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8b978dd5 |
1 | |
2 | package Class::MOP::Class; |
3 | |
4 | use strict; |
5 | use warnings; |
6 | |
7 | use Carp 'confess'; |
0882828e |
8 | use Scalar::Util 'blessed', 'reftype'; |
8b978dd5 |
9 | use Sub::Name 'subname'; |
10 | use B 'svref_2object'; |
11 | |
12 | our $VERSION = '0.01'; |
13 | |
2eb717d5 |
14 | # Self-introspection |
15 | |
16 | sub meta { $_[0]->initialize($_[0]) } |
17 | |
8b978dd5 |
18 | # Creation |
19 | |
bfe4d0fc |
20 | { |
21 | # Metaclasses are singletons, so we cache them here. |
22 | # there is no need to worry about destruction though |
23 | # because they should die only when the program dies. |
24 | # After all, do package definitions even get reaped? |
25 | my %METAS; |
26 | sub initialize { |
27 | my ($class, $package_name) = @_; |
28 | (defined $package_name && $package_name) |
727919c5 |
29 | || confess "You must pass a package name"; |
30 | return $METAS{$package_name} if exists $METAS{$package_name}; |
31 | $METAS{$package_name} = $class->construct_class_instance($package_name); |
32 | } |
33 | |
34 | # NOTE: (meta-circularity) |
35 | # this is a special form of &construct_instance |
36 | # (see below), which is used to construct class |
37 | # meta-object instances. It will be replaces in |
38 | # the bootstrap section in Class::MOP with one |
39 | # which uses the normal &construct_instance. |
40 | sub construct_class_instance { |
41 | my ($class, $package_name) = @_; |
42 | (defined $package_name && $package_name) |
43 | || confess "You must pass a package name"; |
44 | bless { |
e16da3e6 |
45 | '$:pkg' => $package_name, |
46 | '%:attrs' => {} |
727919c5 |
47 | } => blessed($class) || $class |
bfe4d0fc |
48 | } |
8b978dd5 |
49 | } |
50 | |
51 | sub create { |
52 | my ($class, $package_name, $package_version, %options) = @_; |
bfe4d0fc |
53 | (defined $package_name && $package_name) |
8b978dd5 |
54 | || confess "You must pass a package name"; |
55 | my $code = "package $package_name;"; |
56 | $code .= "\$$package_name\:\:VERSION = '$package_version';" |
57 | if defined $package_version; |
58 | eval $code; |
59 | confess "creation of $package_name failed : $@" if $@; |
bfe4d0fc |
60 | my $meta = $class->initialize($package_name); |
8b978dd5 |
61 | $meta->superclasses(@{$options{superclasses}}) |
62 | if exists $options{superclasses}; |
2eb717d5 |
63 | # NOTE: |
64 | # process attributes first, so that they can |
65 | # install accessors, but locally defined methods |
66 | # can then overwrite them. It is maybe a little odd, but |
67 | # I think this should be the order of things. |
68 | if (exists $options{attributes}) { |
cbd9f942 |
69 | foreach my $attr (@{$options{attributes}}) { |
70 | $meta->add_attribute($attr); |
2eb717d5 |
71 | } |
72 | } |
bfe4d0fc |
73 | if (exists $options{methods}) { |
74 | foreach my $method_name (keys %{$options{methods}}) { |
75 | $meta->add_method($method_name, $options{methods}->{$method_name}); |
76 | } |
2eb717d5 |
77 | } |
8b978dd5 |
78 | return $meta; |
79 | } |
80 | |
e16da3e6 |
81 | # Instance Construction |
82 | |
83 | sub construct_instance { |
cbd9f942 |
84 | my ($class, %params) = @_; |
85 | my $instance = {}; |
86 | foreach my $attr (map { $_->{attribute} } $class->compute_all_applicable_attributes()) { |
87 | # if the attr has an init_arg, use that, otherwise, |
88 | # use the attributes name itself as the init_arg |
89 | my $init_arg = $attr->has_init_arg() ? $attr->init_arg() : $attr->name; |
90 | # try to fetch the init arg from the %params ... |
91 | my $val; |
92 | $val = $params{$init_arg} if exists $params{$init_arg}; |
