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 = '0.64_01';
15 $VERSION = eval $VERSION;
16 our $AUTHORITY = 'cpan:STEVAN';
18 use base 'Class::MOP::Module';
28 $package_name = shift;
31 $package_name = $options{package};
34 (defined $package_name && $package_name && !ref($package_name))
35 || confess "You must pass a package name and it cannot be blessed";
37 return Class::MOP::get_metaclass_by_name($package_name)
38 || $class->construct_class_instance(package => $package_name, @_);
41 # NOTE: (meta-circularity)
42 # this is a special form of &construct_instance
43 # (see below), which is used to construct class
44 # meta-object instances for any Class::MOP::*
45 # class. All other classes will use the more
46 # normal &construct_instance.
47 sub construct_class_instance {
49 my $options = @_ == 1 ? $_[0] : {@_};
50 my $package_name = $options->{package};
51 (defined $package_name && $package_name)
52 || confess "You must pass a package name";
54 # return the metaclass if we have it cached,
55 # and it is still defined (it has not been
56 # reaped by DESTROY yet, which can happen
57 # annoyingly enough during global destruction)
59 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
64 # we need to deal with the possibility
65 # of class immutability here, and then
66 # get the name of the class appropriately
68 ? ($class->is_immutable
69 ? $class->get_mutable_metaclass_name()
73 # now create the metaclass
75 if ($class eq 'Class::MOP::Class') {
77 $meta = $class->_new($options)
81 # it is safe to use meta here because
82 # class will always be a subclass of
83 # Class::MOP::Class, which defines meta
84 $meta = $class->meta->construct_instance($options)
87 # and check the metaclass compatibility
88 $meta->check_metaclass_compatability();
90 Class::MOP::store_metaclass_by_name($package_name, $meta);
93 # we need to weaken any anon classes
94 # so that they can call DESTROY properly
95 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
102 my $options = @_ == 1 ? $_[0] : {@_};
105 # inherited from Class::MOP::Package
106 'package' => $options->{package},
109 # since the following attributes will
110 # actually be loaded from the symbol
111 # table, and actually bypass the instance
112 # entirely, we can just leave these things
113 # listed here for reference, because they
114 # should not actually have a value associated
116 'namespace' => \undef,
117 # inherited from Class::MOP::Module
119 'authority' => \undef,
120 # defined in Class::MOP::Class
121 'superclasses' => \undef,
125 'attribute_metaclass' => $options->{'attribute_metaclass'} || 'Class::MOP::Attribute',
126 'method_metaclass' => $options->{'method_metaclass'} || 'Class::MOP::Method',
127 'instance_metaclass' => $options->{'instance_metaclass'} || 'Class::MOP::Instance',
131 sub reset_package_cache_flag { (shift)->{'_package_cache_flag'} = undef }
132 sub update_package_cache_flag {
135 # we can manually update the cache number
136 # since we are actually adding the method
137 # to our cache as well. This avoids us
138 # having to regenerate the method_map.
140 $self->{'_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
143 sub check_metaclass_compatability {
146 # this is always okay ...
147 return if ref($self) eq 'Class::MOP::Class' &&
148 $self->instance_metaclass eq 'Class::MOP::Instance';
150 my @class_list = $self->linearized_isa;
151 shift @class_list; # shift off $self->name
153 foreach my $class_name (@class_list) {
154 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
157 # we need to deal with the possibility
158 # of class immutability here, and then
159 # get the name of the class appropriately
160 my $meta_type = ($meta->is_immutable
161 ? $meta->get_mutable_metaclass_name()
164 ($self->isa($meta_type))
165 || confess $self->name . "->meta => (" . (ref($self)) . ")" .
166 " is not compatible with the " .
167 $class_name . "->meta => (" . ($meta_type) . ")";
169 # we also need to check that instance metaclasses
170 # are compatabile in the same the class.
171 ($self->instance_metaclass->isa($meta->instance_metaclass))
172 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
173 " is not compatible with the " .
174 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
182 # this should be sufficient, if you have a
183 # use case where it is not, write a test and
185 my $ANON_CLASS_SERIAL = 0;
188 # we need a sufficiently annoying prefix
189 # this should suffice for now, this is
190 # used in a couple of places below, so
191 # need to put it up here for now.
192 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
196 no warnings 'uninitialized';
197 $self->name =~ /^$ANON_CLASS_PREFIX/;
200 sub create_anon_class {
201 my ($class, %options) = @_;
202 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
203 return $class->create($package_name, %options);
207 # this will only get called for
208 # anon-classes, all other calls
209 # are assumed to occur during
210 # global destruction and so don't
211 # really need to be handled explicitly
215 return if Class::MOP::in_global_destruction; # it'll happen soon anyway and this just makes things more complicated
217 no warnings 'uninitialized';
218 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
219 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
221 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
222 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
224 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
229 # creating classes with MOP ...
232 my ( $class, @args ) = @_;
234 unshift @args, 'package' if @args % 2 == 1;
236 my (%options) = @args;
237 my $package_name = $options{package};
239 (defined $package_name && $package_name)
240 || confess "You must pass a package name";
242 (ref $options{superclasses} eq 'ARRAY')
243 || confess "You must pass an ARRAY ref of superclasses"
244 if exists $options{superclasses};
246 (ref $options{attributes} eq 'ARRAY')
247 || confess "You must pass an ARRAY ref of attributes"
248 if exists $options{attributes};
250 (ref $options{methods} eq 'HASH')
251 || confess "You must pass an HASH ref of methods"
252 if exists $options{methods};
254 my $code = "package $package_name;";
255 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
256 if exists $options{version};
257 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
258 if exists $options{authority};
261 confess "creation of $package_name failed : $@" if $@;
263 my $meta = $class->initialize($package_name);
266 $meta->add_method('meta' => sub {
267 $class->initialize(ref($_[0]) || $_[0]);
270 $meta->superclasses(@{$options{superclasses}})
271 if exists $options{superclasses};
273 # process attributes first, so that they can
274 # install accessors, but locally defined methods
275 # can then overwrite them. It is maybe a little odd, but
276 # I think this should be the order of things.
