Commit | Line | Data |
8b978dd5 |
1 | |
2 | package Class::MOP::Attribute; |
3 | |
4 | use strict; |
5 | use warnings; |
6 | |
2eb717d5 |
7 | use Carp 'confess'; |
9ec169fe |
8 | use Scalar::Util 'blessed', 'reftype', 'weaken'; |
2eb717d5 |
9 | |
9ec169fe |
10 | our $VERSION = '0.02'; |
8b978dd5 |
11 | |
727919c5 |
12 | sub meta { |
13 | require Class::MOP::Class; |
14 | Class::MOP::Class->initialize($_[0]) |
15 | } |
2eb717d5 |
16 | |
727919c5 |
17 | # NOTE: (meta-circularity) |
18 | # This method will be replaces in the |
19 | # boostrap section of Class::MOP, by |
20 | # a new version which uses the |
21 | # &Class::MOP::Class::construct_instance |
22 | # method to build an attribute meta-object |
23 | # which itself is described with attribute |
24 | # meta-objects. |
25 | # - Ain't meta-circularity grand? :) |
8b978dd5 |
26 | sub new { |
27 | my $class = shift; |
28 | my $name = shift; |
29 | my %options = @_; |
30 | |
cbd9f942 |
31 | (defined $name && $name) |
8b978dd5 |
32 | || confess "You must provide a name for the attribute"; |
2eb717d5 |
33 | (!exists $options{reader} && !exists $options{writer}) |
34 | || confess "You cannot declare an accessor and reader and/or writer functions" |
35 | if exists $options{accessor}; |
7b31baf4 |
36 | |
37 | $options{init_arg} = $name if not exists $options{init_arg}; |
2eb717d5 |
38 | |
8b978dd5 |
39 | bless { |
c50c603e |
40 | name => $name, |
41 | accessor => $options{accessor}, |
42 | reader => $options{reader}, |
43 | writer => $options{writer}, |
44 | predicate => $options{predicate}, |
45 | init_arg => $options{init_arg}, |
9ec169fe |
46 | default => $options{default}, |
47 | # keep a weakened link to the |
48 | # class we are associated with |
49 | associated_class => undef, |
8b978dd5 |
50 | } => $class; |
51 | } |
52 | |
7b31baf4 |
53 | # NOTE: |
54 | # the next bunch of methods will get bootstrapped |
55 | # away in the Class::MOP bootstrapping section |
56 | |
c50c603e |
57 | sub name { $_[0]->{name} } |
58 | |
7b31baf4 |
59 | sub associated_class { $_[0]->{associated_class} } |
60 | |
727919c5 |
61 | sub has_accessor { defined($_[0]->{accessor}) ? 1 : 0 } |
62 | sub has_reader { defined($_[0]->{reader}) ? 1 : 0 } |
63 | sub has_writer { defined($_[0]->{writer}) ? 1 : 0 } |
c50c603e |
64 | sub has_predicate { defined($_[0]->{predicate}) ? 1 : 0 } |
727919c5 |
65 | sub has_init_arg { defined($_[0]->{init_arg}) ? 1 : 0 } |
66 | sub has_default { defined($_[0]->{default}) ? 1 : 0 } |
c50c603e |
67 | |
68 | sub accessor { $_[0]->{accessor} } |
69 | sub reader { $_[0]->{reader} } |
70 | sub writer { $_[0]->{writer} } |
71 | sub predicate { $_[0]->{predicate} } |
72 | sub init_arg { $_[0]->{init_arg} } |
73 | |
7b31baf4 |
74 | # end bootstrapped away method section. |
75 | # (all methods below here are kept intact) |
76 | |
c50c603e |
77 | sub default { |
78 | my $self = shift; |
79 | if (reftype($self->{default}) && reftype($self->{default}) eq 'CODE') { |
727919c5 |
80 | # if the default is a CODE ref, then |
81 | # we pass in the instance and default |
82 | # can return a value based on that |
83 | # instance. Somewhat crude, but works. |
c50c603e |
84 | return $self->{default}->(shift); |
85 | } |
86 | $self->{default}; |
87 | } |
8b978dd5 |
88 | |
9ec169fe |
89 | # class association |
727919c5 |
90 | |
9ec169fe |
91 | sub attach_to_class { |
92 | my ($self, $class) = @_; |
93 | (blessed($class) && $class->isa('Class::MOP::Class')) |
94 | || confess "You must pass a Class::MOP::Class instance (or a subclass)"; |
