Commit | Line | Data |
8b978dd5 |
1 | |
2 | package Class::MOP::Attribute; |
3 | |
4 | use strict; |
5 | use warnings; |
6 | |
2eb717d5 |
7 | use Carp 'confess'; |
c50c603e |
8 | use Scalar::Util 'blessed', 'reftype'; |
2eb717d5 |
9 | |
8b978dd5 |
10 | our $VERSION = '0.01'; |
11 | |
727919c5 |
12 | sub meta { |
13 | require Class::MOP::Class; |
14 | Class::MOP::Class->initialize($_[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}; |
36 | |
8b978dd5 |
37 | bless { |
c50c603e |
38 | name => $name, |
39 | accessor => $options{accessor}, |
40 | reader => $options{reader}, |
41 | writer => $options{writer}, |
42 | predicate => $options{predicate}, |
43 | init_arg => $options{init_arg}, |
44 | default => $options{default} |
8b978dd5 |
45 | } => $class; |
46 | } |
47 | |
c50c603e |
48 | sub name { $_[0]->{name} } |
49 | |
727919c5 |
50 | sub has_accessor { defined($_[0]->{accessor}) ? 1 : 0 } |
51 | sub has_reader { defined($_[0]->{reader}) ? 1 : 0 } |
52 | sub has_writer { defined($_[0]->{writer}) ? 1 : 0 } |
c50c603e |
53 | sub has_predicate { defined($_[0]->{predicate}) ? 1 : 0 } |
727919c5 |
54 | sub has_init_arg { defined($_[0]->{init_arg}) ? 1 : 0 } |
55 | sub has_default { defined($_[0]->{default}) ? 1 : 0 } |
c50c603e |
56 | |
57 | sub accessor { $_[0]->{accessor} } |
58 | sub reader { $_[0]->{reader} } |
59 | sub writer { $_[0]->{writer} } |
60 | sub predicate { $_[0]->{predicate} } |
61 | sub init_arg { $_[0]->{init_arg} } |
62 | |
63 | sub default { |
64 | my $self = shift; |
65 | if (reftype($self->{default}) && reftype($self->{default}) eq 'CODE') { |
727919c5 |
66 | # if the default is a CODE ref, then |
67 | # we pass in the instance and default |
68 | # can return a value based on that |
69 | # instance. Somewhat crude, but works. |
c50c603e |
70 | return $self->{default}->(shift); |
71 | } |
72 | $self->{default}; |
73 | } |
8b978dd5 |
74 | |
727919c5 |
75 | { |
76 | # this is just a utility routine to |
77 | # handle the details of accessors |
78 | my $_inspect_accessor = sub { |
79 | my ($attr_name, $type, $accessor) = @_; |
80 | |
81 | my %ACCESSOR_TEMPLATES = ( |
b51af7f9 |
82 | 'accessor' => qq{sub { |
83 | \$_[0]->{'$attr_name'} = \$_[1] if scalar(\@_) == 2; |
84 | \$_[0]->{'$attr_name'}; |
85 | }}, |
86 | 'reader' => qq{sub { |
87 | \$_[0]->{'$attr_name'}; |
88 | }}, |
89 | 'writer' => qq{sub { |
90 | \$_[0]->{'$attr_name'} = \$_[1]; |
b51af7f9 |
91 | }}, |
92 | 'predicate' => qq{sub { |
52e8a34c |
93 | defined \$_[0]->{'$attr_name'} ? 1 : 0; |
b51af7f9 |
94 | }} |
727919c5 |
95 | ); |
96 | |
c50c603e |
97 | if (reftype($accessor) && reftype($accessor) eq 'HASH') { |
98 | my ($name, $method) = each %{$accessor}; |
727919c5 |
99 | return ($name, Class::MOP::Attribute::Accessor->wrap($method)); |
c50c603e |
100 | } |
101 | else { |
b51af7f9 |
102 | my $method = eval $ACCESSOR_TEMPLATES{$type}; |
103 | confess "Could not create the $type for $attr_name CODE(\n" . $ACCESSOR_TEMPLATES{$type} . "\n) : $@" if $@; |
104 | return ($accessor => Class::MOP::Attribute::Accessor->wrap($method)); |
727919c5 |
105 | } |
106 | }; |
107 | |
108 | sub install_accessors { |
109 | my ($self, $class) = @_; |
110 | (blessed($class) && $class->isa('Class::MOP::Class')) |
111 | || confess "You must pass a Class::MOP::Class instance (or a subclass)"; |
727919c5 |
112 | $class->add_method( |
113 | $_inspect_accessor->($self->name, 'accessor' => $self->accessor()) |
114 | ) if $self->has_accessor(); |
115 | |
116 | $class->add_method( |
117 | $_inspect_accessor->($self->name, 'reader' => $self->reader()) |
