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 | |
b9dfbf78 |
10 | our $VERSION = '0.05'; |
8b978dd5 |
11 | |
727919c5 |
12 | sub meta { |
13 | require Class::MOP::Class; |
aa448b16 |
14 | Class::MOP::Class->initialize(blessed($_[0]) || $_[0]); |
727919c5 |
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"; |
5659d76e |
33 | $options{init_arg} = $name |
34 | if not exists $options{init_arg}; |
2eb717d5 |
35 | |
8b978dd5 |
36 | bless { |
c50c603e |
37 | name => $name, |
38 | accessor => $options{accessor}, |
39 | reader => $options{reader}, |
40 | writer => $options{writer}, |
41 | predicate => $options{predicate}, |
42 | init_arg => $options{init_arg}, |
9ec169fe |
43 | default => $options{default}, |
44 | # keep a weakened link to the |
45 | # class we are associated with |
46 | associated_class => undef, |
8b978dd5 |
47 | } => $class; |
48 | } |
49 | |
7b31baf4 |
50 | # NOTE: |
5659d76e |
51 | # this is a primative (and kludgy) clone operation |
52 | # for now, it will be repleace in the Class::MOP |
53 | # bootstrap with a proper one, however we know |
54 | # that this one will work fine for now. |
55 | sub clone { |
56 | my $self = shift; |
57 | my %options = @_; |
58 | (blessed($self)) |
59 | || confess "Can only clone an instance"; |
60 | return bless { %{$self}, %options } => blessed($self); |
61 | } |
62 | |
63 | # NOTE: |
7b31baf4 |
64 | # the next bunch of methods will get bootstrapped |
65 | # away in the Class::MOP bootstrapping section |
66 | |
c50c603e |
67 | sub name { $_[0]->{name} } |
68 | |
7b31baf4 |
69 | sub associated_class { $_[0]->{associated_class} } |
70 | |
727919c5 |
71 | sub has_accessor { defined($_[0]->{accessor}) ? 1 : 0 } |
72 | sub has_reader { defined($_[0]->{reader}) ? 1 : 0 } |
73 | sub has_writer { defined($_[0]->{writer}) ? 1 : 0 } |
c50c603e |
74 | sub has_predicate { defined($_[0]->{predicate}) ? 1 : 0 } |
727919c5 |
75 | sub has_init_arg { defined($_[0]->{init_arg}) ? 1 : 0 } |
76 | sub has_default { defined($_[0]->{default}) ? 1 : 0 } |
c50c603e |
77 | |
78 | sub accessor { $_[0]->{accessor} } |
79 | sub reader { $_[0]->{reader} } |
80 | sub writer { $_[0]->{writer} } |
81 | sub predicate { $_[0]->{predicate} } |
82 | sub init_arg { $_[0]->{init_arg} } |
83 | |
7b31baf4 |
84 | # end bootstrapped away method section. |
85 | # (all methods below here are kept intact) |
86 | |
c50c603e |
87 | sub default { |
88 | my $self = shift; |
89 | if (reftype($self->{default}) && reftype($self->{default}) eq 'CODE') { |
727919c5 |
90 | # if the default is a CODE ref, then |
91 | # we pass in the instance and default |
92 | # can return a value based on that |
93 | # instance. Somewhat crude, but works. |
c50c603e |
94 | return $self->{default}->(shift); |
95 | } |
96 | $self->{default}; |
97 | } |
8b978dd5 |
98 | |
9ec169fe |
99 | # class association |
727919c5 |
100 | |
9ec169fe |
101 | sub attach_to_class { |
102 | my ($self, $class) = @_; |
103 | (blessed($class) && $class->isa('Class::MOP::Class')) |
104 | || confess "You must pass a Class::MOP::Class instance (or a subclass)"; |
105 | weaken($self->{associated_class} = $class); |
106 | } |
107 | |
108 | sub detach_from_class { |
109 | my $self = shift; |
110 | $self->{associated_class} = undef; |
111 | } |
112 | |
113 | ## Method generation helpers |
114 | |
115 | sub generate_accessor_method { |
116 | my ($self, $attr_name) = @_; |
013b1897 |
117 | sub { |
118 | $_[0]->{$attr_name} = $_[1] if scalar(@_) == 2; |
