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
724 $self->update_package_cache_flag; # the method map will not list aliased methods
728 my ($self, $method_name) = @_;
729 (defined $method_name && $method_name)
730 || confess "You must define a method name";
732 exists $self->get_method_map->{$method_name};
736 my ($self, $method_name) = @_;
737 (defined $method_name && $method_name)
738 || confess "You must define a method name";
741 # I don't really need this here, because
742 # if the method_map is missing a key it
743 # will just return undef for me now
744 # return unless $self->has_method($method_name);
746 return $self->get_method_map->{$method_name};
750 my ($self, $method_name) = @_;
751 (defined $method_name && $method_name)
752 || confess "You must define a method name";
754 my $removed_method = delete $self->get_method_map->{$method_name};
756 $self->remove_package_symbol(
757 { sigil => '&', type => 'CODE', name => $method_name }
760 $removed_method->detach_from_class if $removed_method;
762 $self->update_package_cache_flag; # still valid, since we just removed the method from the map
764 return $removed_method;
767 sub get_method_list {
769 keys %{$self->get_method_map};
772 sub find_method_by_name {
773 my ($self, $method_name) = @_;
774 (defined $method_name && $method_name)
775 || confess "You must define a method name to find";
776 foreach my $class ($self->linearized_isa) {
777 # fetch the meta-class ...
778 my $meta = $self->initialize($class);
779 return $meta->get_method($method_name)
780 if $meta->has_method($method_name);
785 sub get_all_methods {
787 my %methods = map { %{ $self->initialize($_)->get_method_map } } reverse $self->linearized_isa;
788 return values %methods;
792 sub compute_all_applicable_methods {
796 class => $_->package_name,
797 code => $_, # sigh, overloading
799 } shift->get_all_methods(@_);
802 sub find_all_methods_by_name {
803 my ($self, $method_name) = @_;
804 (defined $method_name && $method_name)
805 || confess "You must define a method name to find";
807 foreach my $class ($self->linearized_isa) {
808 # fetch the meta-class ...
809 my $meta = $self->initialize($class);
811 name => $method_name,
813 code => $meta->get_method($method_name)
814 } if $meta->has_method($method_name);
819 sub find_next_method_by_name {
820 my ($self, $method_name) = @_;
821 (defined $method_name && $method_name)
822 || confess "You must define a method name to find";
823 my @cpl = $self->linearized_isa;
824 shift @cpl; # discard ourselves
825 foreach my $class (@cpl) {
826 # fetch the meta-class ...
827 my $meta = $self->initialize($class);
828 return $meta->get_method($method_name)
829 if $meta->has_method($method_name);
838 # either we have an attribute object already
839 # or we need to create one from the args provided
840 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
841 # make sure it is derived from the correct type though
842 ($attribute->isa('Class::MOP::Attribute'))
843 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
845 # first we attach our new attribute
846 # because it might need certain information
847 # about the class which it is attached to
848 $attribute->attach_to_class($self);
850 # then we remove attributes of a conflicting
851 # name here so that we can properly detach
852 # the old attr object, and remove any
853 # accessors it would have generated
854 if ( $self->has_attribute($attribute->name) ) {
855 $self->remove_attribute($attribute->name);
857 $self->invalidate_meta_instances();
860 # then onto installing the new accessors
861 $self->get_attribute_map->{$attribute->name} = $attribute;
863 # invalidate package flag here
864 my $e = do { local $@; eval { $attribute->install_accessors() }; $@ };
866 $self->remove_attribute($attribute->name);
873 sub update_meta_instance_dependencies {
876 if ( $self->{meta_instance_dependencies} ) {
877 return $self->add_meta_instance_dependencies;
881 sub add_meta_instance_dependencies {
884 $self->remove_meta_instance_depdendencies;
886 my @attrs = $self->compute_all_applicable_attributes();
889 my @classes = grep { not $seen{$_->name}++ } map { $_->associated_class } @attrs;
891 foreach my $class ( @classes ) {
892 $class->add_dependent_meta_instance($self);
895 $self->{meta_instance_dependencies} = \@classes;
898 sub remove_meta_instance_depdendencies {
901 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
902 foreach my $class ( @$classes ) {
903 $class->remove_dependent_meta_instance($self);
913 sub add_dependent_meta_instance {
914 my ( $self, $metaclass ) = @_;
915 push @{ $self->{dependent_meta_instances} }, $metaclass;
918 sub remove_dependent_meta_instance {
919 my ( $self, $metaclass ) = @_;
920 my $name = $metaclass->name;
921 @$_ = grep { $_->name ne $name } @$_ for $self->{dependent_meta_instances};
924 sub invalidate_meta_instances {
926 $_->invalidate_meta_instance() for $self, @{ $self->{dependent_meta_instances} };
929 sub invalidate_meta_instance {
931 undef $self->{_meta_instance};
935 my ($self, $attribute_name) = @_;
936 (defined $attribute_name && $attribute_name)
937 || confess "You must define an attribute name";
938 exists $self->get_attribute_map->{$attribute_name};
942 my ($self, $attribute_name) = @_;
943 (defined $attribute_name && $attribute_name)
944 || confess "You must define an attribute name";
945 return $self->get_attribute_map->{$attribute_name}
947 # this will return undef anyway, so no need ...
