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 | |
d7b2249e |
12 | our $VERSION = '0.24'; |
f0480c45 |
13 | our $AUTHORITY = 'cpan:STEVAN'; |
8b978dd5 |
14 | |
b1897d4d |
15 | use base 'Class::MOP::Object'; |
16 | |
727919c5 |
17 | # NOTE: (meta-circularity) |
1d68af04 |
18 | # This method will be replaced in the |
19 | # boostrap section of Class::MOP, by |
20 | # a new version which uses the |
727919c5 |
21 | # &Class::MOP::Class::construct_instance |
22 | # method to build an attribute meta-object |
23 | # which itself is described with attribute |
1d68af04 |
24 | # meta-objects. |
727919c5 |
25 | # - Ain't meta-circularity grand? :) |
8b978dd5 |
26 | sub new { |
27 | my $class = shift; |
28 | my $name = shift; |
1d68af04 |
29 | my %options = @_; |
30 | |
cbd9f942 |
31 | (defined $name && $name) |
8b978dd5 |
32 | || confess "You must provide a name for the attribute"; |
1d68af04 |
33 | |
34 | $options{init_arg} = $name |
5659d76e |
35 | if not exists $options{init_arg}; |
1d68af04 |
36 | if(exists $options{builder}){ |
37 | confess("builder must be a defined scalar value which is a method name") |
38 | if ref $options{builder} || !(defined $options{builder}); |
39 | confess("Setting both default and builder is not allowed.") |
40 | if exists $options{default}; |
8fe581e5 |
41 | } else { |
42 | (is_default_a_coderef(\%options)) |
43 | || confess("References are not allowed as default values, you must ". |
3c0a8087 |
44 | "wrap the default of '$name' in a CODE reference (ex: sub { [] } and not [])") |
8fe581e5 |
45 | if exists $options{default} && ref $options{default}; |
1d68af04 |
46 | } |
2e877f58 |
47 | if( $options{required} and not( defined($options{builder}) || defined($options{init_arg}) || exists $options{default} ) ) { |
48 | confess("A required attribute must have either 'init_arg', 'builder', or 'default'"); |
49 | } |
8b978dd5 |
50 | bless { |
c23184fc |
51 | '$!name' => $name, |
52 | '$!accessor' => $options{accessor}, |
53 | '$!reader' => $options{reader}, |
8ee74136 |
54 | '$!writer' => $options{writer}, |
55 | '$!predicate' => $options{predicate}, |
56 | '$!clearer' => $options{clearer}, |
57 | '$!builder' => $options{builder}, |
58 | '$!init_arg' => $options{init_arg}, |
59 | '$!default' => $options{default}, |
60 | '$!initializer' => $options{initializer}, |
1d68af04 |
61 | # keep a weakened link to the |
9ec169fe |
62 | # class we are associated with |
c23184fc |
63 | '$!associated_class' => undef, |
1d68af04 |
64 | # and a list of the methods |
3545c727 |
65 | # associated with this attr |
c23184fc |
66 | '@!associated_methods' => [], |
8ee74136 |
67 | # NOTE: |
68 | # protect this from silliness |
2e5a2a62 |
69 | init_arg => undef, |
8b978dd5 |
70 | } => $class; |
71 | } |
72 | |
7b31baf4 |
73 | # NOTE: |
1d68af04 |
74 | # this is a primative (and kludgy) clone operation |
16e960bd |
75 | # for now, it will be replaced in the Class::MOP |
1d68af04 |
76 | # bootstrap with a proper one, however we know |
5659d76e |
77 | # that this one will work fine for now. |
78 | sub clone { |
79 | my $self = shift; |
80 | my %options = @_; |
81 | (blessed($self)) |
82 | || confess "Can only clone an instance"; |
83 | return bless { %{$self}, %options } => blessed($self); |
84 | } |
85 | |
bd4e03f9 |
86 | sub initialize_instance_slot { |
f892c0f0 |
87 | my ($self, $meta_instance, $instance, $params) = @_; |
c23184fc |
88 | my $init_arg = $self->{'$!init_arg'}; |
bd4e03f9 |
89 | # try to fetch the init arg from the %params ... |
8d2d4c67 |
90 | |
1d68af04 |
91 | # if nothing was in the %params, we can use the |
bd4e03f9 |
92 | # attribute's default value (if it has one) |
2e877f58 |
93 | if(defined $init_arg and exists $params->{$init_arg}){ |
8ee74136 |
94 | $self->_set_initial_slot_value( |
95 | $meta_instance, |
0ab65f99 |
96 | $instance, |
0ab65f99 |
97 | $params->{$init_arg}, |
0ab65f99 |
98 | ); |
b7bdffc3 |
99 | } |
100 | elsif (defined $self->{'$!default'}) { |
8ee74136 |
101 | $self->_set_initial_slot_value( |
102 | $meta_instance, |
0ab65f99 |
103 | $instance, |
0ab65f99 |
104 | $self->default($instance), |
0ab65f99 |
105 | ); |
b7bdffc3 |
106 | } |
107 | elsif (defined( my $builder = $self->{'$!builder'})) { |
108 | if ($builder = $instance->can($builder)) { |
8ee74136 |
109 | $self->_set_initial_slot_value( |