119 | $_[0]->{$attr_name}; |
120 | }; |
9ec169fe |
121 | } |
122 | |
123 | sub generate_reader_method { |
124 | my ($self, $attr_name) = @_; |
b9dfbf78 |
125 | sub { |
126 | confess "Cannot assign a value to a read-only accessor" if @_ > 1; |
127 | $_[0]->{$attr_name}; |
128 | }; |
9ec169fe |
129 | } |
130 | |
131 | sub generate_writer_method { |
132 | my ($self, $attr_name) = @_; |
013b1897 |
133 | sub { $_[0]->{$attr_name} = $_[1] }; |
9ec169fe |
134 | } |
135 | |
136 | sub generate_predicate_method { |
137 | my ($self, $attr_name) = @_; |
013b1897 |
138 | sub { defined $_[0]->{$attr_name} ? 1 : 0 }; |
9ec169fe |
139 | } |
140 | |
141 | sub process_accessors { |
142 | my ($self, $type, $accessor) = @_; |
013b1897 |
143 | if (reftype($accessor)) { |
144 | (reftype($accessor) eq 'HASH') |
145 | || confess "bad accessor/reader/writer/predicate format, must be a HASH ref"; |
9ec169fe |
146 | my ($name, $method) = each %{$accessor}; |
a4258ffd |
147 | return ($name, Class::MOP::Attribute::Accessor->wrap($method)); |
2eb717d5 |
148 | } |
9ec169fe |
149 | else { |
150 | my $generator = $self->can('generate_' . $type . '_method'); |
151 | ($generator) |
152 | || confess "There is no method generator for the type='$type'"; |
153 | if (my $method = $self->$generator($self->name)) { |
a4258ffd |
154 | return ($accessor => Class::MOP::Attribute::Accessor->wrap($method)); |
9ec169fe |
155 | } |
343203ee |
156 | confess "Could not create the '$type' method for " . $self->name . " because : $@"; |
9ec169fe |
157 | } |
158 | } |
159 | |
160 | sub install_accessors { |
161 | my $self = shift; |
162 | my $class = $self->associated_class; |
c50c603e |
163 | |
9ec169fe |
164 | $class->add_method( |
165 | $self->process_accessors('accessor' => $self->accessor()) |
166 | ) if $self->has_accessor(); |
167 | |
168 | $class->add_method( |
169 | $self->process_accessors('reader' => $self->reader()) |
170 | ) if $self->has_reader(); |
171 | |
172 | $class->add_method( |
173 | $self->process_accessors('writer' => $self->writer()) |
174 | ) if $self->has_writer(); |
175 | |
176 | $class->add_method( |
177 | $self->process_accessors('predicate' => $self->predicate()) |
178 | ) if $self->has_predicate(); |
179 | return; |
2eb717d5 |
180 | } |
181 | |
b51af7f9 |
182 | { |
183 | my $_remove_accessor = sub { |
184 | my ($accessor, $class) = @_; |
c50c603e |
185 | if (reftype($accessor) && reftype($accessor) eq 'HASH') { |
186 | ($accessor) = keys %{$accessor}; |
187 | } |
b51af7f9 |
188 | my $method = $class->get_method($accessor); |
189 | $class->remove_method($accessor) |
2eb717d5 |
190 | if (blessed($method) && $method->isa('Class::MOP::Attribute::Accessor')); |
b51af7f9 |
191 | }; |
c50c603e |
192 | |
b51af7f9 |
193 | sub remove_accessors { |
9ec169fe |
194 | my $self = shift; |
195 | $_remove_accessor->($self->accessor(), $self->associated_class()) if $self->has_accessor(); |
196 | $_remove_accessor->($self->reader(), $self->associated_class()) if $self->has_reader(); |
197 | $_remove_accessor->($self->writer(), $self->associated_class()) if $self->has_writer(); |
198 | $_remove_accessor->($self->predicate(), $self->associated_class()) if $self->has_predicate(); |
b51af7f9 |
199 | return; |
200 | } |
201 | |
8b978dd5 |
202 | } |
203 | |
2eb717d5 |
204 | package Class::MOP::Attribute::Accessor; |
205 | |
206 | use strict; |
207 | use warnings; |
208 | |
727919c5 |
209 | use Class::MOP::Method; |
210 | |
2eb717d5 |
