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 '$:authority' => \undef,
93 # defined in Class::MOP::Class
97 '$: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, %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 ...
208 my $package_name = shift;
210 (defined $package_name && $package_name)
211 || confess "You must pass a package name";
214 || confess "You much pass all parameters as name => value pairs " .
215 "(I found an uneven number of params in \@_)";
219 my $code = "package $package_name;";
220 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
221 if exists $options{version};
222 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
223 if exists $options{authority};
226 confess "creation of $package_name failed : $@" if $@;
228 my $meta = $class->initialize($package_name);
230 $meta->add_method('meta' => sub {
231 $class->initialize(blessed($_[0]) || $_[0]);
234 $meta->superclasses(@{$options{superclasses}})
235 if exists $options{superclasses};
237 # process attributes first, so that they can
238 # install accessors, but locally defined methods
239 # can then overwrite them. It is maybe a little odd, but
240 # I think this should be the order of things.
241 if (exists $options{attributes}) {
242 foreach my $attr (@{$options{attributes}}) {
243 $meta->add_attribute($attr);
246 if (exists $options{methods}) {
247 foreach my $method_name (keys %{$options{methods}}) {
248 $meta->add_method($method_name, $options{methods}->{$method_name});
257 # all these attribute readers will be bootstrapped
258 # away in the Class::MOP bootstrap section
260 sub get_attribute_map { $_[0]->{'%:attributes'} }
261 sub attribute_metaclass { $_[0]->{'$:attribute_metaclass'} }
262 sub method_metaclass { $_[0]->{'$:method_metaclass'} }
263 sub instance_metaclass { $_[0]->{'$:instance_metaclass'} }
266 # this is a prime canidate for conversion to XS
269 my $map = $self->{'%:methods'};
271 my $class_name = $self->name;
272 my $method_metaclass = $self->method_metaclass;
274 foreach my $symbol ($self->list_all_package_symbols('CODE')) {
275 my $code = $self->get_package_symbol('&' . $symbol);
277 next if exists $map->{$symbol} && $map->{$symbol}->body == $code;
279 my $gv = svref_2object($code)->GV;
280 next if ($gv->STASH->NAME || '') ne $class_name &&
281 ($gv->NAME || '') ne '__ANON__';
283 $map->{$symbol} = $method_metaclass->wrap($code);
289 # Instance Construction & Cloning
294 # we need to protect the integrity of the
295 # Class::MOP::Class singletons here, so we
296 # delegate this to &construct_class_instance
297 # which will deal with the singletons
298 return $class->construct_class_instance(@_)
299 if $class->name->isa('Class::MOP::Class');
300 return $class->construct_instance(@_);
303 sub construct_instance {
304 my ($class, %params) = @_;
305 my $meta_instance = $class->get_meta_instance();
306 my $instance = $meta_instance->create_instance();
307 foreach my $attr ($class->compute_all_applicable_attributes()) {
308 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
313 sub get_meta_instance {
315 return $class->instance_metaclass->new(
317 $class->compute_all_applicable_attributes()
323 my $instance = shift;
324 (blessed($instance) && $instance->isa($class->name))
325 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
327 # we need to protect the integrity of the
328 # Class::MOP::Class singletons here, they
329 # should not be cloned.
330 return $instance if $instance->isa('Class::MOP::Class');
331 $class->clone_instance($instance, @_);
335 my ($class, $instance, %params) = @_;
337 || confess "You can only clone instances, \$self is not a blessed instance";
338 my $meta_instance = $class->get_meta_instance();
339 my $clone = $meta_instance->clone_instance($instance);
340 foreach my $key (keys %params) {
341 next unless $meta_instance->is_valid_slot($key);
342 $meta_instance->set_slot_value($clone, $key, $params{$key});
353 @{$self->get_package_symbol('@ISA')} = @supers;
355 # we need to check the metaclass
356 # compatability here so that we can
357 # be sure that the superclass is
358 # not potentially creating an issues
359 # we don't know about
360 $self->check_metaclass_compatability();
362 @{$self->get_package_symbol('@ISA')};
365 sub class_precedence_list {
368 # We need to check for ciruclar inheirtance here.
369 # This will do nothing if all is well, and blow
370 # up otherwise. Yes, it's an ugly hack, better
371 # suggestions are welcome.