95 | weaken($self->{associated_class} = $class); |
96 | } |
97 | |
98 | sub detach_from_class { |
99 | my $self = shift; |
100 | $self->{associated_class} = undef; |
101 | } |
102 | |
103 | ## Method generation helpers |
104 | |
105 | sub generate_accessor_method { |
106 | my ($self, $attr_name) = @_; |
107 | eval qq{sub { |
108 | \$_[0]->{'$attr_name'} = \$_[1] if scalar(\@_) == 2; |
109 | \$_[0]->{'$attr_name'}; |
110 | }}; |
111 | } |
112 | |
113 | sub generate_reader_method { |
114 | my ($self, $attr_name) = @_; |
115 | eval qq{sub { |
116 | \$_[0]->{'$attr_name'}; |
117 | }}; |
118 | } |
119 | |
120 | sub generate_writer_method { |
121 | my ($self, $attr_name) = @_; |
122 | eval qq{sub { |
123 | \$_[0]->{'$attr_name'} = \$_[1]; |
124 | }}; |
125 | } |
126 | |
127 | sub generate_predicate_method { |
128 | my ($self, $attr_name) = @_; |
129 | eval qq{sub { |
130 | defined \$_[0]->{'$attr_name'} ? 1 : 0; |
131 | }}; |
132 | } |
133 | |
134 | sub process_accessors { |
135 | my ($self, $type, $accessor) = @_; |
136 | if (reftype($accessor) && reftype($accessor) eq 'HASH') { |
137 | my ($name, $method) = each %{$accessor}; |
138 | return ($name, Class::MOP::Attribute::Accessor->wrap($method)); |
2eb717d5 |
139 | } |
9ec169fe |
140 | else { |
141 | my $generator = $self->can('generate_' . $type . '_method'); |
142 | ($generator) |
143 | || confess "There is no method generator for the type='$type'"; |
144 | if (my $method = $self->$generator($self->name)) { |
145 | return ($accessor => Class::MOP::Attribute::Accessor->wrap($method)); |
146 | } |
343203ee |
147 | confess "Could not create the '$type' method for " . $self->name . " because : $@"; |
9ec169fe |
148 | } |
149 | } |
150 | |
151 | sub install_accessors { |
152 | my $self = shift; |
153 | my $class = $self->associated_class; |
c50c603e |
154 | |
9ec169fe |
155 | $class->add_method( |
156 | $self->process_accessors('accessor' => $self->accessor()) |
157 | ) if $self->has_accessor(); |
158 | |
159 | $class->add_method( |
160 | $self->process_accessors('reader' => $self->reader()) |
161 | ) if $self->has_reader(); |
162 | |
163 | $class->add_method( |
164 | $self->process_accessors('writer' => $self->writer()) |
165 | ) if $self->has_writer(); |
166 | |
167 | $class->add_method( |
168 | $self->process_accessors('predicate' => $self->predicate()) |
169 | ) if $self->has_predicate(); |
170 | return; |
2eb717d5 |
171 | } |
172 | |
b51af7f9 |
173 | { |
174 | my $_remove_accessor = sub { |
175 | my ($accessor, $class) = @_; |
c50c603e |
176 | if (reftype($accessor) && reftype($accessor) eq 'HASH') { |
177 | ($accessor) = keys %{$accessor}; |
178 | } |
b51af7f9 |
179 | my $method = $class->get_method($accessor); |
180 | $class->remove_method($accessor) |
2eb717d5 |
181 | if (blessed($method) && $method->isa('Class::MOP::Attribute::Accessor')); |
b51af7f9 |
182 | }; |
c50c603e |
183 | |
b51af7f9 |
184 | sub remove_accessors { |
9ec169fe |
185 | my $self = shift; |
186 | $_remove_accessor->($self->accessor(), $self->associated_class()) if $self->has_accessor(); |
187 | $_remove_accessor->($self->reader(), $self->associated_class()) if $self->has_reader(); |
188 | $_remove_accessor->($self->writer(), $self->associated_class()) if $self->has_writer(); |
189 | $_remove_accessor->($self->predicate(), $self->associated_class()) if $self->has_predicate(); |
b51af7f9 |
190 | return; |
191 | } |
192 | |
8b978dd5 |
193 | } |
194 | |
2eb717d5 |
