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'; |
9ec169fe |
10 | use Scalar::Util 'blessed', 'reftype', 'weaken'; |
2eb717d5 |
11 | |
0c6f4c4a |
12 | our $VERSION = '0.23'; |
f0480c45 |
13 | our $AUTHORITY = 'cpan:STEVAN'; |
8b978dd5 |
14 | |
b1897d4d |
15 | use base 'Class::MOP::Object'; |
16 | |
1d68af04 |
17 | sub meta { |
727919c5 |
18 | require Class::MOP::Class; |
aa448b16 |
19 | Class::MOP::Class->initialize(blessed($_[0]) || $_[0]); |
727919c5 |
20 | } |
2eb717d5 |
21 | |
727919c5 |
22 | # NOTE: (meta-circularity) |
1d68af04 |
23 | # This method will be replaced in the |
24 | # boostrap section of Class::MOP, by |
25 | # a new version which uses the |
727919c5 |
26 | # &Class::MOP::Class::construct_instance |
27 | # method to build an attribute meta-object |
28 | # which itself is described with attribute |
1d68af04 |
29 | # meta-objects. |
727919c5 |
30 | # - Ain't meta-circularity grand? :) |
8b978dd5 |
31 | sub new { |
32 | my $class = shift; |
33 | my $name = shift; |
1d68af04 |
34 | my %options = @_; |
35 | |
cbd9f942 |
36 | (defined $name && $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 ". |
49 | "wrap then in a CODE reference (ex: sub { [] } and not [])") |
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 $options{default} ) ) { |
53 | confess("A required attribute must have either 'init_arg', 'builder', or 'default'"); |
54 | } |
8b978dd5 |
55 | bless { |
c23184fc |
56 | '$!name' => $name, |
57 | '$!accessor' => $options{accessor}, |
58 | '$!reader' => $options{reader}, |
2e877f58 |
59 | # NOTE: |
60 | # protect this from silliness |
61 | init_arg => '!............( DO NOT DO THIS )............!', |
c23184fc |
62 | '$!writer' => $options{writer}, |
63 | '$!predicate' => $options{predicate}, |
64 | '$!clearer' => $options{clearer}, |
1d68af04 |
65 | '$!builder' => $options{builder}, |
c23184fc |
66 | '$!init_arg' => $options{init_arg}, |
67 | '$!default' => $options{default}, |
1d68af04 |
68 | # keep a weakened link to the |
9ec169fe |
69 | # class we are associated with |
c23184fc |
70 | '$!associated_class' => undef, |
0ab65f99 |
71 | '$!initializer' => $options{initializer}, |
1d68af04 |
72 | # and a list of the methods |
3545c727 |
73 | # associated with this attr |
c23184fc |
74 | '@!associated_methods' => [], |
8b978dd5 |
75 | } => $class; |
76 | } |
77 | |
7b31baf4 |
78 | # NOTE: |
1d68af04 |
79 | # this is a primative (and kludgy) clone operation |
16e960bd |
80 | # for now, it will be replaced in the Class::MOP |
1d68af04 |
81 | # bootstrap with a proper one, however we know |
5659d76e |
82 | # that this one will work fine for now. |
83 | sub clone { |
84 | my $self = shift; |
85 | my %options = @_; |
86 | (blessed($self)) |
87 | || confess "Can only clone an instance"; |
88 | return bless { %{$self}, %options } => blessed($self); |
89 | } |
90 | |
bd4e03f9 |
91 | sub initialize_instance_slot { |
f892c0f0 |
92 | my ($self, $meta_instance, $instance, $params) = @_; |
c23184fc |
93 | my $init_arg = $self->{'$!init_arg'}; |
bd4e03f9 |
94 | # try to fetch the init arg from the %params ... |
8d2d4c67 |
95 | |
1d68af04 |
96 | # if nothing was in the %params, we can use the |
bd4e03f9 |
97 | # attribute's default value (if it has one) |
2e877f58 |
98 | if(defined $init_arg and exists $params->{$init_arg}){ |
0ab65f99 |
99 | $meta_instance->_set_initial_slot_value( |
100 | $instance, |
101 | $self->name, |
102 | $params->{$init_arg}, |
103 | $self->initializer, |
104 | ); |
b7bdffc3 |
105 | } |
106 | elsif (defined $self->{'$!default'}) { |
0ab65f99 |
107 | $meta_instance->_set_initial_slot_value( |
108 | $instance, |
109 | $self->name, |
110 | $self->default($instance), |
111 | $self->initializer, |
112 | ); |
b7bdffc3 |
113 | } |
114 | elsif (defined( my $builder = $self->{'$!builder'})) { |