93 | # if nothing was in the %params, we can use the |
94 | # attribute's default value (if it has one) |
c50c603e |
95 | $val ||= $attr->default($instance) if $attr->has_default(); |
cbd9f942 |
96 | # now add this to the instance structure |
97 | $instance->{$attr->name} = $val; |
98 | } |
99 | return $instance; |
e16da3e6 |
100 | } |
101 | |
8b978dd5 |
102 | # Informational |
103 | |
e16da3e6 |
104 | sub name { $_[0]->{'$:pkg'} } |
8b978dd5 |
105 | |
106 | sub version { |
107 | my $self = shift; |
108 | no strict 'refs'; |
109 | ${$self->name . '::VERSION'}; |
110 | } |
111 | |
112 | # Inheritance |
113 | |
114 | sub superclasses { |
115 | my $self = shift; |
116 | no strict 'refs'; |
117 | if (@_) { |
118 | my @supers = @_; |
119 | @{$self->name . '::ISA'} = @supers; |
120 | } |
121 | @{$self->name . '::ISA'}; |
122 | } |
123 | |
124 | sub class_precedence_list { |
125 | my $self = shift; |
bfe4d0fc |
126 | # NOTE: |
127 | # We need to check for ciruclar inheirtance here. |
128 | # This will do nothing if all is well, and blow |
129 | # up otherwise. Yes, it's an ugly hack, better |
130 | # suggestions are welcome. |
131 | { $self->name->isa('This is a test for circular inheritance') } |
132 | # ... and no back to our regularly scheduled program |
8b978dd5 |
133 | ( |
134 | $self->name, |
135 | map { |
bfe4d0fc |
136 | $self->initialize($_)->class_precedence_list() |
8b978dd5 |
137 | } $self->superclasses() |
138 | ); |
139 | } |
140 | |
0882828e |
141 | ## Methods |
142 | |
143 | sub add_method { |
144 | my ($self, $method_name, $method) = @_; |
145 | (defined $method_name && $method_name) |
146 | || confess "You must define a method name"; |
a5eca695 |
147 | # use reftype here to allow for blessed subs ... |
0882828e |
148 | (reftype($method) && reftype($method) eq 'CODE') |
149 | || confess "Your code block must be a CODE reference"; |
150 | my $full_method_name = ($self->name . '::' . $method_name); |
151 | |
152 | no strict 'refs'; |
c9b8b7f9 |
153 | no warnings 'redefine'; |
0882828e |
154 | *{$full_method_name} = subname $full_method_name => $method; |
155 | } |
156 | |
bfe4d0fc |
157 | { |
158 | |
159 | ## private utility functions for has_method |
2eb717d5 |
160 | my $_find_subroutine_package_name = sub { eval { svref_2object($_[0])->GV->STASH->NAME } || '' }; |
161 | my $_find_subroutine_name = sub { eval { svref_2object($_[0])->GV->NAME } || '' }; |
bfe4d0fc |
162 | |
163 | sub has_method { |
c9b8b7f9 |
164 | my ($self, $method_name) = @_; |
bfe4d0fc |
165 | (defined $method_name && $method_name) |
166 | || confess "You must define a method name"; |
0882828e |
167 | |
bfe4d0fc |
168 | my $sub_name = ($self->name . '::' . $method_name); |
0882828e |
169 | |
bfe4d0fc |
170 | no strict 'refs'; |
171 | return 0 if !defined(&{$sub_name}); |
172 | return 0 if $_find_subroutine_package_name->(\&{$sub_name}) ne $self->name && |
173 | $_find_subroutine_name->(\&{$sub_name}) ne '__ANON__'; |
174 | return 1; |
175 | } |
176 | |
0882828e |
177 | } |
178 | |
179 | sub get_method { |
c9b8b7f9 |
180 | my ($self, $method_name) = @_; |
0882828e |
181 | (defined $method_name && $method_name) |
182 | || confess "You must define a method name"; |
183 | |
184 | no strict 'refs'; |
185 | return \&{$self->name . '::' . $method_name} |
bfe4d0fc |
186 | if $self->has_method($method_name); |
c9b8b7f9 |
187 | return; # <- make sure to return undef |
188 | } |
189 | |
190 | sub remove_method { |
191 | my ($self, $method_name) = @_; |
192 | (defined $method_name && $method_name) |
193 | || confess "You must define a method name"; |
194 | |