211 | our $VERSION = '0.01'; |
212 | |
213 | our @ISA = ('Class::MOP::Method'); |
214 | |
8b978dd5 |
215 | 1; |
216 | |
217 | __END__ |
218 | |
219 | =pod |
220 | |
221 | =head1 NAME |
222 | |
223 | Class::MOP::Attribute - Attribute Meta Object |
224 | |
225 | =head1 SYNOPSIS |
226 | |
227 | Class::MOP::Attribute->new('$foo' => ( |
fe122940 |
228 | accessor => 'foo', # dual purpose get/set accessor |
229 | predicate => 'has_foo' # predicate check for defined-ness |
230 | init_arg => '-foo', # class->new will look for a -foo key |
231 | default => 'BAR IS BAZ!' # if no -foo key is provided, use this |
8b978dd5 |
232 | )); |
233 | |
234 | Class::MOP::Attribute->new('$.bar' => ( |
fe122940 |
235 | reader => 'bar', # getter |
236 | writer => 'set_bar', # setter |
237 | predicate => 'has_bar' # predicate check for defined-ness |
238 | init_arg => ':bar', # class->new will look for a :bar key |
8b978dd5 |
239 | # no default value means it is undef |
240 | )); |
241 | |
242 | =head1 DESCRIPTION |
243 | |
fe122940 |
244 | The Attribute Protocol is almost entirely an invention of this module, |
245 | and is completely optional to this MOP. This is because Perl 5 does not |
246 | have consistent notion of what is an attribute of a class. There are |
247 | so many ways in which this is done, and very few (if any) are |
248 | easily discoverable by this module. |
552e3d24 |
249 | |
250 | So, all that said, this module attempts to inject some order into this |
fe122940 |
251 | chaos, by introducing a consistent API which can be used to create |
252 | object attributes. |
552e3d24 |
253 | |
254 | =head1 METHODS |
255 | |
256 | =head2 Creation |
257 | |
258 | =over 4 |
259 | |
fe122940 |
260 | =item B<new ($name, ?%options)> |
261 | |
262 | An attribute must (at the very least), have a C<$name>. All other |
a2e85e6c |
263 | C<%options> are contained added as key-value pairs. Acceptable keys |
fe122940 |
264 | are as follows: |
265 | |
5659d76e |
266 | =item B<clone (%options)> |
267 | |
fe122940 |
268 | =over 4 |
269 | |
270 | =item I<init_arg> |
271 | |
272 | This should be a string value representing the expected key in |
273 | an initialization hash. For instance, if we have an I<init_arg> |
274 | value of C<-foo>, then the following code will Just Work. |
275 | |
276 | MyClass->meta->construct_instance(-foo => "Hello There"); |
277 | |
7b31baf4 |
278 | In an init_arg is not assigned, it will automatically use the |
279 | value of C<$name>. |
280 | |
fe122940 |
281 | =item I<default> |
282 | |
283 | The value of this key is the default value which |
284 | C<Class::MOP::Class::construct_instance> will initialize the |
285 | attribute to. |
286 | |
287 | B<NOTE:> |
288 | If the value is a simple scalar (string or number), then it can |
289 | be just passed as is. However, if you wish to initialize it with |
290 | a HASH or ARRAY ref, then you need to wrap that inside a CODE |
291 | reference, like so: |
292 | |
293 | Class::MOP::Attribute->new('@foo' => ( |
294 | default => sub { [] }, |
295 | )); |
296 | |
297 | # or ... |
298 | |
299 | Class::MOP::Attribute->new('%foo' => ( |
300 | default => sub { {} }, |
301 | )); |
302 | |
303 | If you wish to initialize an attribute with a CODE reference |
304 | itself, then you need to wrap that in a subroutine as well, like |
305 | so: |
306 | |
307 | Class::MOP::Attribute->new('&foo' => ( |
308 | default => sub { sub { print "Hello World" } }, |
309 | )); |
310 | |