115 | if ($builder = $instance->can($builder)) { |
0ab65f99 |
116 | $meta_instance->_set_initial_slot_value( |
117 | $instance, |
118 | $self->name, |
119 | $instance->$builder, |
120 | $self->initializer, |
121 | ); |
b7bdffc3 |
122 | } |
123 | else { |
232c4e13 |
124 | confess(blessed($instance)." does not support builder method '". $self->{'$!builder'} ."' for attribute '" . $self->name . "'"); |
8fe581e5 |
125 | } |
1d68af04 |
126 | } |
bd4e03f9 |
127 | } |
128 | |
5659d76e |
129 | # NOTE: |
1d68af04 |
130 | # the next bunch of methods will get bootstrapped |
7b31baf4 |
131 | # away in the Class::MOP bootstrapping section |
132 | |
c23184fc |
133 | sub name { $_[0]->{'$!name'} } |
c50c603e |
134 | |
c23184fc |
135 | sub associated_class { $_[0]->{'$!associated_class'} } |
136 | sub associated_methods { $_[0]->{'@!associated_methods'} } |
7b31baf4 |
137 | |
c23184fc |
138 | sub has_accessor { defined($_[0]->{'$!accessor'}) ? 1 : 0 } |
139 | sub has_reader { defined($_[0]->{'$!reader'}) ? 1 : 0 } |
140 | sub has_writer { defined($_[0]->{'$!writer'}) ? 1 : 0 } |
141 | sub has_predicate { defined($_[0]->{'$!predicate'}) ? 1 : 0 } |
142 | sub has_clearer { defined($_[0]->{'$!clearer'}) ? 1 : 0 } |
1d68af04 |
143 | sub has_builder { defined($_[0]->{'$!builder'}) ? 1 : 0 } |
c23184fc |
144 | sub has_init_arg { defined($_[0]->{'$!init_arg'}) ? 1 : 0 } |
145 | sub has_default { defined($_[0]->{'$!default'}) ? 1 : 0 } |
0ab65f99 |
146 | sub has_initializer { defined($_[0]->{'$!initializer'}) ? 1 : 0 } |
c50c603e |
147 | |
1d68af04 |
148 | sub accessor { $_[0]->{'$!accessor'} } |
c23184fc |
149 | sub reader { $_[0]->{'$!reader'} } |
150 | sub writer { $_[0]->{'$!writer'} } |
151 | sub predicate { $_[0]->{'$!predicate'} } |
152 | sub clearer { $_[0]->{'$!clearer'} } |
1d68af04 |
153 | sub builder { $_[0]->{'$!builder'} } |
c23184fc |
154 | sub init_arg { $_[0]->{'$!init_arg'} } |
0ab65f99 |
155 | sub initializer { $_[0]->{'$!initializer'} } |
c50c603e |
156 | |
7b31baf4 |
157 | # end bootstrapped away method section. |
158 | # (all methods below here are kept intact) |
159 | |
d14f6cbe |
160 | sub get_read_method { |
161 | my $self = shift; |
162 | my $reader = $self->reader || $self->accessor; |
163 | # normal case ... |
164 | return $reader unless ref $reader; |
165 | # the HASH ref case |
166 | my ($name) = %$reader; |
167 | return $name; |
168 | } |
169 | |
170 | sub get_write_method { |
171 | my $self = shift; |
172 | my $writer = $self->writer || $self->accessor; |
173 | # normal case ... |
174 | return $writer unless ref $writer; |
175 | # the HASH ref case |
176 | my ($name) = %$writer; |
177 | return $name; |
178 | } |
b25109b1 |
179 | |
5da16d1b |
180 | sub get_read_method_ref { |
181 | my $self = shift; |
742fb371 |
182 | if ((my $reader = $self->get_read_method) && $self->associated_class) { |
5da16d1b |
183 | return $self->associated_class->get_method($reader); |
184 | } |
185 | else { |
186 | return sub { $self->get_value(@_) }; |
187 | } |
188 | } |
189 | |
190 | sub get_write_method_ref { |
191 | my $self = shift; |
d14f6cbe |
192 | if ((my $writer = $self->get_write_method) && $self->associated_class) { |
742fb371 |
193 | return $self->associated_class->get_method($writer); |
5da16d1b |
194 | } |
195 | else { |
196 | return sub { $self->set_value(@_) }; |
197 | } |
198 | } |
199 | |
1d68af04 |
200 | sub is_default_a_coderef { |
201 | ('CODE' eq (reftype($_[0]->{'$!default'} || $_[0]->{default}) || '')) |
c0cbf4d9 |
202 | } |
203 | |
1d68af04 |
204 | sub default { |
c0cbf4d9 |
205 | my ($self, $instance) = @_; |
9363ea89 |
206 | if (defined $instance && $self->is_default_a_coderef) { |
1d68af04 |
207 | # if the default is a CODE ref, then |
727919c5 |
208 | # we pass in the instance and default |