195 | my $removed_method = $self->get_method($method_name); |
196 | |
197 | no strict 'refs'; |
198 | delete ${$self->name . '::'}{$method_name} |
199 | if defined $removed_method; |
200 | |
201 | return $removed_method; |
202 | } |
203 | |
204 | sub get_method_list { |
205 | my $self = shift; |
206 | no strict 'refs'; |
a5eca695 |
207 | grep { $self->has_method($_) } %{$self->name . '::'}; |
208 | } |
209 | |
210 | sub compute_all_applicable_methods { |
211 | my $self = shift; |
212 | my @methods; |
213 | # keep a record of what we have seen |
214 | # here, this will handle all the |
215 | # inheritence issues because we are |
216 | # using the &class_precedence_list |
217 | my (%seen_class, %seen_method); |
218 | foreach my $class ($self->class_precedence_list()) { |
219 | next if $seen_class{$class}; |
220 | $seen_class{$class}++; |
221 | # fetch the meta-class ... |
222 | my $meta = $self->initialize($class); |
223 | foreach my $method_name ($meta->get_method_list()) { |
224 | next if exists $seen_method{$method_name}; |
225 | $seen_method{$method_name}++; |
226 | push @methods => { |
227 | name => $method_name, |
228 | class => $class, |
229 | code => $meta->get_method($method_name) |
230 | }; |
231 | } |
232 | } |
233 | return @methods; |
234 | } |
235 | |
a5eca695 |
236 | sub find_all_methods_by_name { |
237 | my ($self, $method_name) = @_; |
238 | (defined $method_name && $method_name) |
239 | || confess "You must define a method name to find"; |
240 | my @methods; |
241 | # keep a record of what we have seen |
242 | # here, this will handle all the |
243 | # inheritence issues because we are |
244 | # using the &class_precedence_list |
245 | my %seen_class; |
246 | foreach my $class ($self->class_precedence_list()) { |
247 | next if $seen_class{$class}; |
248 | $seen_class{$class}++; |
249 | # fetch the meta-class ... |
250 | my $meta = $self->initialize($class); |
251 | push @methods => { |
252 | name => $method_name, |
253 | class => $class, |
254 | code => $meta->get_method($method_name) |
255 | } if $meta->has_method($method_name); |
256 | } |
257 | return @methods; |
258 | |
8b978dd5 |
259 | } |
260 | |
552e3d24 |
261 | ## Attributes |
262 | |
e16da3e6 |
263 | sub add_attribute { |
2eb717d5 |
264 | my ($self,$attribute) = @_; |
e16da3e6 |
265 | (blessed($attribute) && $attribute->isa('Class::MOP::Attribute')) |
266 | || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)"; |
2eb717d5 |
267 | $attribute->install_accessors($self); |
268 | $self->{'%:attrs'}->{$attribute->name} = $attribute; |
e16da3e6 |
269 | } |
270 | |
271 | sub has_attribute { |
272 | my ($self, $attribute_name) = @_; |
273 | (defined $attribute_name && $attribute_name) |
274 | || confess "You must define an attribute name"; |
275 | exists $self->{'%:attrs'}->{$attribute_name} ? 1 : 0; |
276 | } |
277 | |
278 | sub get_attribute { |
279 | my ($self, $attribute_name) = @_; |
280 | (defined $attribute_name && $attribute_name) |
281 | || confess "You must define an attribute name"; |
282 | return $self->{'%:attrs'}->{$attribute_name} |
283 | if $self->has_attribute($attribute_name); |
284 | } |
285 | |
286 | sub remove_attribute { |
287 | my ($self, $attribute_name) = @_; |
288 | (defined $attribute_name && $attribute_name) |
289 | || confess "You must define an attribute name"; |
290 | my $removed_attribute = $self->{'%:attrs'}->{$attribute_name}; |
291 | delete $self->{'%:attrs'}->{$attribute_name} |
292 | if defined $removed_attribute; |
2eb717d5 |
293 | $removed_attribute->remove_accessors($self); |
e16da3e6 |
294 | return $removed_attribute; |
295 | } |
296 | |
297 | sub get_attribute_list { |
