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 #warn "Checking $pkg against $class_name && $name against __ANON__";
329 $map->{$symbol} = $method_metaclass->wrap(
331 package_name => $class_name,
339 # Instance Construction & Cloning
344 # we need to protect the integrity of the
345 # Class::MOP::Class singletons here, so we
346 # delegate this to &construct_class_instance
347 # which will deal with the singletons
348 return $class->construct_class_instance(@_)
349 if $class->name->isa('Class::MOP::Class');
350 return $class->construct_instance(@_);
353 sub construct_instance {
354 my ($class, %params) = @_;
355 my $meta_instance = $class->get_meta_instance();
356 my $instance = $meta_instance->create_instance();
357 foreach my $attr ($class->compute_all_applicable_attributes()) {
358 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
361 # this will only work for a HASH instance type
362 if ($class->is_anon_class) {
363 (reftype($instance) eq 'HASH')
364 || confess "Currently only HASH based instances are supported with instance of anon-classes";
366 # At some point we should make this official
367 # as a reserved slot name, but right now I am
368 # going to keep it here.
369 # my $RESERVED_MOP_SLOT = '__MOP__';
370 $instance->{'__MOP__'} = $class;
375 sub get_meta_instance {
377 return $class->instance_metaclass->new(
379 $class->compute_all_applicable_attributes()
385 my $instance = shift;
386 (blessed($instance) && $instance->isa($class->name))
387 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
389 # we need to protect the integrity of the
390 # Class::MOP::Class singletons here, they
391 # should not be cloned.
392 return $instance if $instance->isa('Class::MOP::Class');
393 $class->clone_instance($instance, @_);
397 my ($class, $instance, %params) = @_;
399 || confess "You can only clone instances, \$self is not a blessed instance";
400 my $meta_instance = $class->get_meta_instance();
401 my $clone = $meta_instance->clone_instance($instance);
402 foreach my $attr ($class->compute_all_applicable_attributes()) {
403 if ( defined( my $init_arg = $attr->init_arg ) ) {
404 if (exists $params{$init_arg}) {
405 $attr->set_value($clone, $params{$init_arg});
412 sub rebless_instance {
413 my ($self, $instance, %params) = @_;
416 if ($instance->can('meta')) {
417 ($instance->meta->isa('Class::MOP::Class'))
418 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
419 $old_metaclass = $instance->meta;
422 $old_metaclass = $self->initialize(blessed($instance));
425 my $meta_instance = $self->get_meta_instance();
427 $self->name->isa($old_metaclass->name)
428 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
431 $meta_instance->rebless_instance_structure($instance, $self);
433 foreach my $attr ( $self->compute_all_applicable_attributes ) {
434 if ( $attr->has_value($instance) ) {
435 if ( defined( my $init_arg = $attr->init_arg ) ) {
436 $params{$init_arg} = $attr->get_value($instance)
437 unless exists $params{$init_arg};
440 $attr->set_value($instance, $attr->get_value($instance));
445 foreach my $attr ($self->compute_all_applicable_attributes) {
446 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
458 @{$self->get_package_symbol('@ISA')} = @supers;
460 # we need to check the metaclass
461 # compatibility here so that we can
462 # be sure that the superclass is
463 # not potentially creating an issues
464 # we don't know about
465 $self->check_metaclass_compatability();
467 @{$self->get_package_symbol('@ISA')};
473 my $super_class = $self->name;
476 my $find_derived_classes;
477 $find_derived_classes = sub {
478 my ($outer_class) = @_;
480 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
483 for my $symbol ( keys %$symbol_table_hashref ) {
484 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
485 my $inner_class = $1;
487 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
491 ? "${outer_class}::$inner_class"
494 if ( $class->isa($super_class) and $class ne $super_class ) {
495 push @derived_classes, $class;
498 next SYMBOL if $class eq 'main'; # skip 'main::*'
500 $find_derived_classes->($class);
504 my $root_class = q{};
505 $find_derived_classes->($root_class);
507 undef $find_derived_classes;
509 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
511 return @derived_classes;
516 return @{ mro::get_linear_isa( (shift)->name ) };
519 sub class_precedence_list {
521 my $name = $self->name;
523 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
525 # We need to check for circular inheritance here
526 # if we are are not on 5.10, cause 5.8 detects it
527 # late. This will do nothing if all is well, and
528 # blow up otherwise. Yes, it's an ugly hack, better
529 # suggestions are welcome.
