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 | |
f6ca0704 |
13 | our $VERSION = '0.94'; |
d519662a |
14 | $VERSION = eval $VERSION; |
f0480c45 |
15 | our $AUTHORITY = 'cpan:STEVAN'; |
8b978dd5 |
16 | |
b1897d4d |
17 | use base 'Class::MOP::Object'; |
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 $options{default}; |
8fe581e5 |
46 | } else { |
47 | (is_default_a_coderef(\%options)) |
48 | || confess("References are not allowed as default values, you must ". |
3c0a8087 |
49 | "wrap the default of '$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 | |
5659d76e |
159 | # NOTE: |
1d68af04 |
160 | # the next bunch of methods will get bootstrapped |
7b31baf4 |
161 | # away in the Class::MOP bootstrapping section |
162 | |
8683db0e |
163 | sub associated_class { $_[0]->{'associated_class'} } |
164 | sub associated_methods { $_[0]->{'associated_methods'} } |
165 | |
b3fa93c7 |
166 | sub has_accessor { defined($_[0]->{'accessor'}) } |
167 | sub has_reader { defined($_[0]->{'reader'}) } |
168 | sub has_writer { defined($_[0]->{'writer'}) } |
169 | sub has_predicate { defined($_[0]->{'predicate'}) } |
170 | sub has_clearer { defined($_[0]->{'clearer'}) } |
171 | sub has_builder { defined($_[0]->{'builder'}) } |
172 | sub has_init_arg { defined($_[0]->{'init_arg'}) } |
173 | sub has_default { defined($_[0]->{'default'}) } |
174 | sub has_initializer { defined($_[0]->{'initializer'}) } |
dc9d420c |
175 | sub has_insertion_order { defined($_[0]->{'insertion_order'}) } |
8683db0e |
176 | |
d9d99689 |
177 | sub accessor { $_[0]->{'accessor'} } |
178 | sub reader { $_[0]->{'reader'} } |
179 | sub writer { $_[0]->{'writer'} } |
180 | sub predicate { $_[0]->{'predicate'} } |
181 | sub clearer { $_[0]->{'clearer'} } |
182 | sub builder { $_[0]->{'builder'} } |
183 | sub init_arg { $_[0]->{'init_arg'} } |
184 | sub initializer { $_[0]->{'initializer'} } |
185 | sub definition_context { $_[0]->{'definition_context'} } |
dc9d420c |
186 | sub insertion_order { $_[0]->{'insertion_order'} } |
943cbe2d |
187 | sub _set_insertion_order { $_[0]->{'insertion_order'} = $_[1] } |
c50c603e |
188 | |
7b31baf4 |
189 | # end bootstrapped away method section. |
190 | # (all methods below here are kept intact) |
191 | |
9e517e01 |
192 | sub has_read_method { $_[0]->has_reader || $_[0]->has_accessor } |
193 | sub has_write_method { $_[0]->has_writer || $_[0]->has_accessor } |
194 | |
d14f6cbe |
195 | sub get_read_method { |
196 | my $self = shift; |
197 | my $reader = $self->reader || $self->accessor; |
198 | # normal case ... |
199 | return $reader unless ref $reader; |
200 | # the HASH ref case |
201 | my ($name) = %$reader; |
202 | return $name; |
203 | } |
204 | |
205 | sub get_write_method { |
206 | my $self = shift; |
207 | my $writer = $self->writer || $self->accessor; |
208 | # normal case ... |
209 | return $writer unless ref $writer; |
210 | # the HASH ref case |
211 | my ($name) = %$writer; |
212 | return $name; |
213 | } |
b25109b1 |
214 | |
5da16d1b |
215 | sub get_read_method_ref { |
216 | my $self = shift; |
742fb371 |
217 | if ((my $reader = $self->get_read_method) && $self->associated_class) { |
5da16d1b |
218 | return $self->associated_class->get_method($reader); |
219 | } |
220 | else { |
def5c0b5 |
221 | my $code = sub { $self->get_value(@_) }; |
222 | if (my $class = $self->associated_class) { |
223 | return $class->method_metaclass->wrap( |
224 | $code, |
225 | package_name => $class->name, |
226 | name => '__ANON__' |
227 | ); |
228 | } |
229 | else { |
230 | return $code; |
231 | } |
5da16d1b |
232 | } |
233 | } |
234 | |
235 | sub get_write_method_ref { |
236 | my $self = shift; |
d14f6cbe |
237 | if ((my $writer = $self->get_write_method) && $self->associated_class) { |
742fb371 |
238 | return $self->associated_class->get_method($writer); |
5da16d1b |
239 | } |
240 | else { |
def5c0b5 |
241 | my $code = sub { $self->set_value(@_) }; |
242 | if (my $class = $self->associated_class) { |
243 | return $class->method_metaclass->wrap( |
244 | $code, |
245 | package_name => $class->name, |
246 | name => '__ANON__' |
247 | ); |
248 | } |
249 | else { |
