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';
14 our $VERSION = '0.31';
15 our $AUTHORITY = 'cpan:STEVAN';
17 use base 'Class::MOP::Module';
23 my $package_name = shift;
24 (defined $package_name && $package_name && !blessed($package_name))
25 || confess "You must pass a package name and it cannot be blessed";
26 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
29 $class->construct_class_instance('package' => $package_name, @_);
34 my $package_name = shift;
35 (defined $package_name && $package_name && !blessed($package_name))
36 || confess "You must pass a package name and it cannot be blessed";
37 Class::MOP::remove_metaclass_by_name($package_name);
38 $class->construct_class_instance('package' => $package_name, @_);
41 # NOTE: (meta-circularity)
42 # this is a special form of &construct_instance
43 # (see below), which is used to construct class
44 # meta-object instances for any Class::MOP::*
45 # class. All other classes will use the more
46 # normal &construct_instance.
47 sub construct_class_instance {
50 my $package_name = $options{'package'};
51 (defined $package_name && $package_name)
52 || confess "You must pass a package name";
54 # return the metaclass if we have it cached,
55 # and it is still defined (it has not been
56 # reaped by DESTROY yet, which can happen
57 # annoyingly enough during global destruction)
59 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
64 # we need to deal with the possibility
65 # of class immutability here, and then
66 # get the name of the class appropriately
67 $class = (blessed($class)
68 ? ($class->is_immutable
69 ? $class->get_mutable_metaclass_name()
73 # now create the metaclass
75 if ($class eq 'Class::MOP::Class') {
78 # inherited from Class::MOP::Package
79 '$!package' => $package_name,
82 # since the following attributes will
83 # actually be loaded from the symbol
84 # table, and actually bypass the instance
85 # entirely, we can just leave these things
86 # listed here for reference, because they
87 # should not actually have a value associated
89 '%!namespace' => \undef,
90 # inherited from Class::MOP::Module
91 '$!version' => \undef,
92 '$!authority' => \undef,
93 # defined in Class::MOP::Class
94 '@!superclasses' => \undef,
98 '$!attribute_metaclass' => $options{'attribute_metaclass'} || 'Class::MOP::Attribute',
99 '$!method_metaclass' => $options{'method_metaclass'} || 'Class::MOP::Method',
100 '$!instance_metaclass' => $options{'instance_metaclass'} || 'Class::MOP::Instance',
102 ## uber-private variables
104 # this starts out as undef so that
105 # we can tell the first time the
106 # methods are fetched
108 '$!_package_cache_flag' => undef,
113 # it is safe to use meta here because
114 # class will always be a subclass of
115 # Class::MOP::Class, which defines meta
116 $meta = $class->meta->construct_instance(%options)
119 # and check the metaclass compatibility
120 $meta->check_metaclass_compatability();
122 Class::MOP::store_metaclass_by_name($package_name, $meta);
125 # we need to weaken any anon classes
126 # so that they can call DESTROY properly
127 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
132 sub reset_package_cache_flag { (shift)->{'$!_package_cache_flag'} = undef }
133 sub update_package_cache_flag {
136 # we can manually update the cache number
137 # since we are actually adding the method
138 # to our cache as well. This avoids us
139 # having to regenerate the method_map.
141 $self->{'$!_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
144 sub check_metaclass_compatability {
147 # this is always okay ...
148 return if blessed($self) eq 'Class::MOP::Class' &&
149 $self->instance_metaclass eq 'Class::MOP::Instance';
151 my @class_list = $self->linearized_isa;
152 shift @class_list; # shift off $self->name
154 foreach my $class_name (@class_list) {
155 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
158 # we need to deal with the possibility
159 # of class immutability here, and then
160 # get the name of the class appropriately
161 my $meta_type = ($meta->is_immutable
162 ? $meta->get_mutable_metaclass_name()
165 ($self->isa($meta_type))
166 || confess $self->name . "->meta => (" . (blessed($self)) . ")" .
167 " is not compatible with the " .
168 $class_name . "->meta => (" . ($meta_type) . ")";
170 # we also need to check that instance metaclasses
171 # are compatabile in the same the class.
172 ($self->instance_metaclass->isa($meta->instance_metaclass))
173 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
174 " is not compatible with the " .
175 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
183 # this should be sufficient, if you have a
184 # use case where it is not, write a test and
186 my $ANON_CLASS_SERIAL = 0;
189 # we need a sufficiently annoying prefix
190 # this should suffice for now, this is
191 # used in a couple of places below, so
192 # need to put it up here for now.
193 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
197 no warnings 'uninitialized';
198 $self->name =~ /^$ANON_CLASS_PREFIX/ ? 1 : 0;
201 sub create_anon_class {
202 my ($class, %options) = @_;
203 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
204 return $class->create($package_name, %options);
208 # this will only get called for
209 # anon-classes, all other calls
210 # are assumed to occur during
211 # global destruction and so don't
212 # really need to be handled explicitly
215 no warnings 'uninitialized';
216 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
217 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
219 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
220 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
222 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
227 # creating classes with MOP ...
231 my $package_name = shift;
233 (defined $package_name && $package_name)
234 || confess "You must pass a package name";
237 || confess "You much pass all parameters as name => value pairs " .
