2 package Class::MOP::Class;
7 use Class::MOP::Immutable;
8 use Class::MOP::Instance;
9 use Class::MOP::Method::Wrapped;
12 use Scalar::Util 'blessed', 'reftype', 'weaken';
13 use Sub::Name 'subname';
15 our $VERSION = '0.30';
16 our $AUTHORITY = 'cpan:STEVAN';
18 use base 'Class::MOP::Module';
24 my $package_name = shift;
25 (defined $package_name && $package_name && !blessed($package_name))
26 || confess "You must pass a package name and it cannot be blessed";
27 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
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)
60 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
65 # we need to deal with the possibility
66 # of class immutability here, and then
67 # get the name of the class appropriately
68 $class = (blessed($class)
69 ? ($class->is_immutable
70 ? $class->get_mutable_metaclass_name()
74 # now create the metaclass
76 if ($class eq 'Class::MOP::Class') {
79 # inherited from Class::MOP::Package
80 '$!package' => $package_name,
83 # since the following attributes will
84 # actually be loaded from the symbol
85 # table, and actually bypass the instance
86 # entirely, we can just leave these things
87 # listed here for reference, because they
88 # should not actually have a value associated
90 '%!namespace' => \undef,
91 # inherited from Class::MOP::Module
92 '$!version' => \undef,
93 '$!authority' => \undef,
94 # defined in Class::MOP::Class
95 '@!superclasses' => \undef,
99 '$!attribute_metaclass' => $options{'attribute_metaclass'} || 'Class::MOP::Attribute',
100 '$!method_metaclass' => $options{'method_metaclass'} || 'Class::MOP::Method',
101 '$!instance_metaclass' => $options{'instance_metaclass'} || 'Class::MOP::Instance',
103 ## uber-private variables
105 # this starts out as undef so that
106 # we can tell the first time the
107 # methods are fetched
109 '$!_package_cache_flag' => undef,
114 # it is safe to use meta here because
115 # class will always be a subclass of
116 # Class::MOP::Class, which defines meta
117 $meta = $class->meta->construct_instance(%options)
120 # and check the metaclass compatibility
121 $meta->check_metaclass_compatability();
123 Class::MOP::store_metaclass_by_name($package_name, $meta);
126 # we need to weaken any anon classes
127 # so that they can call DESTROY properly
128 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
133 sub reset_package_cache_flag { (shift)->{'$!_package_cache_flag'} = undef }
134 sub update_package_cache_flag {
137 # we can manually update the cache number
138 # since we are actually adding the method
139 # to our cache as well. This avoids us
140 # having to regenerate the method_map.
142 $self->{'$!_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
145 sub check_metaclass_compatability {
148 # this is always okay ...
149 return if blessed($self) eq 'Class::MOP::Class' &&
150 $self->instance_metaclass eq 'Class::MOP::Instance';
152 my @class_list = $self->linearized_isa;
153 shift @class_list; # shift off $self->name
155 foreach my $class_name (@class_list) {
156 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
159 # we need to deal with the possibility
160 # of class immutability here, and then
161 # get the name of the class appropriately
162 my $meta_type = ($meta->is_immutable
163 ? $meta->get_mutable_metaclass_name()
166 ($self->isa($meta_type))
167 || confess $self->name . "->meta => (" . (blessed($self)) . ")" .
168 " is not compatible with the " .
169 $class_name . "->meta => (" . ($meta_type) . ")";
171 # we also need to check that instance metaclasses
172 # are compatabile in the same the class.
173 ($self->instance_metaclass->isa($meta->instance_metaclass))
174 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
175 " is not compatible with the " .
176 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
184 # this should be sufficient, if you have a
185 # use case where it is not, write a test and
187 my $ANON_CLASS_SERIAL = 0;
190 # we need a sufficiently annoying prefix
191 # this should suffice for now, this is
192 # used in a couple of places below, so
193 # need to put it up here for now.
194 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
198 no warnings 'uninitialized';
199 $self->name =~ /^$ANON_CLASS_PREFIX/ ? 1 : 0;
202 sub create_anon_class {
203 my ($class, %options) = @_;
204 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
205 return $class->create($package_name, %options);
209 # this will only get called for
210 # anon-classes, all other calls
211 # are assumed to occur during
212 # global destruction and so don't
213 # really need to be handled explicitly
216 no warnings 'uninitialized';
217 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
218 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
220 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
221 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
223 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
228 # creating classes with MOP ...
232 my $package_name = shift;
234 (defined $package_name && $package_name)
235 || confess "You must pass a package name";
238 || confess "You much pass all parameters as name => value pairs " .