250 | return $code; |
251 | } |
5da16d1b |
252 | } |
253 | } |
254 | |
1d68af04 |
255 | sub is_default_a_coderef { |
ed337aad |
256 | my ($value) = $_[0]->{'default'}; |
257 | return unless ref($value); |
258 | return ref($value) eq 'CODE' || (blessed($value) && $value->isa('Class::MOP::Method')); |
c0cbf4d9 |
259 | } |
260 | |
1d68af04 |
261 | sub default { |
c0cbf4d9 |
262 | my ($self, $instance) = @_; |
9363ea89 |
263 | if (defined $instance && $self->is_default_a_coderef) { |
1d68af04 |
264 | # if the default is a CODE ref, then |
727919c5 |
265 | # we pass in the instance and default |
1d68af04 |
266 | # can return a value based on that |
727919c5 |
267 | # instance. Somewhat crude, but works. |
8683db0e |
268 | return $self->{'default'}->($instance); |
1d68af04 |
269 | } |
8683db0e |
270 | $self->{'default'}; |
c50c603e |
271 | } |
8b978dd5 |
272 | |
c57c8b10 |
273 | # slots |
274 | |
275 | sub slots { (shift)->name } |
276 | |
1d68af04 |
277 | # class association |
727919c5 |
278 | |
9ec169fe |
279 | sub attach_to_class { |
280 | my ($self, $class) = @_; |
281 | (blessed($class) && $class->isa('Class::MOP::Class')) |
282 | || confess "You must pass a Class::MOP::Class instance (or a subclass)"; |
8683db0e |
283 | weaken($self->{'associated_class'} = $class); |
9ec169fe |
284 | } |
285 | |
286 | sub detach_from_class { |
287 | my $self = shift; |
8683db0e |
288 | $self->{'associated_class'} = undef; |
9ec169fe |
289 | } |
290 | |
1d68af04 |
291 | # method association |
3545c727 |
292 | |
293 | sub associate_method { |
294 | my ($self, $method) = @_; |
8683db0e |
295 | push @{$self->{'associated_methods'}} => $method; |
3545c727 |
296 | } |
297 | |
16e960bd |
298 | ## Slot management |
299 | |
ef91a0e2 |
300 | sub set_initial_value { |
301 | my ($self, $instance, $value) = @_; |
e76b01fb |
302 | $self->_set_initial_slot_value( |
b3fa93c7 |
303 | Class::MOP::Class->initialize(ref($instance))->get_meta_instance, |
8ee74136 |
304 | $instance, |
305 | $value |
306 | ); |
ef91a0e2 |
307 | } |
308 | |
7e5efe15 |
309 | sub set_value { shift->set_raw_value(@_) } |
310 | sub get_value { shift->get_raw_value(@_) } |
311 | |
312 | sub set_raw_value { |
1396f86b |
313 | my ($self, $instance, $value) = @_; |
16e960bd |
314 | |
b3fa93c7 |
315 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
316 | ->get_meta_instance |
317 | ->set_slot_value($instance, $self->name, $value); |
16e960bd |
318 | } |
319 | |
7e5efe15 |
320 | sub get_raw_value { |
1396f86b |
321 | my ($self, $instance) = @_; |
16e960bd |
322 | |
b3fa93c7 |
323 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
324 | ->get_meta_instance |
325 | ->get_slot_value($instance, $self->name); |
16e960bd |
326 | } |
327 | |
3545c727 |
328 | sub has_value { |
329 | my ($self, $instance) = @_; |
1d68af04 |
330 | |
b3fa93c7 |
331 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
332 | ->get_meta_instance |
333 | ->is_slot_initialized($instance, $self->name); |
3545c727 |
334 | } |
335 | |
336 | sub clear_value { |
337 | my ($self, $instance) = @_; |
1d68af04 |
338 | |
b3fa93c7 |
339 | Class::MOP::Class->initialize(ref($instance)) |
da34f054 |
340 | ->get_meta_instance |
341 | ->deinitialize_slot($instance, $self->name); |
3545c727 |
342 | } |
343 | |
ba38bf08 |
344 | ## load em up ... |
c0cbf4d9 |
345 | |
ba38bf08 |
346 | sub accessor_metaclass { 'Class::MOP::Method::Accessor' } |
c0cbf4d9 |
347 | |
45a183fb |
348 | sub _process_accessors { |
c0cbf4d9 |
349 | my ($self, $type, $accessor, $generate_as_inline_methods) = @_; |
d9d99689 |
350 | |
351 | my $method_ctx; |
352 | |
353 | if ( my $ctx = $self->definition_context ) { |
354 | $method_ctx = { %$ctx }; |
355 | } |
356 | |
9b522fc4 |
357 | if (ref($accessor)) { |
358 | (ref($accessor) eq 'HASH') |
7d28758b |
359 | || confess "bad accessor/reader/writer/predicate/clearer format, must be a HASH ref"; |
4d47b77f |
360 | my ($name, $method) = %{$accessor}; |
4c105333 |
361 | $method = $self->accessor_metaclass->wrap( |
362 | $method, |
363 | package_name => $self->associated_class->name, |
364 | name => $name, |
d9d99689 |
365 | definition_context => $method_ctx, |