238 "(I found an uneven number of params in \@_)";
242 (ref $options{superclasses} eq 'ARRAY')
243 || confess "You must pass an ARRAY ref of superclasses"
244 if exists $options{superclasses};
246 (ref $options{attributes} eq 'ARRAY')
247 || confess "You must pass an ARRAY ref of attributes"
248 if exists $options{attributes};
250 (ref $options{methods} eq 'HASH')
251 || confess "You must pass an HASH ref of methods"
252 if exists $options{methods};
254 my $code = "package $package_name;";
255 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
256 if exists $options{version};
257 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
258 if exists $options{authority};
261 confess "creation of $package_name failed : $@" if $@;
263 my $meta = $class->initialize($package_name);
265 $meta->add_method('meta' => sub {
266 $class->initialize(blessed($_[0]) || $_[0]);
269 $meta->superclasses(@{$options{superclasses}})
270 if exists $options{superclasses};
272 # process attributes first, so that they can
273 # install accessors, but locally defined methods
274 # can then overwrite them. It is maybe a little odd, but
275 # I think this should be the order of things.
276 if (exists $options{attributes}) {
277 foreach my $attr (@{$options{attributes}}) {
278 $meta->add_attribute($attr);
281 if (exists $options{methods}) {
282 foreach my $method_name (keys %{$options{methods}}) {
283 $meta->add_method($method_name, $options{methods}->{$method_name});
292 # all these attribute readers will be bootstrapped
293 # away in the Class::MOP bootstrap section
295 sub get_attribute_map { $_[0]->{'%!attributes'} }
296 sub attribute_metaclass { $_[0]->{'$!attribute_metaclass'} }
297 sub method_metaclass { $_[0]->{'$!method_metaclass'} }
298 sub instance_metaclass { $_[0]->{'$!instance_metaclass'} }
301 # this is a prime canidate for conversion to XS
305 if (defined $self->{'$!_package_cache_flag'} &&
306 $self->{'$!_package_cache_flag'} == Class::MOP::check_package_cache_flag($self->name)) {
307 return $self->{'%!methods'};
310 my $map = $self->{'%!methods'};
312 my $class_name = $self->name;
313 my $method_metaclass = $self->method_metaclass;
315 foreach my $symbol ($self->list_all_package_symbols('CODE')) {
316 my $code = $self->get_package_symbol('&' . $symbol);
318 next if exists $map->{$symbol} &&
319 defined $map->{$symbol} &&
320 $map->{$symbol}->body == $code;
322 my ($pkg, $name) = Class::MOP::get_code_info($code);
324 next if ($pkg || '') ne $class_name ||
325 (($name || '') ne '__ANON__' && ($pkg || '') ne $class_name);
327 $map->{$symbol} = $method_metaclass->wrap(
329 package_name => $class_name,
337 # Instance Construction & Cloning
342 # we need to protect the integrity of the
343 # Class::MOP::Class singletons here, so we
344 # delegate this to &construct_class_instance
345 # which will deal with the singletons
346 return $class->construct_class_instance(@_)
347 if $class->name->isa('Class::MOP::Class');
348 return $class->construct_instance(@_);
351 sub construct_instance {
352 my ($class, %params) = @_;
353 my $meta_instance = $class->get_meta_instance();
354 my $instance = $meta_instance->create_instance();
355 foreach my $attr ($class->compute_all_applicable_attributes()) {
356 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
359 # this will only work for a HASH instance type
360 if ($class->is_anon_class) {
361 (reftype($instance) eq 'HASH')
362 || confess "Currently only HASH based instances are supported with instance of anon-classes";
364 # At some point we should make this official
365 # as a reserved slot name, but right now I am
366 # going to keep it here.
367 # my $RESERVED_MOP_SLOT = '__MOP__';
368 $instance->{'__MOP__'} = $class;
373 sub get_meta_instance {
375 return $class->instance_metaclass->new(
377 $class->compute_all_applicable_attributes()
383 my $instance = shift;
384 (blessed($instance) && $instance->isa($class->name))
385 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
387 # we need to protect the integrity of the
388 # Class::MOP::Class singletons here, they
389 # should not be cloned.