110 | $meta_instance, |
0ab65f99 |
111 | $instance, |
0ab65f99 |
112 | $instance->$builder, |
0ab65f99 |
113 | ); |
b7bdffc3 |
114 | } |
115 | else { |
232c4e13 |
116 | confess(blessed($instance)." does not support builder method '". $self->{'$!builder'} ."' for attribute '" . $self->name . "'"); |
8fe581e5 |
117 | } |
1d68af04 |
118 | } |
bd4e03f9 |
119 | } |
120 | |
8ee74136 |
121 | sub _set_initial_slot_value { |
122 | my ($self, $meta_instance, $instance, $value) = @_; |
123 | |
124 | my $slot_name = $self->name; |
125 | |
126 | return $meta_instance->set_slot_value($instance, $slot_name, $value) |
127 | unless $self->has_initializer; |
128 | |
129 | my $callback = sub { |
130 | $meta_instance->set_slot_value($instance, $slot_name, $_[0]); |
131 | }; |
132 | |
133 | my $initializer = $self->initializer; |
134 | |
135 | # most things will just want to set a value, so make it first arg |
136 | $instance->$initializer($value, $callback, $self); |
137 | } |
138 | |
5659d76e |
139 | # NOTE: |
1d68af04 |
140 | # the next bunch of methods will get bootstrapped |
7b31baf4 |
141 | # away in the Class::MOP bootstrapping section |
142 | |
c23184fc |
143 | sub name { $_[0]->{'$!name'} } |
c50c603e |
144 | |
c23184fc |
145 | sub associated_class { $_[0]->{'$!associated_class'} } |
146 | sub associated_methods { $_[0]->{'@!associated_methods'} } |
7b31baf4 |
147 | |
8ee74136 |
148 | sub has_accessor { defined($_[0]->{'$!accessor'}) ? 1 : 0 } |
149 | sub has_reader { defined($_[0]->{'$!reader'}) ? 1 : 0 } |
150 | sub has_writer { defined($_[0]->{'$!writer'}) ? 1 : 0 } |
151 | sub has_predicate { defined($_[0]->{'$!predicate'}) ? 1 : 0 } |
152 | sub has_clearer { defined($_[0]->{'$!clearer'}) ? 1 : 0 } |
153 | sub has_builder { defined($_[0]->{'$!builder'}) ? 1 : 0 } |
154 | sub has_init_arg { defined($_[0]->{'$!init_arg'}) ? 1 : 0 } |
155 | sub has_default { defined($_[0]->{'$!default'}) ? 1 : 0 } |
0ab65f99 |
156 | sub has_initializer { defined($_[0]->{'$!initializer'}) ? 1 : 0 } |
c50c603e |
157 | |
8ee74136 |
158 | sub accessor { $_[0]->{'$!accessor'} } |
159 | sub reader { $_[0]->{'$!reader'} } |
160 | sub writer { $_[0]->{'$!writer'} } |
161 | sub predicate { $_[0]->{'$!predicate'} } |
162 | sub clearer { $_[0]->{'$!clearer'} } |
163 | sub builder { $_[0]->{'$!builder'} } |
164 | sub init_arg { $_[0]->{'$!init_arg'} } |
0ab65f99 |
165 | sub initializer { $_[0]->{'$!initializer'} } |
c50c603e |
166 | |
7b31baf4 |
167 | # end bootstrapped away method section. |
168 | # (all methods below here are kept intact) |
169 | |
9e517e01 |
170 | sub has_read_method { $_[0]->has_reader || $_[0]->has_accessor } |
171 | sub has_write_method { $_[0]->has_writer || $_[0]->has_accessor } |
172 | |
d14f6cbe |
173 | sub get_read_method { |
174 | my $self = shift; |
175 | my $reader = $self->reader || $self->accessor; |
176 | # normal case ... |
177 | return $reader unless ref $reader; |
178 | # the HASH ref case |
179 | my ($name) = %$reader; |
180 | return $name; |
181 | } |
182 | |
183 | sub get_write_method { |
184 | my $self = shift; |
185 | my $writer = $self->writer || $self->accessor; |
186 | # normal case ... |
187 | return $writer unless ref $writer; |
188 | # the HASH ref case |
189 | my ($name) = %$writer; |
190 | return $name; |
191 | } |
b25109b1 |
192 | |
5da16d1b |
193 | sub get_read_method_ref { |
194 | my $self = shift; |
742fb371 |
195 | if ((my $reader = $self->get_read_method) && $self->associated_class) { |
5da16d1b |
196 | return $self->associated_class->get_method($reader); |
197 | } |
198 | else { |
199 | return sub { $self->get_value(@_) }; |
200 | } |
201 | } |
202 | |
203 | sub get_write_method_ref { |
204 | my $self = shift; |
d14f6cbe |
205 | if ((my $writer = $self->get_write_method) && $self->associated_class) { |
742fb371 |
206 | return $self->associated_class->get_method($writer); |
5da16d1b |
207 | } |
208 | else { |
209 | return sub { $self->set_value(@_) }; |
210 | } |
211 | } |
212 | |
1d68af04 |
213 | sub is_default_a_coderef { |
214 | ('CODE' eq (reftype($_[0]->{'$!default'} || $_[0]->{default}) || '')) |
c0cbf4d9 |
215 | } |
216 | |
1d68af04 |
217 | sub default { |
c0cbf4d9 |
218 | my ($self, $instance) = @_; |
9363ea89 |
219 | if (defined $instance && $self->is_default_a_coderef) { |
1d68af04 |
