2 package Class::MOP::Class;
8 use Scalar::Util 'blessed', 'reftype';
9 use Sub::Name 'subname';
10 use B 'svref_2object';
12 our $VERSION = '0.01';
16 sub meta { $_[0]->initialize($_[0]) }
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?
27 my ($class, $package_name) = @_;
28 (defined $package_name && $package_name)
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);
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 for any Class::MOP::*
38 # class. All other classes will use the more
39 # 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 $class = blessed($class) || $class;
45 if ($class =~ /^Class::MOP::/) {
47 '$:pkg' => $package_name,
52 bless $class->meta->construct_instance(':pkg' => $package_name) => $class
58 my ($class, $package_name, $package_version, %options) = @_;
59 (defined $package_name && $package_name)
60 || confess "You must pass a package name";
61 my $code = "package $package_name;";
62 $code .= "\$$package_name\:\:VERSION = '$package_version';"
63 if defined $package_version;
65 confess "creation of $package_name failed : $@" if $@;
66 my $meta = $class->initialize($package_name);
67 $meta->superclasses(@{$options{superclasses}})
68 if exists $options{superclasses};
70 # process attributes first, so that they can
71 # install accessors, but locally defined methods
72 # can then overwrite them. It is maybe a little odd, but
73 # I think this should be the order of things.
74 if (exists $options{attributes}) {
75 foreach my $attr (@{$options{attributes}}) {
76 $meta->add_attribute($attr);
79 if (exists $options{methods}) {
80 foreach my $method_name (keys %{$options{methods}}) {
81 $meta->add_method($method_name, $options{methods}->{$method_name});
87 # Instance Construction
89 sub construct_instance {
90 my ($class, %params) = @_;
92 foreach my $attr (map { $_->{attribute} } $class->compute_all_applicable_attributes()) {
93 # if the attr has an init_arg, use that, otherwise,
94 # use the attributes name itself as the init_arg
95 my $init_arg = $attr->has_init_arg() ? $attr->init_arg() : $attr->name;
96 # try to fetch the init arg from the %params ...
98 $val = $params{$init_arg} if exists $params{$init_arg};
99 # if nothing was in the %params, we can use the
100 # attribute's default value (if it has one)
101 $val ||= $attr->default($instance) if $attr->has_default();
102 # now add this to the instance structure
103 $instance->{$attr->name} = $val;
110 sub name { $_[0]->{'$:pkg'} }
115 ${$self->name . '::VERSION'};
125 @{$self->name . '::ISA'} = @supers;
127 @{$self->name . '::ISA'};
130 sub class_precedence_list {
133 # We need to check for ciruclar inheirtance here.
134 # This will do nothing if all is well, and blow
135 # up otherwise. Yes, it's an ugly hack, better
136 # suggestions are welcome.
137 { $self->name->isa('This is a test for circular inheritance') }
138 # ... and no back to our regularly scheduled program
142 $self->initialize($_)->class_precedence_list()
143 } $self->superclasses()
150 my ($self, $method_name, $method) = @_;
151 (defined $method_name && $method_name)
152 || confess "You must define a method name";
153 # use reftype here to allow for blessed subs ...