372 { ($self->name || return)->isa('This is a test for circular inheritance') }
373 # ... and now back to our regularly scheduled program
377 $self->initialize($_)->class_precedence_list()
378 } $self->superclasses()
385 my ($self, $method_name, $method) = @_;
386 (defined $method_name && $method_name)
387 || confess "You must define a method name";
390 if (blessed($method)) {
391 $body = $method->body;
395 ('CODE' eq (reftype($body) || ''))
396 || confess "Your code block must be a CODE reference";
397 $method = $self->method_metaclass->wrap($body);
399 $self->get_method_map->{$method_name} = $method;
401 my $full_method_name = ($self->name . '::' . $method_name);
402 $self->add_package_symbol("&${method_name}" => subname $full_method_name => $body);
406 my $fetch_and_prepare_method = sub {
407 my ($self, $method_name) = @_;
409 my $method = $self->get_method($method_name);
410 # if we dont have local ...
412 # try to find the next method
413 $method = $self->find_next_method_by_name($method_name);
414 # die if it does not exist
416 || confess "The method '$method_name' is not found in the inherience hierarchy for this class";
417 # and now make sure to wrap it
418 # even if it is already wrapped
419 # because we need a new sub ref
420 $method = Class::MOP::Method::Wrapped->wrap($method);
423 # now make sure we wrap it properly
424 $method = Class::MOP::Method::Wrapped->wrap($method)
425 unless $method->isa('Class::MOP::Method::Wrapped');
427 $self->add_method($method_name => $method);
431 sub add_before_method_modifier {
432 my ($self, $method_name, $method_modifier) = @_;
433 (defined $method_name && $method_name)
434 || confess "You must pass in a method name";
435 my $method = $fetch_and_prepare_method->($self, $method_name);
436 $method->add_before_modifier(subname ':before' => $method_modifier);
439 sub add_after_method_modifier {
440 my ($self, $method_name, $method_modifier) = @_;
441 (defined $method_name && $method_name)
442 || confess "You must pass in a method name";
443 my $method = $fetch_and_prepare_method->($self, $method_name);
444 $method->add_after_modifier(subname ':after' => $method_modifier);
447 sub add_around_method_modifier {
448 my ($self, $method_name, $method_modifier) = @_;
449 (defined $method_name && $method_name)
450 || confess "You must pass in a method name";
451 my $method = $fetch_and_prepare_method->($self, $method_name);
452 $method->add_around_modifier(subname ':around' => $method_modifier);
456 # the methods above used to be named like this:
457 # ${pkg}::${method}:(before|after|around)
458 # but this proved problematic when using one modifier
459 # to wrap multiple methods (something which is likely
460 # to happen pretty regularly IMO). So instead of naming
461 # it like this, I have chosen to just name them purely
462 # with their modifier names, like so:
463 # :(before|after|around)
464 # The fact is that in a stack trace, it will be fairly
465 # evident from the context what method they are attached
466 # to, and so don't need the fully qualified name.
470 my ($self, $method_name, $method) = @_;
471 (defined $method_name && $method_name)
472 || confess "You must define a method name";
474 my $body = (blessed($method) ? $method->body : $method);
475 ('CODE' eq (reftype($body) || ''))
476 || confess "Your code block must be a CODE reference";
478 $self->add_package_symbol("&${method_name}" => $body);
482 my ($self, $method_name) = @_;
483 (defined $method_name && $method_name)
484 || confess "You must define a method name";
486 return 0 unless exists $self->get_method_map->{$method_name};
491 my ($self, $method_name) = @_;
492 (defined $method_name && $method_name)
493 || confess "You must define a method name";
496 # I don't really need this here, because
497 # if the method_map is missing a key it
498 # will just return undef for me now
499 # return unless $self->has_method($method_name);
501 return $self->get_method_map->{$method_name};
505 my ($self, $method_name) = @_;
506 (defined $method_name && $method_name)
507 || confess "You must define a method name";
509 my $removed_method = $self->get_method($method_name);
512 $self->remove_package_symbol("&${method_name}");
513 delete $self->get_method_map->{$method_name};
514 } if defined $removed_method;
516 return $removed_method;
519 sub get_method_list {
521 keys %{$self->get_method_map};
524 sub find_method_by_name {
525 my ($self, $method_name) = @_;
527 return $self->name->can($method_name);
530 sub compute_all_applicable_methods {
533 # keep a record of what we have seen
534 # here, this will handle all the
535 # inheritence issues because we are
536 # using the &class_precedence_list
537 my (%seen_class, %seen_method);
538 foreach my $class ($self->class_precedence_list()) {
539 next if $seen_class{$class};
540 $seen_class{$class}++;
541 # fetch the meta-class ...