277 if (exists $options{attributes}) {
278 foreach my $attr (@{$options{attributes}}) {
279 $meta->add_attribute($attr);
282 if (exists $options{methods}) {
283 foreach my $method_name (keys %{$options{methods}}) {
284 $meta->add_method($method_name, $options{methods}->{$method_name});
293 # all these attribute readers will be bootstrapped
294 # away in the Class::MOP bootstrap section
296 sub get_attribute_map { $_[0]->{'attributes'} }
297 sub attribute_metaclass { $_[0]->{'attribute_metaclass'} }
298 sub method_metaclass { $_[0]->{'method_metaclass'} }
299 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
302 # this is a prime canidate for conversion to XS
306 my $current = Class::MOP::check_package_cache_flag($self->name);
308 if (defined $self->{'_package_cache_flag'} && $self->{'_package_cache_flag'} == $current) {
309 return $self->{'methods'} ||= {};
312 $self->{_package_cache_flag} = $current;
314 my $map = $self->{'methods'} ||= {};
316 my $class_name = $self->name;
317 my $method_metaclass = $self->method_metaclass;
319 my %all_code = $self->get_all_package_symbols('CODE');
321 foreach my $symbol (keys %all_code) {
322 my $code = $all_code{$symbol};
324 next if exists $map->{$symbol} &&
325 defined $map->{$symbol} &&
326 $map->{$symbol}->body == $code;
328 my ($pkg, $name) = Class::MOP::get_code_info($code);
331 # in 5.10 constant.pm the constants show up
332 # as being in the right package, but in pre-5.10
333 # they show up as constant::__ANON__ so we
334 # make an exception here to be sure that things
335 # work as expected in both.
337 unless ($pkg eq 'constant' && $name eq '__ANON__') {
338 next if ($pkg || '') ne $class_name ||
339 (($name || '') ne '__ANON__' && ($pkg || '') ne $class_name);
342 $map->{$symbol} = $method_metaclass->wrap(
344 associated_metaclass => $self,
345 package_name => $class_name,
353 # Instance Construction & Cloning
359 # we need to protect the integrity of the
360 # Class::MOP::Class singletons here, so we
361 # delegate this to &construct_class_instance
362 # which will deal with the singletons
363 return $class->construct_class_instance(@_)
364 if $class->name->isa('Class::MOP::Class');
365 return $class->construct_instance(@_);
368 sub construct_instance {
370 my $params = @_ == 1 ? $_[0] : {@_};
371 my $meta_instance = $class->get_meta_instance();
372 my $instance = $meta_instance->create_instance();
373 foreach my $attr ($class->compute_all_applicable_attributes()) {
374 $attr->initialize_instance_slot($meta_instance, $instance, $params);
377 # this will only work for a HASH instance type
378 if ($class->is_anon_class) {
379 (Scalar::Util::reftype($instance) eq 'HASH')
380 || confess "Currently only HASH based instances are supported with instance of anon-classes";
382 # At some point we should make this official
383 # as a reserved slot name, but right now I am
384 # going to keep it here.
385 # my $RESERVED_MOP_SLOT = '__MOP__';
386 $instance->{'__MOP__'} = $class;
392 sub get_meta_instance {
394 $self->{'_meta_instance'} ||= $self->create_meta_instance();
397 sub create_meta_instance {
400 my $instance = $self->instance_metaclass->new(
401 associated_metaclass => $self,
402 attributes => [ $self->compute_all_applicable_attributes() ],
405 $self->add_meta_instance_dependencies()
406 if $instance->is_dependent_on_superclasses();
413 my $instance = shift;
414 (blessed($instance) && $instance->isa($class->name))
415 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
418 # we need to protect the integrity of the
419 # Class::MOP::Class singletons here, they
420 # should not be cloned.
421 return $instance if $instance->isa('Class::MOP::Class');
422 $class->clone_instance($instance, @_);
426 my ($class, $instance, %params) = @_;
428 || confess "You can only clone instances, ($instance) is not a blessed instance";
429 my $meta_instance = $class->get_meta_instance();
430 my $clone = $meta_instance->clone_instance($instance);
431 foreach my $attr ($class->compute_all_applicable_attributes()) {
432 if ( defined( my $init_arg = $attr->init_arg ) ) {
433 if (exists $params{$init_arg}) {
434 $attr->set_value($clone, $params{$init_arg});
441 sub rebless_instance {
442 my ($self, $instance, %params) = @_;
445 if ($instance->can('meta')) {
446 ($instance->meta->isa('Class::MOP::Class'))
447 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
448 $old_metaclass = $instance->meta;
451 $old_metaclass = $self->initialize(ref($instance));
454 my $meta_instance = $self->get_meta_instance();
456 $self->name->isa($old_metaclass->name)
457 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
460 $meta_instance->rebless_instance_structure($instance, $self);
462 foreach my $attr ( $self->compute_all_applicable_attributes ) {
463 if ( $attr->has_value($instance) ) {
464 if ( defined( my $init_arg = $attr->init_arg ) ) {
465 $params{$init_arg} = $attr->get_value($instance)
466 unless exists $params{$init_arg};
469 $attr->set_value($instance, $attr->get_value($instance));
474 foreach my $attr ($self->compute_all_applicable_attributes) {
475 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
485 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
488 @{$self->get_package_symbol($var_spec)} = @supers;
490 # we need to check the metaclass
491 # compatibility here so that we can
492 # be sure that the superclass is
493 # not potentially creating an issues
494 # we don't know about
495 $self->check_metaclass_compatability();
496 $self->update_meta_instance_dependencies();
498 @{$self->get_package_symbol($var_spec)};
504 my $super_class = $self->name;
506 if ( Class::MOP::HAVE_ISAREV() ) {
507 return @{ $super_class->mro::get_isarev() };
511 my $find_derived_classes;
512 $find_derived_classes = sub {
513 my ($outer_class) = @_;
515 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
518 for my $symbol ( keys %$symbol_table_hashref ) {
519 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
520 my $inner_class = $1;
522 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
526 ? "${outer_class}::$inner_class"
529 if ( $class->isa($super_class) and $class ne $super_class ) {
530 push @derived_classes, $class;
533 next SYMBOL if $class eq 'main'; # skip 'main::*'
535 $find_derived_classes->($class);
539 my $root_class = q{};
540 $find_derived_classes->($root_class);
542 undef $find_derived_classes;
544 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
546 return @derived_classes;
552 return @{ mro::get_linear_isa( (shift)->name ) };
555 sub class_precedence_list {
557 my $name = $self->name;
559 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
561 # We need to check for circular inheritance here
562 # if we are are not on 5.10, cause 5.8 detects it
563 # late. This will do nothing if all is well, and
564 # blow up otherwise. Yes, it's an ugly hack, better
565 # suggestions are welcome.