154 (reftype($method) && reftype($method) eq 'CODE')
155 || confess "Your code block must be a CODE reference";
156 my $full_method_name = ($self->name . '::' . $method_name);
159 no warnings 'redefine';
160 *{$full_method_name} = subname $full_method_name => $method;
165 ## private utility functions for has_method
166 my $_find_subroutine_package_name = sub { eval { svref_2object($_[0])->GV->STASH->NAME } || '' };
167 my $_find_subroutine_name = sub { eval { svref_2object($_[0])->GV->NAME } || '' };
170 my ($self, $method_name) = @_;
171 (defined $method_name && $method_name)
172 || confess "You must define a method name";
174 my $sub_name = ($self->name . '::' . $method_name);
177 return 0 if !defined(&{$sub_name});
178 return 0 if $_find_subroutine_package_name->(\&{$sub_name}) ne $self->name &&
179 $_find_subroutine_name->(\&{$sub_name}) ne '__ANON__';
186 my ($self, $method_name) = @_;
187 (defined $method_name && $method_name)
188 || confess "You must define a method name";
191 return \&{$self->name . '::' . $method_name}
192 if $self->has_method($method_name);
193 return; # <- make sure to return undef
197 my ($self, $method_name) = @_;
198 (defined $method_name && $method_name)
199 || confess "You must define a method name";
201 my $removed_method = $self->get_method($method_name);
204 delete ${$self->name . '::'}{$method_name}
205 if defined $removed_method;
207 return $removed_method;
210 sub get_method_list {
213 grep { $self->has_method($_) } %{$self->name . '::'};
216 sub compute_all_applicable_methods {
219 # keep a record of what we have seen
220 # here, this will handle all the
221 # inheritence issues because we are
222 # using the &class_precedence_list
223 my (%seen_class, %seen_method);
224 foreach my $class ($self->class_precedence_list()) {
225 next if $seen_class{$class};
226 $seen_class{$class}++;
227 # fetch the meta-class ...
228 my $meta = $self->initialize($class);
229 foreach my $method_name ($meta->get_method_list()) {
230 next if exists $seen_method{$method_name};
231 $seen_method{$method_name}++;
233 name => $method_name,
235 code => $meta->get_method($method_name)
242 sub find_all_methods_by_name {
243 my ($self, $method_name) = @_;
244 (defined $method_name && $method_name)
245 || confess "You must define a method name to find";
247 # keep a record of what we have seen
248 # here, this will handle all the
249 # inheritence issues because we are
250 # using the &class_precedence_list
252 foreach my $class ($self->class_precedence_list()) {
253 next if $seen_class{$class};
254 $seen_class{$class}++;
255 # fetch the meta-class ...
256 my $meta = $self->initialize($class);
258 name => $method_name,
260 code => $meta->get_method($method_name)
261 } if $meta->has_method($method_name);
270 my ($self,$attribute) = @_;
271 (blessed($attribute) && $attribute->isa('Class::MOP::Attribute'))
272 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
273 $attribute->install_accessors($self);
274 $self->{'%:attrs'}->{$attribute->name} = $attribute;
278 my ($self, $attribute_name) = @_;
279 (defined $attribute_name && $attribute_name)
280 || confess "You must define an attribute name";
281 exists $self->{'%:attrs'}->{$attribute_name} ? 1 : 0;
285 my ($self, $attribute_name) = @_;
286 (defined $attribute_name && $attribute_name)
287 || confess "You must define an attribute name";
288 return $self->{'%:attrs'}->{$attribute_name}
289 if $self->has_attribute($attribute_name);
292 sub remove_attribute {
293 my ($self, $attribute_name) = @_;
294 (defined $attribute_name && $attribute_name)
295 || confess "You must define an attribute name";
296 my $removed_attribute = $self->{'%:attrs'}->{$attribute_name};
297 delete $self->{'%:attrs'}->{$attribute_name}
298 if defined $removed_attribute;
299 $removed_attribute->remove_accessors($self);
300 return $removed_attribute;
303 sub get_attribute_list {
305 keys %{$self->{'%:attrs'}};
308 sub compute_all_applicable_attributes {
311 # keep a record of what we have seen
312 # here, this will handle all the
313 # inheritence issues because we are
314 # using the &class_precedence_list
315 my (%seen_class, %seen_attr);
316 foreach my $class ($self->class_precedence_list()) {
317 next if $seen_class{$class};
318 $seen_class{$class}++;
319 # fetch the meta-class ...
320 my $meta = $self->initialize($class);
321 foreach my $attr_name ($meta->get_attribute_list()) {
322 next if exists $seen_attr{$attr_name};
323 $seen_attr{$attr_name}++;
327 attribute => $meta->get_attribute($attr_name)
342 Class::MOP::Class - Class Meta Object
346 # use this for introspection ...