542 my $meta = $self->initialize($class);
543 foreach my $method_name ($meta->get_method_list()) {
544 next if exists $seen_method{$method_name};
545 $seen_method{$method_name}++;
547 name => $method_name,
549 code => $meta->get_method($method_name)
556 sub find_all_methods_by_name {
557 my ($self, $method_name) = @_;
558 (defined $method_name && $method_name)
559 || confess "You must define a method name to find";
561 # keep a record of what we have seen
562 # here, this will handle all the
563 # inheritence issues because we are
564 # using the &class_precedence_list
566 foreach my $class ($self->class_precedence_list()) {
567 next if $seen_class{$class};
568 $seen_class{$class}++;
569 # fetch the meta-class ...
570 my $meta = $self->initialize($class);
572 name => $method_name,
574 code => $meta->get_method($method_name)
575 } if $meta->has_method($method_name);
580 sub find_next_method_by_name {
581 my ($self, $method_name) = @_;
582 (defined $method_name && $method_name)
583 || confess "You must define a method name to find";
584 # keep a record of what we have seen
585 # here, this will handle all the
586 # inheritence issues because we are
587 # using the &class_precedence_list
589 my @cpl = $self->class_precedence_list();
590 shift @cpl; # discard ourselves
591 foreach my $class (@cpl) {
592 next if $seen_class{$class};
593 $seen_class{$class}++;
594 # fetch the meta-class ...
595 my $meta = $self->initialize($class);
596 return $meta->get_method($method_name)
597 if $meta->has_method($method_name);
606 # either we have an attribute object already
607 # or we need to create one from the args provided
608 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
609 # make sure it is derived from the correct type though
610 ($attribute->isa('Class::MOP::Attribute'))
611 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
612 $attribute->attach_to_class($self);
613 $attribute->install_accessors();
614 $self->get_attribute_map->{$attribute->name} = $attribute;
618 my ($self, $attribute_name) = @_;
619 (defined $attribute_name && $attribute_name)
620 || confess "You must define an attribute name";
621 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
625 my ($self, $attribute_name) = @_;
626 (defined $attribute_name && $attribute_name)
627 || confess "You must define an attribute name";
628 return $self->get_attribute_map->{$attribute_name}
629 if $self->has_attribute($attribute_name);
633 sub remove_attribute {
634 my ($self, $attribute_name) = @_;
635 (defined $attribute_name && $attribute_name)
636 || confess "You must define an attribute name";
637 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
638 return unless defined $removed_attribute;
639 delete $self->get_attribute_map->{$attribute_name};
640 $removed_attribute->remove_accessors();
641 $removed_attribute->detach_from_class();
642 return $removed_attribute;
645 sub get_attribute_list {
647 keys %{$self->get_attribute_map};
650 sub compute_all_applicable_attributes {
653 # keep a record of what we have seen
654 # here, this will handle all the
655 # inheritence issues because we are
656 # using the &class_precedence_list
657 my (%seen_class, %seen_attr);
658 foreach my $class ($self->class_precedence_list()) {
659 next if $seen_class{$class};
660 $seen_class{$class}++;
661 # fetch the meta-class ...
662 my $meta = $self->initialize($class);
663 foreach my $attr_name ($meta->get_attribute_list()) {
664 next if exists $seen_attr{$attr_name};
665 $seen_attr{$attr_name}++;
666 push @attrs => $meta->get_attribute($attr_name);
672 sub find_attribute_by_name {
673 my ($self, $attr_name) = @_;
674 # keep a record of what we have seen
675 # here, this will handle all the
676 # inheritence issues because we are
677 # using the &class_precedence_list
679 foreach my $class ($self->class_precedence_list()) {
680 next if $seen_class{$class};
681 $seen_class{$class}++;
682 # fetch the meta-class ...
