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, @_);
40 # NOTE: (meta-circularity)
41 # this is a special form of &construct_instance
42 # (see below), which is used to construct class
43 # meta-object instances for any Class::MOP::*
44 # class. All other classes will use the more
45 # normal &construct_instance.
46 sub construct_class_instance {
48 my $options = @_ == 1 ? $_[0] : {@_};
49 my $package_name = $options->{package};
50 (defined $package_name && $package_name)
51 || confess "You must pass a package name";
53 # return the metaclass if we have it cached,
54 # and it is still defined (it has not been
55 # reaped by DESTROY yet, which can happen
56 # annoyingly enough during global destruction)
58 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
63 # we need to deal with the possibility
64 # of class immutability here, and then
65 # get the name of the class appropriately
67 ? ($class->is_immutable
68 ? $class->get_mutable_metaclass_name()
72 # now create the metaclass
74 if ($class eq 'Class::MOP::Class') {
76 $meta = $class->_new($options)
80 # it is safe to use meta here because
81 # class will always be a subclass of
82 # Class::MOP::Class, which defines meta
83 $meta = $class->meta->construct_instance($options)
86 # and check the metaclass compatibility
87 $meta->check_metaclass_compatability();
89 Class::MOP::store_metaclass_by_name($package_name, $meta);
92 # we need to weaken any anon classes
93 # so that they can call DESTROY properly
94 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
101 my $options = @_ == 1 ? $_[0] : {@_};
104 # inherited from Class::MOP::Package
105 'package' => $options->{package},
108 # since the following attributes will
109 # actually be loaded from the symbol
110 # table, and actually bypass the instance
111 # entirely, we can just leave these things
112 # listed here for reference, because they
113 # should not actually have a value associated
115 'namespace' => \undef,
116 # inherited from Class::MOP::Module
118 'authority' => \undef,
119 # defined in Class::MOP::Class
120 'superclasses' => \undef,
124 'attribute_metaclass' => $options->{'attribute_metaclass'} || 'Class::MOP::Attribute',
125 'method_metaclass' => $options->{'method_metaclass'} || 'Class::MOP::Method',
126 'instance_metaclass' => $options->{'instance_metaclass'} || 'Class::MOP::Instance',
130 sub reset_package_cache_flag { (shift)->{'_package_cache_flag'} = undef }
131 sub update_package_cache_flag {
134 # we can manually update the cache number
135 # since we are actually adding the method
136 # to our cache as well. This avoids us
137 # having to regenerate the method_map.
139 $self->{'_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
142 sub check_metaclass_compatability {
145 # this is always okay ...
146 return if ref($self) eq 'Class::MOP::Class' &&
147 $self->instance_metaclass eq 'Class::MOP::Instance';
149 my @class_list = $self->linearized_isa;
150 shift @class_list; # shift off $self->name
152 foreach my $class_name (@class_list) {
153 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
156 # we need to deal with the possibility
157 # of class immutability here, and then
158 # get the name of the class appropriately
159 my $meta_type = ($meta->is_immutable
160 ? $meta->get_mutable_metaclass_name()
163 ($self->isa($meta_type))
164 || confess $self->name . "->meta => (" . (ref($self)) . ")" .
165 " is not compatible with the " .
166 $class_name . "->meta => (" . ($meta_type) . ")";
168 # we also need to check that instance metaclasses
169 # are compatabile in the same the class.
170 ($self->instance_metaclass->isa($meta->instance_metaclass))
171 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
172 " is not compatible with the " .
173 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
181 # this should be sufficient, if you have a
182 # use case where it is not, write a test and
184 my $ANON_CLASS_SERIAL = 0;
187 # we need a sufficiently annoying prefix
188 # this should suffice for now, this is
189 # used in a couple of places below, so
190 # need to put it up here for now.
191 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
195 no warnings 'uninitialized';
196 $self->name =~ /^$ANON_CLASS_PREFIX/;
199 sub create_anon_class {
200 my ($class, %options) = @_;
201 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
202 return $class->create($package_name, %options);
206 # this will only get called for
207 # anon-classes, all other calls
208 # are assumed to occur during
209 # global destruction and so don't
210 # really need to be handled explicitly
214 return if Class::MOP::in_global_destruction; # it'll happen soon anyway and this just makes things more complicated
216 no warnings 'uninitialized';
217 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
218 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
220 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
221 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
223 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
228 # creating classes with MOP ...
231 my ( $class, @args ) = @_;
233 unshift @args, 'package' if @args % 2 == 1;
235 my (%options) = @args;
236 my $package_name = $options{package};
238 (defined $package_name && $package_name)
239 || confess "You must pass a package name";
241 (ref $options{superclasses} eq 'ARRAY')
242 || confess "You must pass an ARRAY ref of superclasses"
243 if exists $options{superclasses};
245 (ref $options{attributes} eq 'ARRAY')
246 || confess "You must pass an ARRAY ref of attributes"
247 if exists $options{attributes};
249 (ref $options{methods} eq 'HASH')
250 || confess "You must pass an HASH ref of methods"
251 if exists $options{methods};
253 my $code = "package $package_name;";
254 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
255 if exists $options{version};
256 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
257 if exists $options{authority};
260 confess "creation of $package_name failed : $@" if $@;
262 my $meta = $class->initialize($package_name);
265 $meta->add_method('meta' => sub {
266 $class->initialize(ref($_[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 my $current = Class::MOP::check_package_cache_flag($self->name);
307 if (defined $self->{'_package_cache_flag'} && $self->{'_package_cache_flag'} == $current) {
308 return $self->{'methods'} ||= {};
311 $self->{_package_cache_flag} = $current;
313 my $map = $self->{'methods'} ||= {};
315 my $class_name = $self->name;
316 my $method_metaclass = $self->method_metaclass;
318 my %all_code = $self->get_all_package_symbols('CODE');
320 foreach my $symbol (keys %all_code) {
321 my $code = $all_code{$symbol};
323 next if exists $map->{$symbol} &&
324 defined $map->{$symbol} &&
325 $map->{$symbol}->body == $code;
327 my ($pkg, $name) = Class::MOP::get_code_info($code);
330 # in 5.10 constant.pm the constants show up
331 # as being in the right package, but in pre-5.10
332 # they show up as constant::__ANON__ so we
333 # make an exception here to be sure that things
334 # work as expected in both.