118 | ) if $self->has_reader(); |
119 | |
120 | $class->add_method( |
121 | $_inspect_accessor->($self->name, 'writer' => $self->writer()) |
122 | ) if $self->has_writer(); |
123 | |
124 | $class->add_method( |
125 | $_inspect_accessor->($self->name, 'predicate' => $self->predicate()) |
126 | ) if $self->has_predicate(); |
b51af7f9 |
127 | return; |
2eb717d5 |
128 | } |
c50c603e |
129 | |
2eb717d5 |
130 | } |
131 | |
b51af7f9 |
132 | { |
133 | my $_remove_accessor = sub { |
134 | my ($accessor, $class) = @_; |
c50c603e |
135 | if (reftype($accessor) && reftype($accessor) eq 'HASH') { |
136 | ($accessor) = keys %{$accessor}; |
137 | } |
b51af7f9 |
138 | my $method = $class->get_method($accessor); |
139 | $class->remove_method($accessor) |
2eb717d5 |
140 | if (blessed($method) && $method->isa('Class::MOP::Attribute::Accessor')); |
b51af7f9 |
141 | }; |
c50c603e |
142 | |
b51af7f9 |
143 | sub remove_accessors { |
144 | my ($self, $class) = @_; |
145 | (blessed($class) && $class->isa('Class::MOP::Class')) |
146 | || confess "You must pass a Class::MOP::Class instance (or a subclass)"; |
147 | $_remove_accessor->($self->accessor(), $class) if $self->has_accessor(); |
148 | $_remove_accessor->($self->reader(), $class) if $self->has_reader(); |
149 | $_remove_accessor->($self->writer(), $class) if $self->has_writer(); |
150 | $_remove_accessor->($self->predicate(), $class) if $self->has_predicate(); |
151 | return; |
152 | } |
153 | |
8b978dd5 |
154 | } |
155 | |
2eb717d5 |
156 | package Class::MOP::Attribute::Accessor; |
157 | |
158 | use strict; |
159 | use warnings; |
160 | |
727919c5 |
161 | use Class::MOP::Method; |
162 | |
2eb717d5 |
163 | our $VERSION = '0.01'; |
164 | |
165 | our @ISA = ('Class::MOP::Method'); |
166 | |
8b978dd5 |
167 | 1; |
168 | |
169 | __END__ |
170 | |
171 | =pod |
172 | |
173 | =head1 NAME |
174 | |
175 | Class::MOP::Attribute - Attribute Meta Object |
176 | |
177 | =head1 SYNOPSIS |
178 | |
179 | Class::MOP::Attribute->new('$foo' => ( |
fe122940 |
180 | accessor => 'foo', # dual purpose get/set accessor |
181 | predicate => 'has_foo' # predicate check for defined-ness |
182 | init_arg => '-foo', # class->new will look for a -foo key |
183 | default => 'BAR IS BAZ!' # if no -foo key is provided, use this |
8b978dd5 |
184 | )); |
185 | |
186 | Class::MOP::Attribute->new('$.bar' => ( |
fe122940 |
187 | reader => 'bar', # getter |
188 | writer => 'set_bar', # setter |
189 | predicate => 'has_bar' # predicate check for defined-ness |
190 | init_arg => ':bar', # class->new will look for a :bar key |
8b978dd5 |
191 | # no default value means it is undef |
192 | )); |
193 | |
194 | =head1 DESCRIPTION |
195 | |
fe122940 |
196 | The Attribute Protocol is almost entirely an invention of this module, |
197 | and is completely optional to this MOP. This is because Perl 5 does not |
198 | have consistent notion of what is an attribute of a class. There are |
199 | so many ways in which this is done, and very few (if any) are |
200 | easily discoverable by this module. |
552e3d24 |
201 | |
202 | So, all that said, this module attempts to inject some order into this |
fe122940 |
203 | chaos, by introducing a consistent API which can be used to create |
204 | object attributes. |
552e3d24 |
205 | |
206 | =head1 METHODS |
207 | |
208 | =head2 Creation |
209 | |
210 | =over 4 |
211 | |
fe122940 |
212 | =item B<new ($name, ?%options)> |
213 | |
214 | An attribute must (at the very least), have a C<$name>. All other |
a2e85e6c |
215 | C<%options> are contained added as key-value pairs. Acceptable keys |
fe122940 |