239 "(I found an uneven number of params in \@_)";
243 (ref $options{superclasses} eq 'ARRAY')
244 || confess "You must pass an ARRAY ref of superclasses"
245 if exists $options{superclasses};
247 (ref $options{attributes} eq 'ARRAY')
248 || confess "You must pass an ARRAY ref of attributes"
249 if exists $options{attributes};
251 (ref $options{methods} eq 'HASH')
252 || confess "You must pass an HASH ref of methods"
253 if exists $options{methods};
255 my $code = "package $package_name;";
256 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
257 if exists $options{version};
258 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
259 if exists $options{authority};
262 confess "creation of $package_name failed : $@" if $@;
264 my $meta = $class->initialize($package_name);
266 $meta->add_method('meta' => sub {
267 $class->initialize(blessed($_[0]) || $_[0]);
270 $meta->superclasses(@{$options{superclasses}})
271 if exists $options{superclasses};
273 # process attributes first, so that they can
274 # install accessors, but locally defined methods
275 # can then overwrite them. It is maybe a little odd, but
276 # I think this should be the order of things.
277 if (exists $options{attributes}) {
278 foreach my $attr (@{$options{attributes}}) {
279 $meta->add_attribute($attr);
282 if (exists $options{methods}) {
283 foreach my $method_name (keys %{$options{methods}}) {
284 $meta->add_method($method_name, $options{methods}->{$method_name});
293 # all these attribute readers will be bootstrapped
294 # away in the Class::MOP bootstrap section
296 sub get_attribute_map { $_[0]->{'%!attributes'} }
297 sub attribute_metaclass { $_[0]->{'$!attribute_metaclass'} }
298 sub method_metaclass { $_[0]->{'$!method_metaclass'} }
299 sub instance_metaclass { $_[0]->{'$!instance_metaclass'} }
302 # this is a prime canidate for conversion to XS
306 if (defined $self->{'$!_package_cache_flag'} &&
307 $self->{'$!_package_cache_flag'} == Class::MOP::check_package_cache_flag($self->name)) {
308 return $self->{'%!methods'};
311 my $map = $self->{'%!methods'};
313 my $class_name = $self->name;
314 my $method_metaclass = $self->method_metaclass;
316 foreach my $symbol ($self->list_all_package_symbols('CODE')) {
317 my $code = $self->get_package_symbol('&' . $symbol);
319 next if exists $map->{$symbol} &&
320 defined $map->{$symbol} &&
321 $map->{$symbol}->body == $code;
323 my ($pkg, $name) = Class::MOP::get_code_info($code);
324 next if ($pkg || '') ne $class_name &&
325 ($name || '') ne '__ANON__';
327 $map->{$symbol} = $method_metaclass->wrap($code);
333 # Instance Construction & Cloning
338 # we need to protect the integrity of the
339 # Class::MOP::Class singletons here, so we
340 # delegate this to &construct_class_instance
341 # which will deal with the singletons
342 return $class->construct_class_instance(@_)
343 if $class->name->isa('Class::MOP::Class');
344 return $class->construct_instance(@_);
347 sub construct_instance {
348 my ($class, %params) = @_;
349 my $meta_instance = $class->get_meta_instance();
350 my $instance = $meta_instance->create_instance();
351 foreach my $attr ($class->compute_all_applicable_attributes()) {
352 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
355 # this will only work for a HASH instance type
356 if ($class->is_anon_class) {
357 (reftype($instance) eq 'HASH')
358 || confess "Currently only HASH based instances are supported with instance of anon-classes";
360 # At some point we should make this official
361 # as a reserved slot name, but right now I am
362 # going to keep it here.
363 # my $RESERVED_MOP_SLOT = '__MOP__';
364 $instance->{'__MOP__'} = $class;
369 sub get_meta_instance {
371 return $class->instance_metaclass->new(
373 $class->compute_all_applicable_attributes()
379 my $instance = shift;
380 (blessed($instance) && $instance->isa($class->name))
381 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
383 # we need to protect the integrity of the
384 # Class::MOP::Class singletons here, they
385 # should not be cloned.
