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 = '0.29';
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);
439 foreach my $attr ($self->compute_all_applicable_attributes) {
440 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
450 @{$self->get_package_symbol('@ISA')} = @supers;
452 # we need to check the metaclass
453 # compatibility here so that we can
454 # be sure that the superclass is
455 # not potentially creating an issues
456 # we don't know about
457 $self->check_metaclass_compatability();
459 @{$self->get_package_symbol('@ISA')};
465 my $super_class = $self->name;
468 my $find_derived_classes;
469 $find_derived_classes = sub {
470 my ($outer_class) = @_;
472 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
475 for my $symbol ( keys %$symbol_table_hashref ) {
476 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
477 my $inner_class = $1;
479 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
483 ? "${outer_class}::$inner_class"
486 if ( $class->isa($super_class) and $class ne $super_class ) {
487 push @derived_classes, $class;
490 next SYMBOL if $class eq 'main'; # skip 'main::*'
492 $find_derived_classes->($class);
496 my $root_class = q{};
497 $find_derived_classes->($root_class);
499 undef $find_derived_classes;
501 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
503 return @derived_classes;
508 if (Class::MOP::IS_RUNNING_ON_5_10()) {
509 return @{ mro::get_linear_isa( (shift)->name ) };
513 return grep { !($seen{$_}++) } (shift)->class_precedence_list;
517 sub class_precedence_list {
520 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
522 # We need to check for circular inheritance here
523 # if we are are not on 5.10, cause 5.8 detects it
524 # late. This will do nothing if all is well, and
525 # blow up otherwise. Yes, it's an ugly hack, better
526 # suggestions are welcome.
528 ($self->name || return)->isa('This is a test for circular inheritance')
534 $self->initialize($_)->class_precedence_list()
535 } $self->superclasses()
542 my ($self, $method_name, $method) = @_;
543 (defined $method_name && $method_name)
544 || confess "You must define a method name";
547 if (blessed($method)) {
548 $body = $method->body;
552 ('CODE' eq (reftype($body) || ''))
553 || confess "Your code block must be a CODE reference";
554 $method = $self->method_metaclass->wrap($body);
556 $self->get_method_map->{$method_name} = $method;
558 my $full_method_name = ($self->name . '::' . $method_name);
559 $self->add_package_symbol("&${method_name}" => subname $full_method_name => $body);
560 $self->update_package_cache_flag;
564 my $fetch_and_prepare_method = sub {
565 my ($self, $method_name) = @_;
567 my $method = $self->get_method($method_name);
568 # if we dont have local ...
570 # try to find the next method
571 $method = $self->find_next_method_by_name($method_name);
572 # die if it does not exist
574 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
575 # and now make sure to wrap it
576 # even if it is already wrapped
577 # because we need a new sub ref
578 $method = Class::MOP::Method::Wrapped->wrap($method);
581 # now make sure we wrap it properly
582 $method = Class::MOP::Method::Wrapped->wrap($method)
583 unless $method->isa('Class::MOP::Method::Wrapped');
585 $self->add_method($method_name => $method);
589 sub add_before_method_modifier {
590 my ($self, $method_name, $method_modifier) = @_;
591 (defined $method_name && $method_name)
592 || confess "You must pass in a method name";
593 my $method = $fetch_and_prepare_method->($self, $method_name);
594 $method->add_before_modifier(subname ':before' => $method_modifier);
597 sub add_after_method_modifier {
598 my ($self, $method_name, $method_modifier) = @_;
599 (defined $method_name && $method_name)
600 || confess "You must pass in a method name";
601 my $method = $fetch_and_prepare_method->($self, $method_name);
602 $method->add_after_modifier(subname ':after' => $method_modifier);
605 sub add_around_method_modifier {
606 my ($self, $method_name, $method_modifier) = @_;
607 (defined $method_name && $method_name)
608 || confess "You must pass in a method name";
609 my $method = $fetch_and_prepare_method->($self, $method_name);
610 $method->add_around_modifier(subname ':around' => $method_modifier);
614 # the methods above used to be named like this:
615 # ${pkg}::${method}:(before|after|around)
616 # but this proved problematic when using one modifier
617 # to wrap multiple methods (something which is likely
618 # to happen pretty regularly IMO). So instead of naming
619 # it like this, I have chosen to just name them purely
620 # with their modifier names, like so:
621 # :(before|after|around)
622 # The fact is that in a stack trace, it will be fairly
623 # evident from the context what method they are attached
624 # to, and so don't need the fully qualified name.