390 return $instance if $instance->isa('Class::MOP::Class');
391 $class->clone_instance($instance, @_);
395 my ($class, $instance, %params) = @_;
397 || confess "You can only clone instances, \$self is not a blessed instance";
398 my $meta_instance = $class->get_meta_instance();
399 my $clone = $meta_instance->clone_instance($instance);
400 foreach my $attr ($class->compute_all_applicable_attributes()) {
401 if ( defined( my $init_arg = $attr->init_arg ) ) {
402 if (exists $params{$init_arg}) {
403 $attr->set_value($clone, $params{$init_arg});
410 sub rebless_instance {
411 my ($self, $instance, %params) = @_;
414 if ($instance->can('meta')) {
415 ($instance->meta->isa('Class::MOP::Class'))
416 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
417 $old_metaclass = $instance->meta;
420 $old_metaclass = $self->initialize(blessed($instance));
423 my $meta_instance = $self->get_meta_instance();
425 $self->name->isa($old_metaclass->name)
426 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
429 $meta_instance->rebless_instance_structure($instance, $self);
431 foreach my $attr ( $self->compute_all_applicable_attributes ) {
432 if ( $attr->has_value($instance) ) {
433 if ( defined( my $init_arg = $attr->init_arg ) ) {
434 $params{$init_arg} = $attr->get_value($instance)
435 unless exists $params{$init_arg};
438 $attr->set_value($instance, $attr->get_value($instance));
443 foreach my $attr ($self->compute_all_applicable_attributes) {
444 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
456 @{$self->get_package_symbol('@ISA')} = @supers;
458 # we need to check the metaclass
459 # compatibility here so that we can
460 # be sure that the superclass is
461 # not potentially creating an issues
462 # we don't know about
463 $self->check_metaclass_compatability();
465 @{$self->get_package_symbol('@ISA')};
471 my $super_class = $self->name;
474 my $find_derived_classes;
475 $find_derived_classes = sub {
476 my ($outer_class) = @_;
478 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
481 for my $symbol ( keys %$symbol_table_hashref ) {
482 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
483 my $inner_class = $1;
485 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
489 ? "${outer_class}::$inner_class"
492 if ( $class->isa($super_class) and $class ne $super_class ) {
493 push @derived_classes, $class;
496 next SYMBOL if $class eq 'main'; # skip 'main::*'
498 $find_derived_classes->($class);
502 my $root_class = q{};
503 $find_derived_classes->($root_class);
505 undef $find_derived_classes;
507 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
509 return @derived_classes;
514 return @{ mro::get_linear_isa( (shift)->name ) };
517 sub class_precedence_list {
519 my $name = $self->name;
521 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
523 # We need to check for circular inheritance here
524 # if we are are not on 5.10, cause 5.8 detects it
525 # late. This will do nothing if all is well, and
526 # blow up otherwise. Yes, it's an ugly hack, better
527 # suggestions are welcome.
529 ($name || return)->isa('This is a test for circular inheritance')
532 # if our mro is c3, we can
533 # just grab the linear_isa
534 if (mro::get_mro($name) eq 'c3') {
535 return @{ mro::get_linear_isa($name) }
539 # we can't grab the linear_isa for dfs
540 # since it has all the duplicates
545 $self->initialize($_)->class_precedence_list()
546 } $self->superclasses()
554 my ($self, $method_name, $method) = @_;
555 (defined $method_name && $method_name)
556 || confess "You must define a method name";
559 if (blessed($method)) {
560 $body = $method->body;
561 if ($method->package_name ne $self->name &&
562 $method->name ne $method_name) {
563 warn "Hello there, got somethig for you."
564 . " Method says " . $method->package_name . " " . $method->name
565 . " Class says " . $self->name . " " . $method_name;
566 $method = $method->clone(
567 package_name => $self->name,
569 ) if $method->can('clone');
574 ('CODE' eq (reftype($body) || ''))
575 || confess "Your code block must be a CODE reference";
576 $method = $self->method_metaclass->wrap(
578 package_name => $self->name,
583 $self->get_method_map->{$method_name} = $method;
585 my $full_method_name = ($self->name . '::' . $method_name);
586 $self->add_package_symbol("&${method_name}" =>
587 Class::MOP::subname($full_method_name => $body)
589 $self->update_package_cache_flag;
593 my $fetch_and_prepare_method = sub {
594 my ($self, $method_name) = @_;
596 my $method = $self->get_method($method_name);
597 # if we dont have local ...
599 # try to find the next method
600 $method = $self->find_next_method_by_name($method_name);
601 # die if it does not exist
603 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
604 # and now make sure to wrap it
605 # even if it is already wrapped
606 # because we need a new sub ref
607 $method = Class::MOP::Method::Wrapped->wrap($method);
610 # now make sure we wrap it properly
611 $method = Class::MOP::Method::Wrapped->wrap($method)
612 unless $method->isa('Class::MOP::Method::Wrapped');
614 $self->add_method($method_name => $method);
618 sub add_before_method_modifier {
619 my ($self, $method_name, $method_modifier) = @_;
620 (defined $method_name && $method_name)
621 || confess "You must pass in a method name";
622 my $method = $fetch_and_prepare_method->($self, $method_name);
623 $method->add_before_modifier(
624 Class::MOP::subname(':before' => $method_modifier)
628 sub add_after_method_modifier {
629 my ($self, $method_name, $method_modifier) = @_;
630 (defined $method_name && $method_name)
631 || confess "You must pass in a method name";
632 my $method = $fetch_and_prepare_method->($self, $method_name);
633 $method->add_after_modifier(
634 Class::MOP::subname(':after' => $method_modifier)
638 sub add_around_method_modifier {
639 my ($self, $method_name, $method_modifier) = @_;
640 (defined $method_name && $method_name)
641 || confess "You must pass in a method name";
642 my $method = $fetch_and_prepare_method->($self, $method_name);
643 $method->add_around_modifier(
644 Class::MOP::subname(':around' => $method_modifier)
649 # the methods above used to be named like this:
650 # ${pkg}::${method}:(before|after|around)
651 # but this proved problematic when using one modifier
652 # to wrap multiple methods (something which is likely
653 # to happen pretty regularly IMO). So instead of naming
654 # it like this, I have chosen to just name them purely
655 # with their modifier names, like so:
656 # :(before|after|around)
657 # The fact is that in a stack trace, it will be fairly
658 # evident from the context what method they are attached
659 # to, and so don't need the fully qualified name.
