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', 'weaken';
14 our $VERSION = '0.65';
15 our $AUTHORITY = 'cpan:STEVAN';
17 use base 'Class::MOP::Module';
27 $package_name = shift;
30 $package_name = $options{package};
33 (defined $package_name && $package_name && !ref($package_name))
34 || confess "You must pass a package name and it cannot be blessed";
36 return Class::MOP::get_metaclass_by_name($package_name)
37 || $class->construct_class_instance(package => $package_name, @_);
42 my $package_name = shift;
43 (defined $package_name && $package_name && !blessed($package_name))
44 || confess "You must pass a package name and it cannot be blessed";
45 Class::MOP::remove_metaclass_by_name($package_name);
46 $class->construct_class_instance('package' => $package_name, @_);
49 # NOTE: (meta-circularity)
50 # this is a special form of &construct_instance
51 # (see below), which is used to construct class
52 # meta-object instances for any Class::MOP::*
53 # class. All other classes will use the more
54 # normal &construct_instance.
55 sub construct_class_instance {
58 my $package_name = $options{'package'};
59 (defined $package_name && $package_name)
60 || confess "You must pass a package name";
62 # return the metaclass if we have it cached,
63 # and it is still defined (it has not been
64 # reaped by DESTROY yet, which can happen
65 # annoyingly enough during global destruction)
67 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
72 # we need to deal with the possibility
73 # of class immutability here, and then
74 # get the name of the class appropriately
76 ? ($class->is_immutable
77 ? $class->get_mutable_metaclass_name()
81 # now create the metaclass
83 if ($class eq 'Class::MOP::Class') {
86 # inherited from Class::MOP::Package
87 'package' => $package_name,
90 # since the following attributes will
91 # actually be loaded from the symbol
92 # table, and actually bypass the instance
93 # entirely, we can just leave these things
94 # listed here for reference, because they
95 # should not actually have a value associated
97 'namespace' => \undef,
98 # inherited from Class::MOP::Module
100 'authority' => \undef,
101 # defined in Class::MOP::Class
102 'superclasses' => \undef,
106 'attribute_metaclass' => $options{'attribute_metaclass'} || 'Class::MOP::Attribute',
107 'method_metaclass' => $options{'method_metaclass'} || 'Class::MOP::Method',
108 'instance_metaclass' => $options{'instance_metaclass'} || 'Class::MOP::Instance',
110 ## uber-private variables
112 # this starts out as undef so that
113 # we can tell the first time the
114 # methods are fetched
116 '_package_cache_flag' => undef,
117 '_meta_instance' => undef,
122 # it is safe to use meta here because
123 # class will always be a subclass of
124 # Class::MOP::Class, which defines meta
125 $meta = $class->meta->construct_instance(%options)
128 # and check the metaclass compatibility
129 $meta->check_metaclass_compatability();
131 Class::MOP::store_metaclass_by_name($package_name, $meta);
134 # we need to weaken any anon classes
135 # so that they can call DESTROY properly
136 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
141 sub reset_package_cache_flag { (shift)->{'_package_cache_flag'} = undef }
142 sub update_package_cache_flag {
145 # we can manually update the cache number
146 # since we are actually adding the method
147 # to our cache as well. This avoids us
148 # having to regenerate the method_map.
150 $self->{'_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
153 sub check_metaclass_compatability {
156 # this is always okay ...
157 return if ref($self) eq 'Class::MOP::Class' &&
158 $self->instance_metaclass eq 'Class::MOP::Instance';
160 my @class_list = $self->linearized_isa;
161 shift @class_list; # shift off $self->name
163 foreach my $class_name (@class_list) {
164 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
167 # we need to deal with the possibility
168 # of class immutability here, and then
169 # get the name of the class appropriately
170 my $meta_type = ($meta->is_immutable
171 ? $meta->get_mutable_metaclass_name()
174 ($self->isa($meta_type))
175 || confess $self->name . "->meta => (" . (ref($self)) . ")" .
176 " is not compatible with the " .
177 $class_name . "->meta => (" . ($meta_type) . ")";
179 # we also need to check that instance metaclasses
180 # are compatabile in the same the class.
181 ($self->instance_metaclass->isa($meta->instance_metaclass))
182 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
183 " is not compatible with the " .
184 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
192 # this should be sufficient, if you have a
193 # use case where it is not, write a test and
195 my $ANON_CLASS_SERIAL = 0;
198 # we need a sufficiently annoying prefix
199 # this should suffice for now, this is
200 # used in a couple of places below, so
201 # need to put it up here for now.
202 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
206 no warnings 'uninitialized';
207 $self->name =~ /^$ANON_CLASS_PREFIX/;
210 sub create_anon_class {
211 my ($class, %options) = @_;
212 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
213 return $class->create($package_name, %options);
217 # this will only get called for
218 # anon-classes, all other calls
219 # are assumed to occur during
220 # global destruction and so don't
221 # really need to be handled explicitly
225 return if Class::MOP::in_global_destruction; # it'll happen soon anyway and this just makes things more complicated
227 no warnings 'uninitialized';
228 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
229 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
231 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
232 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
234 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
239 # creating classes with MOP ...
242 my ( $class, @args ) = @_;
244 unshift @args, 'package' if @args % 2 == 1;
246 my (%options) = @args;
247 my $package_name = $options{package};
249 (defined $package_name && $package_name)
250 || confess "You must pass a package name";
252 (ref $options{superclasses} eq 'ARRAY')
253 || confess "You must pass an ARRAY ref of superclasses"
254 if exists $options{superclasses};
256 (ref $options{attributes} eq 'ARRAY')
257 || confess "You must pass an ARRAY ref of attributes"
258 if exists $options{attributes};
260 (ref $options{methods} eq 'HASH')
261 || confess "You must pass an HASH ref of methods"
262 if exists $options{methods};
264 my $code = "package $package_name;";
265 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
266 if exists $options{version};
267 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
268 if exists $options{authority};
271 confess "creation of $package_name failed : $@" if $@;
273 my $meta = $class->initialize($package_name);
276 $meta->add_method('meta' => sub {
277 $class->initialize(ref($_[0]) || $_[0]);
280 $meta->superclasses(@{$options{superclasses}})
281 if exists $options{superclasses};
283 # process attributes first, so that they can
284 # install accessors, but locally defined methods
285 # can then overwrite them. It is maybe a little odd, but
286 # I think this should be the order of things.