531 ($name || return)->isa('This is a test for circular inheritance')
534 # if our mro is c3, we can
535 # just grab the linear_isa
536 if (mro::get_mro($name) eq 'c3') {
537 return @{ mro::get_linear_isa($name) }
541 # we can't grab the linear_isa for dfs
542 # since it has all the duplicates
547 $self->initialize($_)->class_precedence_list()
548 } $self->superclasses()
556 my ($self, $method_name, $method) = @_;
557 (defined $method_name && $method_name)
558 || confess "You must define a method name";
561 if (blessed($method)) {
562 $body = $method->body;
563 if ($method->package_name ne $self->name &&
564 $method->name ne $method_name) {
565 warn "Hello there, got somethig for you."
566 . " Method says " . $method->package_name . " " . $method->name
567 . " Class says " . $self->name . " " . $method_name;
568 $method = $method->clone(
569 package_name => $self->name,
571 ) if $method->can('clone');
576 ('CODE' eq (reftype($body) || ''))
577 || confess "Your code block must be a CODE reference";
578 $method = $self->method_metaclass->wrap(
580 package_name => $self->name,
585 $self->get_method_map->{$method_name} = $method;
587 my $full_method_name = ($self->name . '::' . $method_name);
588 $self->add_package_symbol("&${method_name}" =>
589 Class::MOP::subname($full_method_name => $body)
591 $self->update_package_cache_flag;
595 my $fetch_and_prepare_method = sub {
596 my ($self, $method_name) = @_;
598 my $method = $self->get_method($method_name);
599 # if we dont have local ...
601 # try to find the next method
602 $method = $self->find_next_method_by_name($method_name);
603 # die if it does not exist
605 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
606 # and now make sure to wrap it
607 # even if it is already wrapped
608 # because we need a new sub ref
609 $method = Class::MOP::Method::Wrapped->wrap($method);
612 # now make sure we wrap it properly
613 $method = Class::MOP::Method::Wrapped->wrap($method)
614 unless $method->isa('Class::MOP::Method::Wrapped');
616 $self->add_method($method_name => $method);
620 sub add_before_method_modifier {
621 my ($self, $method_name, $method_modifier) = @_;
622 (defined $method_name && $method_name)
623 || confess "You must pass in a method name";
624 my $method = $fetch_and_prepare_method->($self, $method_name);
625 $method->add_before_modifier(
626 Class::MOP::subname(':before' => $method_modifier)
630 sub add_after_method_modifier {
631 my ($self, $method_name, $method_modifier) = @_;
632 (defined $method_name && $method_name)
633 || confess "You must pass in a method name";
634 my $method = $fetch_and_prepare_method->($self, $method_name);
635 $method->add_after_modifier(
636 Class::MOP::subname(':after' => $method_modifier)
640 sub add_around_method_modifier {
641 my ($self, $method_name, $method_modifier) = @_;
642 (defined $method_name && $method_name)
643 || confess "You must pass in a method name";
644 my $method = $fetch_and_prepare_method->($self, $method_name);
645 $method->add_around_modifier(
646 Class::MOP::subname(':around' => $method_modifier)
651 # the methods above used to be named like this:
652 # ${pkg}::${method}:(before|after|around)
653 # but this proved problematic when using one modifier
654 # to wrap multiple methods (something which is likely
655 # to happen pretty regularly IMO). So instead of naming
656 # it like this, I have chosen to just name them purely
657 # with their modifier names, like so:
658 # :(before|after|around)
659 # The fact is that in a stack trace, it will be fairly
660 # evident from the context what method they are attached
661 # to, and so don't need the fully qualified name.