1d68af04 |
209 | # can return a value based on that |
727919c5 |
210 | # instance. Somewhat crude, but works. |
c23184fc |
211 | return $self->{'$!default'}->($instance); |
1d68af04 |
212 | } |
c23184fc |
213 | $self->{'$!default'}; |
c50c603e |
214 | } |
8b978dd5 |
215 | |
c57c8b10 |
216 | # slots |
217 | |
218 | sub slots { (shift)->name } |
219 | |
1d68af04 |
220 | # class association |
727919c5 |
221 | |
9ec169fe |
222 | sub attach_to_class { |
223 | my ($self, $class) = @_; |
224 | (blessed($class) && $class->isa('Class::MOP::Class')) |
225 | || confess "You must pass a Class::MOP::Class instance (or a subclass)"; |
1d68af04 |
226 | weaken($self->{'$!associated_class'} = $class); |
9ec169fe |
227 | } |
228 | |
229 | sub detach_from_class { |
230 | my $self = shift; |
1d68af04 |
231 | $self->{'$!associated_class'} = undef; |
9ec169fe |
232 | } |
233 | |
1d68af04 |
234 | # method association |
3545c727 |
235 | |
236 | sub associate_method { |
237 | my ($self, $method) = @_; |
c23184fc |
238 | push @{$self->{'@!associated_methods'}} => $method; |
3545c727 |
239 | } |
240 | |
16e960bd |
241 | ## Slot management |
242 | |
243 | sub set_value { |
1396f86b |
244 | my ($self, $instance, $value) = @_; |
16e960bd |
245 | |
3545c727 |
246 | Class::MOP::Class->initialize(blessed($instance)) |
16e960bd |
247 | ->get_meta_instance |
3545c727 |
248 | ->set_slot_value($instance, $self->name, $value); |
16e960bd |
249 | } |
250 | |
251 | sub get_value { |
1396f86b |
252 | my ($self, $instance) = @_; |
16e960bd |
253 | |
3545c727 |
254 | Class::MOP::Class->initialize(blessed($instance)) |
16e960bd |
255 | ->get_meta_instance |
1396f86b |
256 | ->get_slot_value($instance, $self->name); |
16e960bd |
257 | } |
258 | |
3545c727 |
259 | sub has_value { |
260 | my ($self, $instance) = @_; |
1d68af04 |
261 | |
8d2d4c67 |
262 | Class::MOP::Class->initialize(blessed($instance)) |
263 | ->get_meta_instance |
264 | ->is_slot_initialized($instance, $self->name); |
3545c727 |
265 | } |
266 | |
267 | sub clear_value { |
268 | my ($self, $instance) = @_; |
1d68af04 |
269 | |
3545c727 |
270 | Class::MOP::Class->initialize(blessed($instance)) |
271 | ->get_meta_instance |
1d68af04 |
272 | ->deinitialize_slot($instance, $self->name); |
3545c727 |
273 | } |
274 | |
ba38bf08 |
275 | ## load em up ... |
c0cbf4d9 |
276 | |
ba38bf08 |
277 | sub accessor_metaclass { 'Class::MOP::Method::Accessor' } |
c0cbf4d9 |
278 | |
9ec169fe |
279 | sub process_accessors { |
c0cbf4d9 |
280 | my ($self, $type, $accessor, $generate_as_inline_methods) = @_; |
013b1897 |
281 | if (reftype($accessor)) { |
282 | (reftype($accessor) eq 'HASH') |
7d28758b |
283 | || confess "bad accessor/reader/writer/predicate/clearer format, must be a HASH ref"; |
4d47b77f |
284 | my ($name, $method) = %{$accessor}; |
3545c727 |
285 | $method = $self->accessor_metaclass->wrap($method); |
286 | $self->associate_method($method); |
1d68af04 |
287 | return ($name, $method); |
2eb717d5 |
288 | } |
9ec169fe |
289 | else { |
1d68af04 |
290 | my $inline_me = ($generate_as_inline_methods && $self->associated_class->instance_metaclass->is_inlinable); |
ba38bf08 |
291 | my $method; |
292 | eval { |
293 | $method = $self->accessor_metaclass->new( |
294 | attribute => $self, |
d90b42a6 |
295 | is_inline => $inline_me, |
ba38bf08 |
296 | accessor_type => $type, |
1d68af04 |
297 | ); |
ba38bf08 |
298 | }; |
1d68af04 |
299 | confess "Could not create the '$type' method for " . $self->name . " because : $@" if $@; |
3545c727 |
300 | $self->associate_method($method); |
ba38bf08 |
301 | return ($accessor, $method); |
1d68af04 |
302 | } |
9ec169fe |
303 | } |
304 | |
305 | sub install_accessors { |
c0cbf4d9 |
306 | my $self = shift; |
307 | my $inline = shift; |
308 | my $class = $self->associated_class; |
1d68af04 |