298 | my $self = shift; |
299 | keys %{$self->{'%:attrs'}}; |
300 | } |
301 | |
302 | sub compute_all_applicable_attributes { |
303 | my $self = shift; |
304 | my @attrs; |
305 | # keep a record of what we have seen |
306 | # here, this will handle all the |
307 | # inheritence issues because we are |
308 | # using the &class_precedence_list |
309 | my (%seen_class, %seen_attr); |
310 | foreach my $class ($self->class_precedence_list()) { |
311 | next if $seen_class{$class}; |
312 | $seen_class{$class}++; |
313 | # fetch the meta-class ... |
314 | my $meta = $self->initialize($class); |
315 | foreach my $attr_name ($meta->get_attribute_list()) { |
316 | next if exists $seen_attr{$attr_name}; |
317 | $seen_attr{$attr_name}++; |
318 | push @attrs => { |
319 | name => $attr_name, |
320 | class => $class, |
321 | attribute => $meta->get_attribute($attr_name) |
322 | }; |
323 | } |
324 | } |
325 | return @attrs; |
326 | } |
2eb717d5 |
327 | |
8b978dd5 |
328 | 1; |
329 | |
330 | __END__ |
331 | |
332 | =pod |
333 | |
334 | =head1 NAME |
335 | |
336 | Class::MOP::Class - Class Meta Object |
337 | |
338 | =head1 SYNOPSIS |
339 | |
340 | =head1 DESCRIPTION |
341 | |
552e3d24 |
342 | =head1 METHODS |
343 | |
2eb717d5 |
344 | =head2 Self Introspection |
345 | |
346 | =over 4 |
347 | |
348 | =item B<meta> |
349 | |
350 | This allows Class::MOP::Class to actually introspect itself. |
351 | |
352 | =back |
353 | |
552e3d24 |
354 | =head2 Class construction |
355 | |
356 | These methods handle creating Class objects, which can be used to |
357 | both create new classes, and analyze pre-existing ones. |
358 | |
359 | This module will internally store references to all the instances |
360 | you create with these methods, so that they do not need to be |
361 | created any more than nessecary. Basically, they are singletons. |
362 | |
363 | =over 4 |
364 | |
365 | =item B<create ($package_name, ?$package_version, |
366 | superclasses => ?@superclasses, |
367 | methods => ?%methods, |
368 | attributes => ?%attributes)> |
369 | |
370 | This returns the basic Class object, bringing the specified |
371 | C<$package_name> into existence and adding any of the |
372 | C<$package_version>, C<@superclasses>, C<%methods> and C<%attributes> |
373 | to it. |
374 | |
375 | =item B<initialize ($package_name)> |
376 | |
377 | This initializes a Class object for a given a C<$package_name>. |
378 | |
379 | =back |
380 | |
381 | =head2 Instance construction |
382 | |
383 | =over 4 |
384 | |
cbd9f942 |
385 | =item B<construct_instance (%params)> |
552e3d24 |
386 | |
cbd9f942 |
387 | This will construct and instance using a HASH ref as storage |
552e3d24 |
388 | (currently only HASH references are supported). This will collect all |
389 | the applicable attribute meta-objects and layout out the fields in the |
cbd9f942 |
390 | HASH ref, it will then initialize them using either use the |
552e3d24 |
391 | corresponding key in C<%params> or any default value or initializer |
392 | found in the attribute meta-object. |
393 | |
727919c5 |
394 | =item B<construct_class_instance ($package_name)> |
395 | |
396 | This will construct an instance of B<Class::MOP::Class>, it is |
397 | here so that we can actually "tie the knot" for B<Class::MOP::Class> |
398 | to use C<construct_instance> once all the bootstrapping is done. This |
399 | method is used internally by C<initialize> and should never be called |
400 | from outside of that method really. |
401 | |
552e3d24 |
402 | =back |
403 | |
404 | =head2 Informational |
405 | |
406 | =over 4 |
407 | |
408 | =item B<name> |
409 | |