349 sub meta { Class::MOP::Class->initialize(__PACKAGE__) }
351 # elsewhere in the code ...
353 # add a method to Foo ...
354 Foo->meta->add_method('bar' => sub { ... })
356 # get a list of all the classes searched
357 # the method dispatcher in the correct order
358 Foo->meta->class_precedence_list()
360 # remove a method from Foo
361 Foo->meta->remove_method('bar');
363 # or use this to actually create classes ...
365 Class::MOP::Class->create('Bar' => '0.01' => (
366 superclasses => [ 'Foo' ],
368 Class::MOP:::Attribute->new('$bar'),
369 Class::MOP:::Attribute->new('$baz'),
372 calculate_bar => sub { ... },
373 construct_baz => sub { ... }
379 This is the largest and currently most complex part of the Perl 5
380 meta-object protocol. It controls the introspection and
381 manipulation of Perl 5 classes (and it can create them too). The
382 best way to understand what this module can do, is to read the
383 documentation for each of it's methods.
387 =head2 Self Introspection
393 This will return a B<Class::MOP::Class> instance which is related
394 to this class. Thereby allowing B<Class::MOP::Class> to actually
397 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
398 bootstrap this module by installing a number of attribute meta-objects
399 into it's metaclass. This will allow this class to reap all the benifits
400 of the MOP when subclassing it.
404 =head2 Class construction
406 These methods handle creating Class objects, which can be used to
407 both create new classes, and analyze pre-existing ones.
409 This module will internally store references to all the instances
410 you create with these methods, so that they do not need to be
411 created any more than nessecary. Basically, they are singletons.
415 =item B<create ($package_name, ?$package_version,
416 superclasses => ?@superclasses,
417 methods => ?%methods,
418 attributes => ?%attributes)>
420 This returns the basic Class object, bringing the specified
421 C<$package_name> into existence and adding any of the
422 C<$package_version>, C<@superclasses>, C<%methods> and C<%attributes>
425 =item B<initialize ($package_name)>
427 This initializes a Class object for a given a C<$package_name>.
431 =head2 Instance construction
435 =item B<construct_instance (%params)>
437 This will construct and instance using a HASH ref as storage
438 (currently only HASH references are supported). This will collect all
439 the applicable attribute meta-objects and layout out the fields in the
440 HASH ref, it will then initialize them using either use the
441 corresponding key in C<%params> or any default value or initializer
442 found in the attribute meta-object.
444 =item B<construct_class_instance ($package_name)>
446 This will construct an instance of B<Class::MOP::Class>, it is
447 here so that we can actually "tie the knot" for B<Class::MOP::Class>
448 to use C<construct_instance> once all the bootstrapping is done. This
449 method is used internally by C<initialize> and should never be called
450 from outside of that method really.
460 This is a read-only attribute which returns the package name that
461 the Class is stored in.
465 This is a read-only attribute which returns the C<$VERSION> of the
466 package the Class is stored in.
470 =head2 Inheritance Relationships
474 =item B<superclasses (?@superclasses)>
476 This is a read-write attribute which represents the superclass
477 relationships of this Class. Basically, it can get and set the
480 =item B<class_precedence_list>
482 This computes the a list of the Class's ancestors in the same order
483 in which method dispatch will be done.
491 =item B<add_method ($method_name, $method)>
493 This will take a C<$method_name> and CODE reference to that
494 C<$method> and install it into the Class.
496 B<NOTE> : This does absolutely nothing special to C<$method>
497 other than use B<Sub::Name> to make sure it is tagged with the
498 correct name, and therefore show up correctly in stack traces and
501 =item B<has_method ($method_name)>
503 This just provides a simple way to check if the Class implements
504 a specific C<$method_name>. It will I<not> however, attempt to check
505 if the class inherits the method.
507 This will correctly handle functions defined outside of the package
508 that use a fully qualified name (C<sub Package::name { ... }>).