309 | |
9ec169fe |
310 | $class->add_method( |
c0cbf4d9 |
311 | $self->process_accessors('accessor' => $self->accessor(), $inline) |
9ec169fe |
312 | ) if $self->has_accessor(); |
313 | |
1d68af04 |
314 | $class->add_method( |
c0cbf4d9 |
315 | $self->process_accessors('reader' => $self->reader(), $inline) |
9ec169fe |
316 | ) if $self->has_reader(); |
317 | |
318 | $class->add_method( |
c0cbf4d9 |
319 | $self->process_accessors('writer' => $self->writer(), $inline) |
9ec169fe |
320 | ) if $self->has_writer(); |
321 | |
322 | $class->add_method( |
c0cbf4d9 |
323 | $self->process_accessors('predicate' => $self->predicate(), $inline) |
9ec169fe |
324 | ) if $self->has_predicate(); |
1d68af04 |
325 | |
7d28758b |
326 | $class->add_method( |
327 | $self->process_accessors('clearer' => $self->clearer(), $inline) |
328 | ) if $self->has_clearer(); |
1d68af04 |
329 | |
9ec169fe |
330 | return; |
2eb717d5 |
331 | } |
332 | |
b51af7f9 |
333 | { |
334 | my $_remove_accessor = sub { |
335 | my ($accessor, $class) = @_; |
c50c603e |
336 | if (reftype($accessor) && reftype($accessor) eq 'HASH') { |
337 | ($accessor) = keys %{$accessor}; |
1d68af04 |
338 | } |
339 | my $method = $class->get_method($accessor); |
340 | $class->remove_method($accessor) |
ba38bf08 |
341 | if (blessed($method) && $method->isa('Class::MOP::Method::Accessor')); |
b51af7f9 |
342 | }; |
1d68af04 |
343 | |
b51af7f9 |
344 | sub remove_accessors { |
9ec169fe |
345 | my $self = shift; |
2367814a |
346 | # TODO: |
1d68af04 |
347 | # we really need to make sure to remove from the |
348 | # associates methods here as well. But this is |
349 | # such a slimly used method, I am not worried |
2367814a |
350 | # about it right now. |
9ec169fe |
351 | $_remove_accessor->($self->accessor(), $self->associated_class()) if $self->has_accessor(); |
352 | $_remove_accessor->($self->reader(), $self->associated_class()) if $self->has_reader(); |
353 | $_remove_accessor->($self->writer(), $self->associated_class()) if $self->has_writer(); |
354 | $_remove_accessor->($self->predicate(), $self->associated_class()) if $self->has_predicate(); |
7d28758b |
355 | $_remove_accessor->($self->clearer(), $self->associated_class()) if $self->has_clearer(); |
1d68af04 |
356 | return; |
b51af7f9 |
357 | } |
358 | |
8b978dd5 |
359 | } |
360 | |
361 | 1; |
362 | |
363 | __END__ |
364 | |
365 | =pod |
366 | |
1d68af04 |
367 | =head1 NAME |
8b978dd5 |
368 | |
369 | Class::MOP::Attribute - Attribute Meta Object |
370 | |
371 | =head1 SYNOPSIS |
1d68af04 |
372 | |
8b978dd5 |
373 | Class::MOP::Attribute->new('$foo' => ( |
fe122940 |
374 | accessor => 'foo', # dual purpose get/set accessor |
1d68af04 |
375 | predicate => 'has_foo' # predicate check for defined-ness |
fe122940 |
376 | init_arg => '-foo', # class->new will look for a -foo key |
377 | default => 'BAR IS BAZ!' # if no -foo key is provided, use this |
8b978dd5 |
378 | )); |
1d68af04 |
379 | |
8b978dd5 |
380 | Class::MOP::Attribute->new('$.bar' => ( |
fe122940 |
381 | reader => 'bar', # getter |
1d68af04 |
382 | writer => 'set_bar', # setter |
383 | predicate => 'has_bar' # predicate check for defined-ness |
fe122940 |
384 | init_arg => ':bar', # class->new will look for a :bar key |
8b978dd5 |
385 | # no default value means it is undef |
386 | )); |
387 | |
388 | =head1 DESCRIPTION |
389 | |
fe122940 |
390 | The Attribute Protocol is almost entirely an invention of this module, |
1d68af04 |
391 | and is completely optional to this MOP. This is because Perl 5 does not |
392 | have consistent notion of what is an attribute of a class. There are |
393 | so many ways in which this is done, and very few (if any) are |
fe122940 |
394 | easily discoverable by this module. |
552e3d24 |
395 | |
1d68af04 |
396 | So, all that said, this module attempts to inject some order into this |