567 ($name || return)->isa('This is a test for circular inheritance')
570 # if our mro is c3, we can
571 # just grab the linear_isa
572 if (mro::get_mro($name) eq 'c3') {
573 return @{ mro::get_linear_isa($name) }
577 # we can't grab the linear_isa for dfs
578 # since it has all the duplicates
583 $self->initialize($_)->class_precedence_list()
584 } $self->superclasses()
591 sub wrap_method_body {
592 my ( $self, %args ) = @_;
594 my $body = delete $args{body}; # delete is for compat
596 ('CODE' eq ref($body))
597 || confess "Your code block must be a CODE reference";
599 $self->method_metaclass->wrap( $body => (
600 package_name => $self->name,
606 my ($self, $method_name, $method) = @_;
607 (defined $method_name && $method_name)
608 || confess "You must define a method name";
611 if (blessed($method)) {
612 $body = $method->body;
613 if ($method->package_name ne $self->name &&
614 $method->name ne $method_name) {
615 warn "Hello there, got something for you."
616 . " Method says " . $method->package_name . " " . $method->name
617 . " Class says " . $self->name . " " . $method_name;
618 $method = $method->clone(
619 package_name => $self->name,
621 ) if $method->can('clone');
626 $method = $self->wrap_method_body( body => $body, name => $method_name );
629 $method->attach_to_class($self);
631 $self->get_method_map->{$method_name} = $method;
633 my $full_method_name = ($self->name . '::' . $method_name);
634 $self->add_package_symbol(
635 { sigil => '&', type => 'CODE', name => $method_name },
636 Class::MOP::subname($full_method_name => $body)
639 $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
643 my $fetch_and_prepare_method = sub {
644 my ($self, $method_name) = @_;
646 my $method = $self->get_method($method_name);
647 # if we dont have local ...
649 # try to find the next method
650 $method = $self->find_next_method_by_name($method_name);
651 # die if it does not exist
653 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
654 # and now make sure to wrap it
655 # even if it is already wrapped
656 # because we need a new sub ref
657 $method = Class::MOP::Method::Wrapped->wrap($method);
660 # now make sure we wrap it properly
661 $method = Class::MOP::Method::Wrapped->wrap($method)
662 unless $method->isa('Class::MOP::Method::Wrapped');
664 $self->add_method($method_name => $method);
668 sub add_before_method_modifier {
669 my ($self, $method_name, $method_modifier) = @_;
670 (defined $method_name && $method_name)
671 || confess "You must pass in a method name";
672 my $method = $fetch_and_prepare_method->($self, $method_name);
673 $method->add_before_modifier(
674 Class::MOP::subname(':before' => $method_modifier)
678 sub add_after_method_modifier {
679 my ($self, $method_name, $method_modifier) = @_;
680 (defined $method_name && $method_name)
681 || confess "You must pass in a method name";
682 my $method = $fetch_and_prepare_method->($self, $method_name);
683 $method->add_after_modifier(
684 Class::MOP::subname(':after' => $method_modifier)
688 sub add_around_method_modifier {
689 my ($self, $method_name, $method_modifier) = @_;
690 (defined $method_name && $method_name)
691 || confess "You must pass in a method name";
692 my $method = $fetch_and_prepare_method->($self, $method_name);
693 $method->add_around_modifier(
694 Class::MOP::subname(':around' => $method_modifier)
699 # the methods above used to be named like this:
700 # ${pkg}::${method}:(before|after|around)
701 # but this proved problematic when using one modifier
702 # to wrap multiple methods (something which is likely
703 # to happen pretty regularly IMO). So instead of naming
704 # it like this, I have chosen to just name them purely
705 # with their modifier names, like so:
706 # :(before|after|around)
707 # The fact is that in a stack trace, it will be fairly
708 # evident from the context what method they are attached
709 # to, and so don't need the fully qualified name.
713 my ($self, $method_name, $method) = @_;
714 (defined $method_name && $method_name)
715 || confess "You must define a method name";
717 my $body = (blessed($method) ? $method->body : $method);
718 ('CODE' eq ref($body))
719 || confess "Your code block must be a CODE reference";
721 $self->add_package_symbol(
722 { sigil => '&', type => 'CODE', name => $method_name } => $body
725 $self->update_package_cache_flag; # the method map will not list aliased methods
729 my ($self, $method_name) = @_;
730 (defined $method_name && $method_name)
731 || confess "You must define a method name";
733 exists $self->get_method_map->{$method_name};
737 my ($self, $method_name) = @_;
738 (defined $method_name && $method_name)
739 || confess "You must define a method name";
742 # I don't really need this here, because
743 # if the method_map is missing a key it
744 # will just return undef for me now
745 # return unless $self->has_method($method_name);
747 return $self->get_method_map->{$method_name};
751 my ($self, $method_name) = @_;
752 (defined $method_name && $method_name)
753 || confess "You must define a method name";
755 my $removed_method = delete $self->get_method_map->{$method_name};
757 $self->remove_package_symbol(
758 { sigil => '&', type => 'CODE', name => $method_name }
761 $removed_method->detach_from_class if $removed_method;
763 $self->update_package_cache_flag; # still valid, since we just removed the method from the map
765 return $removed_method;
768 sub get_method_list {
770 keys %{$self->get_method_map};
773 sub find_method_by_name {
774 my ($self, $method_name) = @_;
775 (defined $method_name && $method_name)
776 || confess "You must define a method name to find";
777 foreach my $class ($self->linearized_isa) {
778 # fetch the meta-class ...