336 unless ($pkg eq 'constant' && $name eq '__ANON__') {
337 next if ($pkg || '') ne $class_name ||
338 (($name || '') ne '__ANON__' && ($pkg || '') ne $class_name);
341 $map->{$symbol} = $method_metaclass->wrap(
343 associated_metaclass => $self,
344 package_name => $class_name,
352 # Instance Construction & Cloning
358 # we need to protect the integrity of the
359 # Class::MOP::Class singletons here, so we
360 # delegate this to &construct_class_instance
361 # which will deal with the singletons
362 return $class->construct_class_instance(@_)
363 if $class->name->isa('Class::MOP::Class');
364 return $class->construct_instance(@_);
367 sub construct_instance {
369 my $params = @_ == 1 ? $_[0] : {@_};
370 my $meta_instance = $class->get_meta_instance();
371 my $instance = $meta_instance->create_instance();
372 foreach my $attr ($class->compute_all_applicable_attributes()) {
373 $attr->initialize_instance_slot($meta_instance, $instance, $params);
376 # this will only work for a HASH instance type
377 if ($class->is_anon_class) {
378 (Scalar::Util::reftype($instance) eq 'HASH')
379 || confess "Currently only HASH based instances are supported with instance of anon-classes";
381 # At some point we should make this official
382 # as a reserved slot name, but right now I am
383 # going to keep it here.
384 # my $RESERVED_MOP_SLOT = '__MOP__';
385 $instance->{'__MOP__'} = $class;
391 sub get_meta_instance {
393 $self->{'_meta_instance'} ||= $self->create_meta_instance();
396 sub create_meta_instance {
399 my $instance = $self->instance_metaclass->new(
400 associated_metaclass => $self,
401 attributes => [ $self->compute_all_applicable_attributes() ],
404 $self->add_meta_instance_dependencies()
405 if $instance->is_dependent_on_superclasses();
412 my $instance = shift;
413 (blessed($instance) && $instance->isa($class->name))
414 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
417 # we need to protect the integrity of the
418 # Class::MOP::Class singletons here, they
419 # should not be cloned.
420 return $instance if $instance->isa('Class::MOP::Class');
421 $class->clone_instance($instance, @_);
425 my ($class, $instance, %params) = @_;
427 || confess "You can only clone instances, ($instance) is not a blessed instance";
428 my $meta_instance = $class->get_meta_instance();
429 my $clone = $meta_instance->clone_instance($instance);
430 foreach my $attr ($class->compute_all_applicable_attributes()) {
431 if ( defined( my $init_arg = $attr->init_arg ) ) {
432 if (exists $params{$init_arg}) {
433 $attr->set_value($clone, $params{$init_arg});
440 sub rebless_instance {
441 my ($self, $instance, %params) = @_;
444 if ($instance->can('meta')) {
445 ($instance->meta->isa('Class::MOP::Class'))
446 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
447 $old_metaclass = $instance->meta;
450 $old_metaclass = $self->initialize(ref($instance));
453 my $meta_instance = $self->get_meta_instance();
455 $self->name->isa($old_metaclass->name)
456 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
459 $meta_instance->rebless_instance_structure($instance, $self);
461 foreach my $attr ( $self->compute_all_applicable_attributes ) {
462 if ( $attr->has_value($instance) ) {
463 if ( defined( my $init_arg = $attr->init_arg ) ) {
464 $params{$init_arg} = $attr->get_value($instance)
465 unless exists $params{$init_arg};
468 $attr->set_value($instance, $attr->get_value($instance));
473 foreach my $attr ($self->compute_all_applicable_attributes) {
474 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
484 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
487 @{$self->get_package_symbol($var_spec)} = @supers;
489 # we need to check the metaclass
490 # compatibility here so that we can
491 # be sure that the superclass is
492 # not potentially creating an issues
493 # we don't know about
494 $self->check_metaclass_compatability();
495 $self->update_meta_instance_dependencies();
497 @{$self->get_package_symbol($var_spec)};
503 my $super_class = $self->name;
505 if ( Class::MOP::HAVE_ISAREV() ) {
506 return @{ $super_class->mro::get_isarev() };
510 my $find_derived_classes;
511 $find_derived_classes = sub {
512 my ($outer_class) = @_;
514 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
517 for my $symbol ( keys %$symbol_table_hashref ) {
518 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
519 my $inner_class = $1;
521 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
525 ? "${outer_class}::$inner_class"
528 if ( $class->isa($super_class) and $class ne $super_class ) {
529 push @derived_classes, $class;
532 next SYMBOL if $class eq 'main'; # skip 'main::*'
534 $find_derived_classes->($class);
538 my $root_class = q{};
539 $find_derived_classes->($root_class);
541 undef $find_derived_classes;
543 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
545 return @derived_classes;
551 return @{ mro::get_linear_isa( (shift)->name ) };
554 sub class_precedence_list {
556 my $name = $self->name;
558 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
560 # We need to check for circular inheritance here
561 # if we are are not on 5.10, cause 5.8 detects it
562 # late. This will do nothing if all is well, and
563 # blow up otherwise. Yes, it's an ugly hack, better
564 # suggestions are welcome.
