2 package Class::MOP::Class;
8 use Scalar::Util 'blessed', 'reftype', 'weaken';
9 use Sub::Name 'subname';
10 use B 'svref_2object';
12 our $VERSION = '0.19';
13 our $AUTHORITY = 'cpan:STEVAN';
15 use base 'Class::MOP::Module';
17 use Class::MOP::Instance;
21 sub meta { Class::MOP::Class->initialize(blessed($_[0]) || $_[0]) }
27 my $package_name = shift;
28 (defined $package_name && $package_name && !blessed($package_name))
29 || confess "You must pass a package name and it cannot be blessed";
30 $class->construct_class_instance(':package' => $package_name, @_);
35 my $package_name = shift;
36 (defined $package_name && $package_name && !blessed($package_name))
37 || confess "You must pass a package name and it cannot be blessed";
38 Class::MOP::remove_metaclass_by_name($package_name);
39 $class->construct_class_instance(':package' => $package_name, @_);
42 # NOTE: (meta-circularity)
43 # this is a special form of &construct_instance
44 # (see below), which is used to construct class
45 # meta-object instances for any Class::MOP::*
46 # class. All other classes will use the more
47 # normal &construct_instance.
48 sub construct_class_instance {
51 my $package_name = $options{':package'};
52 (defined $package_name && $package_name)
53 || confess "You must pass a package name";
55 # return the metaclass if we have it cached,
56 # and it is still defined (it has not been
57 # reaped by DESTROY yet, which can happen
58 # annoyingly enough during global destruction)
59 return Class::MOP::get_metaclass_by_name($package_name)
60 if Class::MOP::does_metaclass_exist($package_name);
63 # we need to deal with the possibility
64 # of class immutability here, and then
65 # get the name of the class appropriately
66 $class = (blessed($class)
67 ? ($class->is_immutable
68 ? $class->get_mutable_metaclass_name()
72 $class = blessed($class) || $class;
73 # now create the metaclass
75 if ($class =~ /^Class::MOP::Class$/) {
78 # inherited from Class::MOP::Package
79 '$:package' => $package_name,
82 # since the following attributes will
83 # actually be loaded from the symbol
84 # table, and actually bypass the instance
85 # entirely, we can just leave these things
86 # listed here for reference, because they
87 # should not actually have a value associated
89 '%:namespace' => \undef,
90 # inherited from Class::MOP::Module
91 '$:version' => \undef,
92 '$:authority' => \undef,
93 # defined in Class::MOP::Class
94 '%:methods' => \undef,
97 '$:attribute_metaclass' => $options{':attribute_metaclass'} || 'Class::MOP::Attribute',
98 '$:method_metaclass' => $options{':method_metaclass'} || 'Class::MOP::Method',
99 '$:instance_metaclass' => $options{':instance_metaclass'} || 'Class::MOP::Instance',
104 # it is safe to use meta here because
105 # class will always be a subclass of
106 # Class::MOP::Class, which defines meta
107 $meta = $class->meta->construct_instance(%options)
110 # and check the metaclass compatibility
111 $meta->check_metaclass_compatability();
113 Class::MOP::store_metaclass_by_name($package_name, $meta);
116 # we need to weaken any anon classes
117 # so that they can call DESTROY properly
118 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
123 sub check_metaclass_compatability {
126 # this is always okay ...
127 return if blessed($self) eq 'Class::MOP::Class' &&
128 $self->instance_metaclass eq 'Class::MOP::Instance';
130 my @class_list = $self->class_precedence_list;
131 shift @class_list; # shift off $self->name
133 foreach my $class_name (@class_list) {
134 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
137 # we need to deal with the possibility
138 # of class immutability here, and then
139 # get the name of the class appropriately
140 my $meta_type = ($meta->is_immutable
141 ? $meta->get_mutable_metaclass_name()
144 ($self->isa($meta_type))
145 || confess $self->name . "->meta => (" . (blessed($self)) . ")" .
146 " is not compatible with the " .
147 $class_name . "->meta => (" . ($meta_type) . ")";
149 # we also need to check that instance metaclasses
150 # are compatabile in the same the class.
151 ($self->instance_metaclass->isa($meta->instance_metaclass))
152 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
153 " is not compatible with the " .