311 | And lastly, if the value of your attribute is dependent upon |
312 | some other aspect of the instance structure, then you can take |
313 | advantage of the fact that when the I<default> value is a CODE |
314 | reference, it is passed the raw (unblessed) instance structure |
315 | as it's only argument. So you can do things like this: |
316 | |
317 | Class::MOP::Attribute->new('$object_identity' => ( |
318 | default => sub { Scalar::Util::refaddr($_[0]) }, |
319 | )); |
320 | |
321 | This last feature is fairly limited as there is no gurantee of |
322 | the order of attribute initializations, so you cannot perform |
323 | any kind of dependent initializations. However, if this is |
324 | something you need, you could subclass B<Class::MOP::Class> and |
325 | this class to acheive it. However, this is currently left as |
326 | an exercise to the reader :). |
327 | |
328 | =back |
329 | |
a2e85e6c |
330 | The I<accessor>, I<reader>, I<writer> and I<predicate> keys can |
fe122940 |
331 | contain either; the name of the method and an appropriate default |
332 | one will be generated for you, B<or> a HASH ref containing exactly one |
333 | key (which will be used as the name of the method) and one value, |
334 | which should contain a CODE reference which will be installed as |
335 | the method itself. |
59e7697f |
336 | |
337 | =over 4 |
338 | |
339 | =item I<accessor> |
340 | |
fe122940 |
341 | The I<accessor> is a standard perl-style read/write accessor. It will |
342 | return the value of the attribute, and if a value is passed as an argument, |
343 | it will assign that value to the attribute. |
344 | |
345 | B<NOTE:> |
346 | This method will properly handle the following code, by assigning an |
347 | C<undef> value to the attribute. |
348 | |
349 | $object->set_something(undef); |
350 | |
59e7697f |
351 | =item I<reader> |
352 | |
fe122940 |
353 | This is a basic read-only accessor, it will just return the value of |
354 | the attribute. |
355 | |
59e7697f |
356 | =item I<writer> |
357 | |
fe122940 |
358 | This is a basic write accessor, it accepts a single argument, and |
359 | assigns that value to the attribute. This method does not intentially |
360 | return a value, however perl will return the result of the last |
361 | expression in the subroutine, which returns in this returning the |
362 | same value that it was passed. |
59e7697f |
363 | |
fe122940 |
364 | B<NOTE:> |
365 | This method will properly handle the following code, by assigning an |
366 | C<undef> value to the attribute. |
59e7697f |
367 | |
fe122940 |
368 | $object->set_something(); |
369 | |
370 | =item I<predicate> |
371 | |
372 | This is a basic test to see if the value of the attribute is not |
373 | C<undef>. It will return true (C<1>) if the attribute's value is |
374 | defined, and false (C<0>) otherwise. |
59e7697f |
375 | |
376 | =back |
552e3d24 |
377 | |
378 | =back |
379 | |
380 | =head2 Informational |
381 | |
fe122940 |
382 | These are all basic read-only value accessors for the values |
383 | passed into C<new>. I think they are pretty much self-explanitory. |
384 | |
552e3d24 |
385 | =over 4 |
386 | |
387 | =item B<name> |
388 | |
389 | =item B<accessor> |
390 | |
391 | =item B<reader> |
392 | |
393 | =item B<writer> |
394 | |
c50c603e |
395 | =item B<predicate> |
396 | |
552e3d24 |
397 | =item B<init_arg> |
398 | |
fe122940 |
399 | =item B<default (?$instance)> |
400 | |
401 | As noted in the documentation for C<new> above, if the I<default> |