287 if (exists $options{attributes}) {
288 foreach my $attr (@{$options{attributes}}) {
289 $meta->add_attribute($attr);
292 if (exists $options{methods}) {
293 foreach my $method_name (keys %{$options{methods}}) {
294 $meta->add_method($method_name, $options{methods}->{$method_name});
303 # all these attribute readers will be bootstrapped
304 # away in the Class::MOP bootstrap section
306 sub get_attribute_map { $_[0]->{'attributes'} }
307 sub attribute_metaclass { $_[0]->{'attribute_metaclass'} }
308 sub method_metaclass { $_[0]->{'method_metaclass'} }
309 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
312 # this is a prime canidate for conversion to XS
316 my $current = Class::MOP::check_package_cache_flag($self->name);
318 if (defined $self->{'_package_cache_flag'} && $self->{'_package_cache_flag'} == $current) {
319 return $self->{'methods'};
322 $self->{_package_cache_flag} = $current;
324 my $map = $self->{'methods'};
326 my $class_name = $self->name;
327 my $method_metaclass = $self->method_metaclass;
329 my %all_code = $self->get_all_package_symbols('CODE');
331 foreach my $symbol (keys %all_code) {
332 my $code = $all_code{$symbol};
334 next if exists $map->{$symbol} &&
335 defined $map->{$symbol} &&
336 $map->{$symbol}->body == $code;
338 my ($pkg, $name) = Class::MOP::get_code_info($code);
341 # in 5.10 constant.pm the constants show up
342 # as being in the right package, but in pre-5.10
343 # they show up as constant::__ANON__ so we
344 # make an exception here to be sure that things
345 # work as expected in both.
347 unless ($pkg eq 'constant' && $name eq '__ANON__') {
348 next if ($pkg || '') ne $class_name ||
349 (($name || '') ne '__ANON__' && ($pkg || '') ne $class_name);
352 $map->{$symbol} = $method_metaclass->wrap(
354 associated_metaclass => $self,
355 package_name => $class_name,
363 # Instance Construction & Cloning
369 # we need to protect the integrity of the
370 # Class::MOP::Class singletons here, so we
371 # delegate this to &construct_class_instance
372 # which will deal with the singletons
373 return $class->construct_class_instance(@_)
374 if $class->name->isa('Class::MOP::Class');
375 return $class->construct_instance(@_);
378 sub construct_instance {
379 my ($class, %params) = @_;
380 my $meta_instance = $class->get_meta_instance();
381 my $instance = $meta_instance->create_instance();
382 foreach my $attr ($class->compute_all_applicable_attributes()) {
383 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
386 # this will only work for a HASH instance type
387 if ($class->is_anon_class) {
388 (Scalar::Util::reftype($instance) eq 'HASH')
389 || confess "Currently only HASH based instances are supported with instance of anon-classes";
391 # At some point we should make this official
392 # as a reserved slot name, but right now I am
393 # going to keep it here.
394 # my $RESERVED_MOP_SLOT = '__MOP__';
395 $instance->{'__MOP__'} = $class;
401 sub get_meta_instance {
403 $self->{'_meta_instance'} ||= $self->create_meta_instance();
406 sub create_meta_instance {
409 my $instance = $self->instance_metaclass->new(
410 associated_metaclass => $self,
411 attributes => [ $self->compute_all_applicable_attributes() ],
414 $self->add_meta_instance_dependencies()
415 if $instance->is_dependent_on_superclasses();
422 my $instance = shift;
423 (blessed($instance) && $instance->isa($class->name))
424 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
427 # we need to protect the integrity of the
428 # Class::MOP::Class singletons here, they
429 # should not be cloned.
430 return $instance if $instance->isa('Class::MOP::Class');
431 $class->clone_instance($instance, @_);
435 my ($class, $instance, %params) = @_;
437 || confess "You can only clone instances, ($instance) is not a blessed instance";
438 my $meta_instance = $class->get_meta_instance();
439 my $clone = $meta_instance->clone_instance($instance);
440 foreach my $attr ($class->compute_all_applicable_attributes()) {
441 if ( defined( my $init_arg = $attr->init_arg ) ) {
442 if (exists $params{$init_arg}) {
443 $attr->set_value($clone, $params{$init_arg});
450 sub rebless_instance {
451 my ($self, $instance, %params) = @_;
454 if ($instance->can('meta')) {
455 ($instance->meta->isa('Class::MOP::Class'))
456 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
457 $old_metaclass = $instance->meta;
460 $old_metaclass = $self->initialize(ref($instance));
463 my $meta_instance = $self->get_meta_instance();
465 $self->name->isa($old_metaclass->name)
466 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
469 $meta_instance->rebless_instance_structure($instance, $self);
471 foreach my $attr ( $self->compute_all_applicable_attributes ) {
472 if ( $attr->has_value($instance) ) {
473 if ( defined( my $init_arg = $attr->init_arg ) ) {
474 $params{$init_arg} = $attr->get_value($instance)
475 unless exists $params{$init_arg};
478 $attr->set_value($instance, $attr->get_value($instance));
483 foreach my $attr ($self->compute_all_applicable_attributes) {
484 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
494 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
497 @{$self->get_package_symbol($var_spec)} = @supers;
499 # we need to check the metaclass
500 # compatibility here so that we can
501 # be sure that the superclass is
502 # not potentially creating an issues
503 # we don't know about
504 $self->check_metaclass_compatability();
505 $self->update_meta_instance_dependencies();
507 @{$self->get_package_symbol($var_spec)};
513 my $super_class = $self->name;
515 if ( Class::MOP::HAVE_ISAREV() ) {
516 return @{ $super_class->mro::get_isarev() };
520 my $find_derived_classes;
521 $find_derived_classes = sub {
522 my ($outer_class) = @_;
524 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
527 for my $symbol ( keys %$symbol_table_hashref ) {
528 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
529 my $inner_class = $1;
531 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
535 ? "${outer_class}::$inner_class"
538 if ( $class->isa($super_class) and $class ne $super_class ) {
539 push @derived_classes, $class;
542 next SYMBOL if $class eq 'main'; # skip 'main::*'
544 $find_derived_classes->($class);
548 my $root_class = q{};
549 $find_derived_classes->($root_class);
551 undef $find_derived_classes;
553 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
555 return @derived_classes;
561 return @{ mro::get_linear_isa( (shift)->name ) };
564 sub class_precedence_list {
566 my $name = $self->name;
568 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
570 # We need to check for circular inheritance here
571 # if we are are not on 5.10, cause 5.8 detects it
572 # late. This will do nothing if all is well, and
573 # blow up otherwise. Yes, it's an ugly hack, better
574 # suggestions are welcome.
