1d68af04 |
818 | This will remove the weakened reference to the class. It does B<not> |
819 | remove the attribute itself from the class (or remove it's accessors), |
820 | you must do that yourself if you want too. Actually if that is what |
821 | you want to do, you should probably be looking at |
2367814a |
822 | L<Class::MOP::Class::remove_attribute> instead. |
823 | |
9ec169fe |
824 | =back |
825 | |
552e3d24 |
826 | =head2 Attribute Accessor generation |
827 | |
828 | =over 4 |
829 | |
ba38bf08 |
830 | =item B<accessor_metaclass> |
831 | |
2367814a |
832 | Accessors are generated by an accessor metaclass, which is usually |
1d68af04 |
833 | a subclass of C<Class::MOP::Method::Accessor>. This method returns |
2367814a |
834 | the name of the accessor metaclass that this attribute uses. |
835 | |
836 | =item B<associate_method ($method)> |
837 | |
1d68af04 |
838 | This will associate a C<$method> with the given attribute which is |
839 | used internally by the accessor generator. |
3545c727 |
840 | |
841 | =item B<associated_methods> |
842 | |
1d68af04 |
843 | This will return the list of methods which have been associated with |
127d39a7 |
844 | the C<associate_method> methods. This is a good way of seeing what |
845 | methods are used to manage a given attribute. |
2367814a |
846 | |
9ec169fe |
847 | =item B<install_accessors> |
2eb717d5 |
848 | |
1d68af04 |
849 | This allows the attribute to generate and install code for it's own |
850 | I<accessor/reader/writer/predicate> methods. This is called by |
fe122940 |
851 | C<Class::MOP::Class::add_attribute>. |
2eb717d5 |
852 | |
1d68af04 |
853 | This method will call C<process_accessors> for each of the possible |
9ec169fe |
854 | method types (accessor, reader, writer & predicate). |
855 | |
856 | =item B<process_accessors ($type, $value)> |
857 | |
1d68af04 |
858 | This takes a C<$type> (accessor, reader, writer or predicate), and |
9ec169fe |
859 | a C<$value> (the value passed into the constructor for each of the |
1d68af04 |
860 | different types). It will then either generate the method itself |
861 | (using the C<generate_*_method> methods listed below) or it will |
862 | use the custom method passed through the constructor. |
9ec169fe |
863 | |
9ec169fe |
864 | =item B<remove_accessors> |
2eb717d5 |
865 | |
1d68af04 |
866 | This allows the attribute to remove the method for it's own |
867 | I<accessor/reader/writer/predicate/clearer>. This is called by |
fe122940 |
868 | C<Class::MOP::Class::remove_attribute>. |
2eb717d5 |
869 | |
1d68af04 |
870 | NOTE: This does not currently remove methods from the list returned |
2367814a |
871 | by C<associated_methods>, that is on the TODO list. |
872 | |
2eb717d5 |
873 | =back |
874 | |
875 | =head2 Introspection |
876 | |
877 | =over 4 |
552e3d24 |
878 | |
2eb717d5 |
879 | =item B<meta> |
552e3d24 |
880 | |
1d68af04 |
881 | This will return a B<Class::MOP::Class> instance which is related |
fe122940 |
882 | to this class. |
883 | |
1d68af04 |
884 | It should also be noted that B<Class::MOP> will actually bootstrap |
885 | this module by installing a number of attribute meta-objects into |
127d39a7 |
886 | it's metaclass. This will allow this class to reap all the benefits |
1d68af04 |
887 | of the MOP when subclassing it. |
fe122940 |
888 | |
552e3d24 |
889 | =back |
890 | |
1a09d9cc |
891 | =head1 AUTHORS |
8b978dd5 |
892 | |
a2e85e6c |
893 | Stevan Little E<lt>stevan@iinteractive.comE<gt> |
8b978dd5 |
894 | |
895 | =head1 COPYRIGHT AND LICENSE |
896 | |
69e3ab0a |
897 | Copyright 2006-2008 by Infinity Interactive, Inc. |
8b978dd5 |
898 | |
899 | L<http://www.iinteractive.com> |
900 | |
901 | This library is free software; you can redistribute it and/or modify |
1d68af04 |
902 | it under the same terms as Perl itself. |
8b978dd5 |
903 | |
16e960bd |
904 | =cut |
905 | |
7d28758b |
906 | |