628 my ($self, $method_name, $method) = @_;
629 (defined $method_name && $method_name)
630 || confess "You must define a method name";
632 my $body = (blessed($method) ? $method->body : $method);
633 ('CODE' eq (reftype($body) || ''))
634 || confess "Your code block must be a CODE reference";
636 $self->add_package_symbol("&${method_name}" => $body);
637 $self->update_package_cache_flag;
641 my ($self, $method_name) = @_;
642 (defined $method_name && $method_name)
643 || confess "You must define a method name";
645 return 0 unless exists $self->get_method_map->{$method_name};
650 my ($self, $method_name) = @_;
651 (defined $method_name && $method_name)
652 || confess "You must define a method name";
655 # I don't really need this here, because
656 # if the method_map is missing a key it
657 # will just return undef for me now
658 # return unless $self->has_method($method_name);
660 return $self->get_method_map->{$method_name};
664 my ($self, $method_name) = @_;
665 (defined $method_name && $method_name)
666 || confess "You must define a method name";
668 my $removed_method = delete $self->get_method_map->{$method_name};
670 $self->remove_package_symbol("&${method_name}");
672 $self->update_package_cache_flag;
674 return $removed_method;
677 sub get_method_list {
679 keys %{$self->get_method_map};
682 sub find_method_by_name {
683 my ($self, $method_name) = @_;
684 (defined $method_name && $method_name)
685 || confess "You must define a method name to find";
686 foreach my $class ($self->linearized_isa) {
687 # fetch the meta-class ...
688 my $meta = $self->initialize($class);
689 return $meta->get_method($method_name)
690 if $meta->has_method($method_name);
695 sub compute_all_applicable_methods {
697 my (@methods, %seen_method);
698 foreach my $class ($self->linearized_isa) {
699 # fetch the meta-class ...
700 my $meta = $self->initialize($class);
701 foreach my $method_name ($meta->get_method_list()) {
702 next if exists $seen_method{$method_name};
703 $seen_method{$method_name}++;
705 name => $method_name,
707 code => $meta->get_method($method_name)
714 sub find_all_methods_by_name {
715 my ($self, $method_name) = @_;
716 (defined $method_name && $method_name)
717 || confess "You must define a method name to find";
719 foreach my $class ($self->linearized_isa) {
720 # fetch the meta-class ...
721 my $meta = $self->initialize($class);
723 name => $method_name,
725 code => $meta->get_method($method_name)
726 } if $meta->has_method($method_name);
731 sub find_next_method_by_name {
732 my ($self, $method_name) = @_;
733 (defined $method_name && $method_name)
734 || confess "You must define a method name to find";
735 my @cpl = $self->linearized_isa;
736 shift @cpl; # discard ourselves
737 foreach my $class (@cpl) {
738 # fetch the meta-class ...
739 my $meta = $self->initialize($class);
740 return $meta->get_method($method_name)
741 if $meta->has_method($method_name);
750 # either we have an attribute object already
751 # or we need to create one from the args provided
752 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
753 # make sure it is derived from the correct type though
754 ($attribute->isa('Class::MOP::Attribute'))
755 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
757 # first we attach our new attribute
758 # because it might need certain information
759 # about the class which it is attached to
760 $attribute->attach_to_class($self);
762 # then we remove attributes of a conflicting
763 # name here so that we can properly detach
764 # the old attr object, and remove any
765 # accessors it would have generated
766 $self->remove_attribute($attribute->name)
767 if $self->has_attribute($attribute->name);
769 # then onto installing the new accessors
770 $attribute->install_accessors();
771 $self->get_attribute_map->{$attribute->name} = $attribute;
775 my ($self, $attribute_name) = @_;
776 (defined $attribute_name && $attribute_name)
777 || confess "You must define an attribute name";
778 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
782 my ($self, $attribute_name) = @_;
783 (defined $attribute_name && $attribute_name)
784 || confess "You must define an attribute name";
785 return $self->get_attribute_map->{$attribute_name}
787 # this will return undef anyway, so no need ...