397 | chaos, by introducing a consistent API which can be used to create |
fe122940 |
398 | object attributes. |
552e3d24 |
399 | |
400 | =head1 METHODS |
401 | |
402 | =head2 Creation |
403 | |
404 | =over 4 |
405 | |
fe122940 |
406 | =item B<new ($name, ?%options)> |
407 | |
1d68af04 |
408 | An attribute must (at the very least), have a C<$name>. All other |
a2e85e6c |
409 | C<%options> are contained added as key-value pairs. Acceptable keys |
fe122940 |
410 | are as follows: |
411 | |
412 | =over 4 |
413 | |
414 | =item I<init_arg> |
415 | |
1d68af04 |
416 | This should be a string value representing the expected key in |
417 | an initialization hash. For instance, if we have an I<init_arg> |
fe122940 |
418 | value of C<-foo>, then the following code will Just Work. |
419 | |
420 | MyClass->meta->construct_instance(-foo => "Hello There"); |
421 | |
1d68af04 |
422 | In an init_arg is not assigned, it will automatically use the |
7b31baf4 |
423 | value of C<$name>. |
424 | |
1d68af04 |
425 | =item I<builder> |
426 | |
427 | The value of this key is the name of the method that will be |
428 | called to obtain the value used to initialize the attribute. |
429 | This should be a method in the class associated with the attribute, |
430 | not a method in the attribute class itself. |
fe122940 |
431 | |
4c4a6c41 |
432 | =item I<default> |
433 | |
434 | The value of this key is the default value which |
435 | C<Class::MOP::Class::construct_instance> will initialize the |
436 | attribute to. |
437 | |
fe122940 |
438 | B<NOTE:> |
1d68af04 |
439 | If the value is a simple scalar (string or number), then it can |
440 | be just passed as is. However, if you wish to initialize it with |
441 | a HASH or ARRAY ref, then you need to wrap that inside a CODE |
fe122940 |
442 | reference, like so: |
443 | |
444 | Class::MOP::Attribute->new('@foo' => ( |
445 | default => sub { [] }, |
446 | )); |
1d68af04 |
447 | |
448 | # or ... |
449 | |
fe122940 |
450 | Class::MOP::Attribute->new('%foo' => ( |
451 | default => sub { {} }, |
1d68af04 |
452 | )); |
fe122940 |
453 | |
1d68af04 |
454 | If you wish to initialize an attribute with a CODE reference |
fe122940 |
455 | itself, then you need to wrap that in a subroutine as well, like |
456 | so: |
1d68af04 |
457 | |
fe122940 |
458 | Class::MOP::Attribute->new('&foo' => ( |
459 | default => sub { sub { print "Hello World" } }, |
460 | )); |
461 | |
1d68af04 |
462 | And lastly, if the value of your attribute is dependent upon |
463 | some other aspect of the instance structure, then you can take |
464 | advantage of the fact that when the I<default> value is a CODE |
465 | reference, it is passed the raw (unblessed) instance structure |
fe122940 |
466 | as it's only argument. So you can do things like this: |
467 | |
468 | Class::MOP::Attribute->new('$object_identity' => ( |
469 | default => sub { Scalar::Util::refaddr($_[0]) }, |
470 | )); |
471 | |
1d68af04 |
472 | This last feature is fairly limited as there is no gurantee of |
473 | the order of attribute initializations, so you cannot perform |
474 | any kind of dependent initializations. However, if this is |
475 | something you need, you could subclass B<Class::MOP::Class> and |
476 | this class to acheive it. However, this is currently left as |
fe122940 |
477 | an exercise to the reader :). |
478 | |
479 | =back |
480 | |
7d28758b |
481 | The I<accessor>, I<reader>, I<writer>, I<predicate> and I<clearer> keys can |
482 | contain either; the name of the method and an appropriate default one will be |
483 | generated for you, B<or> a HASH ref containing exactly one key (which will be |
484 | used as the name of the method) and one value, which should contain a CODE |
485 | reference which will be installed as the method itself. |