220 | # if the default is a CODE ref, then |
727919c5 |
221 | # we pass in the instance and default |
1d68af04 |
222 | # can return a value based on that |
727919c5 |
223 | # instance. Somewhat crude, but works. |
c23184fc |
224 | return $self->{'$!default'}->($instance); |
1d68af04 |
225 | } |
c23184fc |
226 | $self->{'$!default'}; |
c50c603e |
227 | } |
8b978dd5 |
228 | |
c57c8b10 |
229 | # slots |
230 | |
231 | sub slots { (shift)->name } |
232 | |
1d68af04 |
233 | # class association |
727919c5 |
234 | |
9ec169fe |
235 | sub attach_to_class { |
236 | my ($self, $class) = @_; |
237 | (blessed($class) && $class->isa('Class::MOP::Class')) |
238 | || confess "You must pass a Class::MOP::Class instance (or a subclass)"; |
1d68af04 |
239 | weaken($self->{'$!associated_class'} = $class); |
9ec169fe |
240 | } |
241 | |
242 | sub detach_from_class { |
243 | my $self = shift; |
1d68af04 |
244 | $self->{'$!associated_class'} = undef; |
9ec169fe |
245 | } |
246 | |
1d68af04 |
247 | # method association |
3545c727 |
248 | |
249 | sub associate_method { |
250 | my ($self, $method) = @_; |
c23184fc |
251 | push @{$self->{'@!associated_methods'}} => $method; |
3545c727 |
252 | } |
253 | |
16e960bd |
254 | ## Slot management |
255 | |
ef91a0e2 |
256 | sub set_initial_value { |
257 | my ($self, $instance, $value) = @_; |
e76b01fb |
258 | $self->_set_initial_slot_value( |
da34f054 |
259 | Class::MOP::Class->initialize(blessed($instance))->get_meta_instance, |
8ee74136 |
260 | $instance, |
261 | $value |
262 | ); |
ef91a0e2 |
263 | } |
264 | |
16e960bd |
265 | sub set_value { |
1396f86b |
266 | my ($self, $instance, $value) = @_; |
16e960bd |
267 | |
da34f054 |
268 | Class::MOP::Class->initialize(blessed($instance)) |
269 | ->get_meta_instance |
270 | ->set_slot_value($instance, $self->name, $value); |
16e960bd |
271 | } |
272 | |
273 | sub get_value { |
1396f86b |
274 | my ($self, $instance) = @_; |
16e960bd |
275 | |
da34f054 |
276 | Class::MOP::Class->initialize(blessed($instance)) |
277 | ->get_meta_instance |
278 | ->get_slot_value($instance, $self->name); |
16e960bd |
279 | } |
280 | |
3545c727 |
281 | sub has_value { |
282 | my ($self, $instance) = @_; |
1d68af04 |
283 | |
da34f054 |
284 | Class::MOP::Class->initialize(blessed($instance)) |
285 | ->get_meta_instance |
286 | ->is_slot_initialized($instance, $self->name); |
3545c727 |
287 | } |
288 | |
289 | sub clear_value { |
290 | my ($self, $instance) = @_; |
1d68af04 |
291 | |
da34f054 |
292 | Class::MOP::Class->initialize(blessed($instance)) |
293 | ->get_meta_instance |
294 | ->deinitialize_slot($instance, $self->name); |
3545c727 |
295 | } |
296 | |
ba38bf08 |
297 | ## load em up ... |
c0cbf4d9 |
298 | |
ba38bf08 |
299 | sub accessor_metaclass { 'Class::MOP::Method::Accessor' } |
c0cbf4d9 |
300 | |
9ec169fe |
301 | sub process_accessors { |
c0cbf4d9 |
302 | my ($self, $type, $accessor, $generate_as_inline_methods) = @_; |
013b1897 |
303 | if (reftype($accessor)) { |
304 | (reftype($accessor) eq 'HASH') |
7d28758b |
305 | || confess "bad accessor/reader/writer/predicate/clearer format, must be a HASH ref"; |
4d47b77f |
306 | my ($name, $method) = %{$accessor}; |
4c105333 |
307 | $method = $self->accessor_metaclass->wrap( |
308 | $method, |
309 | package_name => $self->associated_class->name, |
310 | name => $name, |
311 | ); |
3545c727 |
312 | $self->associate_method($method); |
1d68af04 |
313 | return ($name, $method); |
2eb717d5 |
314 | } |
9ec169fe |
315 | else { |
1d68af04 |
316 | my $inline_me = ($generate_as_inline_methods && $self->associated_class->instance_metaclass->is_inlinable); |
ba38bf08 |
317 | my $method; |
318 | eval { |
319 | $method = $self->accessor_metaclass->new( |
320 | attribute => $self, |
d90b42a6 |
321 | is_inline => $inline_me, |
ba38bf08 |
322 | accessor_type => $type, |
4c105333 |
323 | package_name => $self->associated_class->name, |
324 | name => $accessor, |
1d68af04 |
325 | ); |
ba38bf08 |
326 | }; |
1d68af04 |
327 | confess "Could not create the '$type' method for " . $self->name . " because : $@" if $@; |
3545c727 |
328 | $self->associate_method($method); |
ba38bf08 |
329 | return ($accessor, $method); |
1d68af04 |
330 | } |
9ec169fe |
331 | } |
332 | |
333 | sub install_accessors { |
c0cbf4d9 |
334 | my $self = shift; |
335 | my $inline = shift; |