663 my ($self, $method_name, $method) = @_;
664 (defined $method_name && $method_name)
665 || confess "You must define a method name";
667 my $body = (blessed($method) ? $method->body : $method);
668 ('CODE' eq (reftype($body) || ''))
669 || confess "Your code block must be a CODE reference";
671 $self->add_package_symbol("&${method_name}" => $body);
672 $self->update_package_cache_flag;
676 my ($self, $method_name) = @_;
677 (defined $method_name && $method_name)
678 || confess "You must define a method name";
680 return 0 unless exists $self->get_method_map->{$method_name};
685 my ($self, $method_name) = @_;
686 (defined $method_name && $method_name)
687 || confess "You must define a method name";
690 # I don't really need this here, because
691 # if the method_map is missing a key it
692 # will just return undef for me now
693 # return unless $self->has_method($method_name);
695 return $self->get_method_map->{$method_name};
699 my ($self, $method_name) = @_;
700 (defined $method_name && $method_name)
701 || confess "You must define a method name";
703 my $removed_method = delete $self->get_method_map->{$method_name};
705 $self->remove_package_symbol("&${method_name}");
707 $self->update_package_cache_flag;
709 return $removed_method;
712 sub get_method_list {
714 keys %{$self->get_method_map};
717 sub find_method_by_name {
718 my ($self, $method_name) = @_;
719 (defined $method_name && $method_name)
720 || 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);
724 return $meta->get_method($method_name)
725 if $meta->has_method($method_name);
730 sub compute_all_applicable_methods {
732 my (@methods, %seen_method);
733 foreach my $class ($self->linearized_isa) {
734 # fetch the meta-class ...
735 my $meta = $self->initialize($class);
736 foreach my $method_name ($meta->get_method_list()) {
737 next if exists $seen_method{$method_name};
738 $seen_method{$method_name}++;
740 name => $method_name,
742 code => $meta->get_method($method_name)
749 sub find_all_methods_by_name {
750 my ($self, $method_name) = @_;
751 (defined $method_name && $method_name)
752 || confess "You must define a method name to find";
754 foreach my $class ($self->linearized_isa) {
755 # fetch the meta-class ...
756 my $meta = $self->initialize($class);
758 name => $method_name,
760 code => $meta->get_method($method_name)
761 } if $meta->has_method($method_name);
766 sub find_next_method_by_name {
767 my ($self, $method_name) = @_;
768 (defined $method_name && $method_name)
769 || confess "You must define a method name to find";
770 my @cpl = $self->linearized_isa;
771 shift @cpl; # discard ourselves
772 foreach my $class (@cpl) {
773 # fetch the meta-class ...
774 my $meta = $self->initialize($class);
775 return $meta->get_method($method_name)
776 if $meta->has_method($method_name);
785 # either we have an attribute object already
786 # or we need to create one from the args provided
787 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
788 # make sure it is derived from the correct type though
789 ($attribute->isa('Class::MOP::Attribute'))
790 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
792 # first we attach our new attribute
793 # because it might need certain information
794 # about the class which it is attached to
795 $attribute->attach_to_class($self);
797 # then we remove attributes of a conflicting
798 # name here so that we can properly detach
799 # the old attr object, and remove any
800 # accessors it would have generated
801 $self->remove_attribute($attribute->name)
802 if $self->has_attribute($attribute->name);
804 # then onto installing the new accessors
805 $attribute->install_accessors();
806 $self->get_attribute_map->{$attribute->name} = $attribute;
810 my ($self, $attribute_name) = @_;
811 (defined $attribute_name && $attribute_name)
812 || confess "You must define an attribute name";
813 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
817 my ($self, $attribute_name) = @_;
818 (defined $attribute_name && $attribute_name)
819 || confess "You must define an attribute name";
820 return $self->get_attribute_map->{$attribute_name}
822 # this will return undef anyway, so no need ...
823 # if $self->has_attribute($attribute_name);
827 sub remove_attribute {
828 my ($self, $attribute_name) = @_;
829 (defined $attribute_name && $attribute_name)
830 || confess "You must define an attribute name";
831 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
832 return unless defined $removed_attribute;
833 delete $self->get_attribute_map->{$attribute_name};
834 $removed_attribute->remove_accessors();
835 $removed_attribute->detach_from_class();
836 return $removed_attribute;
839 sub get_attribute_list {
841 keys %{$self->get_attribute_map};
844 sub compute_all_applicable_attributes {
846 my (@attrs, %seen_attr);
847 foreach my $class ($self->linearized_isa) {
848 # fetch the meta-class ...
849 my $meta = $self->initialize($class);
850 foreach my $attr_name ($meta->get_attribute_list()) {
851 next if exists $seen_attr{$attr_name};
852 $seen_attr{$attr_name}++;
853 push @attrs => $meta->get_attribute($attr_name);
859 sub find_attribute_by_name {
860 my ($self, $attr_name) = @_;
861 foreach my $class ($self->linearized_isa) {
862 # fetch the meta-class ...