4c105333 |
366 | ); |
3545c727 |
367 | $self->associate_method($method); |
1d68af04 |
368 | return ($name, $method); |
2eb717d5 |
369 | } |
9ec169fe |
370 | else { |
1d68af04 |
371 | my $inline_me = ($generate_as_inline_methods && $self->associated_class->instance_metaclass->is_inlinable); |
ba38bf08 |
372 | my $method; |
a8344505 |
373 | try { |
d9d99689 |
374 | if ( $method_ctx ) { |
375 | my $desc = "accessor $accessor"; |
376 | if ( $accessor ne $self->name ) { |
377 | $desc .= " of attribute " . $self->name; |
378 | } |
379 | |
380 | $method_ctx->{description} = $desc; |
381 | } |
382 | |
ba38bf08 |
383 | $method = $self->accessor_metaclass->new( |
384 | attribute => $self, |
d90b42a6 |
385 | is_inline => $inline_me, |
ba38bf08 |
386 | accessor_type => $type, |
4c105333 |
387 | package_name => $self->associated_class->name, |
388 | name => $accessor, |
d9d99689 |
389 | definition_context => $method_ctx, |
1d68af04 |
390 | ); |
a8344505 |
391 | } |
392 | catch { |
393 | confess "Could not create the '$type' method for " . $self->name . " because : $_"; |
ba38bf08 |
394 | }; |
3545c727 |
395 | $self->associate_method($method); |
ba38bf08 |
396 | return ($accessor, $method); |
1d68af04 |
397 | } |
9ec169fe |
398 | } |
399 | |
400 | sub install_accessors { |
c0cbf4d9 |
401 | my $self = shift; |
402 | my $inline = shift; |
403 | my $class = $self->associated_class; |
1d68af04 |
404 | |
9ec169fe |
405 | $class->add_method( |
45a183fb |
406 | $self->_process_accessors('accessor' => $self->accessor(), $inline) |
9ec169fe |
407 | ) if $self->has_accessor(); |
408 | |
1d68af04 |
409 | $class->add_method( |
45a183fb |
410 | $self->_process_accessors('reader' => $self->reader(), $inline) |
9ec169fe |
411 | ) if $self->has_reader(); |
412 | |
413 | $class->add_method( |
45a183fb |
414 | $self->_process_accessors('writer' => $self->writer(), $inline) |
9ec169fe |
415 | ) if $self->has_writer(); |
416 | |
417 | $class->add_method( |
45a183fb |
418 | $self->_process_accessors('predicate' => $self->predicate(), $inline) |
9ec169fe |
419 | ) if $self->has_predicate(); |
1d68af04 |
420 | |
7d28758b |
421 | $class->add_method( |
45a183fb |
422 | $self->_process_accessors('clearer' => $self->clearer(), $inline) |
7d28758b |
423 | ) if $self->has_clearer(); |
1d68af04 |
424 | |
9ec169fe |
425 | return; |
2eb717d5 |
426 | } |
427 | |
b51af7f9 |
428 | { |
429 | my $_remove_accessor = sub { |
430 | my ($accessor, $class) = @_; |
9b522fc4 |
431 | if (ref($accessor) && ref($accessor) eq 'HASH') { |
c50c603e |
432 | ($accessor) = keys %{$accessor}; |
1d68af04 |
433 | } |
434 | my $method = $class->get_method($accessor); |
435 | $class->remove_method($accessor) |
b3fa93c7 |
436 | if (ref($method) && $method->isa('Class::MOP::Method::Accessor')); |
b51af7f9 |
437 | }; |
1d68af04 |
438 | |
b51af7f9 |
439 | sub remove_accessors { |
9ec169fe |
440 | my $self = shift; |
2367814a |
441 | # TODO: |
1d68af04 |
442 | # we really need to make sure to remove from the |
443 | # associates methods here as well. But this is |
444 | # such a slimly used method, I am not worried |
2367814a |
445 | # about it right now. |
9ec169fe |
446 | $_remove_accessor->($self->accessor(), $self->associated_class()) if $self->has_accessor(); |
447 | $_remove_accessor->($self->reader(), $self->associated_class()) if $self->has_reader(); |
448 | $_remove_accessor->($self->writer(), $self->associated_class()) if $self->has_writer(); |
449 | $_remove_accessor->($self->predicate(), $self->associated_class()) if $self->has_predicate(); |
7d28758b |
450 | $_remove_accessor->($self->clearer(), $self->associated_class()) if $self->has_clearer(); |
1d68af04 |
451 | return; |
b51af7f9 |
452 | } |
453 | |
8b978dd5 |
454 | } |
455 | |
456 | 1; |
457 | |
458 | __END__ |
459 | |
460 | =pod |
461 | |
1d68af04 |
462 | =head1 NAME |
8b978dd5 |
463 | |
464 | Class::MOP::Attribute - Attribute Meta Object |
465 | |
466 | =head1 SYNOPSIS |
1d68af04 |
467 | |
2e23f7dc |
468 | Class::MOP::Attribute->new( |
469 | foo => ( |
470 | accessor => 'foo', # dual purpose get/set accessor |