788 # if $self->has_attribute($attribute_name);
792 sub remove_attribute {
793 my ($self, $attribute_name) = @_;
794 (defined $attribute_name && $attribute_name)
795 || confess "You must define an attribute name";
796 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
797 return unless defined $removed_attribute;
798 delete $self->get_attribute_map->{$attribute_name};
799 $removed_attribute->remove_accessors();
800 $removed_attribute->detach_from_class();
801 return $removed_attribute;
804 sub get_attribute_list {
806 keys %{$self->get_attribute_map};
809 sub compute_all_applicable_attributes {
811 my (@attrs, %seen_attr);
812 foreach my $class ($self->linearized_isa) {
813 # fetch the meta-class ...
814 my $meta = $self->initialize($class);
815 foreach my $attr_name ($meta->get_attribute_list()) {
816 next if exists $seen_attr{$attr_name};
817 $seen_attr{$attr_name}++;
818 push @attrs => $meta->get_attribute($attr_name);
824 sub find_attribute_by_name {
825 my ($self, $attr_name) = @_;
826 foreach my $class ($self->linearized_isa) {
827 # fetch the meta-class ...
828 my $meta = $self->initialize($class);
829 return $meta->get_attribute($attr_name)
830 if $meta->has_attribute($attr_name);
838 sub is_immutable { 0 }
841 # Why I changed this (groditi)
842 # - One Metaclass may have many Classes through many Metaclass instances
843 # - One Metaclass should only have one Immutable Transformer instance
844 # - Each Class may have different Immutabilizing options
845 # - Therefore each Metaclass instance may have different Immutabilizing options
846 # - We need to store one Immutable Transformer instance per Metaclass
847 # - We need to store one set of Immutable Transformer options per Class
848 # - Upon make_mutable we may delete the Immutabilizing options
849 # - We could clean the immutable Transformer instance when there is no more
850 # immutable Classes of that type, but we can also keep it in case
851 # another class with this same Metaclass becomes immutable. It is a case
852 # of trading of storing an instance to avoid unnecessary instantiations of
853 # Immutable Transformers. You may view this as a memory leak, however
854 # Because we have few Metaclasses, in practice it seems acceptable
855 # - To allow Immutable Transformers instances to be cleaned up we could weaken
856 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
859 my %IMMUTABLE_TRANSFORMERS;
860 my %IMMUTABLE_OPTIONS;
864 my $class = blessed $self || $self;
866 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
867 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
869 $transformer->make_metaclass_immutable($self, \%options);
870 $IMMUTABLE_OPTIONS{$self->name} =
871 { %options, IMMUTABLE_TRANSFORMER => $transformer };
873 if( exists $options{debug} && $options{debug} ){
874 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
875 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
883 return if $self->is_mutable;
884 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
885 confess "unable to find immutabilizing options" unless ref $options;
886 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
887 $transformer->make_metaclass_mutable($self, $options);
892 sub create_immutable_transformer {
894 my $class = Class::MOP::Immutable->new($self, {
895 read_only => [qw/superclasses/],
903 remove_package_symbol
906 class_precedence_list => 'ARRAY',
907 linearized_isa => 'ARRAY',
908 compute_all_applicable_attributes => 'ARRAY',
909 get_meta_instance => 'SCALAR',
910 get_method_map => 'SCALAR',
924 Class::MOP::Class - Class Meta Object
928 # assuming that class Foo
929 # has been defined, you can
931 # use this for introspection ...
933 # add a method to Foo ...
934 Foo->meta->add_method('bar' => sub { ... })
936 # get a list of all the classes searched
937 # the method dispatcher in the correct order
938 Foo->meta->class_precedence_list()
940 # remove a method from Foo
941 Foo->meta->remove_method('bar');
943 # or use this to actually create classes ...
945 Class::MOP::Class->create('Bar' => (
947 superclasses => [ 'Foo' ],
949 Class::MOP:::Attribute->new('$bar'),
950 Class::MOP:::Attribute->new('$baz'),
953 calculate_bar => sub { ... },
954 construct_baz => sub { ... }
960 This is the largest and currently most complex part of the Perl 5
961 meta-object protocol. It controls the introspection and
962 manipulation of Perl 5 classes (and it can create them too). The
963 best way to understand what this module can do, is to read the
964 documentation for each of it's methods.
968 =head2 Self Introspection
974 This will return a B<Class::MOP::Class> instance which is related
975 to this class. Thereby allowing B<Class::MOP::Class> to actually
978 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
979 bootstrap this module by installing a number of attribute meta-objects
980 into it's metaclass. This will allow this class to reap all the benifits
981 of the MOP when subclassing it.