665 my ($self, $method_name, $method) = @_;
666 (defined $method_name && $method_name)
667 || confess "You must define a method name";
669 my $body = (blessed($method) ? $method->body : $method);
670 ('CODE' eq (reftype($body) || ''))
671 || confess "Your code block must be a CODE reference";
673 $self->add_package_symbol("&${method_name}" => $body);
674 $self->update_package_cache_flag;
678 my ($self, $method_name) = @_;
679 (defined $method_name && $method_name)
680 || confess "You must define a method name";
682 return 0 unless exists $self->get_method_map->{$method_name};
687 my ($self, $method_name) = @_;
688 (defined $method_name && $method_name)
689 || confess "You must define a method name";
692 # I don't really need this here, because
693 # if the method_map is missing a key it
694 # will just return undef for me now
695 # return unless $self->has_method($method_name);
697 return $self->get_method_map->{$method_name};
701 my ($self, $method_name) = @_;
702 (defined $method_name && $method_name)
703 || confess "You must define a method name";
705 my $removed_method = delete $self->get_method_map->{$method_name};
707 $self->remove_package_symbol("&${method_name}");
709 $self->update_package_cache_flag;
711 return $removed_method;
714 sub get_method_list {
716 keys %{$self->get_method_map};
719 sub find_method_by_name {
720 my ($self, $method_name) = @_;
721 (defined $method_name && $method_name)
722 || confess "You must define a method name to find";
723 foreach my $class ($self->linearized_isa) {
724 # fetch the meta-class ...
725 my $meta = $self->initialize($class);
726 return $meta->get_method($method_name)
727 if $meta->has_method($method_name);
732 sub compute_all_applicable_methods {
734 my (@methods, %seen_method);
735 foreach my $class ($self->linearized_isa) {
736 # fetch the meta-class ...
737 my $meta = $self->initialize($class);
738 foreach my $method_name ($meta->get_method_list()) {
739 next if exists $seen_method{$method_name};
740 $seen_method{$method_name}++;
742 name => $method_name,
744 code => $meta->get_method($method_name)
751 sub find_all_methods_by_name {
752 my ($self, $method_name) = @_;
753 (defined $method_name && $method_name)
754 || confess "You must define a method name to find";
756 foreach my $class ($self->linearized_isa) {
757 # fetch the meta-class ...
758 my $meta = $self->initialize($class);
760 name => $method_name,
762 code => $meta->get_method($method_name)
763 } if $meta->has_method($method_name);
768 sub find_next_method_by_name {
769 my ($self, $method_name) = @_;
770 (defined $method_name && $method_name)
771 || confess "You must define a method name to find";
772 my @cpl = $self->linearized_isa;
773 shift @cpl; # discard ourselves
774 foreach my $class (@cpl) {
775 # fetch the meta-class ...
776 my $meta = $self->initialize($class);
777 return $meta->get_method($method_name)
778 if $meta->has_method($method_name);
787 # either we have an attribute object already
788 # or we need to create one from the args provided
789 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
790 # make sure it is derived from the correct type though
791 ($attribute->isa('Class::MOP::Attribute'))
792 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
794 # first we attach our new attribute
795 # because it might need certain information
796 # about the class which it is attached to
797 $attribute->attach_to_class($self);
799 # then we remove attributes of a conflicting
800 # name here so that we can properly detach
801 # the old attr object, and remove any
802 # accessors it would have generated
803 $self->remove_attribute($attribute->name)
804 if $self->has_attribute($attribute->name);
806 # then onto installing the new accessors
807 $attribute->install_accessors();
808 $self->get_attribute_map->{$attribute->name} = $attribute;
812 my ($self, $attribute_name) = @_;
813 (defined $attribute_name && $attribute_name)
814 || confess "You must define an attribute name";
815 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
819 my ($self, $attribute_name) = @_;
820 (defined $attribute_name && $attribute_name)
821 || confess "You must define an attribute name";
822 return $self->get_attribute_map->{$attribute_name}
824 # this will return undef anyway, so no need ...
825 # if $self->has_attribute($attribute_name);
829 sub remove_attribute {
830 my ($self, $attribute_name) = @_;
831 (defined $attribute_name && $attribute_name)
832 || confess "You must define an attribute name";
833 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
834 return unless defined $removed_attribute;
835 delete $self->get_attribute_map->{$attribute_name};
836 $removed_attribute->remove_accessors();
837 $removed_attribute->detach_from_class();
838 return $removed_attribute;
841 sub get_attribute_list {
843 keys %{$self->get_attribute_map};
846 sub compute_all_applicable_attributes {
848 my (@attrs, %seen_attr);
849 foreach my $class ($self->linearized_isa) {
850 # fetch the meta-class ...