154 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
162 # this should be sufficient, if you have a
163 # use case where it is not, write a test and
165 my $ANON_CLASS_SERIAL = 0;
168 # we need a sufficiently annoying prefix
169 # this should suffice for now, this is
170 # used in a couple of places below, so
171 # need to put it up here for now.
172 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
176 $self->name =~ /^$ANON_CLASS_PREFIX/ ? 1 : 0;
179 sub create_anon_class {
180 my ($class, %options) = @_;
181 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
182 return $class->create($package_name, '0.00', %options);
186 # this will only get called for
187 # anon-classes, all other calls
188 # are assumed to occur during
189 # global destruction and so don't
190 # really need to be handled explicitly
193 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
194 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
196 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
197 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
199 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
204 # creating classes with MOP ...
207 my ($class, $package_name, $package_version, %options) = @_;
208 (defined $package_name && $package_name)
209 || confess "You must pass a package name";
210 my $code = "package $package_name;";
211 $code .= "\$$package_name\:\:VERSION = '$package_version';"
212 if defined $package_version;
214 confess "creation of $package_name failed : $@" if $@;
215 my $meta = $class->initialize($package_name);
217 $meta->add_method('meta' => sub {
218 $class->initialize(blessed($_[0]) || $_[0]);
221 $meta->superclasses(@{$options{superclasses}})
222 if exists $options{superclasses};
224 # process attributes first, so that they can
225 # install accessors, but locally defined methods
226 # can then overwrite them. It is maybe a little odd, but
227 # I think this should be the order of things.
228 if (exists $options{attributes}) {
229 foreach my $attr (@{$options{attributes}}) {
230 $meta->add_attribute($attr);
233 if (exists $options{methods}) {
234 foreach my $method_name (keys %{$options{methods}}) {
235 $meta->add_method($method_name, $options{methods}->{$method_name});
244 # all these attribute readers will be bootstrapped
245 # away in the Class::MOP bootstrap section
247 sub get_attribute_map { $_[0]->{'%:attributes'} }
248 sub attribute_metaclass { $_[0]->{'$:attribute_metaclass'} }
249 sub method_metaclass { $_[0]->{'$:method_metaclass'} }
250 sub instance_metaclass { $_[0]->{'$:instance_metaclass'} }
255 # there is a faster/better way
256 # to do this, I am sure :)
259 $_ => $self->get_method($_)
261 $self->has_method($_)
262 } $self->list_all_package_symbols
266 # Instance Construction & Cloning
271 # we need to protect the integrity of the
272 # Class::MOP::Class singletons here, so we
273 # delegate this to &construct_class_instance
274 # which will deal with the singletons
275 return $class->construct_class_instance(@_)
276 if $class->name->isa('Class::MOP::Class');
277 return $class->construct_instance(@_);
280 sub construct_instance {
281 my ($class, %params) = @_;
282 my $meta_instance = $class->get_meta_instance();
283 my $instance = $meta_instance->create_instance();
284 foreach my $attr ($class->compute_all_applicable_attributes()) {
285 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
290 sub get_meta_instance {
292 return $class->instance_metaclass->new(
294 $class->compute_all_applicable_attributes()
300 my $instance = shift;
301 (blessed($instance) && $instance->isa($class->name))
302 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
304 # we need to protect the integrity of the
305 # Class::MOP::Class singletons here, they
306 # should not be cloned.
307 return $instance if $instance->isa('Class::MOP::Class');
308 $class->clone_instance($instance, @_);
312 my ($class, $instance, %params) = @_;
314 || confess "You can only clone instances, \$self is not a blessed instance";
315 my $meta_instance = $class->get_meta_instance();
316 my $clone = $meta_instance->clone_instance($instance);
317 foreach my $key (keys %params) {
318 next unless $meta_instance->is_valid_slot($key);
319 $meta_instance->set_slot_value($clone, $key, $params{$key});
330 @{$self->get_package_symbol('@ISA')} = @supers;
332 # we need to check the metaclass
333 # compatability here so that we can
334 # be sure that the superclass is
335 # not potentially creating an issues
336 # we don't know about
337 $self->check_metaclass_compatability();
339 @{$self->get_package_symbol('@ISA')};
342 sub class_precedence_list {
345 # We need to check for ciruclar inheirtance here.
346 # This will do nothing if all is well, and blow
347 # up otherwise. Yes, it's an ugly hack, better
348 # suggestions are welcome.