410 | This is a read-only attribute which returns the package name that |
411 | the Class is stored in. |
412 | |
413 | =item B<version> |
414 | |
415 | This is a read-only attribute which returns the C<$VERSION> of the |
416 | package the Class is stored in. |
417 | |
418 | =back |
419 | |
420 | =head2 Inheritance Relationships |
421 | |
422 | =over 4 |
423 | |
424 | =item B<superclasses (?@superclasses)> |
425 | |
426 | This is a read-write attribute which represents the superclass |
427 | relationships of this Class. Basically, it can get and set the |
428 | C<@ISA> for you. |
429 | |
430 | =item B<class_precedence_list> |
431 | |
432 | This computes the a list of the Class's ancestors in the same order |
433 | in which method dispatch will be done. |
434 | |
435 | =back |
436 | |
437 | =head2 Methods |
438 | |
439 | =over 4 |
440 | |
441 | =item B<add_method ($method_name, $method)> |
442 | |
443 | This will take a C<$method_name> and CODE reference to that |
444 | C<$method> and install it into the Class. |
445 | |
446 | B<NOTE> : This does absolutely nothing special to C<$method> |
447 | other than use B<Sub::Name> to make sure it is tagged with the |
448 | correct name, and therefore show up correctly in stack traces and |
449 | such. |
450 | |
451 | =item B<has_method ($method_name)> |
452 | |
453 | This just provides a simple way to check if the Class implements |
454 | a specific C<$method_name>. It will I<not> however, attempt to check |
455 | if the class inherits the method. |
456 | |
457 | This will correctly handle functions defined outside of the package |
458 | that use a fully qualified name (C<sub Package::name { ... }>). |
459 | |
460 | This will correctly handle functions renamed with B<Sub::Name> and |
461 | installed using the symbol tables. However, if you are naming the |
462 | subroutine outside of the package scope, you must use the fully |
463 | qualified name, including the package name, for C<has_method> to |
464 | correctly identify it. |
465 | |
466 | This will attempt to correctly ignore functions imported from other |
467 | packages using B<Exporter>. It breaks down if the function imported |
468 | is an C<__ANON__> sub (such as with C<use constant>), which very well |
469 | may be a valid method being applied to the class. |
470 | |
471 | In short, this method cannot always be trusted to determine if the |
472 | C<$method_name> is actually a method. However, it will DWIM about |
473 | 90% of the time, so it's a small trade off IMO. |
474 | |
475 | =item B<get_method ($method_name)> |
476 | |
477 | This will return a CODE reference of the specified C<$method_name>, |
478 | or return undef if that method does not exist. |
479 | |
480 | =item B<remove_method ($method_name)> |
481 | |
482 | This will attempt to remove a given C<$method_name> from the Class. |
483 | It will return the CODE reference that it has removed, and will |
484 | attempt to use B<Sub::Name> to clear the methods associated name. |
485 | |
486 | =item B<get_method_list> |
487 | |
488 | This will return a list of method names for all I<locally> defined |
489 | methods. It does B<not> provide a list of all applicable methods, |
490 | including any inherited ones. If you want a list of all applicable |
491 | methods, use the C<compute_all_applicable_methods> method. |
492 | |
493 | =item B<compute_all_applicable_methods> |
494 | |
495 | This will return a list of all the methods names this Class will |
496 | support, taking into account inheritance. The list will be a list of |
497 | HASH references, each one containing the following information; method |