576 ($name || return)->isa('This is a test for circular inheritance')
579 # if our mro is c3, we can
580 # just grab the linear_isa
581 if (mro::get_mro($name) eq 'c3') {
582 return @{ mro::get_linear_isa($name) }
586 # we can't grab the linear_isa for dfs
587 # since it has all the duplicates
592 $self->initialize($_)->class_precedence_list()
593 } $self->superclasses()
601 my ($self, $method_name, $method) = @_;
602 (defined $method_name && $method_name)
603 || confess "You must define a method name";
606 if (blessed($method)) {
607 $body = $method->body;
608 if ($method->package_name ne $self->name &&
609 $method->name ne $method_name) {
610 warn "Hello there, got something for you."
611 . " Method says " . $method->package_name . " " . $method->name
612 . " Class says " . $self->name . " " . $method_name;
613 $method = $method->clone(
614 package_name => $self->name,
616 ) if $method->can('clone');
621 ('CODE' eq ref($body))
622 || confess "Your code block must be a CODE reference";
623 $method = $self->method_metaclass->wrap(
625 package_name => $self->name,
631 $method->attach_to_class($self);
633 $self->get_method_map->{$method_name} = $method;
635 my $full_method_name = ($self->name . '::' . $method_name);
636 $self->add_package_symbol(
637 { sigil => '&', type => 'CODE', name => $method_name },
638 Class::MOP::subname($full_method_name => $body)
641 $self->update_package_cache_flag; # still valid, since we just added the method to the map, and if it was invalid before that then get_method_map updated it
645 my $fetch_and_prepare_method = sub {
646 my ($self, $method_name) = @_;
648 my $method = $self->get_method($method_name);
649 # if we dont have local ...
651 # try to find the next method
652 $method = $self->find_next_method_by_name($method_name);
653 # die if it does not exist
655 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
656 # and now make sure to wrap it
657 # even if it is already wrapped
658 # because we need a new sub ref
659 $method = Class::MOP::Method::Wrapped->wrap($method);
662 # now make sure we wrap it properly
663 $method = Class::MOP::Method::Wrapped->wrap($method)
664 unless $method->isa('Class::MOP::Method::Wrapped');
666 $self->add_method($method_name => $method);
670 sub add_before_method_modifier {
671 my ($self, $method_name, $method_modifier) = @_;
672 (defined $method_name && $method_name)
673 || confess "You must pass in a method name";
674 my $method = $fetch_and_prepare_method->($self, $method_name);
675 $method->add_before_modifier(
676 Class::MOP::subname(':before' => $method_modifier)
680 sub add_after_method_modifier {
681 my ($self, $method_name, $method_modifier) = @_;
682 (defined $method_name && $method_name)
683 || confess "You must pass in a method name";
684 my $method = $fetch_and_prepare_method->($self, $method_name);
685 $method->add_after_modifier(
686 Class::MOP::subname(':after' => $method_modifier)
690 sub add_around_method_modifier {
691 my ($self, $method_name, $method_modifier) = @_;
692 (defined $method_name && $method_name)
693 || confess "You must pass in a method name";
694 my $method = $fetch_and_prepare_method->($self, $method_name);
695 $method->add_around_modifier(
696 Class::MOP::subname(':around' => $method_modifier)
701 # the methods above used to be named like this:
702 # ${pkg}::${method}:(before|after|around)
703 # but this proved problematic when using one modifier
704 # to wrap multiple methods (something which is likely
705 # to happen pretty regularly IMO). So instead of naming
706 # it like this, I have chosen to just name them purely
707 # with their modifier names, like so:
708 # :(before|after|around)
709 # The fact is that in a stack trace, it will be fairly
710 # evident from the context what method they are attached
711 # to, and so don't need the fully qualified name.