779 my $meta = $self->initialize($class);
780 return $meta->get_method($method_name)
781 if $meta->has_method($method_name);
786 sub get_all_methods {
788 my %methods = map { %{ $self->initialize($_)->get_method_map } } reverse $self->linearized_isa;
789 return values %methods;
793 sub compute_all_applicable_methods {
797 class => $_->package_name,
798 code => $_, # sigh, overloading
800 } shift->get_all_methods(@_);
803 sub find_all_methods_by_name {
804 my ($self, $method_name) = @_;
805 (defined $method_name && $method_name)
806 || confess "You must define a method name to find";
808 foreach my $class ($self->linearized_isa) {
809 # fetch the meta-class ...
810 my $meta = $self->initialize($class);
812 name => $method_name,
814 code => $meta->get_method($method_name)
815 } if $meta->has_method($method_name);
820 sub find_next_method_by_name {
821 my ($self, $method_name) = @_;
822 (defined $method_name && $method_name)
823 || confess "You must define a method name to find";
824 my @cpl = $self->linearized_isa;
825 shift @cpl; # discard ourselves
826 foreach my $class (@cpl) {
827 # fetch the meta-class ...
828 my $meta = $self->initialize($class);
829 return $meta->get_method($method_name)
830 if $meta->has_method($method_name);
839 # either we have an attribute object already
840 # or we need to create one from the args provided
841 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
842 # make sure it is derived from the correct type though
843 ($attribute->isa('Class::MOP::Attribute'))
844 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
846 # first we attach our new attribute
847 # because it might need certain information
848 # about the class which it is attached to
849 $attribute->attach_to_class($self);
851 # then we remove attributes of a conflicting
852 # name here so that we can properly detach
853 # the old attr object, and remove any
854 # accessors it would have generated
855 if ( $self->has_attribute($attribute->name) ) {
856 $self->remove_attribute($attribute->name);
858 $self->invalidate_meta_instances();
861 # then onto installing the new accessors
862 $self->get_attribute_map->{$attribute->name} = $attribute;
864 # invalidate package flag here
865 my $e = do { local $@; eval { $attribute->install_accessors() }; $@ };
867 $self->remove_attribute($attribute->name);
874 sub update_meta_instance_dependencies {
877 if ( $self->{meta_instance_dependencies} ) {
878 return $self->add_meta_instance_dependencies;
882 sub add_meta_instance_dependencies {
885 $self->remove_meta_instance_depdendencies;
887 my @attrs = $self->compute_all_applicable_attributes();
890 my @classes = grep { not $seen{$_->name}++ } map { $_->associated_class } @attrs;
892 foreach my $class ( @classes ) {
893 $class->add_dependent_meta_instance($self);
896 $self->{meta_instance_dependencies} = \@classes;
899 sub remove_meta_instance_depdendencies {
902 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
903 foreach my $class ( @$classes ) {
904 $class->remove_dependent_meta_instance($self);
914 sub add_dependent_meta_instance {
915 my ( $self, $metaclass ) = @_;
916 push @{ $self->{dependent_meta_instances} }, $metaclass;
919 sub remove_dependent_meta_instance {
920 my ( $self, $metaclass ) = @_;
921 my $name = $metaclass->name;
922 @$_ = grep { $_->name ne $name } @$_ for $self->{dependent_meta_instances};
925 sub invalidate_meta_instances {
927 $_->invalidate_meta_instance() for $self, @{ $self->{dependent_meta_instances} };
930 sub invalidate_meta_instance {
932 undef $self->{_meta_instance};
936 my ($self, $attribute_name) = @_;
937 (defined $attribute_name && $attribute_name)
938 || confess "You must define an attribute name";
939 exists $self->get_attribute_map->{$attribute_name};
943 my ($self, $attribute_name) = @_;
944 (defined $attribute_name && $attribute_name)
945 || confess "You must define an attribute name";
946 return $self->get_attribute_map->{$attribute_name}
948 # this will return undef anyway, so no need ...
949 # if $self->has_attribute($attribute_name);
953 sub remove_attribute {
954 my ($self, $attribute_name) = @_;
955 (defined $attribute_name && $attribute_name)
956 || confess "You must define an attribute name";
957 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
958 return unless defined $removed_attribute;
959 delete $self->get_attribute_map->{$attribute_name};
960 $self->invalidate_meta_instances();
961 $removed_attribute->remove_accessors();
962 $removed_attribute->detach_from_class();
963 return $removed_attribute;
966 sub get_attribute_list {
968 keys %{$self->get_attribute_map};
971 sub get_all_attributes {
972 shift->compute_all_applicable_attributes(@_);
975 sub compute_all_applicable_attributes {
977 my %attrs = map { %{ $self->initialize($_)->get_attribute_map } } reverse $self->linearized_isa;
978 return values %attrs;
981 sub find_attribute_by_name {
982 my ($self, $attr_name) = @_;
983 foreach my $class ($self->linearized_isa) {
984 # fetch the meta-class ...