216 | are as follows: |
217 | |
218 | =over 4 |
219 | |
220 | =item I<init_arg> |
221 | |
222 | This should be a string value representing the expected key in |
223 | an initialization hash. For instance, if we have an I<init_arg> |
224 | value of C<-foo>, then the following code will Just Work. |
225 | |
226 | MyClass->meta->construct_instance(-foo => "Hello There"); |
227 | |
228 | =item I<default> |
229 | |
230 | The value of this key is the default value which |
231 | C<Class::MOP::Class::construct_instance> will initialize the |
232 | attribute to. |
233 | |
234 | B<NOTE:> |
235 | If the value is a simple scalar (string or number), then it can |
236 | be just passed as is. However, if you wish to initialize it with |
237 | a HASH or ARRAY ref, then you need to wrap that inside a CODE |
238 | reference, like so: |
239 | |
240 | Class::MOP::Attribute->new('@foo' => ( |
241 | default => sub { [] }, |
242 | )); |
243 | |
244 | # or ... |
245 | |
246 | Class::MOP::Attribute->new('%foo' => ( |
247 | default => sub { {} }, |
248 | )); |
249 | |
250 | If you wish to initialize an attribute with a CODE reference |
251 | itself, then you need to wrap that in a subroutine as well, like |
252 | so: |
253 | |
254 | Class::MOP::Attribute->new('&foo' => ( |
255 | default => sub { sub { print "Hello World" } }, |
256 | )); |
257 | |
258 | And lastly, if the value of your attribute is dependent upon |
259 | some other aspect of the instance structure, then you can take |
260 | advantage of the fact that when the I<default> value is a CODE |
261 | reference, it is passed the raw (unblessed) instance structure |
262 | as it's only argument. So you can do things like this: |
263 | |
264 | Class::MOP::Attribute->new('$object_identity' => ( |
265 | default => sub { Scalar::Util::refaddr($_[0]) }, |
266 | )); |
267 | |
268 | This last feature is fairly limited as there is no gurantee of |
269 | the order of attribute initializations, so you cannot perform |
270 | any kind of dependent initializations. However, if this is |
271 | something you need, you could subclass B<Class::MOP::Class> and |
272 | this class to acheive it. However, this is currently left as |
273 | an exercise to the reader :). |
274 | |
275 | =back |
276 | |
a2e85e6c |
277 | The I<accessor>, I<reader>, I<writer> and I<predicate> keys can |
fe122940 |
278 | contain either; the name of the method and an appropriate default |
279 | one will be generated for you, B<or> a HASH ref containing exactly one |
280 | key (which will be used as the name of the method) and one value, |
281 | which should contain a CODE reference which will be installed as |
282 | the method itself. |
59e7697f |
283 | |
284 | =over 4 |
285 | |
286 | =item I<accessor> |
287 | |
fe122940 |
288 | The I<accessor> is a standard perl-style read/write accessor. It will |
289 | return the value of the attribute, and if a value is passed as an argument, |
290 | it will assign that value to the attribute. |
291 | |
292 | B<NOTE:> |
293 | This method will properly handle the following code, by assigning an |
294 | C<undef> value to the attribute. |
295 | |
296 | $object->set_something(undef); |
297 | |
59e7697f |
298 | =item I<reader> |
299 | |
fe122940 |
300 | This is a basic read-only accessor, it will just return the value of |
301 | the attribute. |
302 | |
59e7697f |
303 | =item I<writer> |
304 | |
fe122940 |
305 | This is a basic write accessor, it accepts a single argument, and |
306 | assigns that value to the attribute. This method does not intentially |
307 | return a value, however perl will return the result of the last |