851 my $meta = $self->initialize($class);
852 foreach my $attr_name ($meta->get_attribute_list()) {
853 next if exists $seen_attr{$attr_name};
854 $seen_attr{$attr_name}++;
855 push @attrs => $meta->get_attribute($attr_name);
861 sub find_attribute_by_name {
862 my ($self, $attr_name) = @_;
863 foreach my $class ($self->linearized_isa) {
864 # fetch the meta-class ...
865 my $meta = $self->initialize($class);
866 return $meta->get_attribute($attr_name)
867 if $meta->has_attribute($attr_name);
875 sub is_immutable { 0 }
878 # Why I changed this (groditi)
879 # - One Metaclass may have many Classes through many Metaclass instances
880 # - One Metaclass should only have one Immutable Transformer instance
881 # - Each Class may have different Immutabilizing options
882 # - Therefore each Metaclass instance may have different Immutabilizing options
883 # - We need to store one Immutable Transformer instance per Metaclass
884 # - We need to store one set of Immutable Transformer options per Class
885 # - Upon make_mutable we may delete the Immutabilizing options
886 # - We could clean the immutable Transformer instance when there is no more
887 # immutable Classes of that type, but we can also keep it in case
888 # another class with this same Metaclass becomes immutable. It is a case
889 # of trading of storing an instance to avoid unnecessary instantiations of
890 # Immutable Transformers. You may view this as a memory leak, however
891 # Because we have few Metaclasses, in practice it seems acceptable
892 # - To allow Immutable Transformers instances to be cleaned up we could weaken
893 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
896 my %IMMUTABLE_TRANSFORMERS;
897 my %IMMUTABLE_OPTIONS;
901 my $class = blessed $self || $self;
903 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
904 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
906 $transformer->make_metaclass_immutable($self, \%options);
907 $IMMUTABLE_OPTIONS{$self->name} =
908 { %options, IMMUTABLE_TRANSFORMER => $transformer };
910 if( exists $options{debug} && $options{debug} ){
911 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
912 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
920 return if $self->is_mutable;
921 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
922 confess "unable to find immutabilizing options" unless ref $options;
923 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
924 $transformer->make_metaclass_mutable($self, $options);
929 sub create_immutable_transformer {
931 my $class = Class::MOP::Immutable->new($self, {
932 read_only => [qw/superclasses/],
939 remove_package_symbol
942 class_precedence_list => 'ARRAY',
943 linearized_isa => 'ARRAY',
944 compute_all_applicable_attributes => 'ARRAY',
945 get_meta_instance => 'SCALAR',
946 get_method_map => 'SCALAR',
949 # this is ugly, but so are typeglobs,
950 # so whattayahgonnadoboutit
953 add_package_symbol => sub {
954 my $original = shift;
955 confess "Cannot add package symbols to an immutable metaclass"
956 unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
957 goto $original->body;
972 Class::MOP::Class - Class Meta Object
976 # assuming that class Foo
977 # has been defined, you can
979 # use this for introspection ...
981 # add a method to Foo ...
982 Foo->meta->add_method('bar' => sub { ... })
984 # get a list of all the classes searched
985 # the method dispatcher in the correct order
986 Foo->meta->class_precedence_list()
988 # remove a method from Foo
989 Foo->meta->remove_method('bar');
991 # or use this to actually create classes ...
993 Class::MOP::Class->create('Bar' => (
995 superclasses => [ 'Foo' ],
997 Class::MOP:::Attribute->new('$bar'),
998 Class::MOP:::Attribute->new('$baz'),
1001 calculate_bar => sub { ... },
1002 construct_baz => sub { ... }
1008 This is the largest and currently most complex part of the Perl 5
1009 meta-object protocol. It controls the introspection and
1010 manipulation of Perl 5 classes (and it can create them too). The
1011 best way to understand what this module can do, is to read the
1012 documentation for each of it's methods.
1016 =head2 Self Introspection
1022 This will return a B<Class::MOP::Class> instance which is related
1023 to this class. Thereby allowing B<Class::MOP::Class> to actually
1026 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
1027 bootstrap this module by installing a number of attribute meta-objects
1028 into it's metaclass. This will allow this class to reap all the benifits
1029 of the MOP when subclassing it.
1033 =head2 Class construction
1035 These methods will handle creating B<Class::MOP::Class> objects,
1036 which can be used to both create new classes, and analyze
1037 pre-existing classes.