715 my ($self, $method_name, $method) = @_;
716 (defined $method_name && $method_name)
717 || confess "You must define a method name";
719 my $body = (blessed($method) ? $method->body : $method);
720 ('CODE' eq ref($body))
721 || confess "Your code block must be a CODE reference";
723 $self->add_package_symbol(
724 { sigil => '&', type => 'CODE', name => $method_name } => $body
729 my ($self, $method_name) = @_;
730 (defined $method_name && $method_name)
731 || confess "You must define a method name";
733 return 0 unless exists $self->get_method_map->{$method_name};
738 my ($self, $method_name) = @_;
739 (defined $method_name && $method_name)
740 || confess "You must define a method name";
743 # I don't really need this here, because
744 # if the method_map is missing a key it
745 # will just return undef for me now
746 # return unless $self->has_method($method_name);
748 return $self->get_method_map->{$method_name};
752 my ($self, $method_name) = @_;
753 (defined $method_name && $method_name)
754 || confess "You must define a method name";
756 my $removed_method = delete $self->get_method_map->{$method_name};
758 $self->remove_package_symbol(
759 { sigil => '&', type => 'CODE', name => $method_name }
762 $removed_method->detach_from_class if $removed_method;
764 $self->update_package_cache_flag; # still valid, since we just removed the method from the map
766 return $removed_method;
769 sub get_method_list {
771 keys %{$self->get_method_map};
774 sub find_method_by_name {
775 my ($self, $method_name) = @_;
776 (defined $method_name && $method_name)
777 || confess "You must define a method name to find";
778 foreach my $class ($self->linearized_isa) {
779 # fetch the meta-class ...
780 my $meta = $self->initialize($class);
781 return $meta->get_method($method_name)
782 if $meta->has_method($method_name);
787 sub get_all_methods {
789 my %methods = map { %{ $self->initialize($_)->get_method_map } } reverse $self->linearized_isa;
790 return values %methods;
794 sub compute_all_applicable_methods {
798 class => $_->package_name,
799 code => $_, # sigh, overloading
801 } shift->get_all_methods(@_);
804 sub find_all_methods_by_name {
805 my ($self, $method_name) = @_;
806 (defined $method_name && $method_name)
807 || confess "You must define a method name to find";
809 foreach my $class ($self->linearized_isa) {
810 # fetch the meta-class ...
811 my $meta = $self->initialize($class);
813 name => $method_name,
815 code => $meta->get_method($method_name)
816 } if $meta->has_method($method_name);
821 sub find_next_method_by_name {
822 my ($self, $method_name) = @_;
823 (defined $method_name && $method_name)
824 || confess "You must define a method name to find";
825 my @cpl = $self->linearized_isa;
826 shift @cpl; # discard ourselves
827 foreach my $class (@cpl) {
828 # fetch the meta-class ...
829 my $meta = $self->initialize($class);
830 return $meta->get_method($method_name)
831 if $meta->has_method($method_name);
840 # either we have an attribute object already
841 # or we need to create one from the args provided
842 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
843 # make sure it is derived from the correct type though
844 ($attribute->isa('Class::MOP::Attribute'))
845 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
847 # first we attach our new attribute
848 # because it might need certain information
849 # about the class which it is attached to
850 $attribute->attach_to_class($self);
852 # then we remove attributes of a conflicting
853 # name here so that we can properly detach
854 # the old attr object, and remove any
855 # accessors it would have generated
856 if ( $self->has_attribute($attribute->name) ) {
857 $self->remove_attribute($attribute->name);
859 $self->invalidate_meta_instances();
862 # then onto installing the new accessors
863 $self->get_attribute_map->{$attribute->name} = $attribute;
865 # invalidate package flag here
866 my $e = do { local $@; eval { $attribute->install_accessors() }; $@ };
868 $self->remove_attribute($attribute->name);
875 sub update_meta_instance_dependencies {
878 if ( $self->{meta_instance_dependencies} ) {
879 return $self->add_meta_instance_dependencies;
883 sub add_meta_instance_dependencies {
886 $self->remove_meta_instance_depdendencies;
888 my @attrs = $self->compute_all_applicable_attributes();
891 my @classes = grep { not $seen{$_->name}++ } map { $_->associated_class } @attrs;
893 foreach my $class ( @classes ) {
894 $class->add_dependent_meta_instance($self);
897 $self->{meta_instance_dependencies} = \@classes;
900 sub remove_meta_instance_depdendencies {
903 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
904 foreach my $class ( @$classes ) {
905 $class->remove_dependent_meta_instance($self);
915 sub add_dependent_meta_instance {
916 my ( $self, $metaclass ) = @_;
917 push @{ $self->{dependent_meta_instances} }, $metaclass;
920 sub remove_dependent_meta_instance {
921 my ( $self, $metaclass ) = @_;
922 my $name = $metaclass->name;
923 @$_ = grep { $_->name ne $name } @$_ for $self->{dependent_meta_instances};
926 sub invalidate_meta_instances {
928 $_->invalidate_meta_instance() for $self, @{ $self->{dependent_meta_instances} };
931 sub invalidate_meta_instance {
933 undef $self->{_meta_instance};
937 my ($self, $attribute_name) = @_;
938 (defined $attribute_name && $attribute_name)
939 || confess "You must define an attribute name";
940 exists $self->get_attribute_map->{$attribute_name};
944 my ($self, $attribute_name) = @_;
945 (defined $attribute_name && $attribute_name)
946 || confess "You must define an attribute name";
947 return $self->get_attribute_map->{$attribute_name}
949 # this will return undef anyway, so no need ...
950 # if $self->has_attribute($attribute_name);
954 sub remove_attribute {
955 my ($self, $attribute_name) = @_;
956 (defined $attribute_name && $attribute_name)
957 || confess "You must define an attribute name";
958 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
959 return unless defined $removed_attribute;
960 delete $self->get_attribute_map->{$attribute_name};
961 $self->invalidate_meta_instances();
962 $removed_attribute->remove_accessors();
963 $removed_attribute->detach_from_class();
964 return $removed_attribute;
967 sub get_attribute_list {
969 keys %{$self->get_attribute_map};
972 sub get_all_attributes {
973 shift->compute_all_applicable_attributes(@_);
976 sub compute_all_applicable_attributes {
978 my %attrs = map { %{ $self->initialize($_)->get_attribute_map } } reverse $self->linearized_isa;
979 return values %attrs;
982 sub find_attribute_by_name {
983 my ($self, $attr_name) = @_;
984 foreach my $class ($self->linearized_isa) {
985 # fetch the meta-class ...