985 =head2 Class construction
987 These methods will handle creating B<Class::MOP::Class> objects,
988 which can be used to both create new classes, and analyze
989 pre-existing classes.
991 This module will internally store references to all the instances
992 you create with these methods, so that they do not need to be
993 created any more than nessecary. Basically, they are singletons.
997 =item B<create ($package_name,
998 version =E<gt> ?$version,
999 authority =E<gt> ?$authority,
1000 superclasses =E<gt> ?@superclasses,
1001 methods =E<gt> ?%methods,
1002 attributes =E<gt> ?%attributes)>
1004 This returns a B<Class::MOP::Class> object, bringing the specified
1005 C<$package_name> into existence and adding any of the C<$version>,
1006 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1009 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1010 methods =E<gt> ?%methods,
1011 attributes =E<gt> ?%attributes)>
1013 This will create an anonymous class, it works much like C<create> but
1014 it does not need a C<$package_name>. Instead it will create a suitably
1015 unique package name for you to stash things into.
1017 On very important distinction is that anon classes are destroyed once
1018 the metaclass they are attached to goes out of scope. In the DESTROY
1019 method, the created package will be removed from the symbol table.
1021 It is also worth noting that any instances created with an anon-class
1022 will keep a special reference to the anon-meta which will prevent the
1023 anon-class from going out of scope until all instances of it have also
1024 been destroyed. This however only works for HASH based instance types,
1025 as we use a special reserved slot (C<__MOP__>) to store this.
1027 =item B<initialize ($package_name, %options)>
1029 This initializes and returns returns a B<Class::MOP::Class> object
1030 for a given a C<$package_name>.
1032 =item B<reinitialize ($package_name, %options)>
1034 This removes the old metaclass, and creates a new one in it's place.
1035 Do B<not> use this unless you really know what you are doing, it could
1036 very easily make a very large mess of your program.
1038 =item B<construct_class_instance (%options)>
1040 This will construct an instance of B<Class::MOP::Class>, it is
1041 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1042 to use C<construct_instance> once all the bootstrapping is done. This
1043 method is used internally by C<initialize> and should never be called
1044 from outside of that method really.
1046 =item B<check_metaclass_compatability>
1048 This method is called as the very last thing in the
1049 C<construct_class_instance> method. This will check that the
1050 metaclass you are creating is compatible with the metaclasses of all
1051 your ancestors. For more inforamtion about metaclass compatibility
1052 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1054 =item B<update_package_cache_flag>
1056 This will reset the package cache flag for this particular metaclass
1057 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1058 function. This is very rarely needed from outside of C<Class::MOP::Class>
1059 but in some cases you might want to use it, so it is here.
1061 =item B<reset_package_cache_flag>
1063 Clears the package cache flag to announce to the internals that we need
1064 to rebuild the method map.
1068 =head2 Object instance construction and cloning
1070 These methods are B<entirely optional>, it is up to you whether you want
1075 =item B<instance_metaclass>
1077 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1078 for more information on the instance metaclasses.
1080 =item B<get_meta_instance>
1082 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1083 of a new instance of the class.
1085 =item B<new_object (%params)>
1087 This is a convience method for creating a new object of the class, and
1088 blessing it into the appropriate package as well. Ideally your class
1089 would call a C<new> this method like so:
1092 my ($class, %param) = @_;
1093 $class->meta->new_object(%params);
1096 =item B<construct_instance (%params)>
1098 This method is used to construct an instance structure suitable for
1099 C<bless>-ing into your package of choice. It works in conjunction
1100 with the Attribute protocol to collect all applicable attributes.
1102 This will construct and instance using a HASH ref as storage
1103 (currently only HASH references are supported). This will collect all
1104 the applicable attributes and layout out the fields in the HASH ref,
1105 it will then initialize them using either use the corresponding key
1106 in C<%params> or any default value or initializer found in the
1107 attribute meta-object.
1109 =item B<clone_object ($instance, %params)>
1111 This is a convience method for cloning an object instance, then
1112 blessing it into the appropriate package. This method will call
1113 C<clone_instance>, which performs a shallow copy of the object,
1114 see that methods documentation for more details. Ideally your
1115 class would call a C<clone> this method like so:
1117 sub MyClass::clone {
1118 my ($self, %param) = @_;
1119 $self->meta->clone_object($self, %params);
1122 =item B<clone_instance($instance, %params)>
1124 This method is a compliment of C<construct_instance> (which means if
1125 you override C<construct_instance>, you need to override this one too),
1126 and clones the instance shallowly.