195 | package Class::MOP::Attribute::Accessor; |
196 | |
197 | use strict; |
198 | use warnings; |
199 | |
727919c5 |
200 | use Class::MOP::Method; |
201 | |
2eb717d5 |
202 | our $VERSION = '0.01'; |
203 | |
204 | our @ISA = ('Class::MOP::Method'); |
205 | |
8b978dd5 |
206 | 1; |
207 | |
208 | __END__ |
209 | |
210 | =pod |
211 | |
212 | =head1 NAME |
213 | |
214 | Class::MOP::Attribute - Attribute Meta Object |
215 | |
216 | =head1 SYNOPSIS |
217 | |
218 | Class::MOP::Attribute->new('$foo' => ( |
fe122940 |
219 | accessor => 'foo', # dual purpose get/set accessor |
220 | predicate => 'has_foo' # predicate check for defined-ness |
221 | init_arg => '-foo', # class->new will look for a -foo key |
222 | default => 'BAR IS BAZ!' # if no -foo key is provided, use this |
8b978dd5 |
223 | )); |
224 | |
225 | Class::MOP::Attribute->new('$.bar' => ( |
fe122940 |
226 | reader => 'bar', # getter |
227 | writer => 'set_bar', # setter |
228 | predicate => 'has_bar' # predicate check for defined-ness |
229 | init_arg => ':bar', # class->new will look for a :bar key |
8b978dd5 |
230 | # no default value means it is undef |
231 | )); |
232 | |
233 | =head1 DESCRIPTION |
234 | |
fe122940 |
235 | The Attribute Protocol is almost entirely an invention of this module, |
236 | and is completely optional to this MOP. This is because Perl 5 does not |
237 | have consistent notion of what is an attribute of a class. There are |
238 | so many ways in which this is done, and very few (if any) are |
239 | easily discoverable by this module. |
552e3d24 |
240 | |
241 | So, all that said, this module attempts to inject some order into this |
fe122940 |
242 | chaos, by introducing a consistent API which can be used to create |
243 | object attributes. |
552e3d24 |
244 | |
245 | =head1 METHODS |
246 | |
247 | =head2 Creation |
248 | |
249 | =over 4 |
250 | |
fe122940 |
251 | =item B<new ($name, ?%options)> |
252 | |
253 | An attribute must (at the very least), have a C<$name>. All other |
a2e85e6c |
254 | C<%options> are contained added as key-value pairs. Acceptable keys |
fe122940 |
255 | are as follows: |
256 | |
257 | =over 4 |
258 | |
259 | =item I<init_arg> |
260 | |
261 | This should be a string value representing the expected key in |
262 | an initialization hash. For instance, if we have an I<init_arg> |
263 | value of C<-foo>, then the following code will Just Work. |
264 | |
265 | MyClass->meta->construct_instance(-foo => "Hello There"); |
266 | |
7b31baf4 |
267 | In an init_arg is not assigned, it will automatically use the |
268 | value of C<$name>. |
269 | |
fe122940 |
270 | =item I<default> |
271 | |
272 | The value of this key is the default value which |
273 | C<Class::MOP::Class::construct_instance> will initialize the |
274 | attribute to. |
275 | |
276 | B<NOTE:> |
277 | If the value is a simple scalar (string or number), then it can |
278 | be just passed as is. However, if you wish to initialize it with |
279 | a HASH or ARRAY ref, then you need to wrap that inside a CODE |
280 | reference, like so: |
281 | |
282 | Class::MOP::Attribute->new('@foo' => ( |
283 | default => sub { [] }, |
284 | )); |
285 | |
286 | # or ... |
287 | |
288 | Class::MOP::Attribute->new('%foo' => ( |
289 | default => sub { {} }, |
290 | )); |
291 | |
292 | If you wish to initialize an attribute with a CODE reference |
293 | itself, then you need to wrap that in a subroutine as well, like |
294 | so: |
295 | |
296 | Class::MOP::Attribute->new('&foo' => ( |
297 | default => sub { sub { print "Hello World" } }, |