566 ($name || return)->isa('This is a test for circular inheritance')
569 # if our mro is c3, we can
570 # just grab the linear_isa
571 if (mro::get_mro($name) eq 'c3') {
572 return @{ mro::get_linear_isa($name) }
576 # we can't grab the linear_isa for dfs
577 # since it has all the duplicates
582 $self->initialize($_)->class_precedence_list()
583 } $self->superclasses()
590 sub wrap_method_body {
591 my ( $self, %args ) = @_;
593 my $body = delete $args{body}; # delete is for compat
595 ('CODE' eq ref($body))
596 || confess "Your code block must be a CODE reference";
598 $self->method_metaclass->wrap( $body => (
599 package_name => $self->name,
605 my ($self, $method_name, $method) = @_;
606 (defined $method_name && $method_name)
607 || confess "You must define a method name";
610 if (blessed($method)) {
611 $body = $method->body;
612 if ($method->package_name ne $self->name &&
613 $method->name ne $method_name) {
614 warn "Hello there, got something for you."
615 . " Method says " . $method->package_name . " " . $method->name
616 . " Class says " . $self->name . " " . $method_name;
617 $method = $method->clone(
618 package_name => $self->name,
620 ) if $method->can('clone');
625 $method = $self->wrap_method_body( body => $body, name => $method_name );
628 $method->attach_to_class($self);
630 $self->get_method_map->{$method_name} = $method;
632 my $full_method_name = ($self->name . '::' . $method_name);
633 $self->add_package_symbol(
634 { sigil => '&', type => 'CODE', name => $method_name },
635 Class::MOP::subname($full_method_name => $body)
638 $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
642 my $fetch_and_prepare_method = sub {
643 my ($self, $method_name) = @_;
645 my $method = $self->get_method($method_name);
646 # if we dont have local ...
648 # try to find the next method
649 $method = $self->find_next_method_by_name($method_name);
650 # die if it does not exist
652 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
653 # and now make sure to wrap it
654 # even if it is already wrapped
655 # because we need a new sub ref
656 $method = Class::MOP::Method::Wrapped->wrap($method);
659 # now make sure we wrap it properly
660 $method = Class::MOP::Method::Wrapped->wrap($method)
661 unless $method->isa('Class::MOP::Method::Wrapped');
663 $self->add_method($method_name => $method);
667 sub add_before_method_modifier {
668 my ($self, $method_name, $method_modifier) = @_;
669 (defined $method_name && $method_name)
670 || confess "You must pass in a method name";
671 my $method = $fetch_and_prepare_method->($self, $method_name);
672 $method->add_before_modifier(
673 Class::MOP::subname(':before' => $method_modifier)
677 sub add_after_method_modifier {
678 my ($self, $method_name, $method_modifier) = @_;
679 (defined $method_name && $method_name)
680 || confess "You must pass in a method name";
681 my $method = $fetch_and_prepare_method->($self, $method_name);
682 $method->add_after_modifier(
683 Class::MOP::subname(':after' => $method_modifier)
687 sub add_around_method_modifier {
688 my ($self, $method_name, $method_modifier) = @_;
689 (defined $method_name && $method_name)
690 || confess "You must pass in a method name";
691 my $method = $fetch_and_prepare_method->($self, $method_name);
692 $method->add_around_modifier(
693 Class::MOP::subname(':around' => $method_modifier)
698 # the methods above used to be named like this:
699 # ${pkg}::${method}:(before|after|around)
700 # but this proved problematic when using one modifier
701 # to wrap multiple methods (something which is likely
702 # to happen pretty regularly IMO). So instead of naming
703 # it like this, I have chosen to just name them purely
704 # with their modifier names, like so:
705 # :(before|after|around)
706 # The fact is that in a stack trace, it will be fairly
707 # evident from the context what method they are attached
708 # to, and so don't need the fully qualified name.
712 my ($self, $method_name, $method) = @_;
713 (defined $method_name && $method_name)
714 || confess "You must define a method name";
716 my $body = (blessed($method) ? $method->body : $method);
717 ('CODE' eq ref($body))
718 || confess "Your code block must be a CODE reference";
720 $self->add_package_symbol(
721 { sigil => '&', type => 'CODE', name => $method_name } => $body
726 my ($self, $method_name) = @_;
727 (defined $method_name && $method_name)
728 || confess "You must define a method name";
730 exists $self->get_method_map->{$method_name};
734 my ($self, $method_name) = @_;
735 (defined $method_name && $method_name)
736 || confess "You must define a method name";
739 # I don't really need this here, because
740 # if the method_map is missing a key it
741 # will just return undef for me now
742 # return unless $self->has_method($method_name);
744 return $self->get_method_map->{$method_name};
748 my ($self, $method_name) = @_;
749 (defined $method_name && $method_name)
750 || confess "You must define a method name";
752 my $removed_method = delete $self->get_method_map->{$method_name};
754 $self->remove_package_symbol(
755 { sigil => '&', type => 'CODE', name => $method_name }
758 $removed_method->detach_from_class if $removed_method;
760 $self->update_package_cache_flag; # still valid, since we just removed the method from the map
762 return $removed_method;
765 sub get_method_list {
767 keys %{$self->get_method_map};
770 sub find_method_by_name {
771 my ($self, $method_name) = @_;
772 (defined $method_name && $method_name)
773 || confess "You must define a method name to find";
774 foreach my $class ($self->linearized_isa) {
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);
783 sub get_all_methods {
785 my %methods = map { %{ $self->initialize($_)->get_method_map } } reverse $self->linearized_isa;
786 return values %methods;
790 sub compute_all_applicable_methods {
794 class => $_->package_name,
795 code => $_, # sigh, overloading
797 } shift->get_all_methods(@_);
800 sub find_all_methods_by_name {
801 my ($self, $method_name) = @_;
802 (defined $method_name && $method_name)
803 || confess "You must define a method name to find";
805 foreach my $class ($self->linearized_isa) {
806 # fetch the meta-class ...