471 | predicate => 'has_foo', # predicate check for defined-ness |
472 | init_arg => '-foo', # class->new will look for a -foo key |
473 | default => 'BAR IS BAZ!' # if no -foo key is provided, use this |
474 | ) |
475 | ); |
476 | |
477 | Class::MOP::Attribute->new( |
478 | bar => ( |
479 | reader => 'bar', # getter |
480 | writer => 'set_bar', # setter |
481 | predicate => 'has_bar', # predicate check for defined-ness |
482 | init_arg => ':bar', # class->new will look for a :bar key |
483 | # no default value means it is undef |
484 | ) |
485 | ); |
8b978dd5 |
486 | |
487 | =head1 DESCRIPTION |
488 | |
2e23f7dc |
489 | The Attribute Protocol is almost entirely an invention of |
490 | C<Class::MOP>. Perl 5 does not have a consistent notion of |
491 | attributes. There are so many ways in which this is done, and very few |
492 | (if any) are easily discoverable by this module. |
552e3d24 |
493 | |
2e23f7dc |
494 | With that said, this module attempts to inject some order into this |
1d68af04 |
495 | chaos, by introducing a consistent API which can be used to create |
fe122940 |
496 | object attributes. |
552e3d24 |
497 | |
498 | =head1 METHODS |
499 | |
500 | =head2 Creation |
501 | |
502 | =over 4 |
503 | |
2e23f7dc |
504 | =item B<< Class::MOP::Attribute->new($name, ?%options) >> |
fe122940 |
505 | |
1d68af04 |
506 | An attribute must (at the very least), have a C<$name>. All other |
2e23f7dc |
507 | C<%options> are added as key-value pairs. |
fe122940 |
508 | |
2e23f7dc |
509 | =over 8 |
fe122940 |
510 | |
76187047 |
511 | =item * init_arg |
fe122940 |
512 | |
2e23f7dc |
513 | This is a string value representing the expected key in an |
514 | initialization hash. For instance, if we have an C<init_arg> value of |
515 | C<-foo>, then the following code will Just Work. |
fe122940 |
516 | |
d69fb6b3 |
517 | MyClass->meta->new_object( -foo => 'Hello There' ); |
fe122940 |
518 | |
2e23f7dc |
519 | If an init_arg is not assigned, it will automatically use the |
520 | attribute's name. If C<init_arg> is explicitly set to C<undef>, the |
521 | attribute cannot be specified during initialization. |
7b31baf4 |
522 | |
76187047 |
523 | =item * builder |
1d68af04 |
524 | |
2e23f7dc |
525 | This provides the name of a method that will be called to initialize |
526 | the attribute. This method will be called on the object after it is |
527 | constructed. It is expected to return a valid value for the attribute. |
fe122940 |
528 | |
76187047 |
529 | =item * default |
4c4a6c41 |
530 | |
2e23f7dc |
531 | This can be used to provide an explicit default for initializing the |
532 | attribute. If the default you provide is a subroutine reference, then |
533 | this reference will be called I<as a method> on the object. |
4c4a6c41 |
534 | |
2e23f7dc |
535 | If the value is a simple scalar (string or number), then it can be |
536 | just passed as is. However, if you wish to initialize it with a HASH |
537 | or ARRAY ref, then you need to wrap that inside a subroutine |
538 | reference: |
fe122940 |
539 | |
2e23f7dc |
540 | Class::MOP::Attribute->new( |
541 | 'foo' => ( |
542 | default => sub { [] }, |
543 | ) |
544 | ); |
1d68af04 |
545 | |
546 | # or ... |
547 | |
2e23f7dc |
548 | Class::MOP::Attribute->new( |
549 | 'foo' => ( |
550 | default => sub { {} }, |
551 | ) |
552 | ); |
553 | |
554 | If you wish to initialize an attribute with a subroutine reference |
555 | itself, then you need to wrap that in a subroutine as well: |
556 | |
557 | Class::MOP::Attribute->new( |
558 | 'foo' => ( |
559 | default => sub { |
560 | sub { print "Hello World" } |
561 | }, |
562 | ) |
563 | ); |
564 | |
565 | And lastly, if the value of your attribute is dependent upon some |
566 | other aspect of the instance structure, then you can take advantage of |
567 | the fact that when the C<default> value is called as a method: |
568 | |
569 | Class::MOP::Attribute->new( |
570 | 'object_identity' => ( |
571 | default => sub { Scalar::Util::refaddr( $_[0] ) }, |
572 | ) |
573 | ); |
574 | |
575 | Note that there is no guarantee that attributes are initialized in any |
576 | particular order, so you cannot rely on the value of some other |