298 | )); |
299 | |
300 | And lastly, if the value of your attribute is dependent upon |
301 | some other aspect of the instance structure, then you can take |
302 | advantage of the fact that when the I<default> value is a CODE |
303 | reference, it is passed the raw (unblessed) instance structure |
304 | as it's only argument. So you can do things like this: |
305 | |
306 | Class::MOP::Attribute->new('$object_identity' => ( |
307 | default => sub { Scalar::Util::refaddr($_[0]) }, |
308 | )); |
309 | |
310 | This last feature is fairly limited as there is no gurantee of |
311 | the order of attribute initializations, so you cannot perform |
312 | any kind of dependent initializations. However, if this is |
313 | something you need, you could subclass B<Class::MOP::Class> and |
314 | this class to acheive it. However, this is currently left as |
315 | an exercise to the reader :). |
316 | |
317 | =back |
318 | |
a2e85e6c |
319 | The I<accessor>, I<reader>, I<writer> and I<predicate> keys can |
fe122940 |
320 | contain either; the name of the method and an appropriate default |
321 | one will be generated for you, B<or> a HASH ref containing exactly one |
322 | key (which will be used as the name of the method) and one value, |
323 | which should contain a CODE reference which will be installed as |
324 | the method itself. |
59e7697f |
325 | |
326 | =over 4 |
327 | |
328 | =item I<accessor> |
329 | |
fe122940 |
330 | The I<accessor> is a standard perl-style read/write accessor. It will |
331 | return the value of the attribute, and if a value is passed as an argument, |
332 | it will assign that value to the attribute. |
333 | |
334 | B<NOTE:> |
335 | This method will properly handle the following code, by assigning an |
336 | C<undef> value to the attribute. |
337 | |
338 | $object->set_something(undef); |
339 | |
59e7697f |
340 | =item I<reader> |
341 | |
fe122940 |
342 | This is a basic read-only accessor, it will just return the value of |
343 | the attribute. |
344 | |
59e7697f |
345 | =item I<writer> |
346 | |
fe122940 |
347 | This is a basic write accessor, it accepts a single argument, and |
348 | assigns that value to the attribute. This method does not intentially |
349 | return a value, however perl will return the result of the last |
350 | expression in the subroutine, which returns in this returning the |
351 | same value that it was passed. |
59e7697f |
352 | |
fe122940 |
353 | B<NOTE:> |
354 | This method will properly handle the following code, by assigning an |
355 | C<undef> value to the attribute. |
59e7697f |
356 | |
fe122940 |
357 | $object->set_something(); |
358 | |
359 | =item I<predicate> |
360 | |
361 | This is a basic test to see if the value of the attribute is not |
362 | C<undef>. It will return true (C<1>) if the attribute's value is |
363 | defined, and false (C<0>) otherwise. |
59e7697f |
364 | |
365 | =back |
552e3d24 |
366 | |
367 | =back |
368 | |
369 | =head2 Informational |
370 | |
fe122940 |
371 | These are all basic read-only value accessors for the values |
372 | passed into C<new>. I think they are pretty much self-explanitory. |
373 | |
552e3d24 |
374 | =over 4 |
375 | |
376 | =item B<name> |
377 | |
378 | =item B<accessor> |
379 | |
380 | =item B<reader> |
381 | |
382 | =item B<writer> |
383 | |
c50c603e |
384 | =item B<predicate> |
385 | |
552e3d24 |
386 | =item B<init_arg> |
387 | |
fe122940 |
388 | =item B<default (?$instance)> |
389 | |