948 # if $self->has_attribute($attribute_name);
952 sub remove_attribute {
953 my ($self, $attribute_name) = @_;
954 (defined $attribute_name && $attribute_name)
955 || confess "You must define an attribute name";
956 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
957 return unless defined $removed_attribute;
958 delete $self->get_attribute_map->{$attribute_name};
959 $self->invalidate_meta_instances();
960 $removed_attribute->remove_accessors();
961 $removed_attribute->detach_from_class();
962 return $removed_attribute;
965 sub get_attribute_list {
967 keys %{$self->get_attribute_map};
970 sub get_all_attributes {
971 shift->compute_all_applicable_attributes(@_);
974 sub compute_all_applicable_attributes {
976 my %attrs = map { %{ $self->initialize($_)->get_attribute_map } } reverse $self->linearized_isa;
977 return values %attrs;
980 sub find_attribute_by_name {
981 my ($self, $attr_name) = @_;
982 foreach my $class ($self->linearized_isa) {
983 # fetch the meta-class ...
984 my $meta = $self->initialize($class);
985 return $meta->get_attribute($attr_name)
986 if $meta->has_attribute($attr_name);
991 # check if we can reinitialize
995 # if any local attr is defined
996 return if $self->get_attribute_list;
998 # or any non-declared methods
999 if ( my @methods = values %{ $self->get_method_map } ) {
1000 my $metaclass = $self->method_metaclass;
1001 foreach my $method ( @methods ) {
1002 return if $method->isa("Class::MOP::Method::Generated");
1003 # FIXME do we need to enforce this too? return unless $method->isa($metaclass);
1012 sub is_mutable { 1 }
1013 sub is_immutable { 0 }
1016 # Why I changed this (groditi)
1017 # - One Metaclass may have many Classes through many Metaclass instances
1018 # - One Metaclass should only have one Immutable Transformer instance
1019 # - Each Class may have different Immutabilizing options
1020 # - Therefore each Metaclass instance may have different Immutabilizing options
1021 # - We need to store one Immutable Transformer instance per Metaclass
1022 # - We need to store one set of Immutable Transformer options per Class
1023 # - Upon make_mutable we may delete the Immutabilizing options
1024 # - We could clean the immutable Transformer instance when there is no more
1025 # immutable Classes of that type, but we can also keep it in case
1026 # another class with this same Metaclass becomes immutable. It is a case
1027 # of trading of storing an instance to avoid unnecessary instantiations of
1028 # Immutable Transformers. You may view this as a memory leak, however
1029 # Because we have few Metaclasses, in practice it seems acceptable
1030 # - To allow Immutable Transformers instances to be cleaned up we could weaken
1031 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
1035 my %IMMUTABLE_TRANSFORMERS;
1036 my %IMMUTABLE_OPTIONS;
1038 sub get_immutable_options {
1040 return if $self->is_mutable;
1041 confess "unable to find immutabilizing options"
1042 unless exists $IMMUTABLE_OPTIONS{$self->name};
1043 my %options = %{$IMMUTABLE_OPTIONS{$self->name}};
1044 delete $options{IMMUTABLE_TRANSFORMER};
1048 sub get_immutable_transformer {
1050 if( $self->is_mutable ){
1051 my $class = ref $self || $self;
1052 return $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
1054 confess "unable to find transformer for immutable class"
1055 unless exists $IMMUTABLE_OPTIONS{$self->name};
1056 return $IMMUTABLE_OPTIONS{$self->name}->{IMMUTABLE_TRANSFORMER};
1059 sub make_immutable {
1063 my $transformer = $self->get_immutable_transformer;
1064 $transformer->make_metaclass_immutable($self, \%options);
1065 $IMMUTABLE_OPTIONS{$self->name} =
1066 { %options, IMMUTABLE_TRANSFORMER => $transformer };
1068 if( exists $options{debug} && $options{debug} ){
1069 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
1070 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
1078 return if $self->is_mutable;
1079 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
1080 confess "unable to find immutabilizing options" unless ref $options;
1081 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
1082 $transformer->make_metaclass_mutable($self, $options);
1087 sub create_immutable_transformer {
1089 my $class = Class::MOP::Immutable->new($self, {
1090 read_only => [qw/superclasses/],
1097 remove_package_symbol
1100 class_precedence_list => 'ARRAY',
1101 linearized_isa => 'ARRAY', # FIXME perl 5.10 memoizes this on its own, no need?