985 my $meta = $self->initialize($class);
986 return $meta->get_attribute($attr_name)
987 if $meta->has_attribute($attr_name);
992 # check if we can reinitialize
996 # if any local attr is defined
997 return if $self->get_attribute_list;
999 # or any non-declared methods
1000 if ( my @methods = values %{ $self->get_method_map } ) {
1001 my $metaclass = $self->method_metaclass;
1002 foreach my $method ( @methods ) {
1003 return if $method->isa("Class::MOP::Method::Generated");
1004 # FIXME do we need to enforce this too? return unless $method->isa($metaclass);
1013 sub is_mutable { 1 }
1014 sub is_immutable { 0 }
1017 # Why I changed this (groditi)
1018 # - One Metaclass may have many Classes through many Metaclass instances
1019 # - One Metaclass should only have one Immutable Transformer instance
1020 # - Each Class may have different Immutabilizing options
1021 # - Therefore each Metaclass instance may have different Immutabilizing options
1022 # - We need to store one Immutable Transformer instance per Metaclass
1023 # - We need to store one set of Immutable Transformer options per Class
1024 # - Upon make_mutable we may delete the Immutabilizing options
1025 # - We could clean the immutable Transformer instance when there is no more
1026 # immutable Classes of that type, but we can also keep it in case
1027 # another class with this same Metaclass becomes immutable. It is a case
1028 # of trading of storing an instance to avoid unnecessary instantiations of
1029 # Immutable Transformers. You may view this as a memory leak, however
1030 # Because we have few Metaclasses, in practice it seems acceptable
1031 # - To allow Immutable Transformers instances to be cleaned up we could weaken
1032 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
1036 my %IMMUTABLE_TRANSFORMERS;
1037 my %IMMUTABLE_OPTIONS;
1039 sub get_immutable_options {
1041 return if $self->is_mutable;
1042 confess "unable to find immutabilizing options"
1043 unless exists $IMMUTABLE_OPTIONS{$self->name};
1044 my %options = %{$IMMUTABLE_OPTIONS{$self->name}};
1045 delete $options{IMMUTABLE_TRANSFORMER};
1049 sub get_immutable_transformer {
1051 if( $self->is_mutable ){
1052 my $class = ref $self || $self;
1053 return $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
1055 confess "unable to find transformer for immutable class"
1056 unless exists $IMMUTABLE_OPTIONS{$self->name};
1057 return $IMMUTABLE_OPTIONS{$self->name}->{IMMUTABLE_TRANSFORMER};
1060 sub make_immutable {
1064 my $transformer = $self->get_immutable_transformer;
1065 $transformer->make_metaclass_immutable($self, \%options);
1066 $IMMUTABLE_OPTIONS{$self->name} =
1067 { %options, IMMUTABLE_TRANSFORMER => $transformer };
1069 if( exists $options{debug} && $options{debug} ){
1070 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
1071 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
1079 return if $self->is_mutable;
1080 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
1081 confess "unable to find immutabilizing options" unless ref $options;
1082 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
1083 $transformer->make_metaclass_mutable($self, $options);
1088 sub create_immutable_transformer {
1090 my $class = Class::MOP::Immutable->new($self, {
1091 read_only => [qw/superclasses/],
1098 remove_package_symbol
1101 class_precedence_list => 'ARRAY',
1102 linearized_isa => 'ARRAY', # FIXME perl 5.10 memoizes this on its own, no need?
1103 get_all_methods => 'ARRAY',
1104 #get_all_attributes => 'ARRAY', # it's an alias, no need, but maybe in the future
1105 compute_all_applicable_attributes => 'ARRAY',
1106 get_meta_instance => 'SCALAR',
1107 get_method_map => 'SCALAR',
1110 # this is ugly, but so are typeglobs,
1111 # so whattayahgonnadoboutit
1114 add_package_symbol => sub {
1115 my $original = shift;
1116 confess "Cannot add package symbols to an immutable metaclass"
1117 unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
1118 goto $original->body;
1133 Class::MOP::Class - Class Meta Object
1137 # assuming that class Foo
1138 # has been defined, you can
1140 # use this for introspection ...
1142 # add a method to Foo ...
1143 Foo->meta->add_method('bar' => sub { ... })
1145 # get a list of all the classes searched
1146 # the method dispatcher in the correct order
1147 Foo->meta->class_precedence_list()
1149 # remove a method from Foo
1150 Foo->meta->remove_method('bar');
1152 # or use this to actually create classes ...
1154 Class::MOP::Class->create('Bar' => (
1156 superclasses => [ 'Foo' ],
1158 Class::MOP:::Attribute->new('$bar'),
1159 Class::MOP:::Attribute->new('$baz'),
1162 calculate_bar => sub { ... },
1163 construct_baz => sub { ... }
1169 This is the largest and currently most complex part of the Perl 5
1170 meta-object protocol. It controls the introspection and
1171 manipulation of Perl 5 classes (and it can create them too). The
1172 best way to understand what this module can do, is to read the
1173 documentation for each of it's methods.
1177 =head2 Self Introspection
1183 This will return a B<Class::MOP::Class> instance which is related
1184 to this class. Thereby allowing B<Class::MOP::Class> to actually
1187 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
1188 bootstrap this module by installing a number of attribute meta-objects
1189 into it's metaclass. This will allow this class to reap all the benifits
1190 of the MOP when subclassing it.
1194 =head2 Class construction
1196 These methods will handle creating B<Class::MOP::Class> objects,
1197 which can be used to both create new classes, and analyze
1198 pre-existing classes.
1200 This module will internally store references to all the instances
1201 you create with these methods, so that they do not need to be
1202 created any more than nessecary. Basically, they are singletons.
1206 =item B<create ($package_name,
1207 version =E<gt> ?$version,
1208 authority =E<gt> ?$authority,
1209 superclasses =E<gt> ?@superclasses,
1210 methods =E<gt> ?%methods,
1211 attributes =E<gt> ?%attributes)>
1213 This returns a B<Class::MOP::Class> object, bringing the specified
1214 C<$package_name> into existence and adding any of the C<$version>,
1215 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1218 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1219 methods =E<gt> ?%methods,
1220 attributes =E<gt> ?%attributes)>
1222 This will create an anonymous class, it works much like C<create> but
1223 it does not need a C<$package_name>. Instead it will create a suitably
1224 unique package name for you to stash things into.