863 my $meta = $self->initialize($class);
864 return $meta->get_attribute($attr_name)
865 if $meta->has_attribute($attr_name);
873 sub is_immutable { 0 }
876 # Why I changed this (groditi)
877 # - One Metaclass may have many Classes through many Metaclass instances
878 # - One Metaclass should only have one Immutable Transformer instance
879 # - Each Class may have different Immutabilizing options
880 # - Therefore each Metaclass instance may have different Immutabilizing options
881 # - We need to store one Immutable Transformer instance per Metaclass
882 # - We need to store one set of Immutable Transformer options per Class
883 # - Upon make_mutable we may delete the Immutabilizing options
884 # - We could clean the immutable Transformer instance when there is no more
885 # immutable Classes of that type, but we can also keep it in case
886 # another class with this same Metaclass becomes immutable. It is a case
887 # of trading of storing an instance to avoid unnecessary instantiations of
888 # Immutable Transformers. You may view this as a memory leak, however
889 # Because we have few Metaclasses, in practice it seems acceptable
890 # - To allow Immutable Transformers instances to be cleaned up we could weaken
891 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
894 my %IMMUTABLE_TRANSFORMERS;
895 my %IMMUTABLE_OPTIONS;
899 my $class = blessed $self || $self;
901 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
902 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
904 $transformer->make_metaclass_immutable($self, \%options);
905 $IMMUTABLE_OPTIONS{$self->name} =
906 { %options, IMMUTABLE_TRANSFORMER => $transformer };
908 if( exists $options{debug} && $options{debug} ){
909 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
910 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
918 return if $self->is_mutable;
919 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
920 confess "unable to find immutabilizing options" unless ref $options;
921 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
922 $transformer->make_metaclass_mutable($self, $options);
927 sub create_immutable_transformer {
929 my $class = Class::MOP::Immutable->new($self, {
930 read_only => [qw/superclasses/],
937 remove_package_symbol
940 class_precedence_list => 'ARRAY',
941 linearized_isa => 'ARRAY',
942 compute_all_applicable_attributes => 'ARRAY',
943 get_meta_instance => 'SCALAR',
944 get_method_map => 'SCALAR',
947 # this is ugly, but so are typeglobs,
948 # so whattayahgonnadoboutit
951 add_package_symbol => sub {
952 my $original = shift;
953 confess "Cannot add package symbols to an immutable metaclass"
954 unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
955 goto $original->body;
970 Class::MOP::Class - Class Meta Object
974 # assuming that class Foo
975 # has been defined, you can
977 # use this for introspection ...
979 # add a method to Foo ...
980 Foo->meta->add_method('bar' => sub { ... })
982 # get a list of all the classes searched
983 # the method dispatcher in the correct order
984 Foo->meta->class_precedence_list()
986 # remove a method from Foo
987 Foo->meta->remove_method('bar');
989 # or use this to actually create classes ...
991 Class::MOP::Class->create('Bar' => (
993 superclasses => [ 'Foo' ],
995 Class::MOP:::Attribute->new('$bar'),
996 Class::MOP:::Attribute->new('$baz'),
999 calculate_bar => sub { ... },
1000 construct_baz => sub { ... }
1006 This is the largest and currently most complex part of the Perl 5
1007 meta-object protocol. It controls the introspection and
1008 manipulation of Perl 5 classes (and it can create them too). The
1009 best way to understand what this module can do, is to read the
1010 documentation for each of it's methods.
1014 =head2 Self Introspection
1020 This will return a B<Class::MOP::Class> instance which is related
1021 to this class. Thereby allowing B<Class::MOP::Class> to actually
1024 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
1025 bootstrap this module by installing a number of attribute meta-objects
1026 into it's metaclass. This will allow this class to reap all the benifits
1027 of the MOP when subclassing it.
1031 =head2 Class construction
1033 These methods will handle creating B<Class::MOP::Class> objects,
1034 which can be used to both create new classes, and analyze
1035 pre-existing classes.
1037 This module will internally store references to all the instances
1038 you create with these methods, so that they do not need to be
1039 created any more than nessecary. Basically, they are singletons.
1043 =item B<create ($package_name,
1044 version =E<gt> ?$version,
1045 authority =E<gt> ?$authority,
1046 superclasses =E<gt> ?@superclasses,
1047 methods =E<gt> ?%methods,
1048 attributes =E<gt> ?%attributes)>
1050 This returns a B<Class::MOP::Class> object, bringing the specified
1051 C<$package_name> into existence and adding any of the C<$version>,
1052 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1055 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1056 methods =E<gt> ?%methods,
1057 attributes =E<gt> ?%attributes)>
1059 This will create an anonymous class, it works much like C<create> but
1060 it does not need a C<$package_name>. Instead it will create a suitably
1061 unique package name for you to stash things into.
1063 On very important distinction is that anon classes are destroyed once
1064 the metaclass they are attached to goes out of scope. In the DESTROY
1065 method, the created package will be removed from the symbol table.
1067 It is also worth noting that any instances created with an anon-class
1068 will keep a special reference to the anon-meta which will prevent the
1069 anon-class from going out of scope until all instances of it have also
1070 been destroyed. This however only works for HASH based instance types,
1071 as we use a special reserved slot (C<__MOP__>) to store this.
1073 =item B<initialize ($package_name, %options)>
1075 This initializes and returns returns a B<Class::MOP::Class> object
1076 for a given a C<$package_name>.