577 | attribute when generating the default. |
fe122940 |
578 | |
76187047 |
579 | =item * initializer |
0ef07b33 |
580 | |
2e23f7dc |
581 | This option can be either a method name or a subroutine |
582 | reference. This method will be called when setting the attribute's |
583 | value in the constructor. Unlike C<default> and C<builder>, the |
584 | initializer is only called when a value is provided to the |
585 | constructor. The initializer allows you to munge this value during |
586 | object construction. |
587 | |
588 | The initializer is called as a method with three arguments. The first |
589 | is the value that was passed to the constructor. The second is a |
590 | subroutine reference that can be called to actually set the |
591 | attribute's value, and the last is the associated |
592 | C<Class::MOP::Attribute> object. |
593 | |
594 | This contrived example shows an initializer that sets the attribute to |
595 | twice the given value. |
596 | |
597 | Class::MOP::Attribute->new( |
598 | 'doubled' => ( |
599 | initializer => sub { |
ea62c8ab |
600 | my ( $self, $value, $set, $attr ) = @_; |
2e23f7dc |
601 | $set->( $value * 2 ); |
602 | }, |
603 | ) |
604 | ); |
605 | |
606 | Since an initializer can be a method name, you can easily make |
0ef07b33 |
607 | attribute initialization use the writer: |
608 | |
2e23f7dc |
609 | Class::MOP::Attribute->new( |
610 | 'some_attr' => ( |
611 | writer => 'some_attr', |
612 | initializer => 'some_attr', |
613 | ) |
614 | ); |
0ef07b33 |
615 | |
2e23f7dc |
616 | Your writer will need to examine C<@_> and determine under which |
617 | context it is being called. |
127d39a7 |
618 | |
fe122940 |
619 | =back |
620 | |
2e23f7dc |
621 | The C<accessor>, C<reader>, C<writer>, C<predicate> and C<clearer> |
622 | options all accept the same parameters. You can provide the name of |
623 | the method, in which case an appropriate default method will be |
624 | generated for you. Or instead you can also provide hash reference |
625 | containing exactly one key (the method name) and one value. The value |
626 | should be a subroutine reference, which will be installed as the |
627 | method itself. |
59e7697f |
628 | |
76187047 |
629 | =over 8 |
59e7697f |
630 | |
76187047 |
631 | =item * accessor |
59e7697f |
632 | |
2e23f7dc |
633 | An C<accessor> is a standard Perl-style read/write accessor. It will |
634 | return the value of the attribute, and if a value is passed as an |
635 | argument, it will assign that value to the attribute. |
fe122940 |
636 | |
2e23f7dc |
637 | Note that C<undef> is a legitimate value, so this will work: |
fe122940 |
638 | |
639 | $object->set_something(undef); |
640 | |
76187047 |
641 | =item * reader |
59e7697f |
642 | |
2e23f7dc |
643 | This is a basic read-only accessor. It returns the value of the |
644 | attribute. |
fe122940 |
645 | |
76187047 |
646 | =item * writer |
59e7697f |
647 | |
1d68af04 |
648 | This is a basic write accessor, it accepts a single argument, and |
2e23f7dc |
649 | assigns that value to the attribute. |
59e7697f |
650 | |
2e23f7dc |
651 | Note that C<undef> is a legitimate value, so this will work: |
59e7697f |
652 | |
2e23f7dc |
653 | $object->set_something(undef); |
fe122940 |
654 | |
76187047 |
655 | =item * predicate |
fe122940 |
656 | |
2e23f7dc |
657 | The predicate method returns a boolean indicating whether or not the |
658 | attribute has been explicitly set. |
07dca7e3 |
659 | |
2e23f7dc |
660 | Note that the predicate returns true even if the attribute was set to |
661 | a false value (C<0> or C<undef>). |
07dca7e3 |
662 | |
76187047 |
663 | =item * clearer |
7d28758b |
664 | |
2e23f7dc |
665 | This method will uninitialize the attribute. After an attribute is |
666 | cleared, its C<predicate> will return false. |
7d28758b |
667 | |
76187047 |
668 | =item * definition_context |
f8813817 |
669 | |
670 | Mostly, this exists as a hook for the benefit of Moose. |
671 | |
672 | This option should be a hash reference containing several keys which |
673 | will be used when inlining the attribute's accessors. The keys should |