683 my $meta = $self->initialize($class);
684 return $meta->get_attribute($attr_name)
685 if $meta->has_attribute($attr_name);
693 sub is_immutable { 0 }
696 return Class::MOP::Class::Immutable->make_metaclass_immutable(@_);
707 Class::MOP::Class - Class Meta Object
711 # assuming that class Foo
712 # has been defined, you can
714 # use this for introspection ...
716 # add a method to Foo ...
717 Foo->meta->add_method('bar' => sub { ... })
719 # get a list of all the classes searched
720 # the method dispatcher in the correct order
721 Foo->meta->class_precedence_list()
723 # remove a method from Foo
724 Foo->meta->remove_method('bar');
726 # or use this to actually create classes ...
728 Class::MOP::Class->create('Bar' => (
730 superclasses => [ 'Foo' ],
732 Class::MOP:::Attribute->new('$bar'),
733 Class::MOP:::Attribute->new('$baz'),
736 calculate_bar => sub { ... },
737 construct_baz => sub { ... }
743 This is the largest and currently most complex part of the Perl 5
744 meta-object protocol. It controls the introspection and
745 manipulation of Perl 5 classes (and it can create them too). The
746 best way to understand what this module can do, is to read the
747 documentation for each of it's methods.
751 =head2 Self Introspection
757 This will return a B<Class::MOP::Class> instance which is related
758 to this class. Thereby allowing B<Class::MOP::Class> to actually
761 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
762 bootstrap this module by installing a number of attribute meta-objects
763 into it's metaclass. This will allow this class to reap all the benifits
764 of the MOP when subclassing it.
768 =head2 Class construction
770 These methods will handle creating B<Class::MOP::Class> objects,
771 which can be used to both create new classes, and analyze
772 pre-existing classes.
774 This module will internally store references to all the instances
775 you create with these methods, so that they do not need to be
776 created any more than nessecary. Basically, they are singletons.
780 =item B<create ($package_name,
781 version =E<gt> ?$version,
782 authority =E<gt> ?$authority,
783 superclasses =E<gt> ?@superclasses,
784 methods =E<gt> ?%methods,
785 attributes =E<gt> ?%attributes)>
787 This returns a B<Class::MOP::Class> object, bringing the specified
788 C<$package_name> into existence and adding any of the C<$version>,
789 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
792 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
793 methods =E<gt> ?%methods,
794 attributes =E<gt> ?%attributes)>
796 This will create an anonymous class, it works much like C<create> but
797 it does not need a C<$package_name>. Instead it will create a suitably
798 unique package name for you to stash things into.
800 =item B<initialize ($package_name, %options)>
802 This initializes and returns returns a B<Class::MOP::Class> object
803 for a given a C<$package_name>.
805 =item B<reinitialize ($package_name, %options)>
807 This removes the old metaclass, and creates a new one in it's place.
808 Do B<not> use this unless you really know what you are doing, it could
809 very easily make a very large mess of your program.
811 =item B<construct_class_instance (%options)>
813 This will construct an instance of B<Class::MOP::Class>, it is
814 here so that we can actually "tie the knot" for B<Class::MOP::Class>
815 to use C<construct_instance> once all the bootstrapping is done. This
816 method is used internally by C<initialize> and should never be called
817 from outside of that method really.
819 =item B<check_metaclass_compatability>
821 This method is called as the very last thing in the
822 C<construct_class_instance> method. This will check that the
823 metaclass you are creating is compatible with the metaclasses of all
824 your ancestors. For more inforamtion about metaclass compatibility
825 see the C<About Metaclass compatibility> section in L<Class::MOP>.
829 =head2 Object instance construction and cloning
831 These methods are B<entirely optional>, it is up to you whether you want
836 =item B<instance_metaclass>
838 =item B<get_meta_instance>
840 =item B<new_object (%params)>
842 This is a convience method for creating a new object of the class, and
843 blessing it into the appropriate package as well. Ideally your class
844 would call a C<new> this method like so:
847 my ($class, %param) = @_;
848 $class->meta->new_object(%params);
851 Of course the ideal place for this would actually be in C<UNIVERSAL::>
852 but that is considered bad style, so we do not do that.
854 =item B<construct_instance (%params)>
856 This method is used to construct an instace structure suitable for
857 C<bless>-ing into your package of choice. It works in conjunction
858 with the Attribute protocol to collect all applicable attributes.