59e7697f |
486 | |
487 | =over 4 |
488 | |
489 | =item I<accessor> |
490 | |
1d68af04 |
491 | The I<accessor> is a standard perl-style read/write accessor. It will |
492 | return the value of the attribute, and if a value is passed as an argument, |
fe122940 |
493 | it will assign that value to the attribute. |
494 | |
495 | B<NOTE:> |
1d68af04 |
496 | This method will properly handle the following code, by assigning an |
fe122940 |
497 | C<undef> value to the attribute. |
498 | |
499 | $object->set_something(undef); |
500 | |
59e7697f |
501 | =item I<reader> |
502 | |
1d68af04 |
503 | This is a basic read-only accessor, it will just return the value of |
fe122940 |
504 | the attribute. |
505 | |
59e7697f |
506 | =item I<writer> |
507 | |
1d68af04 |
508 | This is a basic write accessor, it accepts a single argument, and |
509 | assigns that value to the attribute. This method does not intentially |
510 | return a value, however perl will return the result of the last |
511 | expression in the subroutine, which returns in this returning the |
512 | same value that it was passed. |
59e7697f |
513 | |
fe122940 |
514 | B<NOTE:> |
1d68af04 |
515 | This method will properly handle the following code, by assigning an |
fe122940 |
516 | C<undef> value to the attribute. |
59e7697f |
517 | |
fe122940 |
518 | $object->set_something(); |
519 | |
520 | =item I<predicate> |
521 | |
07dca7e3 |
522 | This is a basic test to see if any value has been set for the |
523 | attribute. It will return true (C<1>) if the attribute has been set |
524 | to any value (even C<undef>), and false (C<0>) otherwise. |
525 | |
526 | B<NOTE:> |
527 | The predicate will return true even when you set an attribute's |
528 | value to C<undef>. This behaviour has changed as of version 0.43. In |
529 | older versions, the predicate (erroneously) checked for attribute |
530 | value definedness, instead of presence as it is now. |
531 | |
532 | If you really want to get rid of the value, you have to define and |
533 | use a I<clearer> (see below). |
534 | |
59e7697f |
535 | |
7d28758b |
536 | =item I<clearer> |
537 | |
538 | This is the a method that will uninitialize the attr, reverting lazy values |
539 | back to their "unfulfilled" state. |
540 | |
59e7697f |
541 | =back |
552e3d24 |
542 | |
bd4e03f9 |
543 | =item B<clone (%options)> |
544 | |
545 | =item B<initialize_instance_slot ($instance, $params)> |
546 | |
1d68af04 |
547 | =back |
552e3d24 |
548 | |
16e960bd |
549 | =head2 Value management |
550 | |
1d68af04 |
551 | These methods are basically "backdoors" to the instance, which can be used |
552 | to bypass the regular accessors, but still stay within the context of the MOP. |
2367814a |
553 | |
1d68af04 |
554 | These methods are not for general use, and should only be used if you really |
2367814a |
555 | know what you are doing. |
556 | |
16e960bd |
557 | =over 4 |
558 | |
3545c727 |
559 | =item B<set_value ($instance, $value)> |
16e960bd |
560 | |
561 | Set the value without going through the accessor. Note that this may be done to |
562 | even attributes with just read only accessors. |
563 | |
3545c727 |
564 | =item B<get_value ($instance)> |
16e960bd |
565 | |
566 | Return the value without going through the accessor. Note that this may be done |
567 | even to attributes with just write only accessors. |
568 | |
3545c727 |
569 | =item B<has_value ($instance)> |
570 | |
92d2abfa |
571 | Return a boolean indicating if the item in the C<$instance> has a value in it. |
2367814a |
572 | This is basically what the default C<predicate> method calls. |
573 | |
3545c727 |
574 | =item B<clear_value ($instance)> |
575 | |
2367814a |
576 | This will clear the value in the C<$instance>. This is basically what the default |
1d68af04 |