1226 On very important distinction is that anon classes are destroyed once
1227 the metaclass they are attached to goes out of scope. In the DESTROY
1228 method, the created package will be removed from the symbol table.
1230 It is also worth noting that any instances created with an anon-class
1231 will keep a special reference to the anon-meta which will prevent the
1232 anon-class from going out of scope until all instances of it have also
1233 been destroyed. This however only works for HASH based instance types,
1234 as we use a special reserved slot (C<__MOP__>) to store this.
1236 =item B<initialize ($package_name, %options)>
1238 This initializes and returns returns a B<Class::MOP::Class> object
1239 for a given a C<$package_name>.
1241 =item B<construct_class_instance (%options)>
1243 This will construct an instance of B<Class::MOP::Class>, it is
1244 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1245 to use C<construct_instance> once all the bootstrapping is done. This
1246 method is used internally by C<initialize> and should never be called
1247 from outside of that method really.
1249 =item B<check_metaclass_compatability>
1251 This method is called as the very last thing in the
1252 C<construct_class_instance> method. This will check that the
1253 metaclass you are creating is compatible with the metaclasses of all
1254 your ancestors. For more inforamtion about metaclass compatibility
1255 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1257 =item B<update_package_cache_flag>
1259 This will reset the package cache flag for this particular metaclass
1260 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1261 function. This is very rarely needed from outside of C<Class::MOP::Class>
1262 but in some cases you might want to use it, so it is here.
1264 =item B<reset_package_cache_flag>
1266 Clears the package cache flag to announce to the internals that we need
1267 to rebuild the method map.
1269 =item B<add_meta_instance_dependencies>
1271 Registers this class as dependent on its superclasses.
1273 Only superclasses from which this class inherits attributes will be added.
1275 =item B<remove_meta_instance_depdendencies>
1277 Unregisters this class from its superclasses.
1279 =item B<update_meta_instance_dependencies>
1281 Reregisters if necessary.
1283 =item B<add_dependent_meta_instance> $metaclass
1285 Registers the class as having a meta instance dependent on this class.
1287 =item B<remove_dependent_meta_instance> $metaclass
1289 Remove the class from the list of dependent classes.
1291 =item B<invalidate_meta_instances>
1293 Clears the cached meta instance for this metaclass and all of the registered
1294 classes with dependent meta instances.
1296 Called by C<add_attribute> and C<remove_attribute> to recalculate the attribute
1299 =item B<invalidate_meta_instance>
1301 Used by C<invalidate_meta_instances>.
1305 =head2 Object instance construction and cloning
1307 These methods are B<entirely optional>, it is up to you whether you want
1312 =item B<instance_metaclass>
1314 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1315 for more information on the instance metaclasses.
1317 =item B<get_meta_instance>
1319 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1320 of a new instance of the class.
1322 =item B<create_meta_instance>
1324 Called by C<get_meta_instance> if necessary.
1326 =item B<new_object (%params)>
1328 This is a convience method for creating a new object of the class, and
1329 blessing it into the appropriate package as well. Ideally your class
1330 would call a C<new> this method like so:
1333 my ($class, %param) = @_;
1334 $class->meta->new_object(%params);
1337 =item B<construct_instance (%params)>
1339 This method is used to construct an instance structure suitable for
1340 C<bless>-ing into your package of choice. It works in conjunction
1341 with the Attribute protocol to collect all applicable attributes.
1343 This will construct and instance using a HASH ref as storage
1344 (currently only HASH references are supported). This will collect all
1345 the applicable attributes and layout out the fields in the HASH ref,
1346 it will then initialize them using either use the corresponding key
1347 in C<%params> or any default value or initializer found in the
1348 attribute meta-object.
1350 =item B<clone_object ($instance, %params)>
1352 This is a convience method for cloning an object instance, then
1353 blessing it into the appropriate package. This method will call
1354 C<clone_instance>, which performs a shallow copy of the object,
1355 see that methods documentation for more details. Ideally your
1356 class would call a C<clone> this method like so:
1358 sub MyClass::clone {
1359 my ($self, %param) = @_;
1360 $self->meta->clone_object($self, %params);
1363 =item B<clone_instance($instance, %params)>
1365 This method is a compliment of C<construct_instance> (which means if
1366 you override C<construct_instance>, you need to override this one too),
1367 and clones the instance shallowly.
1369 The cloned structure returned is (like with C<construct_instance>) an
1370 unC<bless>ed HASH reference, it is your responsibility to then bless
1371 this cloned structure into the right class (which C<clone_object> will
1374 As of 0.11, this method will clone the C<$instance> structure shallowly,
1375 as opposed to the deep cloning implemented in prior versions. After much
1376 thought, research and discussion, I have decided that anything but basic
1377 shallow cloning is outside the scope of the meta-object protocol. I
1378 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1379 is too I<context-specific> to be part of the MOP.
1381 =item B<rebless_instance($instance, ?%params)>
1383 This will change the class of C<$instance> to the class of the invoking
1384 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1385 itself. You may pass in optional C<%params> which are like constructor
1386 params and will override anything already defined in the instance.
1390 =head2 Informational
1392 These are a few predicate methods for asking information about the class.
1396 =item B<is_anon_class>
1398 This returns true if the class is a C<Class::MOP::Class> created anon class.
1402 This returns true if the class is still mutable.
1404 =item B<is_immutable>
1406 This returns true if the class has been made immutable.
1408 =item B<is_pristine>
1410 Checks whether the class has any data that will be lost if C<reinitialize> is
1415 =head2 Inheritance Relationships
1419 =item B<superclasses (?@superclasses)>
1421 This is a read-write attribute which represents the superclass
1422 relationships of the class the B<Class::MOP::Class> instance is
1423 associated with. Basically, it can get and set the C<@ISA> for you.