860 This will construct and instance using a HASH ref as storage
861 (currently only HASH references are supported). This will collect all
862 the applicable attributes and layout out the fields in the HASH ref,
863 it will then initialize them using either use the corresponding key
864 in C<%params> or any default value or initializer found in the
865 attribute meta-object.
867 =item B<clone_object ($instance, %params)>
869 This is a convience method for cloning an object instance, then
870 blessing it into the appropriate package. This method will call
871 C<clone_instance>, which performs a shallow copy of the object,
872 see that methods documentation for more details. Ideally your
873 class would call a C<clone> this method like so:
876 my ($self, %param) = @_;
877 $self->meta->clone_object($self, %params);
880 Of course the ideal place for this would actually be in C<UNIVERSAL::>
881 but that is considered bad style, so we do not do that.
883 =item B<clone_instance($instance, %params)>
885 This method is a compliment of C<construct_instance> (which means if
886 you override C<construct_instance>, you need to override this one too),
887 and clones the instance shallowly.
889 The cloned structure returned is (like with C<construct_instance>) an
890 unC<bless>ed HASH reference, it is your responsibility to then bless
891 this cloned structure into the right class (which C<clone_object> will
894 As of 0.11, this method will clone the C<$instance> structure shallowly,
895 as opposed to the deep cloning implemented in prior versions. After much
896 thought, research and discussion, I have decided that anything but basic
897 shallow cloning is outside the scope of the meta-object protocol. I
898 think Yuval "nothingmuch" Kogman put it best when he said that cloning
899 is too I<context-specific> to be part of the MOP.
905 These are a few predicate methods for asking information about the class.
909 =item B<is_anon_class>
913 =item B<is_immutable>
917 =head2 Inheritance Relationships
921 =item B<superclasses (?@superclasses)>
923 This is a read-write attribute which represents the superclass
924 relationships of the class the B<Class::MOP::Class> instance is
925 associated with. Basically, it can get and set the C<@ISA> for you.
928 Perl will occasionally perform some C<@ISA> and method caching, if
929 you decide to change your superclass relationship at runtime (which
930 is quite insane and very much not recommened), then you should be
931 aware of this and the fact that this module does not make any
932 attempt to address this issue.
934 =item B<class_precedence_list>
936 This computes the a list of all the class's ancestors in the same order
937 in which method dispatch will be done. This is similair to
938 what B<Class::ISA::super_path> does, but we don't remove duplicate names.
946 =item B<get_method_map>
948 =item B<method_metaclass>
950 =item B<add_method ($method_name, $method)>
952 This will take a C<$method_name> and CODE reference to that
953 C<$method> and install it into the class's package.
956 This does absolutely nothing special to C<$method>
957 other than use B<Sub::Name> to make sure it is tagged with the
958 correct name, and therefore show up correctly in stack traces and
961 =item B<alias_method ($method_name, $method)>
963 This will take a C<$method_name> and CODE reference to that
964 C<$method> and alias the method into the class's package.
967 Unlike C<add_method>, this will B<not> try to name the
968 C<$method> using B<Sub::Name>, it only aliases the method in
971 =item B<has_method ($method_name)>
973 This just provides a simple way to check if the class implements
974 a specific C<$method_name>. It will I<not> however, attempt to check
975 if the class inherits the method (use C<UNIVERSAL::can> for that).
977 This will correctly handle functions defined outside of the package
978 that use a fully qualified name (C<sub Package::name { ... }>).
980 This will correctly handle functions renamed with B<Sub::Name> and
981 installed using the symbol tables. However, if you are naming the
982 subroutine outside of the package scope, you must use the fully
983 qualified name, including the package name, for C<has_method> to
984 correctly identify it.
986 This will attempt to correctly ignore functions imported from other
987 packages using B<Exporter>. It breaks down if the function imported
988 is an C<__ANON__> sub (such as with C<use constant>), which very well
989 may be a valid method being applied to the class.
991 In short, this method cannot always be trusted to determine if the
992 C<$method_name> is actually a method. However, it will DWIM about
993 90% of the time, so it's a small trade off I think.
995 =item B<get_method ($method_name)>
997 This will return a CODE reference of the specified C<$method_name>,
998 or return undef if that method does not exist.