386 return $instance if $instance->isa('Class::MOP::Class');
387 $class->clone_instance($instance, @_);
391 my ($class, $instance, %params) = @_;
393 || confess "You can only clone instances, \$self is not a blessed instance";
394 my $meta_instance = $class->get_meta_instance();
395 my $clone = $meta_instance->clone_instance($instance);
396 foreach my $attr ($class->compute_all_applicable_attributes()) {
397 if ( defined( my $init_arg = $attr->init_arg ) ) {
398 if (exists $params{$init_arg}) {
399 $attr->set_value($clone, $params{$init_arg});
406 sub rebless_instance {
407 my ($self, $instance, %params) = @_;
410 if ($instance->can('meta')) {
411 ($instance->meta->isa('Class::MOP::Class'))
412 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
413 $old_metaclass = $instance->meta;
416 $old_metaclass = $self->initialize(blessed($instance));
419 my $meta_instance = $self->get_meta_instance();
421 $self->name->isa($old_metaclass->name)
422 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
425 $meta_instance->rebless_instance_structure($instance, $self);
427 foreach my $attr ( $self->compute_all_applicable_attributes ) {
428 if ( $attr->has_value($instance) ) {
429 if ( defined( my $init_arg = $attr->init_arg ) ) {
430 $params{$init_arg} = $attr->get_value($instance)
431 unless exists $params{$init_arg};
434 $attr->set_value($instance, $attr->get_value($instance));
439 foreach my $attr ($self->compute_all_applicable_attributes) {
440 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
452 @{$self->get_package_symbol('@ISA')} = @supers;
454 # we need to check the metaclass
455 # compatibility here so that we can
456 # be sure that the superclass is
457 # not potentially creating an issues
458 # we don't know about
459 $self->check_metaclass_compatability();
461 @{$self->get_package_symbol('@ISA')};
467 my $super_class = $self->name;
470 my $find_derived_classes;
471 $find_derived_classes = sub {
472 my ($outer_class) = @_;
474 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
477 for my $symbol ( keys %$symbol_table_hashref ) {
478 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
479 my $inner_class = $1;
481 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
485 ? "${outer_class}::$inner_class"
488 if ( $class->isa($super_class) and $class ne $super_class ) {
489 push @derived_classes, $class;
492 next SYMBOL if $class eq 'main'; # skip 'main::*'
494 $find_derived_classes->($class);
498 my $root_class = q{};
499 $find_derived_classes->($root_class);
501 undef $find_derived_classes;
503 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
505 return @derived_classes;
510 if (Class::MOP::IS_RUNNING_ON_5_10()) {
511 return @{ mro::get_linear_isa( (shift)->name ) };
515 return grep { !($seen{$_}++) } (shift)->class_precedence_list;
519 sub class_precedence_list {
522 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
524 # We need to check for circular inheritance here
525 # if we are are not on 5.10, cause 5.8 detects it
526 # late. This will do nothing if all is well, and
527 # blow up otherwise. Yes, it's an ugly hack, better
528 # suggestions are welcome.
530 ($self->name || return)->isa('This is a test for circular inheritance')
536 $self->initialize($_)->class_precedence_list()
537 } $self->superclasses()
544 my ($self, $method_name, $method) = @_;
545 (defined $method_name && $method_name)
546 || confess "You must define a method name";
549 if (blessed($method)) {
550 $body = $method->body;
554 ('CODE' eq (reftype($body) || ''))
555 || confess "Your code block must be a CODE reference";
556 $method = $self->method_metaclass->wrap($body);
558 $self->get_method_map->{$method_name} = $method;
560 my $full_method_name = ($self->name . '::' . $method_name);
561 $self->add_package_symbol("&${method_name}" => subname $full_method_name => $body);
562 $self->update_package_cache_flag;
566 my $fetch_and_prepare_method = sub {
567 my ($self, $method_name) = @_;
569 my $method = $self->get_method($method_name);
570 # if we dont have local ...
572 # try to find the next method
573 $method = $self->find_next_method_by_name($method_name);
574 # die if it does not exist
576 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
577 # and now make sure to wrap it
578 # even if it is already wrapped
579 # because we need a new sub ref
580 $method = Class::MOP::Method::Wrapped->wrap($method);
583 # now make sure we wrap it properly
584 $method = Class::MOP::Method::Wrapped->wrap($method)
585 unless $method->isa('Class::MOP::Method::Wrapped');
587 $self->add_method($method_name => $method);
591 sub add_before_method_modifier {
592 my ($self, $method_name, $method_modifier) = @_;
593 (defined $method_name && $method_name)
594 || confess "You must pass in a method name";
595 my $method = $fetch_and_prepare_method->($self, $method_name);
596 $method->add_before_modifier(subname ':before' => $method_modifier);
599 sub add_after_method_modifier {
600 my ($self, $method_name, $method_modifier) = @_;
601 (defined $method_name && $method_name)
602 || confess "You must pass in a method name";
603 my $method = $fetch_and_prepare_method->($self, $method_name);
604 $method->add_after_modifier(subname ':after' => $method_modifier);
607 sub add_around_method_modifier {
608 my ($self, $method_name, $method_modifier) = @_;
609 (defined $method_name && $method_name)
610 || confess "You must pass in a method name";
611 my $method = $fetch_and_prepare_method->($self, $method_name);
612 $method->add_around_modifier(subname ':around' => $method_modifier);
616 # the methods above used to be named like this:
617 # ${pkg}::${method}:(before|after|around)
618 # but this proved problematic when using one modifier
619 # to wrap multiple methods (something which is likely
620 # to happen pretty regularly IMO). So instead of naming
621 # it like this, I have chosen to just name them purely
622 # with their modifier names, like so:
623 # :(before|after|around)
624 # The fact is that in a stack trace, it will be fairly
625 # evident from the context what method they are attached
626 # to, and so don't need the fully qualified name.