674 | include C<line>, the line number where the attribute was created, and |
675 | either C<file> or C<description>. |
676 | |
677 | This information will ultimately be used when eval'ing inlined |
678 | accessor code so that error messages report a useful line and file |
679 | name. |
680 | |
59e7697f |
681 | =back |
552e3d24 |
682 | |
2e23f7dc |
683 | =item B<< $attr->clone(%options) >> |
bd4e03f9 |
684 | |
2e23f7dc |
685 | This clones the attribute. Any options you provide will override the |
686 | settings of the original attribute. You can change the name of the new |
687 | attribute by passing a C<name> key in C<%options>. |
127d39a7 |
688 | |
2e23f7dc |
689 | =back |
bd4e03f9 |
690 | |
2e23f7dc |
691 | =head2 Informational |
127d39a7 |
692 | |
2e23f7dc |
693 | These are all basic read-only accessors for the values passed into |
694 | the constructor. |
552e3d24 |
695 | |
2e23f7dc |
696 | =over 4 |
16e960bd |
697 | |
2e23f7dc |
698 | =item B<< $attr->name >> |
2367814a |
699 | |
76187047 |
700 | Returns the attribute's name. |
701 | |
2e23f7dc |
702 | =item B<< $attr->accessor >> |
2367814a |
703 | |
2e23f7dc |
704 | =item B<< $attr->reader >> |
16e960bd |
705 | |
2e23f7dc |
706 | =item B<< $attr->writer >> |
16e960bd |
707 | |
2e23f7dc |
708 | =item B<< $attr->predicate >> |
16e960bd |
709 | |
2e23f7dc |
710 | =item B<< $attr->clearer >> |
c0921932 |
711 | |
2e23f7dc |
712 | The C<accessor>, C<reader>, C<writer>, C<predicate>, and C<clearer> |
713 | methods all return exactly what was passed to the constructor, so it |
a6710c60 |
714 | can be either a string containing a method name, or a hash reference. |
c0921932 |
715 | |
2e23f7dc |
716 | =item B<< $attr->initializer >> |
16e960bd |
717 | |
a6710c60 |
718 | Returns the initializer as passed to the constructor, so this may be |
2e23f7dc |
719 | either a method name or a subroutine reference. |
16e960bd |
720 | |
2e23f7dc |
721 | =item B<< $attr->init_arg >> |
3545c727 |
722 | |
2e23f7dc |
723 | =item B<< $attr->is_default_a_coderef >> |
2367814a |
724 | |
2e23f7dc |
725 | =item B<< $attr->default($instance) >> |
3545c727 |
726 | |
2e23f7dc |
727 | The C<$instance> argument is optional. If you don't pass it, the |
728 | return value for this method is exactly what was passed to the |
729 | constructor, either a simple scalar or a subroutine reference. |
2367814a |
730 | |
2e23f7dc |
731 | If you I<do> pass an C<$instance> and the default is a subroutine |
732 | reference, then the reference is called as a method on the |
733 | C<$instance> and the generated value is returned. |
16e960bd |
734 | |
2e23f7dc |
735 | =item B<< $attr->slots >> |
552e3d24 |
736 | |
2e23f7dc |
737 | Return a list of slots required by the attribute. This is usually just |
738 | one, the name of the attribute. |
fe122940 |
739 | |
2e23f7dc |
740 | A slot is the name of the hash key used to store the attribute in an |
741 | object instance. |
552e3d24 |
742 | |
2e23f7dc |
743 | =item B<< $attr->get_read_method >> |
552e3d24 |
744 | |
2e23f7dc |
745 | =item B<< $attr->get_write_method >> |
552e3d24 |
746 | |
2e23f7dc |
747 | Returns the name of a method suitable for reading or writing the value |
748 | of the attribute in the associated class. |
552e3d24 |
749 | |
2e23f7dc |
750 | If an attribute is read- or write-only, then these methods can return |
751 | C<undef> as appropriate. |
552e3d24 |
752 | |
2e23f7dc |
753 | =item B<< $attr->has_read_method >> |
c50c603e |
754 | |
2e23f7dc |
755 | =item B<< $attr->has_write_method >> |
7d28758b |
756 | |
2e23f7dc |
757 | This returns a boolean indicating whether the attribute has a I<named> |
758 | read or write method. |
0ab65f99 |
759 | |
2e23f7dc |
760 | =item B<< $attr->get_read_method_ref >> |
552e3d24 |
761 | |
2e23f7dc |
762 | =item B<< $attr->get_write_method_ref >> |
495af518 |
763 | |
2e23f7dc |
764 | Returns the subroutine reference of a method suitable for reading or |
765 | writing the attribute's value in the associated class. These methods |
766 | always return a subroutine reference, regardless of whether or not the |
767 | attribute is read- or write-only. |
768 | |
eeff7496 |