1000 =item B<find_method_by_name ($method_name>
1002 This will return a CODE reference of the specified C<$method_name>,
1003 or return undef if that method does not exist.
1005 Unlike C<get_method> this will also look in the superclasses.
1007 =item B<remove_method ($method_name)>
1009 This will attempt to remove a given C<$method_name> from the class.
1010 It will return the CODE reference that it has removed, and will
1011 attempt to use B<Sub::Name> to clear the methods associated name.
1013 =item B<get_method_list>
1015 This will return a list of method names for all I<locally> defined
1016 methods. It does B<not> provide a list of all applicable methods,
1017 including any inherited ones. If you want a list of all applicable
1018 methods, use the C<compute_all_applicable_methods> method.
1020 =item B<compute_all_applicable_methods>
1022 This will return a list of all the methods names this class will
1023 respond to, taking into account inheritance. The list will be a list of
1024 HASH references, each one containing the following information; method
1025 name, the name of the class in which the method lives and a CODE
1026 reference for the actual method.
1028 =item B<find_all_methods_by_name ($method_name)>
1030 This will traverse the inheritence hierarchy and locate all methods
1031 with a given C<$method_name>. Similar to
1032 C<compute_all_applicable_methods> it returns a list of HASH references
1033 with the following information; method name (which will always be the
1034 same as C<$method_name>), the name of the class in which the method
1035 lives and a CODE reference for the actual method.
1037 The list of methods produced is a distinct list, meaning there are no
1038 duplicates in it. This is especially useful for things like object
1039 initialization and destruction where you only want the method called
1040 once, and in the correct order.
1042 =item B<find_next_method_by_name ($method_name)>
1044 This will return the first method to match a given C<$method_name> in
1045 the superclasses, this is basically equivalent to calling
1046 C<SUPER::$method_name>, but it can be dispatched at runtime.
1050 =head2 Method Modifiers
1052 Method modifiers are a concept borrowed from CLOS, in which a method
1053 can be wrapped with I<before>, I<after> and I<around> method modifiers
1054 that will be called everytime the method is called.
1056 =head3 How method modifiers work?
1058 Method modifiers work by wrapping the original method and then replacing
1059 it in the classes symbol table. The wrappers will handle calling all the
1060 modifiers in the appropariate orders and preserving the calling context
1061 for the original method.
1063 Each method modifier serves a particular purpose, which may not be
1064 obvious to users of other method wrapping modules. To start with, the
1065 return values of I<before> and I<after> modifiers are ignored. This is
1066 because thier purpose is B<not> to filter the input and output of the
1067 primary method (this is done with an I<around> modifier). This may seem
1068 like an odd restriction to some, but doing this allows for simple code
1069 to be added at the begining or end of a method call without jeapordizing
1070 the normal functioning of the primary method or placing any extra
1071 responsibility on the code of the modifier. Of course if you have more
1072 complex needs, then use the I<around> modifier, which uses a variation
1073 of continutation passing style to allow for a high degree of flexibility.
1075 Before and around modifiers are called in last-defined-first-called order,
1076 while after modifiers are called in first-defined-first-called order. So
1077 the call tree might looks something like this:
1087 To see examples of using method modifiers, see the following examples
1088 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1089 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1090 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1092 =head3 What is the performance impact?
1094 Of course there is a performance cost associated with method modifiers,
1095 but we have made every effort to make that cost be directly proportional
1096 to the amount of modifier features you utilize.
1098 The wrapping method does it's best to B<only> do as much work as it
1099 absolutely needs to. In order to do this we have moved some of the
1100 performance costs to set-up time, where they are easier to amortize.
1102 All this said, my benchmarks have indicated the following:
1104 simple wrapper with no modifiers 100% slower
1105 simple wrapper with simple before modifier 400% slower
1106 simple wrapper with simple after modifier 450% slower
1107 simple wrapper with simple around modifier 500-550% slower
1108 simple wrapper with all 3 modifiers 1100% slower
1110 These numbers may seem daunting, but you must remember, every feature
1111 comes with some cost. To put things in perspective, just doing a simple
1112 C<AUTOLOAD> which does nothing but extract the name of the method called
1113 and return it costs about 400% over a normal method call.