630 my ($self, $method_name, $method) = @_;
631 (defined $method_name && $method_name)
632 || confess "You must define a method name";
634 my $body = (blessed($method) ? $method->body : $method);
635 ('CODE' eq (reftype($body) || ''))
636 || confess "Your code block must be a CODE reference";
638 $self->add_package_symbol("&${method_name}" => $body);
639 $self->update_package_cache_flag;
643 my ($self, $method_name) = @_;
644 (defined $method_name && $method_name)
645 || confess "You must define a method name";
647 return 0 unless exists $self->get_method_map->{$method_name};
652 my ($self, $method_name) = @_;
653 (defined $method_name && $method_name)
654 || confess "You must define a method name";
657 # I don't really need this here, because
658 # if the method_map is missing a key it
659 # will just return undef for me now
660 # return unless $self->has_method($method_name);
662 return $self->get_method_map->{$method_name};
666 my ($self, $method_name) = @_;
667 (defined $method_name && $method_name)
668 || confess "You must define a method name";
670 my $removed_method = delete $self->get_method_map->{$method_name};
672 $self->remove_package_symbol("&${method_name}");
674 $self->update_package_cache_flag;
676 return $removed_method;
679 sub get_method_list {
681 keys %{$self->get_method_map};
684 sub find_method_by_name {
685 my ($self, $method_name) = @_;
686 (defined $method_name && $method_name)
687 || confess "You must define a method name to find";
688 foreach my $class ($self->linearized_isa) {
689 # fetch the meta-class ...
690 my $meta = $self->initialize($class);
691 return $meta->get_method($method_name)
692 if $meta->has_method($method_name);
697 sub compute_all_applicable_methods {
699 my (@methods, %seen_method);
700 foreach my $class ($self->linearized_isa) {
701 # fetch the meta-class ...
702 my $meta = $self->initialize($class);
703 foreach my $method_name ($meta->get_method_list()) {
704 next if exists $seen_method{$method_name};
705 $seen_method{$method_name}++;
707 name => $method_name,
709 code => $meta->get_method($method_name)
716 sub find_all_methods_by_name {
717 my ($self, $method_name) = @_;
718 (defined $method_name && $method_name)
719 || confess "You must define a method name to find";
721 foreach my $class ($self->linearized_isa) {
722 # fetch the meta-class ...
723 my $meta = $self->initialize($class);
725 name => $method_name,
727 code => $meta->get_method($method_name)
728 } if $meta->has_method($method_name);
733 sub find_next_method_by_name {
734 my ($self, $method_name) = @_;
735 (defined $method_name && $method_name)
736 || confess "You must define a method name to find";
737 my @cpl = $self->linearized_isa;
738 shift @cpl; # discard ourselves
739 foreach my $class (@cpl) {
740 # fetch the meta-class ...
741 my $meta = $self->initialize($class);
742 return $meta->get_method($method_name)
743 if $meta->has_method($method_name);
752 # either we have an attribute object already
753 # or we need to create one from the args provided
754 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
755 # make sure it is derived from the correct type though
756 ($attribute->isa('Class::MOP::Attribute'))
757 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
759 # first we attach our new attribute
760 # because it might need certain information
761 # about the class which it is attached to
762 $attribute->attach_to_class($self);
764 # then we remove attributes of a conflicting
765 # name here so that we can properly detach
766 # the old attr object, and remove any
767 # accessors it would have generated
768 $self->remove_attribute($attribute->name)
769 if $self->has_attribute($attribute->name);
771 # then onto installing the new accessors
772 $attribute->install_accessors();
773 $self->get_attribute_map->{$attribute->name} = $attribute;
777 my ($self, $attribute_name) = @_;
778 (defined $attribute_name && $attribute_name)
779 || confess "You must define an attribute name";
780 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
784 my ($self, $attribute_name) = @_;
785 (defined $attribute_name && $attribute_name)
786 || confess "You must define an attribute name";
787 return $self->get_attribute_map->{$attribute_name}
789 # this will return undef anyway, so no need ...
790 # if $self->has_attribute($attribute_name);
794 sub remove_attribute {
795 my ($self, $attribute_name) = @_;
796 (defined $attribute_name && $attribute_name)
797 || confess "You must define an attribute name";
798 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
799 return unless defined $removed_attribute;
800 delete $self->get_attribute_map->{$attribute_name};
801 $removed_attribute->remove_accessors();
802 $removed_attribute->detach_from_class();
803 return $removed_attribute;
806 sub get_attribute_list {
808 keys %{$self->get_attribute_map};
811 sub compute_all_applicable_attributes {
813 my (@attrs, %seen_attr);
814 foreach my $class ($self->linearized_isa) {
815 # fetch the meta-class ...
816 my $meta = $self->initialize($class);
817 foreach my $attr_name ($meta->get_attribute_list()) {
818 next if exists $seen_attr{$attr_name};
819 $seen_attr{$attr_name}++;
820 push @attrs => $meta->get_attribute($attr_name);
826 sub find_attribute_by_name {
827 my ($self, $attr_name) = @_;
828 foreach my $class ($self->linearized_isa) {
829 # fetch the meta-class ...