986 my $meta = $self->initialize($class);
987 return $meta->get_attribute($attr_name)
988 if $meta->has_attribute($attr_name);
996 sub is_immutable { 0 }
999 # Why I changed this (groditi)
1000 # - One Metaclass may have many Classes through many Metaclass instances
1001 # - One Metaclass should only have one Immutable Transformer instance
1002 # - Each Class may have different Immutabilizing options
1003 # - Therefore each Metaclass instance may have different Immutabilizing options
1004 # - We need to store one Immutable Transformer instance per Metaclass
1005 # - We need to store one set of Immutable Transformer options per Class
1006 # - Upon make_mutable we may delete the Immutabilizing options
1007 # - We could clean the immutable Transformer instance when there is no more
1008 # immutable Classes of that type, but we can also keep it in case
1009 # another class with this same Metaclass becomes immutable. It is a case
1010 # of trading of storing an instance to avoid unnecessary instantiations of
1011 # Immutable Transformers. You may view this as a memory leak, however
1012 # Because we have few Metaclasses, in practice it seems acceptable
1013 # - To allow Immutable Transformers instances to be cleaned up we could weaken
1014 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
1018 my %IMMUTABLE_TRANSFORMERS;
1019 my %IMMUTABLE_OPTIONS;
1021 sub get_immutable_options {
1023 return if $self->is_mutable;
1024 confess "unable to find immutabilizing options"
1025 unless exists $IMMUTABLE_OPTIONS{$self->name};
1026 my %options = %{$IMMUTABLE_OPTIONS{$self->name}};
1027 delete $options{IMMUTABLE_TRANSFORMER};
1031 sub get_immutable_transformer {
1033 if( $self->is_mutable ){
1034 my $class = ref $self || $self;
1035 return $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
1037 confess "unable to find transformer for immutable class"
1038 unless exists $IMMUTABLE_OPTIONS{$self->name};
1039 return $IMMUTABLE_OPTIONS{$self->name}->{IMMUTABLE_TRANSFORMER};
1042 sub make_immutable {
1046 my $transformer = $self->get_immutable_transformer;
1047 $transformer->make_metaclass_immutable($self, \%options);
1048 $IMMUTABLE_OPTIONS{$self->name} =
1049 { %options, IMMUTABLE_TRANSFORMER => $transformer };
1051 if( exists $options{debug} && $options{debug} ){
1052 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
1053 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
1061 return if $self->is_mutable;
1062 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
1063 confess "unable to find immutabilizing options" unless ref $options;
1064 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
1065 $transformer->make_metaclass_mutable($self, $options);
1070 sub create_immutable_transformer {
1072 my $class = Class::MOP::Immutable->new($self, {
1073 read_only => [qw/superclasses/],
1080 remove_package_symbol
1083 class_precedence_list => 'ARRAY',
1084 linearized_isa => 'ARRAY',
1085 compute_all_applicable_attributes => 'ARRAY',
1086 get_meta_instance => 'SCALAR',
1087 get_method_map => 'SCALAR',
1090 # this is ugly, but so are typeglobs,
1091 # so whattayahgonnadoboutit
1094 add_package_symbol => sub {
1095 my $original = shift;
1096 confess "Cannot add package symbols to an immutable metaclass"
1097 unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
1098 goto $original->body;
1113 Class::MOP::Class - Class Meta Object
1117 # assuming that class Foo
1118 # has been defined, you can
1120 # use this for introspection ...
1122 # add a method to Foo ...
1123 Foo->meta->add_method('bar' => sub { ... })
1125 # get a list of all the classes searched
1126 # the method dispatcher in the correct order
1127 Foo->meta->class_precedence_list()
1129 # remove a method from Foo
1130 Foo->meta->remove_method('bar');
1132 # or use this to actually create classes ...
1134 Class::MOP::Class->create('Bar' => (
1136 superclasses => [ 'Foo' ],
1138 Class::MOP:::Attribute->new('$bar'),
1139 Class::MOP:::Attribute->new('$baz'),
1142 calculate_bar => sub { ... },
1143 construct_baz => sub { ... }
1149 This is the largest and currently most complex part of the Perl 5
1150 meta-object protocol. It controls the introspection and
1151 manipulation of Perl 5 classes (and it can create them too). The
1152 best way to understand what this module can do, is to read the
1153 documentation for each of it's methods.
1157 =head2 Self Introspection
1163 This will return a B<Class::MOP::Class> instance which is related
1164 to this class. Thereby allowing B<Class::MOP::Class> to actually
1167 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
1168 bootstrap this module by installing a number of attribute meta-objects
1169 into it's metaclass. This will allow this class to reap all the benifits
1170 of the MOP when subclassing it.
1174 =head2 Class construction
1176 These methods will handle creating B<Class::MOP::Class> objects,
1177 which can be used to both create new classes, and analyze
1178 pre-existing classes.
1180 This module will internally store references to all the instances
1181 you create with these methods, so that they do not need to be
1182 created any more than nessecary. Basically, they are singletons.
1186 =item B<create ($package_name,
1187 version =E<gt> ?$version,
1188 authority =E<gt> ?$authority,
1189 superclasses =E<gt> ?@superclasses,
1190 methods =E<gt> ?%methods,
1191 attributes =E<gt> ?%attributes)>
1193 This returns a B<Class::MOP::Class> object, bringing the specified
1194 C<$package_name> into existence and adding any of the C<$version>,
1195 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1198 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1199 methods =E<gt> ?%methods,
1200 attributes =E<gt> ?%attributes)>
1202 This will create an anonymous class, it works much like C<create> but
1203 it does not need a C<$package_name>. Instead it will create a suitably
1204 unique package name for you to stash things into.
1206 On very important distinction is that anon classes are destroyed once
1207 the metaclass they are attached to goes out of scope. In the DESTROY
1208 method, the created package will be removed from the symbol table.