349 { ($self->name || return)->isa('This is a test for circular inheritance') }
350 # ... and now back to our regularly scheduled program
354 $self->initialize($_)->class_precedence_list()
355 } $self->superclasses()
362 my ($self, $method_name, $method) = @_;
363 (defined $method_name && $method_name)
364 || confess "You must define a method name";
365 # use reftype here to allow for blessed subs ...
366 ('CODE' eq (reftype($method) || ''))
367 || confess "Your code block must be a CODE reference";
368 my $full_method_name = ($self->name . '::' . $method_name);
371 # dont bless subs, its bad mkay
372 $method = $self->method_metaclass->wrap($method) unless blessed($method);
374 $self->add_package_symbol("&${method_name}" => subname $full_method_name => $method);
378 my $fetch_and_prepare_method = sub {
379 my ($self, $method_name) = @_;
381 my $method = $self->get_method($method_name);
382 # if we dont have local ...
384 # try to find the next method
385 $method = $self->find_next_method_by_name($method_name);
386 # die if it does not exist
388 || confess "The method '$method_name' is not found in the inherience hierarchy for this class";
389 # and now make sure to wrap it
390 # even if it is already wrapped
391 # because we need a new sub ref
392 $method = Class::MOP::Method::Wrapped->wrap($method);
395 # now make sure we wrap it properly
396 $method = Class::MOP::Method::Wrapped->wrap($method)
397 unless $method->isa('Class::MOP::Method::Wrapped');
399 $self->add_method($method_name => $method);
403 sub add_before_method_modifier {
404 my ($self, $method_name, $method_modifier) = @_;
405 (defined $method_name && $method_name)
406 || confess "You must pass in a method name";
407 my $method = $fetch_and_prepare_method->($self, $method_name);
408 $method->add_before_modifier(subname ':before' => $method_modifier);
411 sub add_after_method_modifier {
412 my ($self, $method_name, $method_modifier) = @_;
413 (defined $method_name && $method_name)
414 || confess "You must pass in a method name";
415 my $method = $fetch_and_prepare_method->($self, $method_name);
416 $method->add_after_modifier(subname ':after' => $method_modifier);
419 sub add_around_method_modifier {
420 my ($self, $method_name, $method_modifier) = @_;
421 (defined $method_name && $method_name)
422 || confess "You must pass in a method name";
423 my $method = $fetch_and_prepare_method->($self, $method_name);
424 $method->add_around_modifier(subname ':around' => $method_modifier);
428 # the methods above used to be named like this:
429 # ${pkg}::${method}:(before|after|around)
430 # but this proved problematic when using one modifier
431 # to wrap multiple methods (something which is likely
432 # to happen pretty regularly IMO). So instead of naming
433 # it like this, I have chosen to just name them purely
434 # with their modifier names, like so:
435 # :(before|after|around)
436 # The fact is that in a stack trace, it will be fairly
437 # evident from the context what method they are attached
438 # to, and so don't need the fully qualified name.
442 my ($self, $method_name, $method) = @_;
443 (defined $method_name && $method_name)
444 || confess "You must define a method name";
445 # use reftype here to allow for blessed subs ...
446 ('CODE' eq (reftype($method) || ''))
447 || confess "Your code block must be a CODE reference";
450 # dont bless subs, its bad mkay
451 $method = $self->method_metaclass->wrap($method) unless blessed($method);
453 $self->add_package_symbol("&${method_name}" => $method);
456 sub find_method_by_name {
457 my ($self, $method_name) = @_;
458 return $self->name->can($method_name);
462 my ($self, $method_name) = @_;
463 (defined $method_name && $method_name)
464 || confess "You must define a method name";
466 return 0 if !$self->has_package_symbol("&${method_name}");
467 my $method = $self->get_package_symbol("&${method_name}");
468 return 0 if (svref_2object($method)->GV->STASH->NAME || '') ne $self->name &&
469 (svref_2object($method)->GV->NAME || '') ne '__ANON__';
472 # dont bless subs, its bad mkay
473 $self->method_metaclass->wrap($method) unless blessed($method);
479 my ($self, $method_name) = @_;
480 (defined $method_name && $method_name)
481 || confess "You must define a method name";
483 return unless $self->has_method($method_name);
485 return $self->get_package_symbol("&${method_name}");
489 my ($self, $method_name) = @_;
490 (defined $method_name && $method_name)
491 || confess "You must define a method name";
493 my $removed_method = $self->get_method($method_name);
495 $self->remove_package_symbol("&${method_name}")
496 if defined $removed_method;
498 return $removed_method;
501 sub get_method_list {
503 grep { $self->has_method($_) } $self->list_all_package_symbols;
506 sub compute_all_applicable_methods {
509 # keep a record of what we have seen
510 # here, this will handle all the
511 # inheritence issues because we are
512 # using the &class_precedence_list
513 my (%seen_class, %seen_method);
514 foreach my $class ($self->class_precedence_list()) {
515 next if $seen_class{$class};
516 $seen_class{$class}++;
517 # fetch the meta-class ...