1128 The cloned structure returned is (like with C<construct_instance>) an
1129 unC<bless>ed HASH reference, it is your responsibility to then bless
1130 this cloned structure into the right class (which C<clone_object> will
1133 As of 0.11, this method will clone the C<$instance> structure shallowly,
1134 as opposed to the deep cloning implemented in prior versions. After much
1135 thought, research and discussion, I have decided that anything but basic
1136 shallow cloning is outside the scope of the meta-object protocol. I
1137 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1138 is too I<context-specific> to be part of the MOP.
1140 =item B<rebless_instance($instance, ?%params)>
1142 This will change the class of C<$instance> to the class of the invoking
1143 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1144 itself. You may pass in optional C<%params> which are like constructor
1145 params and will override anything already defined in the instance.
1149 =head2 Informational
1151 These are a few predicate methods for asking information about the class.
1155 =item B<is_anon_class>
1157 This returns true if the class is a C<Class::MOP::Class> created anon class.
1161 This returns true if the class is still mutable.
1163 =item B<is_immutable>
1165 This returns true if the class has been made immutable.
1169 =head2 Inheritance Relationships
1173 =item B<superclasses (?@superclasses)>
1175 This is a read-write attribute which represents the superclass
1176 relationships of the class the B<Class::MOP::Class> instance is
1177 associated with. Basically, it can get and set the C<@ISA> for you.
1179 =item B<class_precedence_list>
1181 This computes the a list of all the class's ancestors in the same order
1182 in which method dispatch will be done. This is similair to what
1183 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1185 =item B<linearized_isa>
1187 This returns a list based on C<class_precedence_list> but with all
1192 This returns a list of subclasses for this class.
1200 =item B<get_method_map>
1202 Returns a HASH ref of name to CODE reference mapping for this class.
1204 =item B<method_metaclass>
1206 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1207 for more information on the method metaclasses.
1209 =item B<add_method ($method_name, $method)>
1211 This will take a C<$method_name> and CODE reference to that
1212 C<$method> and install it into the class's package.
1215 This does absolutely nothing special to C<$method>
1216 other than use B<Sub::Name> to make sure it is tagged with the
1217 correct name, and therefore show up correctly in stack traces and
1220 =item B<alias_method ($method_name, $method)>
1222 This will take a C<$method_name> and CODE reference to that
1223 C<$method> and alias the method into the class's package.
1226 Unlike C<add_method>, this will B<not> try to name the
1227 C<$method> using B<Sub::Name>, it only aliases the method in
1228 the class's package.
1230 =item B<has_method ($method_name)>
1232 This just provides a simple way to check if the class implements
1233 a specific C<$method_name>. It will I<not> however, attempt to check
1234 if the class inherits the method (use C<UNIVERSAL::can> for that).
1236 This will correctly handle functions defined outside of the package
1237 that use a fully qualified name (C<sub Package::name { ... }>).
1239 This will correctly handle functions renamed with B<Sub::Name> and
1240 installed using the symbol tables. However, if you are naming the
1241 subroutine outside of the package scope, you must use the fully
1242 qualified name, including the package name, for C<has_method> to
1243 correctly identify it.
1245 This will attempt to correctly ignore functions imported from other
1246 packages using B<Exporter>. It breaks down if the function imported
1247 is an C<__ANON__> sub (such as with C<use constant>), which very well
1248 may be a valid method being applied to the class.
1250 In short, this method cannot always be trusted to determine if the
1251 C<$method_name> is actually a method. However, it will DWIM about
1252 90% of the time, so it's a small trade off I think.
1254 =item B<get_method ($method_name)>
1256 This will return a Class::MOP::Method instance related to the specified
1257 C<$method_name>, or return undef if that method does not exist.
1259 The Class::MOP::Method is codifiable, so you can use it like a normal
1260 CODE reference, see L<Class::MOP::Method> for more information.
1262 =item B<find_method_by_name ($method_name>
1264 This will return a CODE reference of the specified C<$method_name>,
1265 or return undef if that method does not exist.