830 my $meta = $self->initialize($class);
831 return $meta->get_attribute($attr_name)
832 if $meta->has_attribute($attr_name);
840 sub is_immutable { 0 }
843 # Why I changed this (groditi)
844 # - One Metaclass may have many Classes through many Metaclass instances
845 # - One Metaclass should only have one Immutable Transformer instance
846 # - Each Class may have different Immutabilizing options
847 # - Therefore each Metaclass instance may have different Immutabilizing options
848 # - We need to store one Immutable Transformer instance per Metaclass
849 # - We need to store one set of Immutable Transformer options per Class
850 # - Upon make_mutable we may delete the Immutabilizing options
851 # - We could clean the immutable Transformer instance when there is no more
852 # immutable Classes of that type, but we can also keep it in case
853 # another class with this same Metaclass becomes immutable. It is a case
854 # of trading of storing an instance to avoid unnecessary instantiations of
855 # Immutable Transformers. You may view this as a memory leak, however
856 # Because we have few Metaclasses, in practice it seems acceptable
857 # - To allow Immutable Transformers instances to be cleaned up we could weaken
858 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
861 my %IMMUTABLE_TRANSFORMERS;
862 my %IMMUTABLE_OPTIONS;
866 my $class = blessed $self || $self;
868 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
869 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
871 $transformer->make_metaclass_immutable($self, \%options);
872 $IMMUTABLE_OPTIONS{$self->name} =
873 { %options, IMMUTABLE_TRANSFORMER => $transformer };
875 if( exists $options{debug} && $options{debug} ){
876 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
877 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
885 return if $self->is_mutable;
886 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
887 confess "unable to find immutabilizing options" unless ref $options;
888 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
889 $transformer->make_metaclass_mutable($self, $options);
894 sub create_immutable_transformer {
896 my $class = Class::MOP::Immutable->new($self, {
897 read_only => [qw/superclasses/],
905 remove_package_symbol
908 class_precedence_list => 'ARRAY',
909 linearized_isa => 'ARRAY',
910 compute_all_applicable_attributes => 'ARRAY',
911 get_meta_instance => 'SCALAR',
912 get_method_map => 'SCALAR',
926 Class::MOP::Class - Class Meta Object
930 # assuming that class Foo
931 # has been defined, you can
933 # use this for introspection ...
935 # add a method to Foo ...
936 Foo->meta->add_method('bar' => sub { ... })
938 # get a list of all the classes searched
939 # the method dispatcher in the correct order
940 Foo->meta->class_precedence_list()
942 # remove a method from Foo
943 Foo->meta->remove_method('bar');
945 # or use this to actually create classes ...
947 Class::MOP::Class->create('Bar' => (
949 superclasses => [ 'Foo' ],
951 Class::MOP:::Attribute->new('$bar'),
952 Class::MOP:::Attribute->new('$baz'),
955 calculate_bar => sub { ... },
956 construct_baz => sub { ... }
962 This is the largest and currently most complex part of the Perl 5
963 meta-object protocol. It controls the introspection and
964 manipulation of Perl 5 classes (and it can create them too). The
965 best way to understand what this module can do, is to read the
966 documentation for each of it's methods.
970 =head2 Self Introspection
976 This will return a B<Class::MOP::Class> instance which is related
977 to this class. Thereby allowing B<Class::MOP::Class> to actually
980 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
981 bootstrap this module by installing a number of attribute meta-objects
982 into it's metaclass. This will allow this class to reap all the benifits
983 of the MOP when subclassing it.
987 =head2 Class construction
989 These methods will handle creating B<Class::MOP::Class> objects,
990 which can be used to both create new classes, and analyze
991 pre-existing classes.
993 This module will internally store references to all the instances
994 you create with these methods, so that they do not need to be
995 created any more than nessecary. Basically, they are singletons.
999 =item B<create ($package_name,
1000 version =E<gt> ?$version,
1001 authority =E<gt> ?$authority,
1002 superclasses =E<gt> ?@superclasses,
1003 methods =E<gt> ?%methods,
1004 attributes =E<gt> ?%attributes)>
1006 This returns a B<Class::MOP::Class> object, bringing the specified
1007 C<$package_name> into existence and adding any of the C<$version>,
1008 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1011 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1012 methods =E<gt> ?%methods,
1013 attributes =E<gt> ?%attributes)>
1015 This will create an anonymous class, it works much like C<create> but
1016 it does not need a C<$package_name>. Instead it will create a suitably
1017 unique package name for you to stash things into.
1019 On very important distinction is that anon classes are destroyed once
1020 the metaclass they are attached to goes out of scope. In the DESTROY
1021 method, the created package will be removed from the symbol table.
1023 It is also worth noting that any instances created with an anon-class
1024 will keep a special reference to the anon-meta which will prevent the
1025 anon-class from going out of scope until all instances of it have also
1026 been destroyed. This however only works for HASH based instance types,
1027 as we use a special reserved slot (C<__MOP__>) to store this.
1029 =item B<initialize ($package_name, %options)>
1031 This initializes and returns returns a B<Class::MOP::Class> object
1032 for a given a C<$package_name>.
1034 =item B<reinitialize ($package_name, %options)>
1036 This removes the old metaclass, and creates a new one in it's place.
1037 Do B<not> use this unless you really know what you are doing, it could
1038 very easily make a very large mess of your program.
1040 =item B<construct_class_instance (%options)>
1042 This will construct an instance of B<Class::MOP::Class>, it is
1043 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1044 to use C<construct_instance> once all the bootstrapping is done. This
1045 method is used internally by C<initialize> and should never be called
1046 from outside of that method really.