769 | =item B<< $attr->insertion_order >> |
770 | |
771 | If this attribute has been inserted into a class, this returns a zero |
772 | based index regarding the order of insertion. |
773 | |
2e23f7dc |
774 | =back |
fe122940 |
775 | |
2e23f7dc |
776 | =head2 Informational predicates |
92d2abfa |
777 | |
2e23f7dc |
778 | These are all basic predicate methods for the values passed into C<new>. |
552e3d24 |
779 | |
2e23f7dc |
780 | =over 4 |
c57c8b10 |
781 | |
2e23f7dc |
782 | =item B<< $attr->has_accessor >> |
c57c8b10 |
783 | |
2e23f7dc |
784 | =item B<< $attr->has_reader >> |
b25109b1 |
785 | |
2e23f7dc |
786 | =item B<< $attr->has_writer >> |
b25109b1 |
787 | |
2e23f7dc |
788 | =item B<< $attr->has_predicate >> |
5da16d1b |
789 | |
2e23f7dc |
790 | =item B<< $attr->has_clearer >> |
5da16d1b |
791 | |
2e23f7dc |
792 | =item B<< $attr->has_initializer >> |
5da16d1b |
793 | |
2e23f7dc |
794 | =item B<< $attr->has_init_arg >> |
5da16d1b |
795 | |
2e23f7dc |
796 | This will be I<false> if the C<init_arg> was set to C<undef>. |
b25109b1 |
797 | |
2e23f7dc |
798 | =item B<< $attr->has_default >> |
9e517e01 |
799 | |
2e23f7dc |
800 | This will be I<false> if the C<default> was set to C<undef>, since |
801 | C<undef> is the default C<default> anyway. |
9e517e01 |
802 | |
2e23f7dc |
803 | =item B<< $attr->has_builder >> |
9e517e01 |
804 | |
eeff7496 |
805 | =item B<< $attr->has_insertion_order >> |
806 | |
807 | This will be I<false> if this attribute has not be inserted into a class |
808 | |
552e3d24 |
809 | =back |
810 | |
2e23f7dc |
811 | =head2 Value management |
552e3d24 |
812 | |
a6710c60 |
813 | These methods are basically "back doors" to the instance, and can be |
2e23f7dc |
814 | used to bypass the regular accessors, but still stay within the MOP. |
815 | |
816 | These methods are not for general use, and should only be used if you |
817 | really know what you are doing. |
fe122940 |
818 | |
552e3d24 |
819 | =over 4 |
820 | |
2e23f7dc |
821 | =item B<< $attr->initialize_instance_slot($meta_instance, $instance, $params) >> |
822 | |
823 | This method is used internally to initialize the attribute's slot in |
824 | the object C<$instance>. |
825 | |
826 | The C<$params> is a hash reference of the values passed to the object |
827 | constructor. |
828 | |
829 | It's unlikely that you'll need to call this method yourself. |
552e3d24 |
830 | |
2e23f7dc |
831 | =item B<< $attr->set_value($instance, $value) >> |
552e3d24 |
832 | |
2e23f7dc |
833 | Sets the value without going through the accessor. Note that this |
834 | works even with read-only attributes. |
552e3d24 |
835 | |
7e5efe15 |
836 | =item B<< $attr->set_raw_value($instance, $value) >> |
837 | |
838 | Sets the value with no side effects such as a trigger. |
839 | |
840 | This doesn't actually apply to Class::MOP attributes, only to subclasses. |
841 | |
2e23f7dc |
842 | =item B<< $attr->set_initial_value($instance, $value) >> |
c50c603e |
843 | |
2e23f7dc |
844 | Sets the value without going through the accessor. This method is only |
845 | called when the instance is first being initialized. |
7d28758b |
846 | |
2e23f7dc |
847 | =item B<< $attr->get_value($instance) >> |
0ab65f99 |
848 | |
2e23f7dc |
849 | Returns the value without going through the accessor. Note that this |
850 | works even with write-only accessors. |
552e3d24 |
851 | |
7e5efe15 |
852 | =item B<< $sttr->get_raw_value($instance) >> |
853 | |
854 | Returns the value without any side effects such as lazy attributes. |
855 | |
856 | Doesn't actually apply to Class::MOP attributes, only to subclasses. |
857 | |
2e23f7dc |
858 | =item B<< $attr->has_value($instance) >> |
552e3d24 |
859 | |
2e23f7dc |
860 | Return a boolean indicating whether the attribute has been set in |
861 | C<$instance>. This how the default C<predicate> method works. |
862 | |
863 | =item B<< $attr->clear_value($instance) >> |
864 | |
865 | This will clear the attribute's value in C<$instance>. This is what |
866 | the default C<clearer> calls. |
867 | |
868 | Note that this works even if the attribute does not have any |
869 | associated read, write or clear methods. |