1425 =item B<class_precedence_list>
1427 This computes the a list of all the class's ancestors in the same order
1428 in which method dispatch will be done. This is similair to what
1429 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1431 =item B<linearized_isa>
1433 This returns a list based on C<class_precedence_list> but with all
1438 This returns a list of subclasses for this class.
1446 =item B<get_method_map>
1448 Returns a HASH ref of name to CODE reference mapping for this class.
1450 =item B<method_metaclass>
1452 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1453 for more information on the method metaclasses.
1455 =item B<wrap_method_body(%attrs)>
1457 Wrap a code ref (C<$attrs{body>) with C<method_metaclass>.
1459 =item B<add_method ($method_name, $method, %attrs)>
1461 This will take a C<$method_name> and CODE reference to that
1462 C<$method> and install it into the class's package.
1465 This does absolutely nothing special to C<$method>
1466 other than use B<Sub::Name> to make sure it is tagged with the
1467 correct name, and therefore show up correctly in stack traces and
1470 =item B<alias_method ($method_name, $method)>
1472 This will take a C<$method_name> and CODE reference to that
1473 C<$method> and alias the method into the class's package.
1476 Unlike C<add_method>, this will B<not> try to name the
1477 C<$method> using B<Sub::Name>, it only aliases the method in
1478 the class's package.
1480 =item B<has_method ($method_name)>
1482 This just provides a simple way to check if the class implements
1483 a specific C<$method_name>. It will I<not> however, attempt to check
1484 if the class inherits the method (use C<UNIVERSAL::can> for that).
1486 This will correctly handle functions defined outside of the package
1487 that use a fully qualified name (C<sub Package::name { ... }>).
1489 This will correctly handle functions renamed with B<Sub::Name> and
1490 installed using the symbol tables. However, if you are naming the
1491 subroutine outside of the package scope, you must use the fully
1492 qualified name, including the package name, for C<has_method> to
1493 correctly identify it.
1495 This will attempt to correctly ignore functions imported from other
1496 packages using B<Exporter>. It breaks down if the function imported
1497 is an C<__ANON__> sub (such as with C<use constant>), which very well
1498 may be a valid method being applied to the class.
1500 In short, this method cannot always be trusted to determine if the
1501 C<$method_name> is actually a method. However, it will DWIM about
1502 90% of the time, so it's a small trade off I think.
1504 =item B<get_method ($method_name)>
1506 This will return a Class::MOP::Method instance related to the specified
1507 C<$method_name>, or return undef if that method does not exist.
1509 The Class::MOP::Method is codifiable, so you can use it like a normal
1510 CODE reference, see L<Class::MOP::Method> for more information.
1512 =item B<find_method_by_name ($method_name)>
1514 This will return a CODE reference of the specified C<$method_name>,
1515 or return undef if that method does not exist.
1517 Unlike C<get_method> this will also look in the superclasses.
1519 =item B<remove_method ($method_name)>
1521 This will attempt to remove a given C<$method_name> from the class.
1522 It will return the CODE reference that it has removed, and will
1523 attempt to use B<Sub::Name> to clear the methods associated name.
1525 =item B<get_method_list>
1527 This will return a list of method names for all I<locally> defined
1528 methods. It does B<not> provide a list of all applicable methods,
1529 including any inherited ones. If you want a list of all applicable
1530 methods, use the C<compute_all_applicable_methods> method.
1532 =item B<get_all_methods>
1534 This will traverse the inheritance heirachy and return a list of all
1535 the applicable L<Class::MOP::Method> objects for this class.
1537 =item B<compute_all_applicable_methods>
1541 This method returns a list of hashes describing the all the methods of the
1544 Use L<get_all_methods>, which is easier/better/faster. This method predates
1545 L<Class::MOP::Method>.
1547 =item B<find_all_methods_by_name ($method_name)>
1549 This will traverse the inheritence hierarchy and locate all methods
1550 with a given C<$method_name>. Similar to
1551 C<compute_all_applicable_methods> it returns a list of HASH references
1552 with the following information; method name (which will always be the
1553 same as C<$method_name>), the name of the class in which the method
1554 lives and a CODE reference for the actual method.
1556 The list of methods produced is a distinct list, meaning there are no
1557 duplicates in it. This is especially useful for things like object
1558 initialization and destruction where you only want the method called
1559 once, and in the correct order.
1561 =item B<find_next_method_by_name ($method_name)>
1563 This will return the first method to match a given C<$method_name> in
1564 the superclasses, this is basically equivalent to calling
1565 C<SUPER::$method_name>, but it can be dispatched at runtime.
1569 =head2 Method Modifiers
1571 Method modifiers are a concept borrowed from CLOS, in which a method
1572 can be wrapped with I<before>, I<after> and I<around> method modifiers
1573 that will be called everytime the method is called.
1575 =head3 How method modifiers work?
1577 Method modifiers work by wrapping the original method and then replacing
1578 it in the classes symbol table. The wrappers will handle calling all the
1579 modifiers in the appropariate orders and preserving the calling context
1580 for the original method.
1582 Each method modifier serves a particular purpose, which may not be
1583 obvious to users of other method wrapping modules. To start with, the
1584 return values of I<before> and I<after> modifiers are ignored. This is
1585 because thier purpose is B<not> to filter the input and output of the
1586 primary method (this is done with an I<around> modifier). This may seem
1587 like an odd restriction to some, but doing this allows for simple code
1588 to be added at the begining or end of a method call without jeapordizing
1589 the normal functioning of the primary method or placing any extra
1590 responsibility on the code of the modifier. Of course if you have more
1591 complex needs, then use the I<around> modifier, which uses a variation
1592 of continutation passing style to allow for a high degree of flexibility.
1594 Before and around modifiers are called in last-defined-first-called order,
1595 while after modifiers are called in first-defined-first-called order. So
1596 the call tree might looks something like this:
1606 To see examples of using method modifiers, see the following examples
1607 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1608 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1609 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1611 =head3 What is the performance impact?