1102 get_all_methods => 'ARRAY',
1103 #get_all_attributes => 'ARRAY', # it's an alias, no need, but maybe in the future
1104 compute_all_applicable_attributes => 'ARRAY',
1105 get_meta_instance => 'SCALAR',
1106 get_method_map => 'SCALAR',
1109 # this is ugly, but so are typeglobs,
1110 # so whattayahgonnadoboutit
1113 add_package_symbol => sub {
1114 my $original = shift;
1115 confess "Cannot add package symbols to an immutable metaclass"
1116 unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
1117 goto $original->body;
1132 Class::MOP::Class - Class Meta Object
1136 # assuming that class Foo
1137 # has been defined, you can
1139 # use this for introspection ...
1141 # add a method to Foo ...
1142 Foo->meta->add_method('bar' => sub { ... })
1144 # get a list of all the classes searched
1145 # the method dispatcher in the correct order
1146 Foo->meta->class_precedence_list()
1148 # remove a method from Foo
1149 Foo->meta->remove_method('bar');
1151 # or use this to actually create classes ...
1153 Class::MOP::Class->create('Bar' => (
1155 superclasses => [ 'Foo' ],
1157 Class::MOP:::Attribute->new('$bar'),
1158 Class::MOP:::Attribute->new('$baz'),
1161 calculate_bar => sub { ... },
1162 construct_baz => sub { ... }
1168 This is the largest and currently most complex part of the Perl 5
1169 meta-object protocol. It controls the introspection and
1170 manipulation of Perl 5 classes (and it can create them too). The
1171 best way to understand what this module can do, is to read the
1172 documentation for each of it's methods.
1176 =head2 Self Introspection
1182 This will return a B<Class::MOP::Class> instance which is related
1183 to this class. Thereby allowing B<Class::MOP::Class> to actually
1186 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
1187 bootstrap this module by installing a number of attribute meta-objects
1188 into it's metaclass. This will allow this class to reap all the benifits
1189 of the MOP when subclassing it.
1193 =head2 Class construction
1195 These methods will handle creating B<Class::MOP::Class> objects,
1196 which can be used to both create new classes, and analyze
1197 pre-existing classes.
1199 This module will internally store references to all the instances
1200 you create with these methods, so that they do not need to be
1201 created any more than nessecary. Basically, they are singletons.
1205 =item B<create ($package_name,
1206 version =E<gt> ?$version,
1207 authority =E<gt> ?$authority,
1208 superclasses =E<gt> ?@superclasses,
1209 methods =E<gt> ?%methods,
1210 attributes =E<gt> ?%attributes)>
1212 This returns a B<Class::MOP::Class> object, bringing the specified
1213 C<$package_name> into existence and adding any of the C<$version>,
1214 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1217 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1218 methods =E<gt> ?%methods,
1219 attributes =E<gt> ?%attributes)>
1221 This will create an anonymous class, it works much like C<create> but
1222 it does not need a C<$package_name>. Instead it will create a suitably
1223 unique package name for you to stash things into.
1225 On very important distinction is that anon classes are destroyed once
1226 the metaclass they are attached to goes out of scope. In the DESTROY
1227 method, the created package will be removed from the symbol table.
1229 It is also worth noting that any instances created with an anon-class
1230 will keep a special reference to the anon-meta which will prevent the
1231 anon-class from going out of scope until all instances of it have also
1232 been destroyed. This however only works for HASH based instance types,
1233 as we use a special reserved slot (C<__MOP__>) to store this.