1039 This module will internally store references to all the instances
1040 you create with these methods, so that they do not need to be
1041 created any more than nessecary. Basically, they are singletons.
1045 =item B<create ($package_name,
1046 version =E<gt> ?$version,
1047 authority =E<gt> ?$authority,
1048 superclasses =E<gt> ?@superclasses,
1049 methods =E<gt> ?%methods,
1050 attributes =E<gt> ?%attributes)>
1052 This returns a B<Class::MOP::Class> object, bringing the specified
1053 C<$package_name> into existence and adding any of the C<$version>,
1054 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1057 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1058 methods =E<gt> ?%methods,
1059 attributes =E<gt> ?%attributes)>
1061 This will create an anonymous class, it works much like C<create> but
1062 it does not need a C<$package_name>. Instead it will create a suitably
1063 unique package name for you to stash things into.
1065 On very important distinction is that anon classes are destroyed once
1066 the metaclass they are attached to goes out of scope. In the DESTROY
1067 method, the created package will be removed from the symbol table.
1069 It is also worth noting that any instances created with an anon-class
1070 will keep a special reference to the anon-meta which will prevent the
1071 anon-class from going out of scope until all instances of it have also
1072 been destroyed. This however only works for HASH based instance types,
1073 as we use a special reserved slot (C<__MOP__>) to store this.
1075 =item B<initialize ($package_name, %options)>
1077 This initializes and returns returns a B<Class::MOP::Class> object
1078 for a given a C<$package_name>.
1080 =item B<reinitialize ($package_name, %options)>
1082 This removes the old metaclass, and creates a new one in it's place.
1083 Do B<not> use this unless you really know what you are doing, it could
1084 very easily make a very large mess of your program.
1086 =item B<construct_class_instance (%options)>
1088 This will construct an instance of B<Class::MOP::Class>, it is
1089 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1090 to use C<construct_instance> once all the bootstrapping is done. This
1091 method is used internally by C<initialize> and should never be called
1092 from outside of that method really.
1094 =item B<check_metaclass_compatability>
1096 This method is called as the very last thing in the
1097 C<construct_class_instance> method. This will check that the
1098 metaclass you are creating is compatible with the metaclasses of all
1099 your ancestors. For more inforamtion about metaclass compatibility
1100 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1102 =item B<update_package_cache_flag>
1104 This will reset the package cache flag for this particular metaclass
1105 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1106 function. This is very rarely needed from outside of C<Class::MOP::Class>
1107 but in some cases you might want to use it, so it is here.
1109 =item B<reset_package_cache_flag>
1111 Clears the package cache flag to announce to the internals that we need
1112 to rebuild the method map.
1116 =head2 Object instance construction and cloning
1118 These methods are B<entirely optional>, it is up to you whether you want
1123 =item B<instance_metaclass>
1125 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1126 for more information on the instance metaclasses.
1128 =item B<get_meta_instance>
1130 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1131 of a new instance of the class.
1133 =item B<new_object (%params)>
1135 This is a convience method for creating a new object of the class, and
1136 blessing it into the appropriate package as well. Ideally your class
1137 would call a C<new> this method like so:
1140 my ($class, %param) = @_;
1141 $class->meta->new_object(%params);
1144 =item B<construct_instance (%params)>
1146 This method is used to construct an instance structure suitable for
1147 C<bless>-ing into your package of choice. It works in conjunction
1148 with the Attribute protocol to collect all applicable attributes.
1150 This will construct and instance using a HASH ref as storage
1151 (currently only HASH references are supported). This will collect all
1152 the applicable attributes and layout out the fields in the HASH ref,
1153 it will then initialize them using either use the corresponding key
1154 in C<%params> or any default value or initializer found in the
1155 attribute meta-object.
1157 =item B<clone_object ($instance, %params)>
1159 This is a convience method for cloning an object instance, then
1160 blessing it into the appropriate package. This method will call
1161 C<clone_instance>, which performs a shallow copy of the object,
1162 see that methods documentation for more details. Ideally your
1163 class would call a C<clone> this method like so:
1165 sub MyClass::clone {
1166 my ($self, %param) = @_;
1167 $self->meta->clone_object($self, %params);
1170 =item B<clone_instance($instance, %params)>
1172 This method is a compliment of C<construct_instance> (which means if
1173 you override C<construct_instance>, you need to override this one too),
1174 and clones the instance shallowly.