518 my $meta = $self->initialize($class);
519 foreach my $method_name ($meta->get_method_list()) {
520 next if exists $seen_method{$method_name};
521 $seen_method{$method_name}++;
523 name => $method_name,
525 code => $meta->get_method($method_name)
532 sub find_all_methods_by_name {
533 my ($self, $method_name) = @_;
534 (defined $method_name && $method_name)
535 || confess "You must define a method name to find";
537 # keep a record of what we have seen
538 # here, this will handle all the
539 # inheritence issues because we are
540 # using the &class_precedence_list
542 foreach my $class ($self->class_precedence_list()) {
543 next if $seen_class{$class};
544 $seen_class{$class}++;
545 # fetch the meta-class ...
546 my $meta = $self->initialize($class);
548 name => $method_name,
550 code => $meta->get_method($method_name)
551 } if $meta->has_method($method_name);
556 sub find_next_method_by_name {
557 my ($self, $method_name) = @_;
558 (defined $method_name && $method_name)
559 || confess "You must define a method name to find";
560 # keep a record of what we have seen
561 # here, this will handle all the
562 # inheritence issues because we are
563 # using the &class_precedence_list
565 my @cpl = $self->class_precedence_list();
566 shift @cpl; # discard ourselves
567 foreach my $class (@cpl) {
568 next if $seen_class{$class};
569 $seen_class{$class}++;
570 # fetch the meta-class ...
571 my $meta = $self->initialize($class);
572 return $meta->get_method($method_name)
573 if $meta->has_method($method_name);
582 # either we have an attribute object already
583 # or we need to create one from the args provided
584 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
585 # make sure it is derived from the correct type though
586 ($attribute->isa('Class::MOP::Attribute'))
587 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
588 $attribute->attach_to_class($self);
589 $attribute->install_accessors();
590 $self->get_attribute_map->{$attribute->name} = $attribute;
594 my ($self, $attribute_name) = @_;
595 (defined $attribute_name && $attribute_name)
596 || confess "You must define an attribute name";
597 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
601 my ($self, $attribute_name) = @_;
602 (defined $attribute_name && $attribute_name)
603 || confess "You must define an attribute name";
604 return $self->get_attribute_map->{$attribute_name}
605 if $self->has_attribute($attribute_name);
609 sub remove_attribute {
610 my ($self, $attribute_name) = @_;
611 (defined $attribute_name && $attribute_name)
612 || confess "You must define an attribute name";
613 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
614 return unless defined $removed_attribute;
615 delete $self->get_attribute_map->{$attribute_name};
616 $removed_attribute->remove_accessors();
617 $removed_attribute->detach_from_class();
618 return $removed_attribute;
621 sub get_attribute_list {
623 keys %{$self->get_attribute_map};
626 sub compute_all_applicable_attributes {
629 # keep a record of what we have seen
630 # here, this will handle all the
631 # inheritence issues because we are
632 # using the &class_precedence_list
633 my (%seen_class, %seen_attr);
634 foreach my $class ($self->class_precedence_list()) {
635 next if $seen_class{$class};
636 $seen_class{$class}++;
637 # fetch the meta-class ...
638 my $meta = $self->initialize($class);
639 foreach my $attr_name ($meta->get_attribute_list()) {
640 next if exists $seen_attr{$attr_name};
641 $seen_attr{$attr_name}++;
642 push @attrs => $meta->get_attribute($attr_name);
648 sub find_attribute_by_name {
649 my ($self, $attr_name) = @_;
650 # keep a record of what we have seen
651 # here, this will handle all the
652 # inheritence issues because we are
653 # using the &class_precedence_list
655 foreach my $class ($self->class_precedence_list()) {
656 next if $seen_class{$class};
657 $seen_class{$class}++;
658 # fetch the meta-class ...