402 | value is a CODE reference, this accessor will pass a single additional |
403 | argument C<$instance> into it and return the value. |
552e3d24 |
404 | |
405 | =back |
406 | |
407 | =head2 Informational predicates |
408 | |
a2e85e6c |
409 | These are all basic predicate methods for the values passed into C<new>. |
fe122940 |
410 | |
552e3d24 |
411 | =over 4 |
412 | |
413 | =item B<has_accessor> |
414 | |
552e3d24 |
415 | =item B<has_reader> |
416 | |
552e3d24 |
417 | =item B<has_writer> |
418 | |
c50c603e |
419 | =item B<has_predicate> |
420 | |
552e3d24 |
421 | =item B<has_init_arg> |
422 | |
552e3d24 |
423 | =item B<has_default> |
424 | |
552e3d24 |
425 | =back |
426 | |
9ec169fe |
427 | =head2 Class association |
428 | |
429 | =over 4 |
430 | |
431 | =item B<associated_class> |
432 | |
433 | =item B<attach_to_class ($class)> |
434 | |
435 | =item B<detach_from_class> |
436 | |
437 | =back |
438 | |
552e3d24 |
439 | =head2 Attribute Accessor generation |
440 | |
441 | =over 4 |
442 | |
9ec169fe |
443 | =item B<install_accessors> |
2eb717d5 |
444 | |
445 | This allows the attribute to generate and install code for it's own |
a2e85e6c |
446 | I<accessor/reader/writer/predicate> methods. This is called by |
fe122940 |
447 | C<Class::MOP::Class::add_attribute>. |
2eb717d5 |
448 | |
9ec169fe |
449 | This method will call C<process_accessors> for each of the possible |
450 | method types (accessor, reader, writer & predicate). |
451 | |
452 | =item B<process_accessors ($type, $value)> |
453 | |
454 | This takes a C<$type> (accessor, reader, writer or predicate), and |
455 | a C<$value> (the value passed into the constructor for each of the |
456 | different types). It will then either generate the method itself |
457 | (using the C<generate_*_method> methods listed below) or it will |
458 | use the custom method passed through the constructor. |
459 | |
460 | =over 4 |
461 | |
462 | =item B<generate_accessor_method ($attr_name)> |
463 | |
464 | =item B<generate_predicate_method ($attr_name)> |
465 | |
466 | =item B<generate_reader_method ($attr_name)> |
467 | |
468 | =item B<generate_writer_method ($attr_name)> |
469 | |
470 | =back |
471 | |
472 | =item B<remove_accessors> |
2eb717d5 |
473 | |
474 | This allows the attribute to remove the method for it's own |
a2e85e6c |
475 | I<accessor/reader/writer/predicate>. This is called by |
fe122940 |
476 | C<Class::MOP::Class::remove_attribute>. |
2eb717d5 |
477 | |
478 | =back |
479 | |
480 | =head2 Introspection |
481 | |
482 | =over 4 |
552e3d24 |
483 | |
2eb717d5 |
484 | =item B<meta> |
552e3d24 |
485 | |
fe122940 |
486 | This will return a B<Class::MOP::Class> instance which is related |
487 | to this class. |
488 | |
489 | It should also be noted that B<Class::MOP> will actually bootstrap |
490 | this module by installing a number of attribute meta-objects into |
491 | it's metaclass. This will allow this class to reap all the benifits |
492 | of the MOP when subclassing it. |
493 | |
552e3d24 |
494 | =back |
495 | |
8b978dd5 |
496 | =head1 AUTHOR |
497 | |
a2e85e6c |
498 | Stevan Little E<lt>stevan@iinteractive.comE<gt> |
8b978dd5 |
499 | |
500 | =head1 COPYRIGHT AND LICENSE |
501 | |
502 | Copyright 2006 by Infinity Interactive, Inc. |
503 | |
504 | L<http://www.iinteractive.com> |
505 | |
506 | This library is free software; you can redistribute it and/or modify |
507 | it under the same terms as Perl itself. |
508 | |
9ec169fe |
509 | =cut |