1176 The cloned structure returned is (like with C<construct_instance>) an
1177 unC<bless>ed HASH reference, it is your responsibility to then bless
1178 this cloned structure into the right class (which C<clone_object> will
1181 As of 0.11, this method will clone the C<$instance> structure shallowly,
1182 as opposed to the deep cloning implemented in prior versions. After much
1183 thought, research and discussion, I have decided that anything but basic
1184 shallow cloning is outside the scope of the meta-object protocol. I
1185 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1186 is too I<context-specific> to be part of the MOP.
1188 =item B<rebless_instance($instance, ?%params)>
1190 This will change the class of C<$instance> to the class of the invoking
1191 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1192 itself. You may pass in optional C<%params> which are like constructor
1193 params and will override anything already defined in the instance.
1197 =head2 Informational
1199 These are a few predicate methods for asking information about the class.
1203 =item B<is_anon_class>
1205 This returns true if the class is a C<Class::MOP::Class> created anon class.
1209 This returns true if the class is still mutable.
1211 =item B<is_immutable>
1213 This returns true if the class has been made immutable.
1217 =head2 Inheritance Relationships
1221 =item B<superclasses (?@superclasses)>
1223 This is a read-write attribute which represents the superclass
1224 relationships of the class the B<Class::MOP::Class> instance is
1225 associated with. Basically, it can get and set the C<@ISA> for you.
1227 =item B<class_precedence_list>
1229 This computes the a list of all the class's ancestors in the same order
1230 in which method dispatch will be done. This is similair to what
1231 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1233 =item B<linearized_isa>
1235 This returns a list based on C<class_precedence_list> but with all
1240 This returns a list of subclasses for this class.
1248 =item B<get_method_map>
1250 Returns a HASH ref of name to CODE reference mapping for this class.
1252 =item B<method_metaclass>
1254 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1255 for more information on the method metaclasses.
1257 =item B<add_method ($method_name, $method)>
1259 This will take a C<$method_name> and CODE reference to that
1260 C<$method> and install it into the class's package.
1263 This does absolutely nothing special to C<$method>
1264 other than use B<Sub::Name> to make sure it is tagged with the
1265 correct name, and therefore show up correctly in stack traces and
1268 =item B<alias_method ($method_name, $method)>
1270 This will take a C<$method_name> and CODE reference to that
1271 C<$method> and alias the method into the class's package.
1274 Unlike C<add_method>, this will B<not> try to name the
1275 C<$method> using B<Sub::Name>, it only aliases the method in
1276 the class's package.
1278 =item B<has_method ($method_name)>
1280 This just provides a simple way to check if the class implements
1281 a specific C<$method_name>. It will I<not> however, attempt to check
1282 if the class inherits the method (use C<UNIVERSAL::can> for that).
1284 This will correctly handle functions defined outside of the package
1285 that use a fully qualified name (C<sub Package::name { ... }>).
1287 This will correctly handle functions renamed with B<Sub::Name> and
1288 installed using the symbol tables. However, if you are naming the
1289 subroutine outside of the package scope, you must use the fully
1290 qualified name, including the package name, for C<has_method> to
1291 correctly identify it.
1293 This will attempt to correctly ignore functions imported from other
1294 packages using B<Exporter>. It breaks down if the function imported
1295 is an C<__ANON__> sub (such as with C<use constant>), which very well
1296 may be a valid method being applied to the class.
1298 In short, this method cannot always be trusted to determine if the
1299 C<$method_name> is actually a method. However, it will DWIM about
1300 90% of the time, so it's a small trade off I think.
1302 =item B<get_method ($method_name)>
1304 This will return a Class::MOP::Method instance related to the specified
1305 C<$method_name>, or return undef if that method does not exist.
1307 The Class::MOP::Method is codifiable, so you can use it like a normal
1308 CODE reference, see L<Class::MOP::Method> for more information.
1310 =item B<find_method_by_name ($method_name)>
1312 This will return a CODE reference of the specified C<$method_name>,
1313 or return undef if that method does not exist.
1315 Unlike C<get_method> this will also look in the superclasses.
1317 =item B<remove_method ($method_name)>
1319 This will attempt to remove a given C<$method_name> from the class.
1320 It will return the CODE reference that it has removed, and will
1321 attempt to use B<Sub::Name> to clear the methods associated name.