659 my $meta = $self->initialize($class);
660 return $meta->get_attribute($attr_name)
661 if $meta->has_attribute($attr_name);
669 sub is_immutable { 0 }
672 return Class::MOP::Class::Immutable->make_metaclass_immutable(@_);
683 Class::MOP::Class - Class Meta Object
687 # assuming that class Foo
688 # has been defined, you can
690 # use this for introspection ...
692 # add a method to Foo ...
693 Foo->meta->add_method('bar' => sub { ... })
695 # get a list of all the classes searched
696 # the method dispatcher in the correct order
697 Foo->meta->class_precedence_list()
699 # remove a method from Foo
700 Foo->meta->remove_method('bar');
702 # or use this to actually create classes ...
704 Class::MOP::Class->create('Bar' => '0.01' => (
705 superclasses => [ 'Foo' ],
707 Class::MOP:::Attribute->new('$bar'),
708 Class::MOP:::Attribute->new('$baz'),
711 calculate_bar => sub { ... },
712 construct_baz => sub { ... }
718 This is the largest and currently most complex part of the Perl 5
719 meta-object protocol. It controls the introspection and
720 manipulation of Perl 5 classes (and it can create them too). The
721 best way to understand what this module can do, is to read the
722 documentation for each of it's methods.
726 =head2 Self Introspection
732 This will return a B<Class::MOP::Class> instance which is related
733 to this class. Thereby allowing B<Class::MOP::Class> to actually
736 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
737 bootstrap this module by installing a number of attribute meta-objects
738 into it's metaclass. This will allow this class to reap all the benifits
739 of the MOP when subclassing it.
743 =head2 Class construction
745 These methods will handle creating B<Class::MOP::Class> objects,
746 which can be used to both create new classes, and analyze
747 pre-existing classes.
749 This module will internally store references to all the instances
750 you create with these methods, so that they do not need to be
751 created any more than nessecary. Basically, they are singletons.
755 =item B<create ($package_name, ?$package_version,
756 superclasses =E<gt> ?@superclasses,
757 methods =E<gt> ?%methods,
758 attributes =E<gt> ?%attributes)>
760 This returns a B<Class::MOP::Class> object, bringing the specified
761 C<$package_name> into existence and adding any of the
762 C<$package_version>, C<@superclasses>, C<%methods> and C<%attributes>
765 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
766 methods =E<gt> ?%methods,
767 attributes =E<gt> ?%attributes)>
769 This will create an anonymous class, it works much like C<create> but
770 it does not need a C<$package_name>. Instead it will create a suitably
771 unique package name for you to stash things into.
773 =item B<initialize ($package_name, %options)>
775 This initializes and returns returns a B<Class::MOP::Class> object
776 for a given a C<$package_name>.
778 =item B<reinitialize ($package_name, %options)>
780 This removes the old metaclass, and creates a new one in it's place.
781 Do B<not> use this unless you really know what you are doing, it could
782 very easily make a very large mess of your program.
784 =item B<construct_class_instance (%options)>
786 This will construct an instance of B<Class::MOP::Class>, it is
787 here so that we can actually "tie the knot" for B<Class::MOP::Class>
788 to use C<construct_instance> once all the bootstrapping is done. This
789 method is used internally by C<initialize> and should never be called
790 from outside of that method really.
792 =item B<check_metaclass_compatability>
794 This method is called as the very last thing in the
795 C<construct_class_instance> method. This will check that the
796 metaclass you are creating is compatible with the metaclasses of all
797 your ancestors. For more inforamtion about metaclass compatibility
798 see the C<About Metaclass compatibility> section in L<Class::MOP>.
802 =head2 Object instance construction and cloning
804 These methods are B<entirely optional>, it is up to you whether you want
809 =item B<instance_metaclass>
811 =item B<get_meta_instance>
813 =item B<new_object (%params)>
815 This is a convience method for creating a new object of the class, and
816 blessing it into the appropriate package as well. Ideally your class
817 would call a C<new> this method like so:
820 my ($class, %param) = @_;
821 $class->meta->new_object(%params);
824 Of course the ideal place for this would actually be in C<UNIVERSAL::>
825 but that is considered bad style, so we do not do that.