807 my $meta = $self->initialize($class);
809 name => $method_name,
811 code => $meta->get_method($method_name)
812 } if $meta->has_method($method_name);
817 sub find_next_method_by_name {
818 my ($self, $method_name) = @_;
819 (defined $method_name && $method_name)
820 || confess "You must define a method name to find";
821 my @cpl = $self->linearized_isa;
822 shift @cpl; # discard ourselves
823 foreach my $class (@cpl) {
824 # fetch the meta-class ...
825 my $meta = $self->initialize($class);
826 return $meta->get_method($method_name)
827 if $meta->has_method($method_name);
836 # either we have an attribute object already
837 # or we need to create one from the args provided
838 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
839 # make sure it is derived from the correct type though
840 ($attribute->isa('Class::MOP::Attribute'))
841 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
843 # first we attach our new attribute
844 # because it might need certain information
845 # about the class which it is attached to
846 $attribute->attach_to_class($self);
848 # then we remove attributes of a conflicting
849 # name here so that we can properly detach
850 # the old attr object, and remove any
851 # accessors it would have generated
852 if ( $self->has_attribute($attribute->name) ) {
853 $self->remove_attribute($attribute->name);
855 $self->invalidate_meta_instances();
858 # then onto installing the new accessors
859 $self->get_attribute_map->{$attribute->name} = $attribute;
861 # invalidate package flag here
862 my $e = do { local $@; eval { $attribute->install_accessors() }; $@ };
864 $self->remove_attribute($attribute->name);
871 sub update_meta_instance_dependencies {
874 if ( $self->{meta_instance_dependencies} ) {
875 return $self->add_meta_instance_dependencies;
879 sub add_meta_instance_dependencies {
882 $self->remove_meta_instance_depdendencies;
884 my @attrs = $self->compute_all_applicable_attributes();
887 my @classes = grep { not $seen{$_->name}++ } map { $_->associated_class } @attrs;
889 foreach my $class ( @classes ) {
890 $class->add_dependent_meta_instance($self);
893 $self->{meta_instance_dependencies} = \@classes;
896 sub remove_meta_instance_depdendencies {
899 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
900 foreach my $class ( @$classes ) {
901 $class->remove_dependent_meta_instance($self);
911 sub add_dependent_meta_instance {
912 my ( $self, $metaclass ) = @_;
913 push @{ $self->{dependent_meta_instances} }, $metaclass;
916 sub remove_dependent_meta_instance {
917 my ( $self, $metaclass ) = @_;
918 my $name = $metaclass->name;
919 @$_ = grep { $_->name ne $name } @$_ for $self->{dependent_meta_instances};
922 sub invalidate_meta_instances {
924 $_->invalidate_meta_instance() for $self, @{ $self->{dependent_meta_instances} };
927 sub invalidate_meta_instance {
929 undef $self->{_meta_instance};
933 my ($self, $attribute_name) = @_;
934 (defined $attribute_name && $attribute_name)
935 || confess "You must define an attribute name";
936 exists $self->get_attribute_map->{$attribute_name};
940 my ($self, $attribute_name) = @_;
941 (defined $attribute_name && $attribute_name)
942 || confess "You must define an attribute name";
943 return $self->get_attribute_map->{$attribute_name}
945 # this will return undef anyway, so no need ...
946 # if $self->has_attribute($attribute_name);
950 sub remove_attribute {
951 my ($self, $attribute_name) = @_;
952 (defined $attribute_name && $attribute_name)
953 || confess "You must define an attribute name";
954 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
955 return unless defined $removed_attribute;
956 delete $self->get_attribute_map->{$attribute_name};
957 $self->invalidate_meta_instances();
958 $removed_attribute->remove_accessors();
959 $removed_attribute->detach_from_class();
960 return $removed_attribute;
963 sub get_attribute_list {
965 keys %{$self->get_attribute_map};
968 sub get_all_attributes {
969 shift->compute_all_applicable_attributes(@_);
972 sub compute_all_applicable_attributes {
974 my %attrs = map { %{ $self->initialize($_)->get_attribute_map } } reverse $self->linearized_isa;
975 return values %attrs;
978 sub find_attribute_by_name {
979 my ($self, $attr_name) = @_;
980 foreach my $class ($self->linearized_isa) {
981 # fetch the meta-class ...