336 | my $class = $self->associated_class; |
1d68af04 |
337 | |
9ec169fe |
338 | $class->add_method( |
c0cbf4d9 |
339 | $self->process_accessors('accessor' => $self->accessor(), $inline) |
9ec169fe |
340 | ) if $self->has_accessor(); |
341 | |
1d68af04 |
342 | $class->add_method( |
c0cbf4d9 |
343 | $self->process_accessors('reader' => $self->reader(), $inline) |
9ec169fe |
344 | ) if $self->has_reader(); |
345 | |
346 | $class->add_method( |
c0cbf4d9 |
347 | $self->process_accessors('writer' => $self->writer(), $inline) |
9ec169fe |
348 | ) if $self->has_writer(); |
349 | |
350 | $class->add_method( |
c0cbf4d9 |
351 | $self->process_accessors('predicate' => $self->predicate(), $inline) |
9ec169fe |
352 | ) if $self->has_predicate(); |
1d68af04 |
353 | |
7d28758b |
354 | $class->add_method( |
355 | $self->process_accessors('clearer' => $self->clearer(), $inline) |
356 | ) if $self->has_clearer(); |
1d68af04 |
357 | |
9ec169fe |
358 | return; |
2eb717d5 |
359 | } |
360 | |
b51af7f9 |
361 | { |
362 | my $_remove_accessor = sub { |
363 | my ($accessor, $class) = @_; |
c50c603e |
364 | if (reftype($accessor) && reftype($accessor) eq 'HASH') { |
365 | ($accessor) = keys %{$accessor}; |
1d68af04 |
366 | } |
367 | my $method = $class->get_method($accessor); |
368 | $class->remove_method($accessor) |
ba38bf08 |
369 | if (blessed($method) && $method->isa('Class::MOP::Method::Accessor')); |
b51af7f9 |
370 | }; |
1d68af04 |
371 | |
b51af7f9 |
372 | sub remove_accessors { |
9ec169fe |
373 | my $self = shift; |
2367814a |
374 | # TODO: |
1d68af04 |
375 | # we really need to make sure to remove from the |
376 | # associates methods here as well. But this is |
377 | # such a slimly used method, I am not worried |
2367814a |
378 | # about it right now. |
9ec169fe |
379 | $_remove_accessor->($self->accessor(), $self->associated_class()) if $self->has_accessor(); |
380 | $_remove_accessor->($self->reader(), $self->associated_class()) if $self->has_reader(); |
381 | $_remove_accessor->($self->writer(), $self->associated_class()) if $self->has_writer(); |
382 | $_remove_accessor->($self->predicate(), $self->associated_class()) if $self->has_predicate(); |
7d28758b |
383 | $_remove_accessor->($self->clearer(), $self->associated_class()) if $self->has_clearer(); |
1d68af04 |
384 | return; |
b51af7f9 |
385 | } |
386 | |
8b978dd5 |
387 | } |
388 | |
389 | 1; |
390 | |
391 | __END__ |
392 | |
393 | =pod |
394 | |
1d68af04 |
395 | =head1 NAME |
8b978dd5 |
396 | |
397 | Class::MOP::Attribute - Attribute Meta Object |
398 | |
399 | =head1 SYNOPSIS |
1d68af04 |
400 | |
8b978dd5 |
401 | Class::MOP::Attribute->new('$foo' => ( |
fe122940 |
402 | accessor => 'foo', # dual purpose get/set accessor |
1d68af04 |
403 | predicate => 'has_foo' # predicate check for defined-ness |
fe122940 |
404 | init_arg => '-foo', # class->new will look for a -foo key |
405 | default => 'BAR IS BAZ!' # if no -foo key is provided, use this |
8b978dd5 |
406 | )); |
1d68af04 |
407 | |
8b978dd5 |
408 | Class::MOP::Attribute->new('$.bar' => ( |
fe122940 |
409 | reader => 'bar', # getter |
1d68af04 |
410 | writer => 'set_bar', # setter |
411 | predicate => 'has_bar' # predicate check for defined-ness |
fe122940 |
412 | init_arg => ':bar', # class->new will look for a :bar key |
8b978dd5 |
413 | # no default value means it is undef |
414 | )); |
415 | |
416 | =head1 DESCRIPTION |
417 | |
fe122940 |
418 | The Attribute Protocol is almost entirely an invention of this module, |
1d68af04 |
419 | and is completely optional to this MOP. This is because Perl 5 does not |
420 | have consistent notion of what is an attribute of a class. There are |
421 | so many ways in which this is done, and very few (if any) are |
fe122940 |
422 | easily discoverable by this module. |
552e3d24 |
423 | |
1d68af04 |
424 | So, all that said, this module attempts to inject some order into this |
425 | chaos, by introducing a consistent API which can be used to create |
fe122940 |
426 | object attributes. |
552e3d24 |
427 | |
428 | =head1 METHODS |
429 | |
430 | =head2 Creation |
431 | |
432 | =over 4 |
433 | |
fe122940 |
434 | =item B<new ($name, ?%options)> |
435 | |
1d68af04 |
436 | An attribute must (at the very least), have a C<$name>. All other |
a2e85e6c |
437 | C<%options> are contained added as key-value pairs. Acceptable keys |