1078 =item B<reinitialize ($package_name, %options)>
1080 This removes the old metaclass, and creates a new one in it's place.
1081 Do B<not> use this unless you really know what you are doing, it could
1082 very easily make a very large mess of your program.
1084 =item B<construct_class_instance (%options)>
1086 This will construct an instance of B<Class::MOP::Class>, it is
1087 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1088 to use C<construct_instance> once all the bootstrapping is done. This
1089 method is used internally by C<initialize> and should never be called
1090 from outside of that method really.
1092 =item B<check_metaclass_compatability>
1094 This method is called as the very last thing in the
1095 C<construct_class_instance> method. This will check that the
1096 metaclass you are creating is compatible with the metaclasses of all
1097 your ancestors. For more inforamtion about metaclass compatibility
1098 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1100 =item B<update_package_cache_flag>
1102 This will reset the package cache flag for this particular metaclass
1103 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1104 function. This is very rarely needed from outside of C<Class::MOP::Class>
1105 but in some cases you might want to use it, so it is here.
1107 =item B<reset_package_cache_flag>
1109 Clears the package cache flag to announce to the internals that we need
1110 to rebuild the method map.
1114 =head2 Object instance construction and cloning
1116 These methods are B<entirely optional>, it is up to you whether you want
1121 =item B<instance_metaclass>
1123 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1124 for more information on the instance metaclasses.
1126 =item B<get_meta_instance>
1128 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1129 of a new instance of the class.
1131 =item B<new_object (%params)>
1133 This is a convience method for creating a new object of the class, and
1134 blessing it into the appropriate package as well. Ideally your class
1135 would call a C<new> this method like so:
1138 my ($class, %param) = @_;
1139 $class->meta->new_object(%params);
1142 =item B<construct_instance (%params)>
1144 This method is used to construct an instance structure suitable for
1145 C<bless>-ing into your package of choice. It works in conjunction
1146 with the Attribute protocol to collect all applicable attributes.
1148 This will construct and instance using a HASH ref as storage
1149 (currently only HASH references are supported). This will collect all
1150 the applicable attributes and layout out the fields in the HASH ref,
1151 it will then initialize them using either use the corresponding key
1152 in C<%params> or any default value or initializer found in the
1153 attribute meta-object.
1155 =item B<clone_object ($instance, %params)>
1157 This is a convience method for cloning an object instance, then
1158 blessing it into the appropriate package. This method will call
1159 C<clone_instance>, which performs a shallow copy of the object,
1160 see that methods documentation for more details. Ideally your
1161 class would call a C<clone> this method like so:
1163 sub MyClass::clone {
1164 my ($self, %param) = @_;
1165 $self->meta->clone_object($self, %params);
1168 =item B<clone_instance($instance, %params)>
1170 This method is a compliment of C<construct_instance> (which means if
1171 you override C<construct_instance>, you need to override this one too),
1172 and clones the instance shallowly.
1174 The cloned structure returned is (like with C<construct_instance>) an
1175 unC<bless>ed HASH reference, it is your responsibility to then bless
1176 this cloned structure into the right class (which C<clone_object> will
1179 As of 0.11, this method will clone the C<$instance> structure shallowly,
1180 as opposed to the deep cloning implemented in prior versions. After much
1181 thought, research and discussion, I have decided that anything but basic
1182 shallow cloning is outside the scope of the meta-object protocol. I
1183 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1184 is too I<context-specific> to be part of the MOP.
1186 =item B<rebless_instance($instance, ?%params)>
1188 This will change the class of C<$instance> to the class of the invoking
1189 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1190 itself. You may pass in optional C<%params> which are like constructor
1191 params and will override anything already defined in the instance.
1195 =head2 Informational
1197 These are a few predicate methods for asking information about the class.
1201 =item B<is_anon_class>
1203 This returns true if the class is a C<Class::MOP::Class> created anon class.
1207 This returns true if the class is still mutable.
1209 =item B<is_immutable>
1211 This returns true if the class has been made immutable.
1215 =head2 Inheritance Relationships
1219 =item B<superclasses (?@superclasses)>
1221 This is a read-write attribute which represents the superclass
1222 relationships of the class the B<Class::MOP::Class> instance is
1223 associated with. Basically, it can get and set the C<@ISA> for you.
1225 =item B<class_precedence_list>
1227 This computes the a list of all the class's ancestors in the same order
1228 in which method dispatch will be done. This is similair to what
1229 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1231 =item B<linearized_isa>
1233 This returns a list based on C<class_precedence_list> but with all
1238 This returns a list of subclasses for this class.
1246 =item B<get_method_map>
1248 Returns a HASH ref of name to CODE reference mapping for this class.
1250 =item B<method_metaclass>
1252 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1253 for more information on the method metaclasses.
1255 =item B<add_method ($method_name, $method)>
1257 This will take a C<$method_name> and CODE reference to that
1258 C<$method> and install it into the class's package.
1261 This does absolutely nothing special to C<$method>
1262 other than use B<Sub::Name> to make sure it is tagged with the
1263 correct name, and therefore show up correctly in stack traces and
1266 =item B<alias_method ($method_name, $method)>
1268 This will take a C<$method_name> and CODE reference to that
1269 C<$method> and alias the method into the class's package.
1272 Unlike C<add_method>, this will B<not> try to name the
1273 C<$method> using B<Sub::Name>, it only aliases the method in
1274 the class's package.