982 my $meta = $self->initialize($class);
983 return $meta->get_attribute($attr_name)
984 if $meta->has_attribute($attr_name);
989 # check if we can reinitialize
993 # if any local attr is defined
994 return if $self->get_attribute_list;
996 # or any non-declared methods
997 if ( my @methods = values %{ $self->get_method_map } ) {
998 my $metaclass = $self->method_metaclass;
999 foreach my $method ( @methods ) {
1000 return if $method->isa("Class::MOP::Method::Generated");
1001 # FIXME do we need to enforce this too? return unless $method->isa($metaclass);
1010 sub is_mutable { 1 }
1011 sub is_immutable { 0 }
1014 # Why I changed this (groditi)
1015 # - One Metaclass may have many Classes through many Metaclass instances
1016 # - One Metaclass should only have one Immutable Transformer instance
1017 # - Each Class may have different Immutabilizing options
1018 # - Therefore each Metaclass instance may have different Immutabilizing options
1019 # - We need to store one Immutable Transformer instance per Metaclass
1020 # - We need to store one set of Immutable Transformer options per Class
1021 # - Upon make_mutable we may delete the Immutabilizing options
1022 # - We could clean the immutable Transformer instance when there is no more
1023 # immutable Classes of that type, but we can also keep it in case
1024 # another class with this same Metaclass becomes immutable. It is a case
1025 # of trading of storing an instance to avoid unnecessary instantiations of
1026 # Immutable Transformers. You may view this as a memory leak, however
1027 # Because we have few Metaclasses, in practice it seems acceptable
1028 # - To allow Immutable Transformers instances to be cleaned up we could weaken
1029 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
1033 my %IMMUTABLE_TRANSFORMERS;
1034 my %IMMUTABLE_OPTIONS;
1036 sub get_immutable_options {
1038 return if $self->is_mutable;
1039 confess "unable to find immutabilizing options"
1040 unless exists $IMMUTABLE_OPTIONS{$self->name};
1041 my %options = %{$IMMUTABLE_OPTIONS{$self->name}};
1042 delete $options{IMMUTABLE_TRANSFORMER};
1046 sub get_immutable_transformer {
1048 if( $self->is_mutable ){
1049 my $class = ref $self || $self;
1050 return $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
1052 confess "unable to find transformer for immutable class"
1053 unless exists $IMMUTABLE_OPTIONS{$self->name};
1054 return $IMMUTABLE_OPTIONS{$self->name}->{IMMUTABLE_TRANSFORMER};
1057 sub make_immutable {
1061 my $transformer = $self->get_immutable_transformer;
1062 $transformer->make_metaclass_immutable($self, \%options);
1063 $IMMUTABLE_OPTIONS{$self->name} =
1064 { %options, IMMUTABLE_TRANSFORMER => $transformer };
1066 if( exists $options{debug} && $options{debug} ){
1067 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
1068 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
1076 return if $self->is_mutable;
1077 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
1078 confess "unable to find immutabilizing options" unless ref $options;
1079 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
1080 $transformer->make_metaclass_mutable($self, $options);
1085 sub create_immutable_transformer {
1087 my $class = Class::MOP::Immutable->new($self, {
1088 read_only => [qw/superclasses/],
1095 remove_package_symbol
1098 class_precedence_list => 'ARRAY',
1099 linearized_isa => 'ARRAY', # FIXME perl 5.10 memoizes this on its own, no need?
1100 get_all_methods => 'ARRAY',
1101 #get_all_attributes => 'ARRAY', # it's an alias, no need, but maybe in the future
1102 compute_all_applicable_attributes => 'ARRAY',
1103 get_meta_instance => 'SCALAR',
1104 get_method_map => 'SCALAR',
1107 # this is ugly, but so are typeglobs,
1108 # so whattayahgonnadoboutit
1111 add_package_symbol => sub {
1112 my $original = shift;
1113 confess "Cannot add package symbols to an immutable metaclass"
1114 unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
1115 goto $original->body;
1130 Class::MOP::Class - Class Meta Object
1134 # assuming that class Foo
1135 # has been defined, you can
1137 # use this for introspection ...
1139 # add a method to Foo ...
1140 Foo->meta->add_method('bar' => sub { ... })
1142 # get a list of all the classes searched
1143 # the method dispatcher in the correct order
1144 Foo->meta->class_precedence_list()
1146 # remove a method from Foo
1147 Foo->meta->remove_method('bar');
1149 # or use this to actually create classes ...
1151 Class::MOP::Class->create('Bar' => (
1153 superclasses => [ 'Foo' ],
1155 Class::MOP:::Attribute->new('$bar'),
1156 Class::MOP:::Attribute->new('$baz'),
1159 calculate_bar => sub { ... },
1160 construct_baz => sub { ... }
1166 This is the largest and currently most complex part of the Perl 5
1167 meta-object protocol. It controls the introspection and
1168 manipulation of Perl 5 classes (and it can create them too). The
1169 best way to understand what this module can do, is to read the
1170 documentation for each of it's methods.
1174 =head2 Self Introspection
1180 This will return a B<Class::MOP::Class> instance which is related
1181 to this class. Thereby allowing B<Class::MOP::Class> to actually
1184 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
1185 bootstrap this module by installing a number of attribute meta-objects
1186 into it's metaclass. This will allow this class to reap all the benifits
1187 of the MOP when subclassing it.
1191 =head2 Class construction
1193 These methods will handle creating B<Class::MOP::Class> objects,
1194 which can be used to both create new classes, and analyze
1195 pre-existing classes.
1197 This module will internally store references to all the instances
1198 you create with these methods, so that they do not need to be
1199 created any more than nessecary. Basically, they are singletons.
1203 =item B<create ($package_name,
1204 version =E<gt> ?$version,
1205 authority =E<gt> ?$authority,
1206 superclasses =E<gt> ?@superclasses,
1207 methods =E<gt> ?%methods,
1208 attributes =E<gt> ?%attributes)>
1210 This returns a B<Class::MOP::Class> object, bringing the specified
1211 C<$package_name> into existence and adding any of the C<$version>,
1212 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1215 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1216 methods =E<gt> ?%methods,
1217 attributes =E<gt> ?%attributes)>
1219 This will create an anonymous class, it works much like C<create> but
1220 it does not need a C<$package_name>. Instead it will create a suitably
1221 unique package name for you to stash things into.
1223 On very important distinction is that anon classes are destroyed once
1224 the metaclass they are attached to goes out of scope. In the DESTROY
1225 method, the created package will be removed from the symbol table.
1227 It is also worth noting that any instances created with an anon-class
1228 will keep a special reference to the anon-meta which will prevent the
1229 anon-class from going out of scope until all instances of it have also
1230 been destroyed. This however only works for HASH based instance types,
1231 as we use a special reserved slot (C<__MOP__>) to store this.