fe122940 |
438 | are as follows: |
439 | |
440 | =over 4 |
441 | |
442 | =item I<init_arg> |
443 | |
1d68af04 |
444 | This should be a string value representing the expected key in |
445 | an initialization hash. For instance, if we have an I<init_arg> |
fe122940 |
446 | value of C<-foo>, then the following code will Just Work. |
447 | |
448 | MyClass->meta->construct_instance(-foo => "Hello There"); |
449 | |
1d68af04 |
450 | In an init_arg is not assigned, it will automatically use the |
0ef07b33 |
451 | value of C<$name>. If an explicit C<undef> is given for an init_arg, |
452 | an attribute value can't be specified during initialization. |
7b31baf4 |
453 | |
1d68af04 |
454 | =item I<builder> |
455 | |
456 | The value of this key is the name of the method that will be |
457 | called to obtain the value used to initialize the attribute. |
458 | This should be a method in the class associated with the attribute, |
459 | not a method in the attribute class itself. |
fe122940 |
460 | |
4c4a6c41 |
461 | =item I<default> |
462 | |
463 | The value of this key is the default value which |
464 | C<Class::MOP::Class::construct_instance> will initialize the |
465 | attribute to. |
466 | |
fe122940 |
467 | B<NOTE:> |
1d68af04 |
468 | If the value is a simple scalar (string or number), then it can |
469 | be just passed as is. However, if you wish to initialize it with |
470 | a HASH or ARRAY ref, then you need to wrap that inside a CODE |
fe122940 |
471 | reference, like so: |
472 | |
473 | Class::MOP::Attribute->new('@foo' => ( |
474 | default => sub { [] }, |
475 | )); |
1d68af04 |
476 | |
477 | # or ... |
478 | |
fe122940 |
479 | Class::MOP::Attribute->new('%foo' => ( |
480 | default => sub { {} }, |
1d68af04 |
481 | )); |
fe122940 |
482 | |
1d68af04 |
483 | If you wish to initialize an attribute with a CODE reference |
fe122940 |
484 | itself, then you need to wrap that in a subroutine as well, like |
485 | so: |
1d68af04 |
486 | |
fe122940 |
487 | Class::MOP::Attribute->new('&foo' => ( |
488 | default => sub { sub { print "Hello World" } }, |
489 | )); |
490 | |
1d68af04 |
491 | And lastly, if the value of your attribute is dependent upon |
492 | some other aspect of the instance structure, then you can take |
493 | advantage of the fact that when the I<default> value is a CODE |
127d39a7 |
494 | reference, it is passed the (as yet unfinished) instance structure |
fe122940 |
495 | as it's only argument. So you can do things like this: |
496 | |
497 | Class::MOP::Attribute->new('$object_identity' => ( |
498 | default => sub { Scalar::Util::refaddr($_[0]) }, |
499 | )); |
500 | |
1d68af04 |
501 | This last feature is fairly limited as there is no gurantee of |
502 | the order of attribute initializations, so you cannot perform |
503 | any kind of dependent initializations. However, if this is |
504 | something you need, you could subclass B<Class::MOP::Class> and |
505 | this class to acheive it. However, this is currently left as |
fe122940 |
506 | an exercise to the reader :). |
507 | |
0ef07b33 |
508 | =item I<initializer> |
509 | |
510 | This may be a method name (referring to a method on the class with this |
511 | attribute) or a CODE ref. The initializer is used to set the attribute value |
512 | on an instance when the attribute is set during instance initialization. When |
513 | called, it is passed the instance (as the invocant), the value to set, a |
514 | slot-setting CODE ref, and the attribute meta-instance. The slot-setting code |
515 | is provided to make it easy to set the (possibly altered) value on the instance |
516 | without going through several more method calls. |
517 | |
0ef07b33 |
518 | This contrived example shows an initializer that sets the attribute to twice |
519 | the given value. |
520 | |
521 | Class::MOP::Attribute->new('$doubled' => ( |
522 | initializer => sub { |
523 | my ($instance, $value, $set) = @_; |
524 | $set->($value * 2); |
525 | }, |
526 | )); |
527 | |
528 | As method names can be given as initializers, one can easily make |
529 | attribute initialization use the writer: |
530 | |
531 | Class::MOP::Attribute->new('$some_attr' => ( |
532 | writer => 'some_attr', |
533 | initializer => 'some_attr', |
534 | )); |
535 | |
127d39a7 |
536 | Your writer will simply need to examine it's C<@_> and determine under |