1613 Of course there is a performance cost associated with method modifiers,
1614 but we have made every effort to make that cost be directly proportional
1615 to the amount of modifier features you utilize.
1617 The wrapping method does it's best to B<only> do as much work as it
1618 absolutely needs to. In order to do this we have moved some of the
1619 performance costs to set-up time, where they are easier to amortize.
1621 All this said, my benchmarks have indicated the following:
1623 simple wrapper with no modifiers 100% slower
1624 simple wrapper with simple before modifier 400% slower
1625 simple wrapper with simple after modifier 450% slower
1626 simple wrapper with simple around modifier 500-550% slower
1627 simple wrapper with all 3 modifiers 1100% slower
1629 These numbers may seem daunting, but you must remember, every feature
1630 comes with some cost. To put things in perspective, just doing a simple
1631 C<AUTOLOAD> which does nothing but extract the name of the method called
1632 and return it costs about 400% over a normal method call.
1636 =item B<add_before_method_modifier ($method_name, $code)>
1638 This will wrap the method at C<$method_name> and the supplied C<$code>
1639 will be passed the C<@_> arguments, and called before the original
1640 method is called. As specified above, the return value of the I<before>
1641 method modifiers is ignored, and it's ability to modify C<@_> is
1642 fairly limited. If you need to do either of these things, use an
1643 C<around> method modifier.
1645 =item B<add_after_method_modifier ($method_name, $code)>
1647 This will wrap the method at C<$method_name> so that the original
1648 method will be called, it's return values stashed, and then the
1649 supplied C<$code> will be passed the C<@_> arguments, and called.
1650 As specified above, the return value of the I<after> method
1651 modifiers is ignored, and it cannot modify the return values of
1652 the original method. If you need to do either of these things, use an
1653 C<around> method modifier.
1655 =item B<add_around_method_modifier ($method_name, $code)>
1657 This will wrap the method at C<$method_name> so that C<$code>
1658 will be called and passed the original method as an extra argument
1659 at the begining of the C<@_> argument list. This is a variation of
1660 continuation passing style, where the function prepended to C<@_>
1661 can be considered a continuation. It is up to C<$code> if it calls
1662 the original method or not, there is no restriction on what the
1663 C<$code> can or cannot do.
1669 It should be noted that since there is no one consistent way to define
1670 the attributes of a class in Perl 5. These methods can only work with
1671 the information given, and can not easily discover information on
1672 their own. See L<Class::MOP::Attribute> for more details.
1676 =item B<attribute_metaclass>
1678 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1679 for more information on the attribute metaclasses.
1681 =item B<get_attribute_map>
1683 This returns a HASH ref of name to attribute meta-object mapping.
1685 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1687 This stores the C<$attribute_meta_object> (or creates one from the
1688 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1689 instance associated with the given class. Unlike methods, attributes
1690 within the MOP are stored as meta-information only. They will be used
1691 later to construct instances from (see C<construct_instance> above).
1692 More details about the attribute meta-objects can be found in the
1693 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1696 It should be noted that any accessor, reader/writer or predicate
1697 methods which the C<$attribute_meta_object> has will be installed
1698 into the class at this time.
1701 If an attribute already exists for C<$attribute_name>, the old one
1702 will be removed (as well as removing all it's accessors), and then
1705 =item B<has_attribute ($attribute_name)>
1707 Checks to see if this class has an attribute by the name of
1708 C<$attribute_name> and returns a boolean.
1710 =item B<get_attribute ($attribute_name)>
1712 Returns the attribute meta-object associated with C<$attribute_name>,
1713 if none is found, it will return undef.
1715 =item B<remove_attribute ($attribute_name)>
1717 This will remove the attribute meta-object stored at
1718 C<$attribute_name>, then return the removed attribute meta-object.
1721 Removing an attribute will only affect future instances of
1722 the class, it will not make any attempt to remove the attribute from
1723 any existing instances of the class.
1725 It should be noted that any accessor, reader/writer or predicate
1726 methods which the attribute meta-object stored at C<$attribute_name>
1727 has will be removed from the class at this time. This B<will> make
1728 these attributes somewhat inaccessable in previously created
1729 instances. But if you are crazy enough to do this at runtime, then
1730 you are crazy enough to deal with something like this :).
1732 =item B<get_attribute_list>
1734 This returns a list of attribute names which are defined in the local
1735 class. If you want a list of all applicable attributes for a class,
1736 use the C<compute_all_applicable_attributes> method.
1738 =item B<compute_all_applicable_attributes>
1740 =item B<get_all_attributes>
1742 This will traverse the inheritance heirachy and return a list of all
1743 the applicable L<Class::MOP::Attribute> objects for this class.
1745 C<get_all_attributes> is an alias for consistency with C<get_all_methods>.
1747 =item B<find_attribute_by_name ($attr_name)>
1749 This method will traverse the inheritance heirachy and find the
1750 first attribute whose name matches C<$attr_name>, then return it.
1751 It will return undef if nothing is found.
1755 =head2 Class Immutability
1759 =item B<make_immutable (%options)>
1761 This method will invoke a tranforamtion upon the class which will
1762 make it immutable. Details of this transformation can be found in
1763 the L<Class::MOP::Immutable> documentation.
1765 =item B<make_mutable>
1767 This method will reverse tranforamtion upon the class which
1770 =item B<get_immutable_transformer>
1772 Return a transformer suitable for making this class immutable or, if this
1773 class is immutable, the transformer used to make it immutable.
1775 =item B<get_immutable_options>
1777 If the class is immutable, return the options used to make it immutable.
1779 =item B<create_immutable_transformer>
1781 Create a transformer suitable for making this class immutable
1787 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1789 =head1 COPYRIGHT AND LICENSE
1791 Copyright 2006-2008 by Infinity Interactive, Inc.
1793 L<http://www.iinteractive.com>
1795 This library is free software; you can redistribute it and/or modify
1796 it under the same terms as Perl itself.