1233 =item B<initialize ($package_name, %options)>
1235 This initializes and returns returns a B<Class::MOP::Class> object
1236 for a given a C<$package_name>.
1238 =item B<construct_class_instance (%options)>
1240 This will construct an instance of B<Class::MOP::Class>, it is
1241 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1242 to use C<construct_instance> once all the bootstrapping is done. This
1243 method is used internally by C<initialize> and should never be called
1244 from outside of that method really.
1246 =item B<check_metaclass_compatability>
1248 This method is called as the very last thing in the
1249 C<construct_class_instance> method. This will check that the
1250 metaclass you are creating is compatible with the metaclasses of all
1251 your ancestors. For more inforamtion about metaclass compatibility
1252 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1254 =item B<update_package_cache_flag>
1256 This will reset the package cache flag for this particular metaclass
1257 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1258 function. This is very rarely needed from outside of C<Class::MOP::Class>
1259 but in some cases you might want to use it, so it is here.
1261 =item B<reset_package_cache_flag>
1263 Clears the package cache flag to announce to the internals that we need
1264 to rebuild the method map.
1266 =item B<add_meta_instance_dependencies>
1268 Registers this class as dependent on its superclasses.
1270 Only superclasses from which this class inherits attributes will be added.
1272 =item B<remove_meta_instance_depdendencies>
1274 Unregisters this class from its superclasses.
1276 =item B<update_meta_instance_dependencies>
1278 Reregisters if necessary.
1280 =item B<add_dependent_meta_instance> $metaclass
1282 Registers the class as having a meta instance dependent on this class.
1284 =item B<remove_dependent_meta_instance> $metaclass
1286 Remove the class from the list of dependent classes.
1288 =item B<invalidate_meta_instances>
1290 Clears the cached meta instance for this metaclass and all of the registered
1291 classes with dependent meta instances.
1293 Called by C<add_attribute> and C<remove_attribute> to recalculate the attribute
1296 =item B<invalidate_meta_instance>
1298 Used by C<invalidate_meta_instances>.
1302 =head2 Object instance construction and cloning
1304 These methods are B<entirely optional>, it is up to you whether you want
1309 =item B<instance_metaclass>
1311 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1312 for more information on the instance metaclasses.
1314 =item B<get_meta_instance>
1316 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1317 of a new instance of the class.
1319 =item B<create_meta_instance>
1321 Called by C<get_meta_instance> if necessary.
1323 =item B<new_object (%params)>
1325 This is a convience method for creating a new object of the class, and
1326 blessing it into the appropriate package as well. Ideally your class
1327 would call a C<new> this method like so:
1330 my ($class, %param) = @_;
1331 $class->meta->new_object(%params);
1334 =item B<construct_instance (%params)>
1336 This method is used to construct an instance structure suitable for
1337 C<bless>-ing into your package of choice. It works in conjunction
1338 with the Attribute protocol to collect all applicable attributes.
1340 This will construct and instance using a HASH ref as storage
1341 (currently only HASH references are supported). This will collect all
1342 the applicable attributes and layout out the fields in the HASH ref,
1343 it will then initialize them using either use the corresponding key
1344 in C<%params> or any default value or initializer found in the
1345 attribute meta-object.
1347 =item B<clone_object ($instance, %params)>
1349 This is a convience method for cloning an object instance, then
1350 blessing it into the appropriate package. This method will call
1351 C<clone_instance>, which performs a shallow copy of the object,
1352 see that methods documentation for more details. Ideally your
1353 class would call a C<clone> this method like so:
1355 sub MyClass::clone {
1356 my ($self, %param) = @_;
1357 $self->meta->clone_object($self, %params);
1360 =item B<clone_instance($instance, %params)>
1362 This method is a compliment of C<construct_instance> (which means if
1363 you override C<construct_instance>, you need to override this one too),
1364 and clones the instance shallowly.
1366 The cloned structure returned is (like with C<construct_instance>) an
1367 unC<bless>ed HASH reference, it is your responsibility to then bless
1368 this cloned structure into the right class (which C<clone_object> will
1371 As of 0.11, this method will clone the C<$instance> structure shallowly,
1372 as opposed to the deep cloning implemented in prior versions. After much
1373 thought, research and discussion, I have decided that anything but basic
1374 shallow cloning is outside the scope of the meta-object protocol. I
1375 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1376 is too I<context-specific> to be part of the MOP.
1378 =item B<rebless_instance($instance, ?%params)>
1380 This will change the class of C<$instance> to the class of the invoking
1381 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1382 itself. You may pass in optional C<%params> which are like constructor
1383 params and will override anything already defined in the instance.
1387 =head2 Informational
1389 These are a few predicate methods for asking information about the class.
1393 =item B<is_anon_class>
1395 This returns true if the class is a C<Class::MOP::Class> created anon class.
1399 This returns true if the class is still mutable.
1401 =item B<is_immutable>
1403 This returns true if the class has been made immutable.
1405 =item B<is_pristine>
1407 Checks whether the class has any data that will be lost if C<reinitialize> is
1412 =head2 Inheritance Relationships
1416 =item B<superclasses (?@superclasses)>
1418 This is a read-write attribute which represents the superclass
1419 relationships of the class the B<Class::MOP::Class> instance is
1420 associated with. Basically, it can get and set the C<@ISA> for you.
1422 =item B<class_precedence_list>
1424 This computes the a list of all the class's ancestors in the same order
1425 in which method dispatch will be done. This is similair to what
1426 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1428 =item B<linearized_isa>
1430 This returns a list based on C<class_precedence_list> but with all
1435 This returns a list of subclasses for this class.
1443 =item B<get_method_map>
1445 Returns a HASH ref of name to CODE reference mapping for this class.
1447 =item B<method_metaclass>
1449 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1450 for more information on the method metaclasses.