1210 It is also worth noting that any instances created with an anon-class
1211 will keep a special reference to the anon-meta which will prevent the
1212 anon-class from going out of scope until all instances of it have also
1213 been destroyed. This however only works for HASH based instance types,
1214 as we use a special reserved slot (C<__MOP__>) to store this.
1216 =item B<initialize ($package_name, %options)>
1218 This initializes and returns returns a B<Class::MOP::Class> object
1219 for a given a C<$package_name>.
1221 =item B<reinitialize ($package_name, %options)>
1223 This removes the old metaclass, and creates a new one in it's place.
1224 Do B<not> use this unless you really know what you are doing, it could
1225 very easily make a very large mess of your program.
1227 =item B<construct_class_instance (%options)>
1229 This will construct an instance of B<Class::MOP::Class>, it is
1230 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1231 to use C<construct_instance> once all the bootstrapping is done. This
1232 method is used internally by C<initialize> and should never be called
1233 from outside of that method really.
1235 =item B<check_metaclass_compatability>
1237 This method is called as the very last thing in the
1238 C<construct_class_instance> method. This will check that the
1239 metaclass you are creating is compatible with the metaclasses of all
1240 your ancestors. For more inforamtion about metaclass compatibility
1241 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1243 =item B<update_package_cache_flag>
1245 This will reset the package cache flag for this particular metaclass
1246 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1247 function. This is very rarely needed from outside of C<Class::MOP::Class>
1248 but in some cases you might want to use it, so it is here.
1250 =item B<reset_package_cache_flag>
1252 Clears the package cache flag to announce to the internals that we need
1253 to rebuild the method map.
1255 =item B<add_meta_instance_dependencies>
1257 Registers this class as dependent on its superclasses.
1259 Only superclasses from which this class inherits attributes will be added.
1261 =item B<remove_meta_instance_depdendencies>
1263 Unregisters this class from its superclasses.
1265 =item B<update_meta_instance_dependencies>
1267 Reregisters if necessary.
1269 =item B<add_dependent_meta_instance> $metaclass
1271 Registers the class as having a meta instance dependent on this class.
1273 =item B<remove_dependent_meta_instance> $metaclass
1275 Remove the class from the list of dependent classes.
1277 =item B<invalidate_meta_instances>
1279 Clears the cached meta instance for this metaclass and all of the registered
1280 classes with dependent meta instances.
1282 Called by C<add_attribute> and C<remove_attribute> to recalculate the attribute
1285 =item B<invalidate_meta_instance>
1287 Used by C<invalidate_meta_instances>.
1291 =head2 Object instance construction and cloning
1293 These methods are B<entirely optional>, it is up to you whether you want
1298 =item B<instance_metaclass>
1300 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1301 for more information on the instance metaclasses.
1303 =item B<get_meta_instance>
1305 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1306 of a new instance of the class.
1308 =item B<create_meta_instance>
1310 Called by C<get_meta_instance> if necessary.
1312 =item B<new_object (%params)>
1314 This is a convience method for creating a new object of the class, and
1315 blessing it into the appropriate package as well. Ideally your class
1316 would call a C<new> this method like so:
1319 my ($class, %param) = @_;
1320 $class->meta->new_object(%params);
1323 =item B<construct_instance (%params)>
1325 This method is used to construct an instance structure suitable for
1326 C<bless>-ing into your package of choice. It works in conjunction
1327 with the Attribute protocol to collect all applicable attributes.
1329 This will construct and instance using a HASH ref as storage
1330 (currently only HASH references are supported). This will collect all
1331 the applicable attributes and layout out the fields in the HASH ref,
1332 it will then initialize them using either use the corresponding key
1333 in C<%params> or any default value or initializer found in the
1334 attribute meta-object.
1336 =item B<clone_object ($instance, %params)>
1338 This is a convience method for cloning an object instance, then
1339 blessing it into the appropriate package. This method will call
1340 C<clone_instance>, which performs a shallow copy of the object,
1341 see that methods documentation for more details. Ideally your
1342 class would call a C<clone> this method like so:
1344 sub MyClass::clone {
1345 my ($self, %param) = @_;
1346 $self->meta->clone_object($self, %params);
1349 =item B<clone_instance($instance, %params)>
1351 This method is a compliment of C<construct_instance> (which means if
1352 you override C<construct_instance>, you need to override this one too),
1353 and clones the instance shallowly.
1355 The cloned structure returned is (like with C<construct_instance>) an
1356 unC<bless>ed HASH reference, it is your responsibility to then bless
1357 this cloned structure into the right class (which C<clone_object> will
1360 As of 0.11, this method will clone the C<$instance> structure shallowly,
1361 as opposed to the deep cloning implemented in prior versions. After much
1362 thought, research and discussion, I have decided that anything but basic
1363 shallow cloning is outside the scope of the meta-object protocol. I
1364 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1365 is too I<context-specific> to be part of the MOP.
1367 =item B<rebless_instance($instance, ?%params)>
1369 This will change the class of C<$instance> to the class of the invoking
1370 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1371 itself. You may pass in optional C<%params> which are like constructor
1372 params and will override anything already defined in the instance.
1376 =head2 Informational
1378 These are a few predicate methods for asking information about the class.
1382 =item B<is_anon_class>
1384 This returns true if the class is a C<Class::MOP::Class> created anon class.
1388 This returns true if the class is still mutable.
1390 =item B<is_immutable>
1392 This returns true if the class has been made immutable.
1396 =head2 Inheritance Relationships
1400 =item B<superclasses (?@superclasses)>
1402 This is a read-write attribute which represents the superclass
1403 relationships of the class the B<Class::MOP::Class> instance is
1404 associated with. Basically, it can get and set the C<@ISA> for you.