577 | C<clearer> would call. Note that this may be done even if the attirbute does not |
2367814a |
578 | have any associated read, write or clear methods. |
579 | |
16e960bd |
580 | =back |
581 | |
552e3d24 |
582 | =head2 Informational |
583 | |
1d68af04 |
584 | These are all basic read-only value accessors for the values |
fe122940 |
585 | passed into C<new>. I think they are pretty much self-explanitory. |
586 | |
552e3d24 |
587 | =over 4 |
588 | |
589 | =item B<name> |
590 | |
591 | =item B<accessor> |
592 | |
593 | =item B<reader> |
594 | |
595 | =item B<writer> |
596 | |
c50c603e |
597 | =item B<predicate> |
598 | |
7d28758b |
599 | =item B<clearer> |
600 | |
0ab65f99 |
601 | =item B<initializer> |
602 | |
552e3d24 |
603 | =item B<init_arg> |
604 | |
495af518 |
605 | =item B<is_default_a_coderef> |
606 | |
fe122940 |
607 | =item B<default (?$instance)> |
608 | |
92d2abfa |
609 | Return the default value for the attribute. |
610 | |
611 | If you pass in an C<$instance> argument to this accessor and the |
612 | I<default> is a CODE reference, then the CODE reference will be |
613 | executed with the C<$instance> as its argument. |
552e3d24 |
614 | |
c57c8b10 |
615 | =item B<slots> |
616 | |
92d2abfa |
617 | Return a list of slots required by the attribute. This is usually |
c57c8b10 |
618 | just one, which is the name of the attribute. |
619 | |
b25109b1 |
620 | =item B<get_read_method> |
621 | |
622 | =item B<get_write_method> |
623 | |
5da16d1b |
624 | Return the name of a method name suitable for reading / writing the value |
625 | of the attribute in the associated class. Suitable for use whether |
626 | C<reader> and C<writer> or C<accessor> was used. |
627 | |
628 | =item B<get_read_method_ref> |
629 | |
630 | =item B<get_write_method_ref> |
631 | |
632 | Return the CODE reference of a method suitable for reading / writing the |
633 | value of the attribute in the associated class. Suitable for use whether |
634 | C<reader> and C<writer> or C<accessor> was specified or not. |
635 | |
636 | NOTE: If not reader/writer/accessor was specified, this will use the |
637 | attribute get_value/set_value methods, which can be very inefficient. |
b25109b1 |
638 | |
552e3d24 |
639 | =back |
640 | |
641 | =head2 Informational predicates |
642 | |
a2e85e6c |
643 | These are all basic predicate methods for the values passed into C<new>. |
fe122940 |
644 | |
552e3d24 |
645 | =over 4 |
646 | |
647 | =item B<has_accessor> |
648 | |
552e3d24 |
649 | =item B<has_reader> |
650 | |
552e3d24 |
651 | =item B<has_writer> |
652 | |
c50c603e |
653 | =item B<has_predicate> |
654 | |
7d28758b |
655 | =item B<has_clearer> |
656 | |
0ab65f99 |
657 | =item B<has_initializer> |
658 | |
552e3d24 |
659 | =item B<has_init_arg> |
660 | |
552e3d24 |
661 | =item B<has_default> |
662 | |
bf731086 |
663 | =item B<has_builder> |
664 | |
552e3d24 |
665 | =back |
666 | |
9ec169fe |
667 | =head2 Class association |
668 | |
1d68af04 |
669 | These methods allow you to manage the attributes association with |
670 | the class that contains it. These methods should not be used |
2367814a |
671 | lightly, nor are they very magical, they are mostly used internally |
672 | and by metaclass instances. |
673 | |
9ec169fe |
674 | =over 4 |
675 | |
676 | =item B<associated_class> |
677 | |
2367814a |
678 | This returns the metaclass this attribute is associated with. |
679 | |
9ec169fe |
680 | =item B<attach_to_class ($class)> |
681 | |
1d68af04 |
682 | This will store a weaken reference to C<$class> internally. You should |
2367814a |
683 | note that just changing the class assocation will not remove the attribute |
684 | from it's old class, and initialize it (and it's accessors) in the new |
685 | C<$class>. It is up to you to do this manually. |
686 | |