1117 =item B<add_before_method_modifier ($method_name, $code)>
1119 This will wrap the method at C<$method_name> and the supplied C<$code>
1120 will be passed the C<@_> arguments, and called before the original
1121 method is called. As specified above, the return value of the I<before>
1122 method modifiers is ignored, and it's ability to modify C<@_> is
1123 fairly limited. If you need to do either of these things, use an
1124 C<around> method modifier.
1126 =item B<add_after_method_modifier ($method_name, $code)>
1128 This will wrap the method at C<$method_name> so that the original
1129 method will be called, it's return values stashed, and then the
1130 supplied C<$code> will be passed the C<@_> arguments, and called.
1131 As specified above, the return value of the I<after> method
1132 modifiers is ignored, and it cannot modify the return values of
1133 the original method. If you need to do either of these things, use an
1134 C<around> method modifier.
1136 =item B<add_around_method_modifier ($method_name, $code)>
1138 This will wrap the method at C<$method_name> so that C<$code>
1139 will be called and passed the original method as an extra argument
1140 at the begining of the C<@_> argument list. This is a variation of
1141 continuation passing style, where the function prepended to C<@_>
1142 can be considered a continuation. It is up to C<$code> if it calls
1143 the original method or not, there is no restriction on what the
1144 C<$code> can or cannot do.
1150 It should be noted that since there is no one consistent way to define
1151 the attributes of a class in Perl 5. These methods can only work with
1152 the information given, and can not easily discover information on
1153 their own. See L<Class::MOP::Attribute> for more details.
1157 =item B<attribute_metaclass>
1159 =item B<get_attribute_map>
1161 =item B<add_attribute ($attribute_name, $attribute_meta_object)>
1163 This stores a C<$attribute_meta_object> in the B<Class::MOP::Class>
1164 instance associated with the given class, and associates it with
1165 the C<$attribute_name>. Unlike methods, attributes within the MOP
1166 are stored as meta-information only. They will be used later to
1167 construct instances from (see C<construct_instance> above).
1168 More details about the attribute meta-objects can be found in the
1169 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1172 It should be noted that any accessor, reader/writer or predicate
1173 methods which the C<$attribute_meta_object> has will be installed
1174 into the class at this time.
1176 =item B<has_attribute ($attribute_name)>
1178 Checks to see if this class has an attribute by the name of
1179 C<$attribute_name> and returns a boolean.
1181 =item B<get_attribute ($attribute_name)>
1183 Returns the attribute meta-object associated with C<$attribute_name>,
1184 if none is found, it will return undef.
1186 =item B<remove_attribute ($attribute_name)>
1188 This will remove the attribute meta-object stored at
1189 C<$attribute_name>, then return the removed attribute meta-object.
1192 Removing an attribute will only affect future instances of
1193 the class, it will not make any attempt to remove the attribute from
1194 any existing instances of the class.
1196 It should be noted that any accessor, reader/writer or predicate
1197 methods which the attribute meta-object stored at C<$attribute_name>
1198 has will be removed from the class at this time. This B<will> make
1199 these attributes somewhat inaccessable in previously created
1200 instances. But if you are crazy enough to do this at runtime, then
1201 you are crazy enough to deal with something like this :).
1203 =item B<get_attribute_list>
1205 This returns a list of attribute names which are defined in the local
1206 class. If you want a list of all applicable attributes for a class,
1207 use the C<compute_all_applicable_attributes> method.
1209 =item B<compute_all_applicable_attributes>
1211 This will traverse the inheritance heirachy and return a list of all
1212 the applicable attributes for this class. It does not construct a
1213 HASH reference like C<compute_all_applicable_methods> because all
1214 that same information is discoverable through the attribute
1217 =item B<find_attribute_by_name ($attr_name)>
1219 This method will traverse the inheritance heirachy and find the
1220 first attribute whose name matches C<$attr_name>, then return it.
1221 It will return undef if nothing is found.
1225 =head2 Class closing
1229 =item B<make_immutable>
1235 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1237 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
1239 =head1 COPYRIGHT AND LICENSE
1241 Copyright 2006 by Infinity Interactive, Inc.
1243 L<http://www.iinteractive.com>
1245 This library is free software; you can redistribute it and/or modify
1246 it under the same terms as Perl itself.