537 | which context it is being called. |
538 | |
fe122940 |
539 | =back |
540 | |
7d28758b |
541 | The I<accessor>, I<reader>, I<writer>, I<predicate> and I<clearer> keys can |
542 | contain either; the name of the method and an appropriate default one will be |
543 | generated for you, B<or> a HASH ref containing exactly one key (which will be |
544 | used as the name of the method) and one value, which should contain a CODE |
545 | reference which will be installed as the method itself. |
59e7697f |
546 | |
547 | =over 4 |
548 | |
549 | =item I<accessor> |
550 | |
1d68af04 |
551 | The I<accessor> is a standard perl-style read/write accessor. It will |
552 | return the value of the attribute, and if a value is passed as an argument, |
fe122940 |
553 | it will assign that value to the attribute. |
554 | |
555 | B<NOTE:> |
1d68af04 |
556 | This method will properly handle the following code, by assigning an |
fe122940 |
557 | C<undef> value to the attribute. |
558 | |
559 | $object->set_something(undef); |
560 | |
59e7697f |
561 | =item I<reader> |
562 | |
1d68af04 |
563 | This is a basic read-only accessor, it will just return the value of |
fe122940 |
564 | the attribute. |
565 | |
59e7697f |
566 | =item I<writer> |
567 | |
1d68af04 |
568 | This is a basic write accessor, it accepts a single argument, and |
569 | assigns that value to the attribute. This method does not intentially |
570 | return a value, however perl will return the result of the last |
571 | expression in the subroutine, which returns in this returning the |
572 | same value that it was passed. |
59e7697f |
573 | |
fe122940 |
574 | B<NOTE:> |
1d68af04 |
575 | This method will properly handle the following code, by assigning an |
fe122940 |
576 | C<undef> value to the attribute. |
59e7697f |
577 | |
fe122940 |
578 | $object->set_something(); |
579 | |
580 | =item I<predicate> |
581 | |
07dca7e3 |
582 | This is a basic test to see if any value has been set for the |
583 | attribute. It will return true (C<1>) if the attribute has been set |
584 | to any value (even C<undef>), and false (C<0>) otherwise. |
585 | |
586 | B<NOTE:> |
587 | The predicate will return true even when you set an attribute's |
588 | value to C<undef>. This behaviour has changed as of version 0.43. In |
589 | older versions, the predicate (erroneously) checked for attribute |
590 | value definedness, instead of presence as it is now. |
591 | |
592 | If you really want to get rid of the value, you have to define and |
593 | use a I<clearer> (see below). |
594 | |
7d28758b |
595 | =item I<clearer> |
596 | |
597 | This is the a method that will uninitialize the attr, reverting lazy values |
598 | back to their "unfulfilled" state. |
599 | |
59e7697f |
600 | =back |
552e3d24 |
601 | |
bd4e03f9 |
602 | =item B<clone (%options)> |
603 | |
127d39a7 |
604 | This will return a clone of the attribute instance, allowing the overriding |
605 | of various attributes through the C<%options> supplied. |
606 | |
bd4e03f9 |
607 | =item B<initialize_instance_slot ($instance, $params)> |
608 | |
127d39a7 |
609 | This method is used internally to initialize the approriate slot for this |
610 | attribute in a given C<$instance>, the C<$params> passed are those that were |
611 | passed to the constructor. |
612 | |
1d68af04 |
613 | =back |
552e3d24 |
614 | |
16e960bd |
615 | =head2 Value management |
616 | |
1d68af04 |
617 | These methods are basically "backdoors" to the instance, which can be used |
618 | to bypass the regular accessors, but still stay within the context of the MOP. |
2367814a |
619 | |
1d68af04 |
620 | These methods are not for general use, and should only be used if you really |
2367814a |
621 | know what you are doing. |
622 | |
16e960bd |
623 | =over 4 |
624 | |
3545c727 |
625 | =item B<set_value ($instance, $value)> |
16e960bd |
626 | |
627 | Set the value without going through the accessor. Note that this may be done to |
628 | even attributes with just read only accessors. |
629 | |
c0921932 |
630 | =item B<set_initial_value ($instance, $value)> |
631 | |
632 | This method sets the value without going through the accessor -- but it is only |
633 | called when the instance data is first initialized. |
634 | |
3545c727 |
635 | =item B<get_value ($instance)> |