1235 =item B<initialize ($package_name, %options)>
1237 This initializes and returns returns a B<Class::MOP::Class> object
1238 for a given a C<$package_name>.
1240 =item B<construct_class_instance (%options)>
1242 This will construct an instance of B<Class::MOP::Class>, it is
1243 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1244 to use C<construct_instance> once all the bootstrapping is done. This
1245 method is used internally by C<initialize> and should never be called
1246 from outside of that method really.
1248 =item B<check_metaclass_compatability>
1250 This method is called as the very last thing in the
1251 C<construct_class_instance> method. This will check that the
1252 metaclass you are creating is compatible with the metaclasses of all
1253 your ancestors. For more inforamtion about metaclass compatibility
1254 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1256 =item B<update_package_cache_flag>
1258 This will reset the package cache flag for this particular metaclass
1259 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1260 function. This is very rarely needed from outside of C<Class::MOP::Class>
1261 but in some cases you might want to use it, so it is here.
1263 =item B<reset_package_cache_flag>
1265 Clears the package cache flag to announce to the internals that we need
1266 to rebuild the method map.
1268 =item B<add_meta_instance_dependencies>
1270 Registers this class as dependent on its superclasses.
1272 Only superclasses from which this class inherits attributes will be added.
1274 =item B<remove_meta_instance_depdendencies>
1276 Unregisters this class from its superclasses.
1278 =item B<update_meta_instance_dependencies>
1280 Reregisters if necessary.
1282 =item B<add_dependent_meta_instance> $metaclass
1284 Registers the class as having a meta instance dependent on this class.
1286 =item B<remove_dependent_meta_instance> $metaclass
1288 Remove the class from the list of dependent classes.
1290 =item B<invalidate_meta_instances>
1292 Clears the cached meta instance for this metaclass and all of the registered
1293 classes with dependent meta instances.
1295 Called by C<add_attribute> and C<remove_attribute> to recalculate the attribute
1298 =item B<invalidate_meta_instance>
1300 Used by C<invalidate_meta_instances>.
1304 =head2 Object instance construction and cloning
1306 These methods are B<entirely optional>, it is up to you whether you want
1311 =item B<instance_metaclass>
1313 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1314 for more information on the instance metaclasses.
1316 =item B<get_meta_instance>
1318 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1319 of a new instance of the class.
1321 =item B<create_meta_instance>
1323 Called by C<get_meta_instance> if necessary.
1325 =item B<new_object (%params)>
1327 This is a convience method for creating a new object of the class, and
1328 blessing it into the appropriate package as well. Ideally your class
1329 would call a C<new> this method like so:
1332 my ($class, %param) = @_;
1333 $class->meta->new_object(%params);
1336 =item B<construct_instance (%params)>
1338 This method is used to construct an instance structure suitable for
1339 C<bless>-ing into your package of choice. It works in conjunction
1340 with the Attribute protocol to collect all applicable attributes.
1342 This will construct and instance using a HASH ref as storage
1343 (currently only HASH references are supported). This will collect all
1344 the applicable attributes and layout out the fields in the HASH ref,
1345 it will then initialize them using either use the corresponding key
1346 in C<%params> or any default value or initializer found in the
1347 attribute meta-object.
1349 =item B<clone_object ($instance, %params)>
1351 This is a convience method for cloning an object instance, then
1352 blessing it into the appropriate package. This method will call
1353 C<clone_instance>, which performs a shallow copy of the object,
1354 see that methods documentation for more details. Ideally your
1355 class would call a C<clone> this method like so:
1357 sub MyClass::clone {
1358 my ($self, %param) = @_;
1359 $self->meta->clone_object($self, %params);
1362 =item B<clone_instance($instance, %params)>
1364 This method is a compliment of C<construct_instance> (which means if
1365 you override C<construct_instance>, you need to override this one too),
1366 and clones the instance shallowly.
1368 The cloned structure returned is (like with C<construct_instance>) an
1369 unC<bless>ed HASH reference, it is your responsibility to then bless
1370 this cloned structure into the right class (which C<clone_object> will
1373 As of 0.11, this method will clone the C<$instance> structure shallowly,
1374 as opposed to the deep cloning implemented in prior versions. After much
1375 thought, research and discussion, I have decided that anything but basic
1376 shallow cloning is outside the scope of the meta-object protocol. I
1377 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1378 is too I<context-specific> to be part of the MOP.