1452 =item B<wrap_method_body(%attrs)>
1454 Wrap a code ref (C<$attrs{body>) with C<method_metaclass>.
1456 =item B<add_method ($method_name, $method, %attrs)>
1458 This will take a C<$method_name> and CODE reference to that
1459 C<$method> and install it into the class's package.
1462 This does absolutely nothing special to C<$method>
1463 other than use B<Sub::Name> to make sure it is tagged with the
1464 correct name, and therefore show up correctly in stack traces and
1467 =item B<alias_method ($method_name, $method)>
1469 This will take a C<$method_name> and CODE reference to that
1470 C<$method> and alias the method into the class's package.
1473 Unlike C<add_method>, this will B<not> try to name the
1474 C<$method> using B<Sub::Name>, it only aliases the method in
1475 the class's package.
1477 =item B<has_method ($method_name)>
1479 This just provides a simple way to check if the class implements
1480 a specific C<$method_name>. It will I<not> however, attempt to check
1481 if the class inherits the method (use C<UNIVERSAL::can> for that).
1483 This will correctly handle functions defined outside of the package
1484 that use a fully qualified name (C<sub Package::name { ... }>).
1486 This will correctly handle functions renamed with B<Sub::Name> and
1487 installed using the symbol tables. However, if you are naming the
1488 subroutine outside of the package scope, you must use the fully
1489 qualified name, including the package name, for C<has_method> to
1490 correctly identify it.
1492 This will attempt to correctly ignore functions imported from other
1493 packages using B<Exporter>. It breaks down if the function imported
1494 is an C<__ANON__> sub (such as with C<use constant>), which very well
1495 may be a valid method being applied to the class.
1497 In short, this method cannot always be trusted to determine if the
1498 C<$method_name> is actually a method. However, it will DWIM about
1499 90% of the time, so it's a small trade off I think.
1501 =item B<get_method ($method_name)>
1503 This will return a Class::MOP::Method instance related to the specified
1504 C<$method_name>, or return undef if that method does not exist.
1506 The Class::MOP::Method is codifiable, so you can use it like a normal
1507 CODE reference, see L<Class::MOP::Method> for more information.
1509 =item B<find_method_by_name ($method_name)>
1511 This will return a CODE reference of the specified C<$method_name>,
1512 or return undef if that method does not exist.
1514 Unlike C<get_method> this will also look in the superclasses.
1516 =item B<remove_method ($method_name)>
1518 This will attempt to remove a given C<$method_name> from the class.
1519 It will return the CODE reference that it has removed, and will
1520 attempt to use B<Sub::Name> to clear the methods associated name.
1522 =item B<get_method_list>
1524 This will return a list of method names for all I<locally> defined
1525 methods. It does B<not> provide a list of all applicable methods,
1526 including any inherited ones. If you want a list of all applicable
1527 methods, use the C<compute_all_applicable_methods> method.
1529 =item B<get_all_methods>
1531 This will traverse the inheritance heirachy and return a list of all
1532 the applicable L<Class::MOP::Method> objects for this class.
1534 =item B<compute_all_applicable_methods>
1538 This method returns a list of hashes describing the all the methods of the
1541 Use L<get_all_methods>, which is easier/better/faster. This method predates
1542 L<Class::MOP::Method>.
1544 =item B<find_all_methods_by_name ($method_name)>
1546 This will traverse the inheritence hierarchy and locate all methods
1547 with a given C<$method_name>. Similar to
1548 C<compute_all_applicable_methods> it returns a list of HASH references
1549 with the following information; method name (which will always be the
1550 same as C<$method_name>), the name of the class in which the method
1551 lives and a CODE reference for the actual method.
1553 The list of methods produced is a distinct list, meaning there are no
1554 duplicates in it. This is especially useful for things like object
1555 initialization and destruction where you only want the method called
1556 once, and in the correct order.
1558 =item B<find_next_method_by_name ($method_name)>
1560 This will return the first method to match a given C<$method_name> in
1561 the superclasses, this is basically equivalent to calling
1562 C<SUPER::$method_name>, but it can be dispatched at runtime.
1566 =head2 Method Modifiers
1568 Method modifiers are a concept borrowed from CLOS, in which a method
1569 can be wrapped with I<before>, I<after> and I<around> method modifiers
1570 that will be called everytime the method is called.
1572 =head3 How method modifiers work?
1574 Method modifiers work by wrapping the original method and then replacing
1575 it in the classes symbol table. The wrappers will handle calling all the
1576 modifiers in the appropariate orders and preserving the calling context
1577 for the original method.
1579 Each method modifier serves a particular purpose, which may not be
1580 obvious to users of other method wrapping modules. To start with, the
1581 return values of I<before> and I<after> modifiers are ignored. This is
1582 because thier purpose is B<not> to filter the input and output of the
1583 primary method (this is done with an I<around> modifier). This may seem
1584 like an odd restriction to some, but doing this allows for simple code
1585 to be added at the begining or end of a method call without jeapordizing
1586 the normal functioning of the primary method or placing any extra
1587 responsibility on the code of the modifier. Of course if you have more
1588 complex needs, then use the I<around> modifier, which uses a variation
1589 of continutation passing style to allow for a high degree of flexibility.
1591 Before and around modifiers are called in last-defined-first-called order,
1592 while after modifiers are called in first-defined-first-called order. So
1593 the call tree might looks something like this:
1603 To see examples of using method modifiers, see the following examples
1604 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1605 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1606 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1608 =head3 What is the performance impact?
1610 Of course there is a performance cost associated with method modifiers,
1611 but we have made every effort to make that cost be directly proportional
1612 to the amount of modifier features you utilize.