1267 Unlike C<get_method> this will also look in the superclasses.
1269 =item B<remove_method ($method_name)>
1271 This will attempt to remove a given C<$method_name> from the class.
1272 It will return the CODE reference that it has removed, and will
1273 attempt to use B<Sub::Name> to clear the methods associated name.
1275 =item B<get_method_list>
1277 This will return a list of method names for all I<locally> defined
1278 methods. It does B<not> provide a list of all applicable methods,
1279 including any inherited ones. If you want a list of all applicable
1280 methods, use the C<compute_all_applicable_methods> method.
1282 =item B<compute_all_applicable_methods>
1284 This will return a list of all the methods names this class will
1285 respond to, taking into account inheritance. The list will be a list of
1286 HASH references, each one containing the following information; method
1287 name, the name of the class in which the method lives and a CODE
1288 reference for the actual method.
1290 =item B<find_all_methods_by_name ($method_name)>
1292 This will traverse the inheritence hierarchy and locate all methods
1293 with a given C<$method_name>. Similar to
1294 C<compute_all_applicable_methods> it returns a list of HASH references
1295 with the following information; method name (which will always be the
1296 same as C<$method_name>), the name of the class in which the method
1297 lives and a CODE reference for the actual method.
1299 The list of methods produced is a distinct list, meaning there are no
1300 duplicates in it. This is especially useful for things like object
1301 initialization and destruction where you only want the method called
1302 once, and in the correct order.
1304 =item B<find_next_method_by_name ($method_name)>
1306 This will return the first method to match a given C<$method_name> in
1307 the superclasses, this is basically equivalent to calling
1308 C<SUPER::$method_name>, but it can be dispatched at runtime.
1312 =head2 Method Modifiers
1314 Method modifiers are a concept borrowed from CLOS, in which a method
1315 can be wrapped with I<before>, I<after> and I<around> method modifiers
1316 that will be called everytime the method is called.
1318 =head3 How method modifiers work?
1320 Method modifiers work by wrapping the original method and then replacing
1321 it in the classes symbol table. The wrappers will handle calling all the
1322 modifiers in the appropariate orders and preserving the calling context
1323 for the original method.
1325 Each method modifier serves a particular purpose, which may not be
1326 obvious to users of other method wrapping modules. To start with, the
1327 return values of I<before> and I<after> modifiers are ignored. This is
1328 because thier purpose is B<not> to filter the input and output of the
1329 primary method (this is done with an I<around> modifier). This may seem
1330 like an odd restriction to some, but doing this allows for simple code
1331 to be added at the begining or end of a method call without jeapordizing
1332 the normal functioning of the primary method or placing any extra
1333 responsibility on the code of the modifier. Of course if you have more
1334 complex needs, then use the I<around> modifier, which uses a variation
1335 of continutation passing style to allow for a high degree of flexibility.
1337 Before and around modifiers are called in last-defined-first-called order,
1338 while after modifiers are called in first-defined-first-called order. So
1339 the call tree might looks something like this:
1349 To see examples of using method modifiers, see the following examples
1350 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1351 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1352 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1354 =head3 What is the performance impact?
1356 Of course there is a performance cost associated with method modifiers,
1357 but we have made every effort to make that cost be directly proportional
1358 to the amount of modifier features you utilize.
1360 The wrapping method does it's best to B<only> do as much work as it
1361 absolutely needs to. In order to do this we have moved some of the
1362 performance costs to set-up time, where they are easier to amortize.
1364 All this said, my benchmarks have indicated the following:
1366 simple wrapper with no modifiers 100% slower
1367 simple wrapper with simple before modifier 400% slower
1368 simple wrapper with simple after modifier 450% slower
1369 simple wrapper with simple around modifier 500-550% slower
1370 simple wrapper with all 3 modifiers 1100% slower
1372 These numbers may seem daunting, but you must remember, every feature
1373 comes with some cost. To put things in perspective, just doing a simple
1374 C<AUTOLOAD> which does nothing but extract the name of the method called
1375 and return it costs about 400% over a normal method call.
1379 =item B<add_before_method_modifier ($method_name, $code)>
1381 This will wrap the method at C<$method_name> and the supplied C<$code>
1382 will be passed the C<@_> arguments, and called before the original
1383 method is called. As specified above, the return value of the I<before>
1384 method modifiers is ignored, and it's ability to modify C<@_> is
1385 fairly limited. If you need to do either of these things, use an
1386 C<around> method modifier.
1388 =item B<add_after_method_modifier ($method_name, $code)>
1390 This will wrap the method at C<$method_name> so that the original
1391 method will be called, it's return values stashed, and then the
1392 supplied C<$code> will be passed the C<@_> arguments, and called.