1380 =item B<rebless_instance($instance, ?%params)>
1382 This will change the class of C<$instance> to the class of the invoking
1383 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1384 itself. You may pass in optional C<%params> which are like constructor
1385 params and will override anything already defined in the instance.
1389 =head2 Informational
1391 These are a few predicate methods for asking information about the class.
1395 =item B<is_anon_class>
1397 This returns true if the class is a C<Class::MOP::Class> created anon class.
1401 This returns true if the class is still mutable.
1403 =item B<is_immutable>
1405 This returns true if the class has been made immutable.
1407 =item B<is_pristine>
1409 Checks whether the class has any data that will be lost if C<reinitialize> is
1414 =head2 Inheritance Relationships
1418 =item B<superclasses (?@superclasses)>
1420 This is a read-write attribute which represents the superclass
1421 relationships of the class the B<Class::MOP::Class> instance is
1422 associated with. Basically, it can get and set the C<@ISA> for you.
1424 =item B<class_precedence_list>
1426 This computes the a list of all the class's ancestors in the same order
1427 in which method dispatch will be done. This is similair to what
1428 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1430 =item B<linearized_isa>
1432 This returns a list based on C<class_precedence_list> but with all
1437 This returns a list of subclasses for this class.
1445 =item B<get_method_map>
1447 Returns a HASH ref of name to CODE reference mapping for this class.
1449 =item B<method_metaclass>
1451 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1452 for more information on the method metaclasses.
1454 =item B<wrap_method_body(%attrs)>
1456 Wrap a code ref (C<$attrs{body>) with C<method_metaclass>.
1458 =item B<add_method ($method_name, $method, %attrs)>
1460 This will take a C<$method_name> and CODE reference to that
1461 C<$method> and install it into the class's package.
1464 This does absolutely nothing special to C<$method>
1465 other than use B<Sub::Name> to make sure it is tagged with the
1466 correct name, and therefore show up correctly in stack traces and
1469 =item B<alias_method ($method_name, $method)>
1471 This will take a C<$method_name> and CODE reference to that
1472 C<$method> and alias the method into the class's package.
1475 Unlike C<add_method>, this will B<not> try to name the
1476 C<$method> using B<Sub::Name>, it only aliases the method in
1477 the class's package.
1479 =item B<has_method ($method_name)>
1481 This just provides a simple way to check if the class implements
1482 a specific C<$method_name>. It will I<not> however, attempt to check
1483 if the class inherits the method (use C<UNIVERSAL::can> for that).
1485 This will correctly handle functions defined outside of the package
1486 that use a fully qualified name (C<sub Package::name { ... }>).
1488 This will correctly handle functions renamed with B<Sub::Name> and
1489 installed using the symbol tables. However, if you are naming the
1490 subroutine outside of the package scope, you must use the fully
1491 qualified name, including the package name, for C<has_method> to
1492 correctly identify it.
1494 This will attempt to correctly ignore functions imported from other
1495 packages using B<Exporter>. It breaks down if the function imported
1496 is an C<__ANON__> sub (such as with C<use constant>), which very well
1497 may be a valid method being applied to the class.
1499 In short, this method cannot always be trusted to determine if the
1500 C<$method_name> is actually a method. However, it will DWIM about
1501 90% of the time, so it's a small trade off I think.
1503 =item B<get_method ($method_name)>
1505 This will return a Class::MOP::Method instance related to the specified
1506 C<$method_name>, or return undef if that method does not exist.
1508 The Class::MOP::Method is codifiable, so you can use it like a normal
1509 CODE reference, see L<Class::MOP::Method> for more information.
1511 =item B<find_method_by_name ($method_name)>
1513 This will return a CODE reference of the specified C<$method_name>,
1514 or return undef if that method does not exist.
1516 Unlike C<get_method> this will also look in the superclasses.
1518 =item B<remove_method ($method_name)>
1520 This will attempt to remove a given C<$method_name> from the class.
1521 It will return the CODE reference that it has removed, and will
1522 attempt to use B<Sub::Name> to clear the methods associated name.
1524 =item B<get_method_list>
1526 This will return a list of method names for all I<locally> defined
1527 methods. It does B<not> provide a list of all applicable methods,
1528 including any inherited ones. If you want a list of all applicable
1529 methods, use the C<compute_all_applicable_methods> method.