16e960bd |
636 | |
637 | Return the value without going through the accessor. Note that this may be done |
638 | even to attributes with just write only accessors. |
639 | |
3545c727 |
640 | =item B<has_value ($instance)> |
641 | |
92d2abfa |
642 | Return a boolean indicating if the item in the C<$instance> has a value in it. |
2367814a |
643 | This is basically what the default C<predicate> method calls. |
644 | |
3545c727 |
645 | =item B<clear_value ($instance)> |
646 | |
2367814a |
647 | This will clear the value in the C<$instance>. This is basically what the default |
1d68af04 |
648 | C<clearer> would call. Note that this may be done even if the attirbute does not |
2367814a |
649 | have any associated read, write or clear methods. |
650 | |
16e960bd |
651 | =back |
652 | |
552e3d24 |
653 | =head2 Informational |
654 | |
1d68af04 |
655 | These are all basic read-only value accessors for the values |
fe122940 |
656 | passed into C<new>. I think they are pretty much self-explanitory. |
657 | |
552e3d24 |
658 | =over 4 |
659 | |
660 | =item B<name> |
661 | |
662 | =item B<accessor> |
663 | |
664 | =item B<reader> |
665 | |
666 | =item B<writer> |
667 | |
c50c603e |
668 | =item B<predicate> |
669 | |
7d28758b |
670 | =item B<clearer> |
671 | |
0ab65f99 |
672 | =item B<initializer> |
673 | |
552e3d24 |
674 | =item B<init_arg> |
675 | |
495af518 |
676 | =item B<is_default_a_coderef> |
677 | |
fe122940 |
678 | =item B<default (?$instance)> |
679 | |
92d2abfa |
680 | Return the default value for the attribute. |
681 | |
682 | If you pass in an C<$instance> argument to this accessor and the |
683 | I<default> is a CODE reference, then the CODE reference will be |
684 | executed with the C<$instance> as its argument. |
552e3d24 |
685 | |
c57c8b10 |
686 | =item B<slots> |
687 | |
92d2abfa |
688 | Return a list of slots required by the attribute. This is usually |
c57c8b10 |
689 | just one, which is the name of the attribute. |
690 | |
b25109b1 |
691 | =item B<get_read_method> |
692 | |
693 | =item B<get_write_method> |
694 | |
5da16d1b |
695 | Return the name of a method name suitable for reading / writing the value |
696 | of the attribute in the associated class. Suitable for use whether |
697 | C<reader> and C<writer> or C<accessor> was used. |
698 | |
699 | =item B<get_read_method_ref> |
700 | |
701 | =item B<get_write_method_ref> |
702 | |
703 | Return the CODE reference of a method suitable for reading / writing the |
704 | value of the attribute in the associated class. Suitable for use whether |
705 | C<reader> and C<writer> or C<accessor> was specified or not. |
706 | |
127d39a7 |
707 | NOTE: If no reader/writer/accessor was specified, this will use the |
5da16d1b |
708 | attribute get_value/set_value methods, which can be very inefficient. |
b25109b1 |
709 | |
9e517e01 |
710 | =item B<has_read_method> |
711 | |
712 | =item B<has_write_method> |
713 | |
714 | Return whether a method exists suitable for reading / writing the value |
715 | of the attribute in the associated class. Suitable for use whether |
716 | C<reader> and C<writer> or C<accessor> was used. |
717 | |
552e3d24 |
718 | =back |
719 | |
720 | =head2 Informational predicates |
721 | |
a2e85e6c |
722 | These are all basic predicate methods for the values passed into C<new>. |
fe122940 |
723 | |
552e3d24 |
724 | =over 4 |
725 | |
726 | =item B<has_accessor> |
727 | |
552e3d24 |
728 | =item B<has_reader> |
729 | |
552e3d24 |
730 | =item B<has_writer> |
731 | |
c50c603e |
732 | =item B<has_predicate> |
733 | |
7d28758b |
734 | =item B<has_clearer> |
735 | |
0ab65f99 |
736 | =item B<has_initializer> |
737 | |
552e3d24 |
738 | =item B<has_init_arg> |
739 | |
552e3d24 |
740 | =item B<has_default> |
741 | |
bf731086 |
742 | =item B<has_builder> |
743 | |
552e3d24 |
744 | =back |
745 | |
9ec169fe |
746 | =head2 Class association |
747 | |
1d68af04 |
748 | These methods allow you to manage the attributes association with |
749 | the class that contains it. These methods should not be used |
2367814a |
750 | lightly, nor are they very magical, they are mostly used internally |
751 | and by metaclass instances. |
752 | |
9ec169fe |
753 | =over 4 |
754 | |
755 | =item B<associated_class> |
756 | |
2367814a |
757 | This returns the metaclass this attribute is associated with. |