1276 =item B<has_method ($method_name)>
1278 This just provides a simple way to check if the class implements
1279 a specific C<$method_name>. It will I<not> however, attempt to check
1280 if the class inherits the method (use C<UNIVERSAL::can> for that).
1282 This will correctly handle functions defined outside of the package
1283 that use a fully qualified name (C<sub Package::name { ... }>).
1285 This will correctly handle functions renamed with B<Sub::Name> and
1286 installed using the symbol tables. However, if you are naming the
1287 subroutine outside of the package scope, you must use the fully
1288 qualified name, including the package name, for C<has_method> to
1289 correctly identify it.
1291 This will attempt to correctly ignore functions imported from other
1292 packages using B<Exporter>. It breaks down if the function imported
1293 is an C<__ANON__> sub (such as with C<use constant>), which very well
1294 may be a valid method being applied to the class.
1296 In short, this method cannot always be trusted to determine if the
1297 C<$method_name> is actually a method. However, it will DWIM about
1298 90% of the time, so it's a small trade off I think.
1300 =item B<get_method ($method_name)>
1302 This will return a Class::MOP::Method instance related to the specified
1303 C<$method_name>, or return undef if that method does not exist.
1305 The Class::MOP::Method is codifiable, so you can use it like a normal
1306 CODE reference, see L<Class::MOP::Method> for more information.
1308 =item B<find_method_by_name ($method_name)>
1310 This will return a CODE reference of the specified C<$method_name>,
1311 or return undef if that method does not exist.
1313 Unlike C<get_method> this will also look in the superclasses.
1315 =item B<remove_method ($method_name)>
1317 This will attempt to remove a given C<$method_name> from the class.
1318 It will return the CODE reference that it has removed, and will
1319 attempt to use B<Sub::Name> to clear the methods associated name.
1321 =item B<get_method_list>
1323 This will return a list of method names for all I<locally> defined
1324 methods. It does B<not> provide a list of all applicable methods,
1325 including any inherited ones. If you want a list of all applicable
1326 methods, use the C<compute_all_applicable_methods> method.
1328 =item B<compute_all_applicable_methods>
1330 This will return a list of all the methods names this class will
1331 respond to, taking into account inheritance. The list will be a list of
1332 HASH references, each one containing the following information; method
1333 name, the name of the class in which the method lives and a CODE
1334 reference for the actual method.
1336 =item B<find_all_methods_by_name ($method_name)>
1338 This will traverse the inheritence hierarchy and locate all methods
1339 with a given C<$method_name>. Similar to
1340 C<compute_all_applicable_methods> it returns a list of HASH references
1341 with the following information; method name (which will always be the
1342 same as C<$method_name>), the name of the class in which the method
1343 lives and a CODE reference for the actual method.
1345 The list of methods produced is a distinct list, meaning there are no
1346 duplicates in it. This is especially useful for things like object
1347 initialization and destruction where you only want the method called
1348 once, and in the correct order.
1350 =item B<find_next_method_by_name ($method_name)>
1352 This will return the first method to match a given C<$method_name> in
1353 the superclasses, this is basically equivalent to calling
1354 C<SUPER::$method_name>, but it can be dispatched at runtime.
1358 =head2 Method Modifiers
1360 Method modifiers are a concept borrowed from CLOS, in which a method
1361 can be wrapped with I<before>, I<after> and I<around> method modifiers
1362 that will be called everytime the method is called.
1364 =head3 How method modifiers work?
1366 Method modifiers work by wrapping the original method and then replacing
1367 it in the classes symbol table. The wrappers will handle calling all the
1368 modifiers in the appropariate orders and preserving the calling context
1369 for the original method.
1371 Each method modifier serves a particular purpose, which may not be
1372 obvious to users of other method wrapping modules. To start with, the
1373 return values of I<before> and I<after> modifiers are ignored. This is
1374 because thier purpose is B<not> to filter the input and output of the
1375 primary method (this is done with an I<around> modifier). This may seem
1376 like an odd restriction to some, but doing this allows for simple code
1377 to be added at the begining or end of a method call without jeapordizing
1378 the normal functioning of the primary method or placing any extra
1379 responsibility on the code of the modifier. Of course if you have more
1380 complex needs, then use the I<around> modifier, which uses a variation
1381 of continutation passing style to allow for a high degree of flexibility.
1383 Before and around modifiers are called in last-defined-first-called order,
1384 while after modifiers are called in first-defined-first-called order. So
1385 the call tree might looks something like this:
1395 To see examples of using method modifiers, see the following examples
1396 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1397 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1398 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1400 =head3 What is the performance impact?
1402 Of course there is a performance cost associated with method modifiers,
1403 but we have made every effort to make that cost be directly proportional
1404 to the amount of modifier features you utilize.
1406 The wrapping method does it's best to B<only> do as much work as it
1407 absolutely needs to. In order to do this we have moved some of the
1408 performance costs to set-up time, where they are easier to amortize.