1393 As specified above, the return value of the I<after> method
1394 modifiers is ignored, and it cannot modify the return values of
1395 the original method. If you need to do either of these things, use an
1396 C<around> method modifier.
1398 =item B<add_around_method_modifier ($method_name, $code)>
1400 This will wrap the method at C<$method_name> so that C<$code>
1401 will be called and passed the original method as an extra argument
1402 at the begining of the C<@_> argument list. This is a variation of
1403 continuation passing style, where the function prepended to C<@_>
1404 can be considered a continuation. It is up to C<$code> if it calls
1405 the original method or not, there is no restriction on what the
1406 C<$code> can or cannot do.
1412 It should be noted that since there is no one consistent way to define
1413 the attributes of a class in Perl 5. These methods can only work with
1414 the information given, and can not easily discover information on
1415 their own. See L<Class::MOP::Attribute> for more details.
1419 =item B<attribute_metaclass>
1421 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1422 for more information on the attribute metaclasses.
1424 =item B<get_attribute_map>
1426 This returns a HASH ref of name to attribute meta-object mapping.
1428 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1430 This stores the C<$attribute_meta_object> (or creates one from the
1431 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1432 instance associated with the given class. Unlike methods, attributes
1433 within the MOP are stored as meta-information only. They will be used
1434 later to construct instances from (see C<construct_instance> above).
1435 More details about the attribute meta-objects can be found in the
1436 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1439 It should be noted that any accessor, reader/writer or predicate
1440 methods which the C<$attribute_meta_object> has will be installed
1441 into the class at this time.
1444 If an attribute already exists for C<$attribute_name>, the old one
1445 will be removed (as well as removing all it's accessors), and then
1448 =item B<has_attribute ($attribute_name)>
1450 Checks to see if this class has an attribute by the name of
1451 C<$attribute_name> and returns a boolean.
1453 =item B<get_attribute ($attribute_name)>
1455 Returns the attribute meta-object associated with C<$attribute_name>,
1456 if none is found, it will return undef.
1458 =item B<remove_attribute ($attribute_name)>
1460 This will remove the attribute meta-object stored at
1461 C<$attribute_name>, then return the removed attribute meta-object.
1464 Removing an attribute will only affect future instances of
1465 the class, it will not make any attempt to remove the attribute from
1466 any existing instances of the class.
1468 It should be noted that any accessor, reader/writer or predicate
1469 methods which the attribute meta-object stored at C<$attribute_name>
1470 has will be removed from the class at this time. This B<will> make
1471 these attributes somewhat inaccessable in previously created
1472 instances. But if you are crazy enough to do this at runtime, then
1473 you are crazy enough to deal with something like this :).
1475 =item B<get_attribute_list>
1477 This returns a list of attribute names which are defined in the local
1478 class. If you want a list of all applicable attributes for a class,
1479 use the C<compute_all_applicable_attributes> method.
1481 =item B<compute_all_applicable_attributes>
1483 This will traverse the inheritance heirachy and return a list of all
1484 the applicable attributes for this class. It does not construct a
1485 HASH reference like C<compute_all_applicable_methods> because all
1486 that same information is discoverable through the attribute
1489 =item B<find_attribute_by_name ($attr_name)>
1491 This method will traverse the inheritance heirachy and find the
1492 first attribute whose name matches C<$attr_name>, then return it.
1493 It will return undef if nothing is found.
1497 =head2 Class Immutability
1501 =item B<make_immutable (%options)>
1503 This method will invoke a tranforamtion upon the class which will
1504 make it immutable. Details of this transformation can be found in
1505 the L<Class::MOP::Immutable> documentation.
1507 =item B<make_mutable>
1509 This method will reverse tranforamtion upon the class which
1512 =item B<create_immutable_transformer>
1514 Create a transformer suitable for making this class immutable
1520 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1522 =head1 COPYRIGHT AND LICENSE
1524 Copyright 2006-2008 by Infinity Interactive, Inc.
1526 L<http://www.iinteractive.com>
1528 This library is free software; you can redistribute it and/or modify
1529 it under the same terms as Perl itself.