390 | As noted in the documentation for C<new> above, if the I<default> |
391 | value is a CODE reference, this accessor will pass a single additional |
392 | argument C<$instance> into it and return the value. |
552e3d24 |
393 | |
394 | =back |
395 | |
396 | =head2 Informational predicates |
397 | |
a2e85e6c |
398 | These are all basic predicate methods for the values passed into C<new>. |
fe122940 |
399 | |
552e3d24 |
400 | =over 4 |
401 | |
402 | =item B<has_accessor> |
403 | |
552e3d24 |
404 | =item B<has_reader> |
405 | |
552e3d24 |
406 | =item B<has_writer> |
407 | |
c50c603e |
408 | =item B<has_predicate> |
409 | |
552e3d24 |
410 | =item B<has_init_arg> |
411 | |
552e3d24 |
412 | =item B<has_default> |
413 | |
552e3d24 |
414 | =back |
415 | |
9ec169fe |
416 | =head2 Class association |
417 | |
418 | =over 4 |
419 | |
420 | =item B<associated_class> |
421 | |
422 | =item B<attach_to_class ($class)> |
423 | |
424 | =item B<detach_from_class> |
425 | |
426 | =back |
427 | |
552e3d24 |
428 | =head2 Attribute Accessor generation |
429 | |
430 | =over 4 |
431 | |
9ec169fe |
432 | =item B<install_accessors> |
2eb717d5 |
433 | |
434 | This allows the attribute to generate and install code for it's own |
a2e85e6c |
435 | I<accessor/reader/writer/predicate> methods. This is called by |
fe122940 |
436 | C<Class::MOP::Class::add_attribute>. |
2eb717d5 |
437 | |
9ec169fe |
438 | This method will call C<process_accessors> for each of the possible |
439 | method types (accessor, reader, writer & predicate). |
440 | |
441 | =item B<process_accessors ($type, $value)> |
442 | |
443 | This takes a C<$type> (accessor, reader, writer or predicate), and |
444 | a C<$value> (the value passed into the constructor for each of the |
445 | different types). It will then either generate the method itself |
446 | (using the C<generate_*_method> methods listed below) or it will |
447 | use the custom method passed through the constructor. |
448 | |
449 | =over 4 |
450 | |
451 | =item B<generate_accessor_method ($attr_name)> |
452 | |
453 | =item B<generate_predicate_method ($attr_name)> |
454 | |
455 | =item B<generate_reader_method ($attr_name)> |
456 | |
457 | =item B<generate_writer_method ($attr_name)> |
458 | |
459 | =back |
460 | |
461 | =item B<remove_accessors> |
2eb717d5 |
462 | |
463 | This allows the attribute to remove the method for it's own |
a2e85e6c |
464 | I<accessor/reader/writer/predicate>. This is called by |
fe122940 |
465 | C<Class::MOP::Class::remove_attribute>. |
2eb717d5 |
466 | |
467 | =back |
468 | |
469 | =head2 Introspection |
470 | |
471 | =over 4 |
552e3d24 |
472 | |
2eb717d5 |
473 | =item B<meta> |
552e3d24 |
474 | |
fe122940 |
475 | This will return a B<Class::MOP::Class> instance which is related |
476 | to this class. |
477 | |
478 | It should also be noted that B<Class::MOP> will actually bootstrap |
479 | this module by installing a number of attribute meta-objects into |
480 | it's metaclass. This will allow this class to reap all the benifits |
481 | of the MOP when subclassing it. |
482 | |
552e3d24 |
483 | =back |
484 | |
8b978dd5 |
485 | =head1 AUTHOR |
486 | |
a2e85e6c |
487 | Stevan Little E<lt>stevan@iinteractive.comE<gt> |
8b978dd5 |
488 | |
489 | =head1 COPYRIGHT AND LICENSE |
490 | |
491 | Copyright 2006 by Infinity Interactive, Inc. |
492 | |
493 | L<http://www.iinteractive.com> |
494 | |
495 | This library is free software; you can redistribute it and/or modify |
496 | it under the same terms as Perl itself. |
497 | |
9ec169fe |
498 | =cut |