1323 =item B<get_method_list>
1325 This will return a list of method names for all I<locally> defined
1326 methods. It does B<not> provide a list of all applicable methods,
1327 including any inherited ones. If you want a list of all applicable
1328 methods, use the C<compute_all_applicable_methods> method.
1330 =item B<compute_all_applicable_methods>
1332 This will return a list of all the methods names this class will
1333 respond to, taking into account inheritance. The list will be a list of
1334 HASH references, each one containing the following information; method
1335 name, the name of the class in which the method lives and a CODE
1336 reference for the actual method.
1338 =item B<find_all_methods_by_name ($method_name)>
1340 This will traverse the inheritence hierarchy and locate all methods
1341 with a given C<$method_name>. Similar to
1342 C<compute_all_applicable_methods> it returns a list of HASH references
1343 with the following information; method name (which will always be the
1344 same as C<$method_name>), the name of the class in which the method
1345 lives and a CODE reference for the actual method.
1347 The list of methods produced is a distinct list, meaning there are no
1348 duplicates in it. This is especially useful for things like object
1349 initialization and destruction where you only want the method called
1350 once, and in the correct order.
1352 =item B<find_next_method_by_name ($method_name)>
1354 This will return the first method to match a given C<$method_name> in
1355 the superclasses, this is basically equivalent to calling
1356 C<SUPER::$method_name>, but it can be dispatched at runtime.
1360 =head2 Method Modifiers
1362 Method modifiers are a concept borrowed from CLOS, in which a method
1363 can be wrapped with I<before>, I<after> and I<around> method modifiers
1364 that will be called everytime the method is called.
1366 =head3 How method modifiers work?
1368 Method modifiers work by wrapping the original method and then replacing
1369 it in the classes symbol table. The wrappers will handle calling all the
1370 modifiers in the appropariate orders and preserving the calling context
1371 for the original method.
1373 Each method modifier serves a particular purpose, which may not be
1374 obvious to users of other method wrapping modules. To start with, the
1375 return values of I<before> and I<after> modifiers are ignored. This is
1376 because thier purpose is B<not> to filter the input and output of the
1377 primary method (this is done with an I<around> modifier). This may seem
1378 like an odd restriction to some, but doing this allows for simple code
1379 to be added at the begining or end of a method call without jeapordizing
1380 the normal functioning of the primary method or placing any extra
1381 responsibility on the code of the modifier. Of course if you have more
1382 complex needs, then use the I<around> modifier, which uses a variation
1383 of continutation passing style to allow for a high degree of flexibility.
1385 Before and around modifiers are called in last-defined-first-called order,
1386 while after modifiers are called in first-defined-first-called order. So
1387 the call tree might looks something like this:
1397 To see examples of using method modifiers, see the following examples
1398 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1399 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1400 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1402 =head3 What is the performance impact?
1404 Of course there is a performance cost associated with method modifiers,
1405 but we have made every effort to make that cost be directly proportional
1406 to the amount of modifier features you utilize.
1408 The wrapping method does it's best to B<only> do as much work as it
1409 absolutely needs to. In order to do this we have moved some of the
1410 performance costs to set-up time, where they are easier to amortize.
1412 All this said, my benchmarks have indicated the following:
1414 simple wrapper with no modifiers 100% slower
1415 simple wrapper with simple before modifier 400% slower
1416 simple wrapper with simple after modifier 450% slower
1417 simple wrapper with simple around modifier 500-550% slower
1418 simple wrapper with all 3 modifiers 1100% slower
1420 These numbers may seem daunting, but you must remember, every feature
1421 comes with some cost. To put things in perspective, just doing a simple
1422 C<AUTOLOAD> which does nothing but extract the name of the method called
1423 and return it costs about 400% over a normal method call.
1427 =item B<add_before_method_modifier ($method_name, $code)>
1429 This will wrap the method at C<$method_name> and the supplied C<$code>
1430 will be passed the C<@_> arguments, and called before the original
1431 method is called. As specified above, the return value of the I<before>
1432 method modifiers is ignored, and it's ability to modify C<@_> is
1433 fairly limited. If you need to do either of these things, use an
1434 C<around> method modifier.
1436 =item B<add_after_method_modifier ($method_name, $code)>
1438 This will wrap the method at C<$method_name> so that the original
1439 method will be called, it's return values stashed, and then the
1440 supplied C<$code> will be passed the C<@_> arguments, and called.