1048 =item B<check_metaclass_compatability>
1050 This method is called as the very last thing in the
1051 C<construct_class_instance> method. This will check that the
1052 metaclass you are creating is compatible with the metaclasses of all
1053 your ancestors. For more inforamtion about metaclass compatibility
1054 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1056 =item B<update_package_cache_flag>
1058 This will reset the package cache flag for this particular metaclass
1059 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1060 function. This is very rarely needed from outside of C<Class::MOP::Class>
1061 but in some cases you might want to use it, so it is here.
1063 =item B<reset_package_cache_flag>
1065 Clears the package cache flag to announce to the internals that we need
1066 to rebuild the method map.
1070 =head2 Object instance construction and cloning
1072 These methods are B<entirely optional>, it is up to you whether you want
1077 =item B<instance_metaclass>
1079 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1080 for more information on the instance metaclasses.
1082 =item B<get_meta_instance>
1084 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1085 of a new instance of the class.
1087 =item B<new_object (%params)>
1089 This is a convience method for creating a new object of the class, and
1090 blessing it into the appropriate package as well. Ideally your class
1091 would call a C<new> this method like so:
1094 my ($class, %param) = @_;
1095 $class->meta->new_object(%params);
1098 =item B<construct_instance (%params)>
1100 This method is used to construct an instance structure suitable for
1101 C<bless>-ing into your package of choice. It works in conjunction
1102 with the Attribute protocol to collect all applicable attributes.
1104 This will construct and instance using a HASH ref as storage
1105 (currently only HASH references are supported). This will collect all
1106 the applicable attributes and layout out the fields in the HASH ref,
1107 it will then initialize them using either use the corresponding key
1108 in C<%params> or any default value or initializer found in the
1109 attribute meta-object.
1111 =item B<clone_object ($instance, %params)>
1113 This is a convience method for cloning an object instance, then
1114 blessing it into the appropriate package. This method will call
1115 C<clone_instance>, which performs a shallow copy of the object,
1116 see that methods documentation for more details. Ideally your
1117 class would call a C<clone> this method like so:
1119 sub MyClass::clone {
1120 my ($self, %param) = @_;
1121 $self->meta->clone_object($self, %params);
1124 =item B<clone_instance($instance, %params)>
1126 This method is a compliment of C<construct_instance> (which means if
1127 you override C<construct_instance>, you need to override this one too),
1128 and clones the instance shallowly.
1130 The cloned structure returned is (like with C<construct_instance>) an
1131 unC<bless>ed HASH reference, it is your responsibility to then bless
1132 this cloned structure into the right class (which C<clone_object> will
1135 As of 0.11, this method will clone the C<$instance> structure shallowly,
1136 as opposed to the deep cloning implemented in prior versions. After much
1137 thought, research and discussion, I have decided that anything but basic
1138 shallow cloning is outside the scope of the meta-object protocol. I
1139 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1140 is too I<context-specific> to be part of the MOP.
1142 =item B<rebless_instance($instance, ?%params)>
1144 This will change the class of C<$instance> to the class of the invoking
1145 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1146 itself. You may pass in optional C<%params> which are like constructor
1147 params and will override anything already defined in the instance.
1151 =head2 Informational
1153 These are a few predicate methods for asking information about the class.
1157 =item B<is_anon_class>
1159 This returns true if the class is a C<Class::MOP::Class> created anon class.
1163 This returns true if the class is still mutable.
1165 =item B<is_immutable>
1167 This returns true if the class has been made immutable.
1171 =head2 Inheritance Relationships
1175 =item B<superclasses (?@superclasses)>
1177 This is a read-write attribute which represents the superclass
1178 relationships of the class the B<Class::MOP::Class> instance is
1179 associated with. Basically, it can get and set the C<@ISA> for you.
1181 =item B<class_precedence_list>
1183 This computes the a list of all the class's ancestors in the same order
1184 in which method dispatch will be done. This is similair to what
1185 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1187 =item B<linearized_isa>
1189 This returns a list based on C<class_precedence_list> but with all
1194 This returns a list of subclasses for this class.
1202 =item B<get_method_map>
1204 Returns a HASH ref of name to CODE reference mapping for this class.
1206 =item B<method_metaclass>
1208 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1209 for more information on the method metaclasses.
1211 =item B<add_method ($method_name, $method)>
1213 This will take a C<$method_name> and CODE reference to that
1214 C<$method> and install it into the class's package.
1217 This does absolutely nothing special to C<$method>
1218 other than use B<Sub::Name> to make sure it is tagged with the
1219 correct name, and therefore show up correctly in stack traces and
1222 =item B<alias_method ($method_name, $method)>
1224 This will take a C<$method_name> and CODE reference to that
1225 C<$method> and alias the method into the class's package.
1228 Unlike C<add_method>, this will B<not> try to name the
1229 C<$method> using B<Sub::Name>, it only aliases the method in
1230 the class's package.
1232 =item B<has_method ($method_name)>
1234 This just provides a simple way to check if the class implements
1235 a specific C<$method_name>. It will I<not> however, attempt to check
1236 if the class inherits the method (use C<UNIVERSAL::can> for that).