1406 =item B<class_precedence_list>
1408 This computes the a list of all the class's ancestors in the same order
1409 in which method dispatch will be done. This is similair to what
1410 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1412 =item B<linearized_isa>
1414 This returns a list based on C<class_precedence_list> but with all
1419 This returns a list of subclasses for this class.
1427 =item B<get_method_map>
1429 Returns a HASH ref of name to CODE reference mapping for this class.
1431 =item B<method_metaclass>
1433 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1434 for more information on the method metaclasses.
1436 =item B<add_method ($method_name, $method)>
1438 This will take a C<$method_name> and CODE reference to that
1439 C<$method> and install it into the class's package.
1442 This does absolutely nothing special to C<$method>
1443 other than use B<Sub::Name> to make sure it is tagged with the
1444 correct name, and therefore show up correctly in stack traces and
1447 =item B<alias_method ($method_name, $method)>
1449 This will take a C<$method_name> and CODE reference to that
1450 C<$method> and alias the method into the class's package.
1453 Unlike C<add_method>, this will B<not> try to name the
1454 C<$method> using B<Sub::Name>, it only aliases the method in
1455 the class's package.
1457 =item B<has_method ($method_name)>
1459 This just provides a simple way to check if the class implements
1460 a specific C<$method_name>. It will I<not> however, attempt to check
1461 if the class inherits the method (use C<UNIVERSAL::can> for that).
1463 This will correctly handle functions defined outside of the package
1464 that use a fully qualified name (C<sub Package::name { ... }>).
1466 This will correctly handle functions renamed with B<Sub::Name> and
1467 installed using the symbol tables. However, if you are naming the
1468 subroutine outside of the package scope, you must use the fully
1469 qualified name, including the package name, for C<has_method> to
1470 correctly identify it.
1472 This will attempt to correctly ignore functions imported from other
1473 packages using B<Exporter>. It breaks down if the function imported
1474 is an C<__ANON__> sub (such as with C<use constant>), which very well
1475 may be a valid method being applied to the class.
1477 In short, this method cannot always be trusted to determine if the
1478 C<$method_name> is actually a method. However, it will DWIM about
1479 90% of the time, so it's a small trade off I think.
1481 =item B<get_method ($method_name)>
1483 This will return a Class::MOP::Method instance related to the specified
1484 C<$method_name>, or return undef if that method does not exist.
1486 The Class::MOP::Method is codifiable, so you can use it like a normal
1487 CODE reference, see L<Class::MOP::Method> for more information.
1489 =item B<find_method_by_name ($method_name)>
1491 This will return a CODE reference of the specified C<$method_name>,
1492 or return undef if that method does not exist.
1494 Unlike C<get_method> this will also look in the superclasses.
1496 =item B<remove_method ($method_name)>
1498 This will attempt to remove a given C<$method_name> from the class.
1499 It will return the CODE reference that it has removed, and will
1500 attempt to use B<Sub::Name> to clear the methods associated name.
1502 =item B<get_method_list>
1504 This will return a list of method names for all I<locally> defined
1505 methods. It does B<not> provide a list of all applicable methods,
1506 including any inherited ones. If you want a list of all applicable
1507 methods, use the C<compute_all_applicable_methods> method.
1509 =item B<get_all_methods>
1511 This will traverse the inheritance heirachy and return a list of all
1512 the applicable L<Class::MOP::Method> objects for this class.
1514 =item B<compute_all_applicable_methods>
1518 This method returns a list of hashes describing the all the methods of the
1521 Use L<get_all_methods>, which is easier/better/faster. This method predates
1522 L<Class::MOP::Method>.
1524 =item B<find_all_methods_by_name ($method_name)>
1526 This will traverse the inheritence hierarchy and locate all methods
1527 with a given C<$method_name>. Similar to
1528 C<compute_all_applicable_methods> it returns a list of HASH references
1529 with the following information; method name (which will always be the
1530 same as C<$method_name>), the name of the class in which the method
1531 lives and a CODE reference for the actual method.
1533 The list of methods produced is a distinct list, meaning there are no
1534 duplicates in it. This is especially useful for things like object
1535 initialization and destruction where you only want the method called
1536 once, and in the correct order.
1538 =item B<find_next_method_by_name ($method_name)>
1540 This will return the first method to match a given C<$method_name> in
1541 the superclasses, this is basically equivalent to calling
1542 C<SUPER::$method_name>, but it can be dispatched at runtime.
1546 =head2 Method Modifiers
1548 Method modifiers are a concept borrowed from CLOS, in which a method
1549 can be wrapped with I<before>, I<after> and I<around> method modifiers
1550 that will be called everytime the method is called.
1552 =head3 How method modifiers work?
1554 Method modifiers work by wrapping the original method and then replacing
1555 it in the classes symbol table. The wrappers will handle calling all the
1556 modifiers in the appropariate orders and preserving the calling context
1557 for the original method.
1559 Each method modifier serves a particular purpose, which may not be
1560 obvious to users of other method wrapping modules. To start with, the
1561 return values of I<before> and I<after> modifiers are ignored. This is
1562 because thier purpose is B<not> to filter the input and output of the
1563 primary method (this is done with an I<around> modifier). This may seem
1564 like an odd restriction to some, but doing this allows for simple code
1565 to be added at the begining or end of a method call without jeapordizing
1566 the normal functioning of the primary method or placing any extra
1567 responsibility on the code of the modifier. Of course if you have more
1568 complex needs, then use the I<around> modifier, which uses a variation
1569 of continutation passing style to allow for a high degree of flexibility.
1571 Before and around modifiers are called in last-defined-first-called order,
1572 while after modifiers are called in first-defined-first-called order. So
1573 the call tree might looks something like this:
1583 To see examples of using method modifiers, see the following examples
1584 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1585 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1586 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1588 =head3 What is the performance impact?
1590 Of course there is a performance cost associated with method modifiers,
1591 but we have made every effort to make that cost be directly proportional
1592 to the amount of modifier features you utilize.