827 =item B<construct_instance (%params)>
829 This method is used to construct an instace structure suitable for
830 C<bless>-ing into your package of choice. It works in conjunction
831 with the Attribute protocol to collect all applicable attributes.
833 This will construct and instance using a HASH ref as storage
834 (currently only HASH references are supported). This will collect all
835 the applicable attributes and layout out the fields in the HASH ref,
836 it will then initialize them using either use the corresponding key
837 in C<%params> or any default value or initializer found in the
838 attribute meta-object.
840 =item B<clone_object ($instance, %params)>
842 This is a convience method for cloning an object instance, then
843 blessing it into the appropriate package. This method will call
844 C<clone_instance>, which performs a shallow copy of the object,
845 see that methods documentation for more details. Ideally your
846 class would call a C<clone> this method like so:
849 my ($self, %param) = @_;
850 $self->meta->clone_object($self, %params);
853 Of course the ideal place for this would actually be in C<UNIVERSAL::>
854 but that is considered bad style, so we do not do that.
856 =item B<clone_instance($instance, %params)>
858 This method is a compliment of C<construct_instance> (which means if
859 you override C<construct_instance>, you need to override this one too),
860 and clones the instance shallowly.
862 The cloned structure returned is (like with C<construct_instance>) an
863 unC<bless>ed HASH reference, it is your responsibility to then bless
864 this cloned structure into the right class (which C<clone_object> will
867 As of 0.11, this method will clone the C<$instance> structure shallowly,
868 as opposed to the deep cloning implemented in prior versions. After much
869 thought, research and discussion, I have decided that anything but basic
870 shallow cloning is outside the scope of the meta-object protocol. I
871 think Yuval "nothingmuch" Kogman put it best when he said that cloning
872 is too I<context-specific> to be part of the MOP.
878 These are a few predicate methods for asking information about the class.
882 =item B<is_anon_class>
886 =item B<is_immutable>
890 =head2 Inheritance Relationships
894 =item B<superclasses (?@superclasses)>
896 This is a read-write attribute which represents the superclass
897 relationships of the class the B<Class::MOP::Class> instance is
898 associated with. Basically, it can get and set the C<@ISA> for you.
901 Perl will occasionally perform some C<@ISA> and method caching, if
902 you decide to change your superclass relationship at runtime (which
903 is quite insane and very much not recommened), then you should be
904 aware of this and the fact that this module does not make any
905 attempt to address this issue.
907 =item B<class_precedence_list>
909 This computes the a list of all the class's ancestors in the same order
910 in which method dispatch will be done. This is similair to
911 what B<Class::ISA::super_path> does, but we don't remove duplicate names.
919 =item B<get_method_map>
921 =item B<method_metaclass>
923 =item B<add_method ($method_name, $method)>
925 This will take a C<$method_name> and CODE reference to that
926 C<$method> and install it into the class's package.
929 This does absolutely nothing special to C<$method>
930 other than use B<Sub::Name> to make sure it is tagged with the
931 correct name, and therefore show up correctly in stack traces and
934 =item B<alias_method ($method_name, $method)>
936 This will take a C<$method_name> and CODE reference to that
937 C<$method> and alias the method into the class's package.
940 Unlike C<add_method>, this will B<not> try to name the
941 C<$method> using B<Sub::Name>, it only aliases the method in
944 =item B<has_method ($method_name)>
946 This just provides a simple way to check if the class implements
947 a specific C<$method_name>. It will I<not> however, attempt to check
948 if the class inherits the method (use C<UNIVERSAL::can> for that).
950 This will correctly handle functions defined outside of the package
951 that use a fully qualified name (C<sub Package::name { ... }>).
953 This will correctly handle functions renamed with B<Sub::Name> and
954 installed using the symbol tables. However, if you are naming the
955 subroutine outside of the package scope, you must use the fully
956 qualified name, including the package name, for C<has_method> to
957 correctly identify it.
959 This will attempt to correctly ignore functions imported from other
960 packages using B<Exporter>. It breaks down if the function imported
961 is an C<__ANON__> sub (such as with C<use constant>), which very well
962 may be a valid method being applied to the class.
964 In short, this method cannot always be trusted to determine if the
965 C<$method_name> is actually a method. However, it will DWIM about
966 90% of the time, so it's a small trade off I think.