1531 =item B<get_all_methods>
1533 This will traverse the inheritance heirachy and return a list of all
1534 the applicable L<Class::MOP::Method> objects for this class.
1536 =item B<compute_all_applicable_methods>
1540 This method returns a list of hashes describing the all the methods of the
1543 Use L<get_all_methods>, which is easier/better/faster. This method predates
1544 L<Class::MOP::Method>.
1546 =item B<find_all_methods_by_name ($method_name)>
1548 This will traverse the inheritence hierarchy and locate all methods
1549 with a given C<$method_name>. Similar to
1550 C<compute_all_applicable_methods> it returns a list of HASH references
1551 with the following information; method name (which will always be the
1552 same as C<$method_name>), the name of the class in which the method
1553 lives and a CODE reference for the actual method.
1555 The list of methods produced is a distinct list, meaning there are no
1556 duplicates in it. This is especially useful for things like object
1557 initialization and destruction where you only want the method called
1558 once, and in the correct order.
1560 =item B<find_next_method_by_name ($method_name)>
1562 This will return the first method to match a given C<$method_name> in
1563 the superclasses, this is basically equivalent to calling
1564 C<SUPER::$method_name>, but it can be dispatched at runtime.
1568 =head2 Method Modifiers
1570 Method modifiers are a concept borrowed from CLOS, in which a method
1571 can be wrapped with I<before>, I<after> and I<around> method modifiers
1572 that will be called everytime the method is called.
1574 =head3 How method modifiers work?
1576 Method modifiers work by wrapping the original method and then replacing
1577 it in the classes symbol table. The wrappers will handle calling all the
1578 modifiers in the appropariate orders and preserving the calling context
1579 for the original method.
1581 Each method modifier serves a particular purpose, which may not be
1582 obvious to users of other method wrapping modules. To start with, the
1583 return values of I<before> and I<after> modifiers are ignored. This is
1584 because thier purpose is B<not> to filter the input and output of the
1585 primary method (this is done with an I<around> modifier). This may seem
1586 like an odd restriction to some, but doing this allows for simple code
1587 to be added at the begining or end of a method call without jeapordizing
1588 the normal functioning of the primary method or placing any extra
1589 responsibility on the code of the modifier. Of course if you have more
1590 complex needs, then use the I<around> modifier, which uses a variation
1591 of continutation passing style to allow for a high degree of flexibility.
1593 Before and around modifiers are called in last-defined-first-called order,
1594 while after modifiers are called in first-defined-first-called order. So
1595 the call tree might looks something like this:
1605 To see examples of using method modifiers, see the following examples
1606 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1607 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1608 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1610 =head3 What is the performance impact?
1612 Of course there is a performance cost associated with method modifiers,
1613 but we have made every effort to make that cost be directly proportional
1614 to the amount of modifier features you utilize.
1616 The wrapping method does it's best to B<only> do as much work as it
1617 absolutely needs to. In order to do this we have moved some of the
1618 performance costs to set-up time, where they are easier to amortize.
1620 All this said, my benchmarks have indicated the following:
1622 simple wrapper with no modifiers 100% slower
1623 simple wrapper with simple before modifier 400% slower
1624 simple wrapper with simple after modifier 450% slower
1625 simple wrapper with simple around modifier 500-550% slower
1626 simple wrapper with all 3 modifiers 1100% slower
1628 These numbers may seem daunting, but you must remember, every feature
1629 comes with some cost. To put things in perspective, just doing a simple
1630 C<AUTOLOAD> which does nothing but extract the name of the method called
1631 and return it costs about 400% over a normal method call.
1635 =item B<add_before_method_modifier ($method_name, $code)>
1637 This will wrap the method at C<$method_name> and the supplied C<$code>
1638 will be passed the C<@_> arguments, and called before the original
1639 method is called. As specified above, the return value of the I<before>
1640 method modifiers is ignored, and it's ability to modify C<@_> is
1641 fairly limited. If you need to do either of these things, use an
1642 C<around> method modifier.
1644 =item B<add_after_method_modifier ($method_name, $code)>
1646 This will wrap the method at C<$method_name> so that the original
1647 method will be called, it's return values stashed, and then the
1648 supplied C<$code> will be passed the C<@_> arguments, and called.