1594 The wrapping method does it's best to B<only> do as much work as it
1595 absolutely needs to. In order to do this we have moved some of the
1596 performance costs to set-up time, where they are easier to amortize.
1598 All this said, my benchmarks have indicated the following:
1600 simple wrapper with no modifiers 100% slower
1601 simple wrapper with simple before modifier 400% slower
1602 simple wrapper with simple after modifier 450% slower
1603 simple wrapper with simple around modifier 500-550% slower
1604 simple wrapper with all 3 modifiers 1100% slower
1606 These numbers may seem daunting, but you must remember, every feature
1607 comes with some cost. To put things in perspective, just doing a simple
1608 C<AUTOLOAD> which does nothing but extract the name of the method called
1609 and return it costs about 400% over a normal method call.
1613 =item B<add_before_method_modifier ($method_name, $code)>
1615 This will wrap the method at C<$method_name> and the supplied C<$code>
1616 will be passed the C<@_> arguments, and called before the original
1617 method is called. As specified above, the return value of the I<before>
1618 method modifiers is ignored, and it's ability to modify C<@_> is
1619 fairly limited. If you need to do either of these things, use an
1620 C<around> method modifier.
1622 =item B<add_after_method_modifier ($method_name, $code)>
1624 This will wrap the method at C<$method_name> so that the original
1625 method will be called, it's return values stashed, and then the
1626 supplied C<$code> will be passed the C<@_> arguments, and called.
1627 As specified above, the return value of the I<after> method
1628 modifiers is ignored, and it cannot modify the return values of
1629 the original method. If you need to do either of these things, use an
1630 C<around> method modifier.
1632 =item B<add_around_method_modifier ($method_name, $code)>
1634 This will wrap the method at C<$method_name> so that C<$code>
1635 will be called and passed the original method as an extra argument
1636 at the begining of the C<@_> argument list. This is a variation of
1637 continuation passing style, where the function prepended to C<@_>
1638 can be considered a continuation. It is up to C<$code> if it calls
1639 the original method or not, there is no restriction on what the
1640 C<$code> can or cannot do.
1646 It should be noted that since there is no one consistent way to define
1647 the attributes of a class in Perl 5. These methods can only work with
1648 the information given, and can not easily discover information on
1649 their own. See L<Class::MOP::Attribute> for more details.
1653 =item B<attribute_metaclass>
1655 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1656 for more information on the attribute metaclasses.
1658 =item B<get_attribute_map>
1660 This returns a HASH ref of name to attribute meta-object mapping.
1662 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1664 This stores the C<$attribute_meta_object> (or creates one from the
1665 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1666 instance associated with the given class. Unlike methods, attributes
1667 within the MOP are stored as meta-information only. They will be used
1668 later to construct instances from (see C<construct_instance> above).
1669 More details about the attribute meta-objects can be found in the
1670 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1673 It should be noted that any accessor, reader/writer or predicate
1674 methods which the C<$attribute_meta_object> has will be installed
1675 into the class at this time.
1678 If an attribute already exists for C<$attribute_name>, the old one
1679 will be removed (as well as removing all it's accessors), and then
1682 =item B<has_attribute ($attribute_name)>
1684 Checks to see if this class has an attribute by the name of
1685 C<$attribute_name> and returns a boolean.
1687 =item B<get_attribute ($attribute_name)>
1689 Returns the attribute meta-object associated with C<$attribute_name>,
1690 if none is found, it will return undef.
1692 =item B<remove_attribute ($attribute_name)>
1694 This will remove the attribute meta-object stored at
1695 C<$attribute_name>, then return the removed attribute meta-object.
1698 Removing an attribute will only affect future instances of
1699 the class, it will not make any attempt to remove the attribute from
1700 any existing instances of the class.
1702 It should be noted that any accessor, reader/writer or predicate
1703 methods which the attribute meta-object stored at C<$attribute_name>
1704 has will be removed from the class at this time. This B<will> make
1705 these attributes somewhat inaccessable in previously created
1706 instances. But if you are crazy enough to do this at runtime, then
1707 you are crazy enough to deal with something like this :).
1709 =item B<get_attribute_list>
1711 This returns a list of attribute names which are defined in the local
1712 class. If you want a list of all applicable attributes for a class,
1713 use the C<compute_all_applicable_attributes> method.
1715 =item B<compute_all_applicable_attributes>
1717 =item B<get_all_attributes>
1719 This will traverse the inheritance heirachy and return a list of all
1720 the applicable L<Class::MOP::Attribute> objects for this class.
1722 C<get_all_attributes> is an alias for consistency with C<get_all_methods>.
1724 =item B<find_attribute_by_name ($attr_name)>
1726 This method will traverse the inheritance heirachy and find the
1727 first attribute whose name matches C<$attr_name>, then return it.
1728 It will return undef if nothing is found.
1732 =head2 Class Immutability
1736 =item B<make_immutable (%options)>
1738 This method will invoke a tranforamtion upon the class which will
1739 make it immutable. Details of this transformation can be found in
1740 the L<Class::MOP::Immutable> documentation.
1742 =item B<make_mutable>
1744 This method will reverse tranforamtion upon the class which
1747 =item B<get_immutable_transformer>
1749 Return a transformer suitable for making this class immutable or, if this
1750 class is immutable, the transformer used to make it immutable.
1752 =item B<get_immutable_options>
1754 If the class is immutable, return the options used to make it immutable.
1756 =item B<create_immutable_transformer>
1758 Create a transformer suitable for making this class immutable
1764 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1766 =head1 COPYRIGHT AND LICENSE
1768 Copyright 2006-2008 by Infinity Interactive, Inc.
1770 L<http://www.iinteractive.com>
1772 This library is free software; you can redistribute it and/or modify
1773 it under the same terms as Perl itself.