1614 The wrapping method does it's best to B<only> do as much work as it
1615 absolutely needs to. In order to do this we have moved some of the
1616 performance costs to set-up time, where they are easier to amortize.
1618 All this said, my benchmarks have indicated the following:
1620 simple wrapper with no modifiers 100% slower
1621 simple wrapper with simple before modifier 400% slower
1622 simple wrapper with simple after modifier 450% slower
1623 simple wrapper with simple around modifier 500-550% slower
1624 simple wrapper with all 3 modifiers 1100% slower
1626 These numbers may seem daunting, but you must remember, every feature
1627 comes with some cost. To put things in perspective, just doing a simple
1628 C<AUTOLOAD> which does nothing but extract the name of the method called
1629 and return it costs about 400% over a normal method call.
1633 =item B<add_before_method_modifier ($method_name, $code)>
1635 This will wrap the method at C<$method_name> and the supplied C<$code>
1636 will be passed the C<@_> arguments, and called before the original
1637 method is called. As specified above, the return value of the I<before>
1638 method modifiers is ignored, and it's ability to modify C<@_> is
1639 fairly limited. If you need to do either of these things, use an
1640 C<around> method modifier.
1642 =item B<add_after_method_modifier ($method_name, $code)>
1644 This will wrap the method at C<$method_name> so that the original
1645 method will be called, it's return values stashed, and then the
1646 supplied C<$code> will be passed the C<@_> arguments, and called.
1647 As specified above, the return value of the I<after> method
1648 modifiers is ignored, and it cannot modify the return values of
1649 the original method. If you need to do either of these things, use an
1650 C<around> method modifier.
1652 =item B<add_around_method_modifier ($method_name, $code)>
1654 This will wrap the method at C<$method_name> so that C<$code>
1655 will be called and passed the original method as an extra argument
1656 at the begining of the C<@_> argument list. This is a variation of
1657 continuation passing style, where the function prepended to C<@_>
1658 can be considered a continuation. It is up to C<$code> if it calls
1659 the original method or not, there is no restriction on what the
1660 C<$code> can or cannot do.
1666 It should be noted that since there is no one consistent way to define
1667 the attributes of a class in Perl 5. These methods can only work with
1668 the information given, and can not easily discover information on
1669 their own. See L<Class::MOP::Attribute> for more details.
1673 =item B<attribute_metaclass>
1675 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1676 for more information on the attribute metaclasses.
1678 =item B<get_attribute_map>
1680 This returns a HASH ref of name to attribute meta-object mapping.
1682 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1684 This stores the C<$attribute_meta_object> (or creates one from the
1685 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1686 instance associated with the given class. Unlike methods, attributes
1687 within the MOP are stored as meta-information only. They will be used
1688 later to construct instances from (see C<construct_instance> above).
1689 More details about the attribute meta-objects can be found in the
1690 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1693 It should be noted that any accessor, reader/writer or predicate
1694 methods which the C<$attribute_meta_object> has will be installed
1695 into the class at this time.
1698 If an attribute already exists for C<$attribute_name>, the old one
1699 will be removed (as well as removing all it's accessors), and then
1702 =item B<has_attribute ($attribute_name)>
1704 Checks to see if this class has an attribute by the name of
1705 C<$attribute_name> and returns a boolean.
1707 =item B<get_attribute ($attribute_name)>
1709 Returns the attribute meta-object associated with C<$attribute_name>,
1710 if none is found, it will return undef.
1712 =item B<remove_attribute ($attribute_name)>
1714 This will remove the attribute meta-object stored at
1715 C<$attribute_name>, then return the removed attribute meta-object.
1718 Removing an attribute will only affect future instances of
1719 the class, it will not make any attempt to remove the attribute from
1720 any existing instances of the class.
1722 It should be noted that any accessor, reader/writer or predicate
1723 methods which the attribute meta-object stored at C<$attribute_name>
1724 has will be removed from the class at this time. This B<will> make
1725 these attributes somewhat inaccessable in previously created
1726 instances. But if you are crazy enough to do this at runtime, then
1727 you are crazy enough to deal with something like this :).
1729 =item B<get_attribute_list>
1731 This returns a list of attribute names which are defined in the local
1732 class. If you want a list of all applicable attributes for a class,
1733 use the C<compute_all_applicable_attributes> method.
1735 =item B<compute_all_applicable_attributes>
1737 =item B<get_all_attributes>
1739 This will traverse the inheritance heirachy and return a list of all
1740 the applicable L<Class::MOP::Attribute> objects for this class.
1742 C<get_all_attributes> is an alias for consistency with C<get_all_methods>.
1744 =item B<find_attribute_by_name ($attr_name)>
1746 This method will traverse the inheritance heirachy and find the
1747 first attribute whose name matches C<$attr_name>, then return it.
1748 It will return undef if nothing is found.
1752 =head2 Class Immutability
1756 =item B<make_immutable (%options)>
1758 This method will invoke a tranforamtion upon the class which will
1759 make it immutable. Details of this transformation can be found in
1760 the L<Class::MOP::Immutable> documentation.
1762 =item B<make_mutable>
1764 This method will reverse tranforamtion upon the class which
1767 =item B<get_immutable_transformer>
1769 Return a transformer suitable for making this class immutable or, if this
1770 class is immutable, the transformer used to make it immutable.
1772 =item B<get_immutable_options>
1774 If the class is immutable, return the options used to make it immutable.
1776 =item B<create_immutable_transformer>
1778 Create a transformer suitable for making this class immutable
1784 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1786 =head1 COPYRIGHT AND LICENSE
1788 Copyright 2006-2008 by Infinity Interactive, Inc.
1790 L<http://www.iinteractive.com>
1792 This library is free software; you can redistribute it and/or modify
1793 it under the same terms as Perl itself.