1410 All this said, my benchmarks have indicated the following:
1412 simple wrapper with no modifiers 100% slower
1413 simple wrapper with simple before modifier 400% slower
1414 simple wrapper with simple after modifier 450% slower
1415 simple wrapper with simple around modifier 500-550% slower
1416 simple wrapper with all 3 modifiers 1100% slower
1418 These numbers may seem daunting, but you must remember, every feature
1419 comes with some cost. To put things in perspective, just doing a simple
1420 C<AUTOLOAD> which does nothing but extract the name of the method called
1421 and return it costs about 400% over a normal method call.
1425 =item B<add_before_method_modifier ($method_name, $code)>
1427 This will wrap the method at C<$method_name> and the supplied C<$code>
1428 will be passed the C<@_> arguments, and called before the original
1429 method is called. As specified above, the return value of the I<before>
1430 method modifiers is ignored, and it's ability to modify C<@_> is
1431 fairly limited. If you need to do either of these things, use an
1432 C<around> method modifier.
1434 =item B<add_after_method_modifier ($method_name, $code)>
1436 This will wrap the method at C<$method_name> so that the original
1437 method will be called, it's return values stashed, and then the
1438 supplied C<$code> will be passed the C<@_> arguments, and called.
1439 As specified above, the return value of the I<after> method
1440 modifiers is ignored, and it cannot modify the return values of
1441 the original method. If you need to do either of these things, use an
1442 C<around> method modifier.
1444 =item B<add_around_method_modifier ($method_name, $code)>
1446 This will wrap the method at C<$method_name> so that C<$code>
1447 will be called and passed the original method as an extra argument
1448 at the begining of the C<@_> argument list. This is a variation of
1449 continuation passing style, where the function prepended to C<@_>
1450 can be considered a continuation. It is up to C<$code> if it calls
1451 the original method or not, there is no restriction on what the
1452 C<$code> can or cannot do.
1458 It should be noted that since there is no one consistent way to define
1459 the attributes of a class in Perl 5. These methods can only work with
1460 the information given, and can not easily discover information on
1461 their own. See L<Class::MOP::Attribute> for more details.
1465 =item B<attribute_metaclass>
1467 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1468 for more information on the attribute metaclasses.
1470 =item B<get_attribute_map>
1472 This returns a HASH ref of name to attribute meta-object mapping.
1474 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1476 This stores the C<$attribute_meta_object> (or creates one from the
1477 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1478 instance associated with the given class. Unlike methods, attributes
1479 within the MOP are stored as meta-information only. They will be used
1480 later to construct instances from (see C<construct_instance> above).
1481 More details about the attribute meta-objects can be found in the
1482 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1485 It should be noted that any accessor, reader/writer or predicate
1486 methods which the C<$attribute_meta_object> has will be installed
1487 into the class at this time.
1490 If an attribute already exists for C<$attribute_name>, the old one
1491 will be removed (as well as removing all it's accessors), and then
1494 =item B<has_attribute ($attribute_name)>
1496 Checks to see if this class has an attribute by the name of
1497 C<$attribute_name> and returns a boolean.
1499 =item B<get_attribute ($attribute_name)>
1501 Returns the attribute meta-object associated with C<$attribute_name>,
1502 if none is found, it will return undef.
1504 =item B<remove_attribute ($attribute_name)>
1506 This will remove the attribute meta-object stored at
1507 C<$attribute_name>, then return the removed attribute meta-object.
1510 Removing an attribute will only affect future instances of
1511 the class, it will not make any attempt to remove the attribute from
1512 any existing instances of the class.
1514 It should be noted that any accessor, reader/writer or predicate
1515 methods which the attribute meta-object stored at C<$attribute_name>
1516 has will be removed from the class at this time. This B<will> make
1517 these attributes somewhat inaccessable in previously created
1518 instances. But if you are crazy enough to do this at runtime, then
1519 you are crazy enough to deal with something like this :).
1521 =item B<get_attribute_list>
1523 This returns a list of attribute names which are defined in the local
1524 class. If you want a list of all applicable attributes for a class,
1525 use the C<compute_all_applicable_attributes> method.
1527 =item B<compute_all_applicable_attributes>
1529 This will traverse the inheritance heirachy and return a list of all
1530 the applicable attributes for this class. It does not construct a
1531 HASH reference like C<compute_all_applicable_methods> because all
1532 that same information is discoverable through the attribute
1535 =item B<find_attribute_by_name ($attr_name)>
1537 This method will traverse the inheritance heirachy and find the
1538 first attribute whose name matches C<$attr_name>, then return it.
1539 It will return undef if nothing is found.
1543 =head2 Class Immutability
1547 =item B<make_immutable (%options)>
1549 This method will invoke a tranforamtion upon the class which will
1550 make it immutable. Details of this transformation can be found in
1551 the L<Class::MOP::Immutable> documentation.
1553 =item B<make_mutable>
1555 This method will reverse tranforamtion upon the class which
1558 =item B<create_immutable_transformer>
1560 Create a transformer suitable for making this class immutable
1566 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1568 =head1 COPYRIGHT AND LICENSE
1570 Copyright 2006-2008 by Infinity Interactive, Inc.
1572 L<http://www.iinteractive.com>
1574 This library is free software; you can redistribute it and/or modify
1575 it under the same terms as Perl itself.