1441 As specified above, the return value of the I<after> method
1442 modifiers is ignored, and it cannot modify the return values of
1443 the original method. If you need to do either of these things, use an
1444 C<around> method modifier.
1446 =item B<add_around_method_modifier ($method_name, $code)>
1448 This will wrap the method at C<$method_name> so that C<$code>
1449 will be called and passed the original method as an extra argument
1450 at the begining of the C<@_> argument list. This is a variation of
1451 continuation passing style, where the function prepended to C<@_>
1452 can be considered a continuation. It is up to C<$code> if it calls
1453 the original method or not, there is no restriction on what the
1454 C<$code> can or cannot do.
1460 It should be noted that since there is no one consistent way to define
1461 the attributes of a class in Perl 5. These methods can only work with
1462 the information given, and can not easily discover information on
1463 their own. See L<Class::MOP::Attribute> for more details.
1467 =item B<attribute_metaclass>
1469 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1470 for more information on the attribute metaclasses.
1472 =item B<get_attribute_map>
1474 This returns a HASH ref of name to attribute meta-object mapping.
1476 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1478 This stores the C<$attribute_meta_object> (or creates one from the
1479 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1480 instance associated with the given class. Unlike methods, attributes
1481 within the MOP are stored as meta-information only. They will be used
1482 later to construct instances from (see C<construct_instance> above).
1483 More details about the attribute meta-objects can be found in the
1484 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1487 It should be noted that any accessor, reader/writer or predicate
1488 methods which the C<$attribute_meta_object> has will be installed
1489 into the class at this time.
1492 If an attribute already exists for C<$attribute_name>, the old one
1493 will be removed (as well as removing all it's accessors), and then
1496 =item B<has_attribute ($attribute_name)>
1498 Checks to see if this class has an attribute by the name of
1499 C<$attribute_name> and returns a boolean.
1501 =item B<get_attribute ($attribute_name)>
1503 Returns the attribute meta-object associated with C<$attribute_name>,
1504 if none is found, it will return undef.
1506 =item B<remove_attribute ($attribute_name)>
1508 This will remove the attribute meta-object stored at
1509 C<$attribute_name>, then return the removed attribute meta-object.
1512 Removing an attribute will only affect future instances of
1513 the class, it will not make any attempt to remove the attribute from
1514 any existing instances of the class.
1516 It should be noted that any accessor, reader/writer or predicate
1517 methods which the attribute meta-object stored at C<$attribute_name>
1518 has will be removed from the class at this time. This B<will> make
1519 these attributes somewhat inaccessable in previously created
1520 instances. But if you are crazy enough to do this at runtime, then
1521 you are crazy enough to deal with something like this :).
1523 =item B<get_attribute_list>
1525 This returns a list of attribute names which are defined in the local
1526 class. If you want a list of all applicable attributes for a class,
1527 use the C<compute_all_applicable_attributes> method.
1529 =item B<compute_all_applicable_attributes>
1531 This will traverse the inheritance heirachy and return a list of all
1532 the applicable attributes for this class. It does not construct a
1533 HASH reference like C<compute_all_applicable_methods> because all
1534 that same information is discoverable through the attribute
1537 =item B<find_attribute_by_name ($attr_name)>
1539 This method will traverse the inheritance heirachy and find the
1540 first attribute whose name matches C<$attr_name>, then return it.
1541 It will return undef if nothing is found.
1545 =head2 Class Immutability
1549 =item B<make_immutable (%options)>
1551 This method will invoke a tranforamtion upon the class which will
1552 make it immutable. Details of this transformation can be found in
1553 the L<Class::MOP::Immutable> documentation.
1555 =item B<make_mutable>
1557 This method will reverse tranforamtion upon the class which
1560 =item B<create_immutable_transformer>
1562 Create a transformer suitable for making this class immutable
1568 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1570 =head1 COPYRIGHT AND LICENSE
1572 Copyright 2006-2008 by Infinity Interactive, Inc.
1574 L<http://www.iinteractive.com>
1576 This library is free software; you can redistribute it and/or modify
1577 it under the same terms as Perl itself.