968 =item B<get_method ($method_name)>
970 This will return a CODE reference of the specified C<$method_name>,
971 or return undef if that method does not exist.
973 =item B<find_method_by_name ($method_name>
975 This will return a CODE reference of the specified C<$method_name>,
976 or return undef if that method does not exist.
978 Unlike C<get_method> this will also look in the superclasses.
980 =item B<remove_method ($method_name)>
982 This will attempt to remove a given C<$method_name> from the class.
983 It will return the CODE reference that it has removed, and will
984 attempt to use B<Sub::Name> to clear the methods associated name.
986 =item B<get_method_list>
988 This will return a list of method names for all I<locally> defined
989 methods. It does B<not> provide a list of all applicable methods,
990 including any inherited ones. If you want a list of all applicable
991 methods, use the C<compute_all_applicable_methods> method.
993 =item B<compute_all_applicable_methods>
995 This will return a list of all the methods names this class will
996 respond to, taking into account inheritance. The list will be a list of
997 HASH references, each one containing the following information; method
998 name, the name of the class in which the method lives and a CODE
999 reference for the actual method.
1001 =item B<find_all_methods_by_name ($method_name)>
1003 This will traverse the inheritence hierarchy and locate all methods
1004 with a given C<$method_name>. Similar to
1005 C<compute_all_applicable_methods> it returns a list of HASH references
1006 with the following information; method name (which will always be the
1007 same as C<$method_name>), the name of the class in which the method
1008 lives and a CODE reference for the actual method.
1010 The list of methods produced is a distinct list, meaning there are no
1011 duplicates in it. This is especially useful for things like object
1012 initialization and destruction where you only want the method called
1013 once, and in the correct order.
1015 =item B<find_next_method_by_name ($method_name)>
1017 This will return the first method to match a given C<$method_name> in
1018 the superclasses, this is basically equivalent to calling
1019 C<SUPER::$method_name>, but it can be dispatched at runtime.
1023 =head2 Method Modifiers
1025 Method modifiers are a concept borrowed from CLOS, in which a method
1026 can be wrapped with I<before>, I<after> and I<around> method modifiers
1027 that will be called everytime the method is called.
1029 =head3 How method modifiers work?
1031 Method modifiers work by wrapping the original method and then replacing
1032 it in the classes symbol table. The wrappers will handle calling all the
1033 modifiers in the appropariate orders and preserving the calling context
1034 for the original method.
1036 Each method modifier serves a particular purpose, which may not be
1037 obvious to users of other method wrapping modules. To start with, the
1038 return values of I<before> and I<after> modifiers are ignored. This is
1039 because thier purpose is B<not> to filter the input and output of the
1040 primary method (this is done with an I<around> modifier). This may seem
1041 like an odd restriction to some, but doing this allows for simple code
1042 to be added at the begining or end of a method call without jeapordizing
1043 the normal functioning of the primary method or placing any extra
1044 responsibility on the code of the modifier. Of course if you have more
1045 complex needs, then use the I<around> modifier, which uses a variation
1046 of continutation passing style to allow for a high degree of flexibility.
1048 Before and around modifiers are called in last-defined-first-called order,
1049 while after modifiers are called in first-defined-first-called order. So
1050 the call tree might looks something like this:
1060 To see examples of using method modifiers, see the following examples
1061 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1062 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1063 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1065 =head3 What is the performance impact?
1067 Of course there is a performance cost associated with method modifiers,
1068 but we have made every effort to make that cost be directly proportional
1069 to the amount of modifier features you utilize.
1071 The wrapping method does it's best to B<only> do as much work as it
1072 absolutely needs to. In order to do this we have moved some of the
1073 performance costs to set-up time, where they are easier to amortize.
1075 All this said, my benchmarks have indicated the following:
1077 simple wrapper with no modifiers 100% slower
1078 simple wrapper with simple before modifier 400% slower
1079 simple wrapper with simple after modifier 450% slower
1080 simple wrapper with simple around modifier 500-550% slower
1081 simple wrapper with all 3 modifiers 1100% slower
1083 These numbers may seem daunting, but you must remember, every feature
1084 comes with some cost. To put things in perspective, just doing a simple
1085 C<AUTOLOAD> which does nothing but extract the name of the method called
1086 and return it costs about 400% over a normal method call.