498 | name, the name of the class in which the method lives and a CODE |
499 | reference for the actual method. |
500 | |
501 | =item B<find_all_methods_by_name ($method_name)> |
502 | |
503 | This will traverse the inheritence hierarchy and locate all methods |
504 | with a given C<$method_name>. Similar to |
505 | C<compute_all_applicable_methods> it returns a list of HASH references |
506 | with the following information; method name (which will always be the |
507 | same as C<$method_name>), the name of the class in which the method |
508 | lives and a CODE reference for the actual method. |
509 | |
510 | The list of methods produced is a distinct list, meaning there are no |
511 | duplicates in it. This is especially useful for things like object |
512 | initialization and destruction where you only want the method called |
513 | once, and in the correct order. |
514 | |
515 | =back |
516 | |
517 | =head2 Attributes |
518 | |
519 | It should be noted that since there is no one consistent way to define |
520 | the attributes of a class in Perl 5. These methods can only work with |
521 | the information given, and can not easily discover information on |
522 | their own. |
523 | |
524 | =over 4 |
525 | |
526 | =item B<add_attribute ($attribute_name, $attribute_meta_object)> |
527 | |
528 | This stores a C<$attribute_meta_object> in the Class object and |
529 | associates it with the C<$attribute_name>. Unlike methods, attributes |
530 | within the MOP are stored as meta-information only. They will be used |
531 | later to construct instances from (see C<construct_instance> above). |
532 | More details about the attribute meta-objects can be found in the |
533 | L<The Attribute protocol> section of this document. |
534 | |
535 | =item B<has_attribute ($attribute_name)> |
536 | |
537 | Checks to see if this Class has an attribute by the name of |
538 | C<$attribute_name> and returns a boolean. |
539 | |
540 | =item B<get_attribute ($attribute_name)> |
541 | |
542 | Returns the attribute meta-object associated with C<$attribute_name>, |
543 | if none is found, it will return undef. |
544 | |
545 | =item B<remove_attribute ($attribute_name)> |
546 | |
547 | This will remove the attribute meta-object stored at |
548 | C<$attribute_name>, then return the removed attribute meta-object. |
549 | |
550 | B<NOTE:> Removing an attribute will only affect future instances of |
551 | the class, it will not make any attempt to remove the attribute from |
552 | any existing instances of the class. |
553 | |
554 | =item B<get_attribute_list> |
555 | |
556 | This returns a list of attribute names which are defined in the local |
557 | class. If you want a list of all applicable attributes for a class, |
558 | use the C<compute_all_applicable_attributes> method. |
559 | |
560 | =item B<compute_all_applicable_attributes> |
561 | |
562 | This will traverse the inheritance heirachy and return a list of HASH |
563 | references for all the applicable attributes for this class. The HASH |
564 | references will contain the following information; the attribute name, |
565 | the class which the attribute is associated with and the actual |
2eb717d5 |
566 | attribute meta-object. |
552e3d24 |
567 | |
568 | =back |
569 | |
8b978dd5 |
570 | =head1 AUTHOR |
571 | |
572 | Stevan Little E<gt>stevan@iinteractive.comE<lt> |
573 | |
574 | =head1 COPYRIGHT AND LICENSE |
575 | |
576 | Copyright 2006 by Infinity Interactive, Inc. |
577 | |
578 | L<http://www.iinteractive.com> |
579 | |
580 | This library is free software; you can redistribute it and/or modify |
581 | it under the same terms as Perl itself. |
582 | |
583 | =cut |