758 | |
9ec169fe |
759 | =item B<attach_to_class ($class)> |
760 | |
1d68af04 |
761 | This will store a weaken reference to C<$class> internally. You should |
2367814a |
762 | note that just changing the class assocation will not remove the attribute |
763 | from it's old class, and initialize it (and it's accessors) in the new |
764 | C<$class>. It is up to you to do this manually. |
765 | |
9ec169fe |
766 | =item B<detach_from_class> |
767 | |
1d68af04 |
768 | This will remove the weakened reference to the class. It does B<not> |
769 | remove the attribute itself from the class (or remove it's accessors), |
770 | you must do that yourself if you want too. Actually if that is what |
771 | you want to do, you should probably be looking at |
2367814a |
772 | L<Class::MOP::Class::remove_attribute> instead. |
773 | |
9ec169fe |
774 | =back |
775 | |
552e3d24 |
776 | =head2 Attribute Accessor generation |
777 | |
778 | =over 4 |
779 | |
ba38bf08 |
780 | =item B<accessor_metaclass> |
781 | |
2367814a |
782 | Accessors are generated by an accessor metaclass, which is usually |
1d68af04 |
783 | a subclass of C<Class::MOP::Method::Accessor>. This method returns |
2367814a |
784 | the name of the accessor metaclass that this attribute uses. |
785 | |
786 | =item B<associate_method ($method)> |
787 | |
1d68af04 |
788 | This will associate a C<$method> with the given attribute which is |
789 | used internally by the accessor generator. |
3545c727 |
790 | |
791 | =item B<associated_methods> |
792 | |
1d68af04 |
793 | This will return the list of methods which have been associated with |
127d39a7 |
794 | the C<associate_method> methods. This is a good way of seeing what |
795 | methods are used to manage a given attribute. |
2367814a |
796 | |
9ec169fe |
797 | =item B<install_accessors> |
2eb717d5 |
798 | |
1d68af04 |
799 | This allows the attribute to generate and install code for it's own |
800 | I<accessor/reader/writer/predicate> methods. This is called by |
fe122940 |
801 | C<Class::MOP::Class::add_attribute>. |
2eb717d5 |
802 | |
1d68af04 |
803 | This method will call C<process_accessors> for each of the possible |
9ec169fe |
804 | method types (accessor, reader, writer & predicate). |
805 | |
806 | =item B<process_accessors ($type, $value)> |
807 | |
1d68af04 |
808 | This takes a C<$type> (accessor, reader, writer or predicate), and |
9ec169fe |
809 | a C<$value> (the value passed into the constructor for each of the |
1d68af04 |
810 | different types). It will then either generate the method itself |
811 | (using the C<generate_*_method> methods listed below) or it will |
812 | use the custom method passed through the constructor. |
9ec169fe |
813 | |
9ec169fe |
814 | =item B<remove_accessors> |
2eb717d5 |
815 | |
1d68af04 |
816 | This allows the attribute to remove the method for it's own |
817 | I<accessor/reader/writer/predicate/clearer>. This is called by |
fe122940 |
818 | C<Class::MOP::Class::remove_attribute>. |
2eb717d5 |
819 | |
1d68af04 |
820 | NOTE: This does not currently remove methods from the list returned |
2367814a |
821 | by C<associated_methods>, that is on the TODO list. |
822 | |
2eb717d5 |
823 | =back |
824 | |
825 | =head2 Introspection |
826 | |
827 | =over 4 |
552e3d24 |
828 | |
2eb717d5 |
829 | =item B<meta> |
552e3d24 |
830 | |
1d68af04 |
831 | This will return a B<Class::MOP::Class> instance which is related |
fe122940 |
832 | to this class. |
833 | |
1d68af04 |
834 | It should also be noted that B<Class::MOP> will actually bootstrap |
835 | this module by installing a number of attribute meta-objects into |
127d39a7 |
836 | it's metaclass. This will allow this class to reap all the benefits |
1d68af04 |
837 | of the MOP when subclassing it. |
fe122940 |
838 | |
552e3d24 |
839 | =back |
840 | |
1a09d9cc |
841 | =head1 AUTHORS |
8b978dd5 |
842 | |
a2e85e6c |
843 | Stevan Little E<lt>stevan@iinteractive.comE<gt> |
8b978dd5 |
844 | |
845 | =head1 COPYRIGHT AND LICENSE |
846 | |
69e3ab0a |
847 | Copyright 2006-2008 by Infinity Interactive, Inc. |
8b978dd5 |
848 | |
849 | L<http://www.iinteractive.com> |
850 | |
851 | This library is free software; you can redistribute it and/or modify |
1d68af04 |
852 | it under the same terms as Perl itself. |
8b978dd5 |
853 | |
16e960bd |
854 | =cut |
855 | |
7d28758b |
856 | |