9ec169fe |
687 | =item B<detach_from_class> |
688 | |
1d68af04 |
689 | This will remove the weakened reference to the class. It does B<not> |
690 | remove the attribute itself from the class (or remove it's accessors), |
691 | you must do that yourself if you want too. Actually if that is what |
692 | you want to do, you should probably be looking at |
2367814a |
693 | L<Class::MOP::Class::remove_attribute> instead. |
694 | |
9ec169fe |
695 | =back |
696 | |
552e3d24 |
697 | =head2 Attribute Accessor generation |
698 | |
699 | =over 4 |
700 | |
ba38bf08 |
701 | =item B<accessor_metaclass> |
702 | |
2367814a |
703 | Accessors are generated by an accessor metaclass, which is usually |
1d68af04 |
704 | a subclass of C<Class::MOP::Method::Accessor>. This method returns |
2367814a |
705 | the name of the accessor metaclass that this attribute uses. |
706 | |
707 | =item B<associate_method ($method)> |
708 | |
1d68af04 |
709 | This will associate a C<$method> with the given attribute which is |
710 | used internally by the accessor generator. |
3545c727 |
711 | |
712 | =item B<associated_methods> |
713 | |
1d68af04 |
714 | This will return the list of methods which have been associated with |
715 | the C<associate_method> methods. |
2367814a |
716 | |
9ec169fe |
717 | =item B<install_accessors> |
2eb717d5 |
718 | |
1d68af04 |
719 | This allows the attribute to generate and install code for it's own |
720 | I<accessor/reader/writer/predicate> methods. This is called by |
fe122940 |
721 | C<Class::MOP::Class::add_attribute>. |
2eb717d5 |
722 | |
1d68af04 |
723 | This method will call C<process_accessors> for each of the possible |
9ec169fe |
724 | method types (accessor, reader, writer & predicate). |
725 | |
726 | =item B<process_accessors ($type, $value)> |
727 | |
1d68af04 |
728 | This takes a C<$type> (accessor, reader, writer or predicate), and |
9ec169fe |
729 | a C<$value> (the value passed into the constructor for each of the |
1d68af04 |
730 | different types). It will then either generate the method itself |
731 | (using the C<generate_*_method> methods listed below) or it will |
732 | use the custom method passed through the constructor. |
9ec169fe |
733 | |
9ec169fe |
734 | =item B<remove_accessors> |
2eb717d5 |
735 | |
1d68af04 |
736 | This allows the attribute to remove the method for it's own |
737 | I<accessor/reader/writer/predicate/clearer>. This is called by |
fe122940 |
738 | C<Class::MOP::Class::remove_attribute>. |
2eb717d5 |
739 | |
1d68af04 |
740 | NOTE: This does not currently remove methods from the list returned |
2367814a |
741 | by C<associated_methods>, that is on the TODO list. |
742 | |
2eb717d5 |
743 | =back |
744 | |
745 | =head2 Introspection |
746 | |
747 | =over 4 |
552e3d24 |
748 | |
2eb717d5 |
749 | =item B<meta> |
552e3d24 |
750 | |
1d68af04 |
751 | This will return a B<Class::MOP::Class> instance which is related |
fe122940 |
752 | to this class. |
753 | |
1d68af04 |
754 | It should also be noted that B<Class::MOP> will actually bootstrap |
755 | this module by installing a number of attribute meta-objects into |
756 | it's metaclass. This will allow this class to reap all the benifits |
757 | of the MOP when subclassing it. |
fe122940 |
758 | |
552e3d24 |
759 | =back |
760 | |
1a09d9cc |
761 | =head1 AUTHORS |
8b978dd5 |
762 | |
a2e85e6c |
763 | Stevan Little E<lt>stevan@iinteractive.comE<gt> |
8b978dd5 |
764 | |
765 | =head1 COPYRIGHT AND LICENSE |
766 | |
69e3ab0a |
767 | Copyright 2006-2008 by Infinity Interactive, Inc. |
8b978dd5 |
768 | |
769 | L<http://www.iinteractive.com> |
770 | |
771 | This library is free software; you can redistribute it and/or modify |
1d68af04 |
772 | it under the same terms as Perl itself. |
8b978dd5 |
773 | |
16e960bd |
774 | =cut |
775 | |
7d28758b |
776 | |