1238 This will correctly handle functions defined outside of the package
1239 that use a fully qualified name (C<sub Package::name { ... }>).
1241 This will correctly handle functions renamed with B<Sub::Name> and
1242 installed using the symbol tables. However, if you are naming the
1243 subroutine outside of the package scope, you must use the fully
1244 qualified name, including the package name, for C<has_method> to
1245 correctly identify it.
1247 This will attempt to correctly ignore functions imported from other
1248 packages using B<Exporter>. It breaks down if the function imported
1249 is an C<__ANON__> sub (such as with C<use constant>), which very well
1250 may be a valid method being applied to the class.
1252 In short, this method cannot always be trusted to determine if the
1253 C<$method_name> is actually a method. However, it will DWIM about
1254 90% of the time, so it's a small trade off I think.
1256 =item B<get_method ($method_name)>
1258 This will return a Class::MOP::Method instance related to the specified
1259 C<$method_name>, or return undef if that method does not exist.
1261 The Class::MOP::Method is codifiable, so you can use it like a normal
1262 CODE reference, see L<Class::MOP::Method> for more information.
1264 =item B<find_method_by_name ($method_name>
1266 This will return a CODE reference of the specified C<$method_name>,
1267 or return undef if that method does not exist.
1269 Unlike C<get_method> this will also look in the superclasses.
1271 =item B<remove_method ($method_name)>
1273 This will attempt to remove a given C<$method_name> from the class.
1274 It will return the CODE reference that it has removed, and will
1275 attempt to use B<Sub::Name> to clear the methods associated name.
1277 =item B<get_method_list>
1279 This will return a list of method names for all I<locally> defined
1280 methods. It does B<not> provide a list of all applicable methods,
1281 including any inherited ones. If you want a list of all applicable
1282 methods, use the C<compute_all_applicable_methods> method.
1284 =item B<compute_all_applicable_methods>
1286 This will return a list of all the methods names this class will
1287 respond to, taking into account inheritance. The list will be a list of
1288 HASH references, each one containing the following information; method
1289 name, the name of the class in which the method lives and a CODE
1290 reference for the actual method.
1292 =item B<find_all_methods_by_name ($method_name)>
1294 This will traverse the inheritence hierarchy and locate all methods
1295 with a given C<$method_name>. Similar to
1296 C<compute_all_applicable_methods> it returns a list of HASH references
1297 with the following information; method name (which will always be the
1298 same as C<$method_name>), the name of the class in which the method
1299 lives and a CODE reference for the actual method.
1301 The list of methods produced is a distinct list, meaning there are no
1302 duplicates in it. This is especially useful for things like object
1303 initialization and destruction where you only want the method called
1304 once, and in the correct order.
1306 =item B<find_next_method_by_name ($method_name)>
1308 This will return the first method to match a given C<$method_name> in
1309 the superclasses, this is basically equivalent to calling
1310 C<SUPER::$method_name>, but it can be dispatched at runtime.
1314 =head2 Method Modifiers
1316 Method modifiers are a concept borrowed from CLOS, in which a method
1317 can be wrapped with I<before>, I<after> and I<around> method modifiers
1318 that will be called everytime the method is called.
1320 =head3 How method modifiers work?
1322 Method modifiers work by wrapping the original method and then replacing
1323 it in the classes symbol table. The wrappers will handle calling all the
1324 modifiers in the appropariate orders and preserving the calling context
1325 for the original method.
1327 Each method modifier serves a particular purpose, which may not be
1328 obvious to users of other method wrapping modules. To start with, the
1329 return values of I<before> and I<after> modifiers are ignored. This is
1330 because thier purpose is B<not> to filter the input and output of the
1331 primary method (this is done with an I<around> modifier). This may seem
1332 like an odd restriction to some, but doing this allows for simple code
1333 to be added at the begining or end of a method call without jeapordizing
1334 the normal functioning of the primary method or placing any extra
1335 responsibility on the code of the modifier. Of course if you have more
1336 complex needs, then use the I<around> modifier, which uses a variation
1337 of continutation passing style to allow for a high degree of flexibility.
1339 Before and around modifiers are called in last-defined-first-called order,
1340 while after modifiers are called in first-defined-first-called order. So
1341 the call tree might looks something like this:
1351 To see examples of using method modifiers, see the following examples
1352 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1353 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1354 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1356 =head3 What is the performance impact?
1358 Of course there is a performance cost associated with method modifiers,
1359 but we have made every effort to make that cost be directly proportional
1360 to the amount of modifier features you utilize.
1362 The wrapping method does it's best to B<only> do as much work as it
1363 absolutely needs to. In order to do this we have moved some of the
1364 performance costs to set-up time, where they are easier to amortize.