510 This will correctly handle functions renamed with B<Sub::Name> and
511 installed using the symbol tables. However, if you are naming the
512 subroutine outside of the package scope, you must use the fully
513 qualified name, including the package name, for C<has_method> to
514 correctly identify it.
516 This will attempt to correctly ignore functions imported from other
517 packages using B<Exporter>. It breaks down if the function imported
518 is an C<__ANON__> sub (such as with C<use constant>), which very well
519 may be a valid method being applied to the class.
521 In short, this method cannot always be trusted to determine if the
522 C<$method_name> is actually a method. However, it will DWIM about
523 90% of the time, so it's a small trade off IMO.
525 =item B<get_method ($method_name)>
527 This will return a CODE reference of the specified C<$method_name>,
528 or return undef if that method does not exist.
530 =item B<remove_method ($method_name)>
532 This will attempt to remove a given C<$method_name> from the Class.
533 It will return the CODE reference that it has removed, and will
534 attempt to use B<Sub::Name> to clear the methods associated name.
536 =item B<get_method_list>
538 This will return a list of method names for all I<locally> defined
539 methods. It does B<not> provide a list of all applicable methods,
540 including any inherited ones. If you want a list of all applicable
541 methods, use the C<compute_all_applicable_methods> method.
543 =item B<compute_all_applicable_methods>
545 This will return a list of all the methods names this Class will
546 support, taking into account inheritance. The list will be a list of
547 HASH references, each one containing the following information; method
548 name, the name of the class in which the method lives and a CODE
549 reference for the actual method.
551 =item B<find_all_methods_by_name ($method_name)>
553 This will traverse the inheritence hierarchy and locate all methods
554 with a given C<$method_name>. Similar to
555 C<compute_all_applicable_methods> it returns a list of HASH references
556 with the following information; method name (which will always be the
557 same as C<$method_name>), the name of the class in which the method
558 lives and a CODE reference for the actual method.
560 The list of methods produced is a distinct list, meaning there are no
561 duplicates in it. This is especially useful for things like object
562 initialization and destruction where you only want the method called
563 once, and in the correct order.
569 It should be noted that since there is no one consistent way to define
570 the attributes of a class in Perl 5. These methods can only work with
571 the information given, and can not easily discover information on
576 =item B<add_attribute ($attribute_name, $attribute_meta_object)>
578 This stores a C<$attribute_meta_object> in the Class object and
579 associates it with the C<$attribute_name>. Unlike methods, attributes
580 within the MOP are stored as meta-information only. They will be used
581 later to construct instances from (see C<construct_instance> above).
582 More details about the attribute meta-objects can be found in the
583 L<The Attribute protocol> section of this document.
585 =item B<has_attribute ($attribute_name)>
587 Checks to see if this Class has an attribute by the name of
588 C<$attribute_name> and returns a boolean.
590 =item B<get_attribute ($attribute_name)>
592 Returns the attribute meta-object associated with C<$attribute_name>,
593 if none is found, it will return undef.
595 =item B<remove_attribute ($attribute_name)>
597 This will remove the attribute meta-object stored at
598 C<$attribute_name>, then return the removed attribute meta-object.
600 B<NOTE:> Removing an attribute will only affect future instances of
601 the class, it will not make any attempt to remove the attribute from
602 any existing instances of the class.
604 =item B<get_attribute_list>
606 This returns a list of attribute names which are defined in the local
607 class. If you want a list of all applicable attributes for a class,
608 use the C<compute_all_applicable_attributes> method.
610 =item B<compute_all_applicable_attributes>
612 This will traverse the inheritance heirachy and return a list of HASH
613 references for all the applicable attributes for this class. The HASH
614 references will contain the following information; the attribute name,
615 the class which the attribute is associated with and the actual
616 attribute meta-object.
622 Stevan Little E<gt>stevan@iinteractive.comE<lt>
624 =head1 COPYRIGHT AND LICENSE
626 Copyright 2006 by Infinity Interactive, Inc.
628 L<http://www.iinteractive.com>
630 This library is free software; you can redistribute it and/or modify
631 it under the same terms as Perl itself.