308 | expression in the subroutine, which returns in this returning the |
309 | same value that it was passed. |
59e7697f |
310 | |
fe122940 |
311 | B<NOTE:> |
312 | This method will properly handle the following code, by assigning an |
313 | C<undef> value to the attribute. |
59e7697f |
314 | |
fe122940 |
315 | $object->set_something(); |
316 | |
317 | =item I<predicate> |
318 | |
319 | This is a basic test to see if the value of the attribute is not |
320 | C<undef>. It will return true (C<1>) if the attribute's value is |
321 | defined, and false (C<0>) otherwise. |
59e7697f |
322 | |
323 | =back |
552e3d24 |
324 | |
325 | =back |
326 | |
327 | =head2 Informational |
328 | |
fe122940 |
329 | These are all basic read-only value accessors for the values |
330 | passed into C<new>. I think they are pretty much self-explanitory. |
331 | |
552e3d24 |
332 | =over 4 |
333 | |
334 | =item B<name> |
335 | |
336 | =item B<accessor> |
337 | |
338 | =item B<reader> |
339 | |
340 | =item B<writer> |
341 | |
c50c603e |
342 | =item B<predicate> |
343 | |
552e3d24 |
344 | =item B<init_arg> |
345 | |
fe122940 |
346 | =item B<default (?$instance)> |
347 | |
348 | As noted in the documentation for C<new> above, if the I<default> |
349 | value is a CODE reference, this accessor will pass a single additional |
350 | argument C<$instance> into it and return the value. |
552e3d24 |
351 | |
352 | =back |
353 | |
354 | =head2 Informational predicates |
355 | |
a2e85e6c |
356 | These are all basic predicate methods for the values passed into C<new>. |
fe122940 |
357 | |
552e3d24 |
358 | =over 4 |
359 | |
360 | =item B<has_accessor> |
361 | |
552e3d24 |
362 | =item B<has_reader> |
363 | |
552e3d24 |
364 | =item B<has_writer> |
365 | |
c50c603e |
366 | =item B<has_predicate> |
367 | |
552e3d24 |
368 | =item B<has_init_arg> |
369 | |
552e3d24 |
370 | =item B<has_default> |
371 | |
552e3d24 |
372 | =back |
373 | |
374 | =head2 Attribute Accessor generation |
375 | |
376 | =over 4 |
377 | |
2eb717d5 |
378 | =item B<install_accessors ($class)> |
379 | |
380 | This allows the attribute to generate and install code for it's own |
a2e85e6c |
381 | I<accessor/reader/writer/predicate> methods. This is called by |
fe122940 |
382 | C<Class::MOP::Class::add_attribute>. |
2eb717d5 |
383 | |
384 | =item B<remove_accessors ($class)> |
385 | |
386 | This allows the attribute to remove the method for it's own |
a2e85e6c |
387 | I<accessor/reader/writer/predicate>. This is called by |
fe122940 |
388 | C<Class::MOP::Class::remove_attribute>. |
2eb717d5 |
389 | |
390 | =back |
391 | |
392 | =head2 Introspection |
393 | |
394 | =over 4 |
552e3d24 |
395 | |
2eb717d5 |
396 | =item B<meta> |
552e3d24 |
397 | |
fe122940 |
398 | This will return a B<Class::MOP::Class> instance which is related |
399 | to this class. |
400 | |
401 | It should also be noted that B<Class::MOP> will actually bootstrap |
402 | this module by installing a number of attribute meta-objects into |
403 | it's metaclass. This will allow this class to reap all the benifits |
404 | of the MOP when subclassing it. |
405 | |
552e3d24 |
406 | =back |
407 | |
8b978dd5 |
408 | =head1 AUTHOR |
409 | |
a2e85e6c |
410 | Stevan Little E<lt>stevan@iinteractive.comE<gt> |
8b978dd5 |
411 | |
412 | =head1 COPYRIGHT AND LICENSE |
413 | |
414 | Copyright 2006 by Infinity Interactive, Inc. |
415 | |
416 | L<http://www.iinteractive.com> |
417 | |
418 | This library is free software; you can redistribute it and/or modify |
419 | it under the same terms as Perl itself. |
420 | |
421 | =cut |