1366 All this said, my benchmarks have indicated the following:
1368 simple wrapper with no modifiers 100% slower
1369 simple wrapper with simple before modifier 400% slower
1370 simple wrapper with simple after modifier 450% slower
1371 simple wrapper with simple around modifier 500-550% slower
1372 simple wrapper with all 3 modifiers 1100% slower
1374 These numbers may seem daunting, but you must remember, every feature
1375 comes with some cost. To put things in perspective, just doing a simple
1376 C<AUTOLOAD> which does nothing but extract the name of the method called
1377 and return it costs about 400% over a normal method call.
1381 =item B<add_before_method_modifier ($method_name, $code)>
1383 This will wrap the method at C<$method_name> and the supplied C<$code>
1384 will be passed the C<@_> arguments, and called before the original
1385 method is called. As specified above, the return value of the I<before>
1386 method modifiers is ignored, and it's ability to modify C<@_> is
1387 fairly limited. If you need to do either of these things, use an
1388 C<around> method modifier.
1390 =item B<add_after_method_modifier ($method_name, $code)>
1392 This will wrap the method at C<$method_name> so that the original
1393 method will be called, it's return values stashed, and then the
1394 supplied C<$code> will be passed the C<@_> arguments, and called.
1395 As specified above, the return value of the I<after> method
1396 modifiers is ignored, and it cannot modify the return values of
1397 the original method. If you need to do either of these things, use an
1398 C<around> method modifier.
1400 =item B<add_around_method_modifier ($method_name, $code)>
1402 This will wrap the method at C<$method_name> so that C<$code>
1403 will be called and passed the original method as an extra argument
1404 at the begining of the C<@_> argument list. This is a variation of
1405 continuation passing style, where the function prepended to C<@_>
1406 can be considered a continuation. It is up to C<$code> if it calls
1407 the original method or not, there is no restriction on what the
1408 C<$code> can or cannot do.
1414 It should be noted that since there is no one consistent way to define
1415 the attributes of a class in Perl 5. These methods can only work with
1416 the information given, and can not easily discover information on
1417 their own. See L<Class::MOP::Attribute> for more details.
1421 =item B<attribute_metaclass>
1423 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1424 for more information on the attribute metaclasses.
1426 =item B<get_attribute_map>
1428 This returns a HASH ref of name to attribute meta-object mapping.
1430 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1432 This stores the C<$attribute_meta_object> (or creates one from the
1433 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1434 instance associated with the given class. Unlike methods, attributes
1435 within the MOP are stored as meta-information only. They will be used
1436 later to construct instances from (see C<construct_instance> above).
1437 More details about the attribute meta-objects can be found in the
1438 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1441 It should be noted that any accessor, reader/writer or predicate
1442 methods which the C<$attribute_meta_object> has will be installed
1443 into the class at this time.
1446 If an attribute already exists for C<$attribute_name>, the old one
1447 will be removed (as well as removing all it's accessors), and then
1450 =item B<has_attribute ($attribute_name)>
1452 Checks to see if this class has an attribute by the name of
1453 C<$attribute_name> and returns a boolean.
1455 =item B<get_attribute ($attribute_name)>
1457 Returns the attribute meta-object associated with C<$attribute_name>,
1458 if none is found, it will return undef.
1460 =item B<remove_attribute ($attribute_name)>
1462 This will remove the attribute meta-object stored at
1463 C<$attribute_name>, then return the removed attribute meta-object.
1466 Removing an attribute will only affect future instances of
1467 the class, it will not make any attempt to remove the attribute from
1468 any existing instances of the class.
1470 It should be noted that any accessor, reader/writer or predicate
1471 methods which the attribute meta-object stored at C<$attribute_name>
1472 has will be removed from the class at this time. This B<will> make
1473 these attributes somewhat inaccessable in previously created
1474 instances. But if you are crazy enough to do this at runtime, then
1475 you are crazy enough to deal with something like this :).
1477 =item B<get_attribute_list>
1479 This returns a list of attribute names which are defined in the local
1480 class. If you want a list of all applicable attributes for a class,
1481 use the C<compute_all_applicable_attributes> method.
1483 =item B<compute_all_applicable_attributes>
1485 This will traverse the inheritance heirachy and return a list of all
1486 the applicable attributes for this class. It does not construct a
1487 HASH reference like C<compute_all_applicable_methods> because all
1488 that same information is discoverable through the attribute
1491 =item B<find_attribute_by_name ($attr_name)>
1493 This method will traverse the inheritance heirachy and find the
1494 first attribute whose name matches C<$attr_name>, then return it.
1495 It will return undef if nothing is found.
1499 =head2 Class Immutability
1503 =item B<make_immutable (%options)>
1505 This method will invoke a tranforamtion upon the class which will
1506 make it immutable. Details of this transformation can be found in
1507 the L<Class::MOP::Immutable> documentation.
1509 =item B<make_mutable>
1511 This method will reverse tranforamtion upon the class which
1514 =item B<create_immutable_transformer>
1516 Create a transformer suitable for making this class immutable
1522 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1524 =head1 COPYRIGHT AND LICENSE
1526 Copyright 2006-2008 by Infinity Interactive, Inc.
1528 L<http://www.iinteractive.com>
1530 This library is free software; you can redistribute it and/or modify
1531 it under the same terms as Perl itself.