bf731086 |
870 | |
552e3d24 |
871 | =back |
872 | |
9ec169fe |
873 | =head2 Class association |
874 | |
1d68af04 |
875 | These methods allow you to manage the attributes association with |
876 | the class that contains it. These methods should not be used |
2367814a |
877 | lightly, nor are they very magical, they are mostly used internally |
878 | and by metaclass instances. |
879 | |
9ec169fe |
880 | =over 4 |
881 | |
2e23f7dc |
882 | =item B<< $attr->associated_class >> |
883 | |
884 | This returns the C<Class::MOP::Class> with which this attribute is |
885 | associated, if any. |
886 | |
887 | =item B<< $attr->attach_to_class($metaclass) >> |
9ec169fe |
888 | |
2e23f7dc |
889 | This method stores a weakened reference to the C<$metaclass> object |
890 | internally. |
2367814a |
891 | |
2e23f7dc |
892 | This method does not remove the attribute from its old class, |
893 | nor does it create any accessors in the new class. |
9ec169fe |
894 | |
2e23f7dc |
895 | It is probably best to use the L<Class::MOP::Class> C<add_attribute> |
896 | method instead. |
2367814a |
897 | |
2e23f7dc |
898 | =item B<< $attr->detach_from_class >> |
9ec169fe |
899 | |
2e23f7dc |
900 | This method removes the associate metaclass object from the attribute |
901 | it has one. |
902 | |
903 | This method does not remove the attribute itself from the class, or |
904 | remove its accessors. |
905 | |
906 | It is probably best to use the L<Class::MOP::Class> |
907 | C<remove_attribute> method instead. |
2367814a |
908 | |
9ec169fe |
909 | =back |
910 | |
552e3d24 |
911 | =head2 Attribute Accessor generation |
912 | |
913 | =over 4 |
914 | |
2e23f7dc |
915 | =item B<< $attr->accessor_metaclass >> |
ba38bf08 |
916 | |
2e23f7dc |
917 | Accessor methods are generated using an accessor metaclass. By |
918 | default, this is L<Class::MOP::Method::Accessor>. This method returns |
2367814a |
919 | the name of the accessor metaclass that this attribute uses. |
920 | |
2e23f7dc |
921 | =item B<< $attr->associate_method($method) >> |
2367814a |
922 | |
2e23f7dc |
923 | This associates a L<Class::MOP::Method> object with the |
924 | attribute. Typically, this is called internally when an attribute |
925 | generates its accessors. |
3545c727 |
926 | |
2e23f7dc |
927 | =item B<< $attr->associated_methods >> |
3545c727 |
928 | |
2e23f7dc |
929 | This returns the list of methods which have been associated with the |
930 | attribute. |
2367814a |
931 | |
2e23f7dc |
932 | =item B<< $attr->install_accessors >> |
2eb717d5 |
933 | |
2e23f7dc |
934 | This method generates and installs code the attributes various |
935 | accessors. It is typically called from the L<Class::MOP::Class> |
936 | C<add_attribute> method. |
2eb717d5 |
937 | |
2e23f7dc |
938 | =item B<< $attr->remove_accessors >> |
2eb717d5 |
939 | |
2e23f7dc |
940 | This method removes all of the accessors associated with the |
941 | attribute. |
2eb717d5 |
942 | |
2e23f7dc |
943 | This does not currently remove methods from the list returned by |
944 | C<associated_methods>. |
2367814a |
945 | |
2eb717d5 |
946 | =back |
947 | |
948 | =head2 Introspection |
949 | |
950 | =over 4 |
552e3d24 |
951 | |
45b4c423 |
952 | =item B<< Class::MOP::Attribute->meta >> |
552e3d24 |
953 | |
2e23f7dc |
954 | This will return a L<Class::MOP::Class> instance for this class. |
fe122940 |
955 | |
2e23f7dc |
956 | It should also be noted that L<Class::MOP> will actually bootstrap |
957 | this module by installing a number of attribute meta-objects into its |
958 | metaclass. |
fe122940 |
959 | |
552e3d24 |
960 | =back |
961 | |
1a09d9cc |
962 | =head1 AUTHORS |
8b978dd5 |
963 | |
a2e85e6c |
964 | Stevan Little E<lt>stevan@iinteractive.comE<gt> |
8b978dd5 |
965 | |
966 | =head1 COPYRIGHT AND LICENSE |
967 | |
070bb6c9 |
968 | Copyright 2006-2009 by Infinity Interactive, Inc. |
8b978dd5 |
969 | |
970 | L<http://www.iinteractive.com> |
971 | |
972 | This library is free software; you can redistribute it and/or modify |
1d68af04 |
973 | it under the same terms as Perl itself. |
8b978dd5 |
974 | |
16e960bd |
975 | =cut |
976 | |
7d28758b |
977 | |