1090 =item B<add_before_method_modifier ($method_name, $code)>
1092 This will wrap the method at C<$method_name> and the supplied C<$code>
1093 will be passed the C<@_> arguments, and called before the original
1094 method is called. As specified above, the return value of the I<before>
1095 method modifiers is ignored, and it's ability to modify C<@_> is
1096 fairly limited. If you need to do either of these things, use an
1097 C<around> method modifier.
1099 =item B<add_after_method_modifier ($method_name, $code)>
1101 This will wrap the method at C<$method_name> so that the original
1102 method will be called, it's return values stashed, and then the
1103 supplied C<$code> will be passed the C<@_> arguments, and called.
1104 As specified above, the return value of the I<after> method
1105 modifiers is ignored, and it cannot modify the return values of
1106 the original method. If you need to do either of these things, use an
1107 C<around> method modifier.
1109 =item B<add_around_method_modifier ($method_name, $code)>
1111 This will wrap the method at C<$method_name> so that C<$code>
1112 will be called and passed the original method as an extra argument
1113 at the begining of the C<@_> argument list. This is a variation of
1114 continuation passing style, where the function prepended to C<@_>
1115 can be considered a continuation. It is up to C<$code> if it calls
1116 the original method or not, there is no restriction on what the
1117 C<$code> can or cannot do.
1123 It should be noted that since there is no one consistent way to define
1124 the attributes of a class in Perl 5. These methods can only work with
1125 the information given, and can not easily discover information on
1126 their own. See L<Class::MOP::Attribute> for more details.
1130 =item B<attribute_metaclass>
1132 =item B<get_attribute_map>
1134 =item B<add_attribute ($attribute_name, $attribute_meta_object)>
1136 This stores a C<$attribute_meta_object> in the B<Class::MOP::Class>
1137 instance associated with the given class, and associates it with
1138 the C<$attribute_name>. Unlike methods, attributes within the MOP
1139 are stored as meta-information only. They will be used later to
1140 construct instances from (see C<construct_instance> above).
1141 More details about the attribute meta-objects can be found in the
1142 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1145 It should be noted that any accessor, reader/writer or predicate
1146 methods which the C<$attribute_meta_object> has will be installed
1147 into the class at this time.
1149 =item B<has_attribute ($attribute_name)>
1151 Checks to see if this class has an attribute by the name of
1152 C<$attribute_name> and returns a boolean.
1154 =item B<get_attribute ($attribute_name)>
1156 Returns the attribute meta-object associated with C<$attribute_name>,
1157 if none is found, it will return undef.
1159 =item B<remove_attribute ($attribute_name)>
1161 This will remove the attribute meta-object stored at
1162 C<$attribute_name>, then return the removed attribute meta-object.
1165 Removing an attribute will only affect future instances of
1166 the class, it will not make any attempt to remove the attribute from
1167 any existing instances of the class.
1169 It should be noted that any accessor, reader/writer or predicate
1170 methods which the attribute meta-object stored at C<$attribute_name>
1171 has will be removed from the class at this time. This B<will> make
1172 these attributes somewhat inaccessable in previously created
1173 instances. But if you are crazy enough to do this at runtime, then
1174 you are crazy enough to deal with something like this :).
1176 =item B<get_attribute_list>
1178 This returns a list of attribute names which are defined in the local
1179 class. If you want a list of all applicable attributes for a class,
1180 use the C<compute_all_applicable_attributes> method.
1182 =item B<compute_all_applicable_attributes>
1184 This will traverse the inheritance heirachy and return a list of all
1185 the applicable attributes for this class. It does not construct a
1186 HASH reference like C<compute_all_applicable_methods> because all
1187 that same information is discoverable through the attribute
1190 =item B<find_attribute_by_name ($attr_name)>
1192 This method will traverse the inheritance heirachy and find the
1193 first attribute whose name matches C<$attr_name>, then return it.
1194 It will return undef if nothing is found.
1198 =head2 Class closing
1202 =item B<make_immutable>
1208 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1210 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
1212 =head1 COPYRIGHT AND LICENSE
1214 Copyright 2006 by Infinity Interactive, Inc.
1216 L<http://www.iinteractive.com>
1218 This library is free software; you can redistribute it and/or modify
1219 it under the same terms as Perl itself.