1649 As specified above, the return value of the I<after> method
1650 modifiers is ignored, and it cannot modify the return values of
1651 the original method. If you need to do either of these things, use an
1652 C<around> method modifier.
1654 =item B<add_around_method_modifier ($method_name, $code)>
1656 This will wrap the method at C<$method_name> so that C<$code>
1657 will be called and passed the original method as an extra argument
1658 at the begining of the C<@_> argument list. This is a variation of
1659 continuation passing style, where the function prepended to C<@_>
1660 can be considered a continuation. It is up to C<$code> if it calls
1661 the original method or not, there is no restriction on what the
1662 C<$code> can or cannot do.
1668 It should be noted that since there is no one consistent way to define
1669 the attributes of a class in Perl 5. These methods can only work with
1670 the information given, and can not easily discover information on
1671 their own. See L<Class::MOP::Attribute> for more details.
1675 =item B<attribute_metaclass>
1677 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1678 for more information on the attribute metaclasses.
1680 =item B<get_attribute_map>
1682 This returns a HASH ref of name to attribute meta-object mapping.
1684 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1686 This stores the C<$attribute_meta_object> (or creates one from the
1687 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1688 instance associated with the given class. Unlike methods, attributes
1689 within the MOP are stored as meta-information only. They will be used
1690 later to construct instances from (see C<construct_instance> above).
1691 More details about the attribute meta-objects can be found in the
1692 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1695 It should be noted that any accessor, reader/writer or predicate
1696 methods which the C<$attribute_meta_object> has will be installed
1697 into the class at this time.
1700 If an attribute already exists for C<$attribute_name>, the old one
1701 will be removed (as well as removing all it's accessors), and then
1704 =item B<has_attribute ($attribute_name)>
1706 Checks to see if this class has an attribute by the name of
1707 C<$attribute_name> and returns a boolean.
1709 =item B<get_attribute ($attribute_name)>
1711 Returns the attribute meta-object associated with C<$attribute_name>,
1712 if none is found, it will return undef.
1714 =item B<remove_attribute ($attribute_name)>
1716 This will remove the attribute meta-object stored at
1717 C<$attribute_name>, then return the removed attribute meta-object.
1720 Removing an attribute will only affect future instances of
1721 the class, it will not make any attempt to remove the attribute from
1722 any existing instances of the class.
1724 It should be noted that any accessor, reader/writer or predicate
1725 methods which the attribute meta-object stored at C<$attribute_name>
1726 has will be removed from the class at this time. This B<will> make
1727 these attributes somewhat inaccessable in previously created
1728 instances. But if you are crazy enough to do this at runtime, then
1729 you are crazy enough to deal with something like this :).
1731 =item B<get_attribute_list>
1733 This returns a list of attribute names which are defined in the local
1734 class. If you want a list of all applicable attributes for a class,
1735 use the C<compute_all_applicable_attributes> method.
1737 =item B<compute_all_applicable_attributes>
1739 =item B<get_all_attributes>
1741 This will traverse the inheritance heirachy and return a list of all
1742 the applicable L<Class::MOP::Attribute> objects for this class.
1744 C<get_all_attributes> is an alias for consistency with C<get_all_methods>.
1746 =item B<find_attribute_by_name ($attr_name)>
1748 This method will traverse the inheritance heirachy and find the
1749 first attribute whose name matches C<$attr_name>, then return it.
1750 It will return undef if nothing is found.
1754 =head2 Class Immutability
1758 =item B<make_immutable (%options)>
1760 This method will invoke a tranforamtion upon the class which will
1761 make it immutable. Details of this transformation can be found in
1762 the L<Class::MOP::Immutable> documentation.
1764 =item B<make_mutable>
1766 This method will reverse tranforamtion upon the class which
1769 =item B<get_immutable_transformer>
1771 Return a transformer suitable for making this class immutable or, if this
1772 class is immutable, the transformer used to make it immutable.
1774 =item B<get_immutable_options>
1776 If the class is immutable, return the options used to make it immutable.
1778 =item B<create_immutable_transformer>
1780 Create a transformer suitable for making this class immutable
1786 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1788 =head1 COPYRIGHT AND LICENSE
1790 Copyright 2006-2008 by Infinity Interactive, Inc.
1792 L<http://www.iinteractive.com>
1794 This library is free software; you can redistribute it and/or modify
1795 it under the same terms as Perl itself.