2 package Class::MOP::Class;
7 use Class::MOP::Immutable;
8 use Class::MOP::Instance;
9 use Class::MOP::Method::Wrapped;
12 use Scalar::Util 'blessed', 'reftype', 'weaken';
14 our $VERSION = '0.31';
15 our $AUTHORITY = 'cpan:STEVAN';
17 use base 'Class::MOP::Module';
23 my $package_name = shift;
24 (defined $package_name && $package_name && !blessed($package_name))
25 || confess "You must pass a package name and it cannot be blessed";
26 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
29 $class->construct_class_instance('package' => $package_name, @_);
34 my $package_name = shift;
35 (defined $package_name && $package_name && !blessed($package_name))
36 || confess "You must pass a package name and it cannot be blessed";
37 Class::MOP::remove_metaclass_by_name($package_name);
38 $class->construct_class_instance('package' => $package_name, @_);
41 # NOTE: (meta-circularity)
42 # this is a special form of &construct_instance
43 # (see below), which is used to construct class
44 # meta-object instances for any Class::MOP::*
45 # class. All other classes will use the more
46 # normal &construct_instance.
47 sub construct_class_instance {
50 my $package_name = $options{'package'};
51 (defined $package_name && $package_name)
52 || confess "You must pass a package name";
54 # return the metaclass if we have it cached,
55 # and it is still defined (it has not been
56 # reaped by DESTROY yet, which can happen
57 # annoyingly enough during global destruction)
59 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
64 # we need to deal with the possibility
65 # of class immutability here, and then
66 # get the name of the class appropriately
67 $class = (blessed($class)
68 ? ($class->is_immutable
69 ? $class->get_mutable_metaclass_name()
73 # now create the metaclass
75 if ($class eq 'Class::MOP::Class') {
78 # inherited from Class::MOP::Package
79 '$!package' => $package_name,
82 # since the following attributes will
83 # actually be loaded from the symbol
84 # table, and actually bypass the instance
85 # entirely, we can just leave these things
86 # listed here for reference, because they
87 # should not actually have a value associated
89 '%!namespace' => \undef,
90 # inherited from Class::MOP::Module
91 '$!version' => \undef,
92 '$!authority' => \undef,
93 # defined in Class::MOP::Class
94 '@!superclasses' => \undef,
98 '$!attribute_metaclass' => $options{'attribute_metaclass'} || 'Class::MOP::Attribute',
99 '$!method_metaclass' => $options{'method_metaclass'} || 'Class::MOP::Method',
100 '$!instance_metaclass' => $options{'instance_metaclass'} || 'Class::MOP::Instance',
102 ## uber-private variables
104 # this starts out as undef so that
105 # we can tell the first time the
106 # methods are fetched
108 '$!_package_cache_flag' => undef,
113 # it is safe to use meta here because
114 # class will always be a subclass of
115 # Class::MOP::Class, which defines meta
116 $meta = $class->meta->construct_instance(%options)
119 # and check the metaclass compatibility
120 $meta->check_metaclass_compatability();
122 Class::MOP::store_metaclass_by_name($package_name, $meta);
125 # we need to weaken any anon classes
126 # so that they can call DESTROY properly
127 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
132 sub reset_package_cache_flag { (shift)->{'$!_package_cache_flag'} = undef }
133 sub update_package_cache_flag {
136 # we can manually update the cache number
137 # since we are actually adding the method
138 # to our cache as well. This avoids us
139 # having to regenerate the method_map.
141 $self->{'$!_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
144 sub check_metaclass_compatability {
147 # this is always okay ...
148 return if blessed($self) eq 'Class::MOP::Class' &&
149 $self->instance_metaclass eq 'Class::MOP::Instance';
151 my @class_list = $self->linearized_isa;
152 shift @class_list; # shift off $self->name
154 foreach my $class_name (@class_list) {
155 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
158 # we need to deal with the possibility
159 # of class immutability here, and then
160 # get the name of the class appropriately
161 my $meta_type = ($meta->is_immutable
162 ? $meta->get_mutable_metaclass_name()
165 ($self->isa($meta_type))
166 || confess $self->name . "->meta => (" . (blessed($self)) . ")" .
167 " is not compatible with the " .
168 $class_name . "->meta => (" . ($meta_type) . ")";
170 # we also need to check that instance metaclasses
171 # are compatabile in the same the class.
172 ($self->instance_metaclass->isa($meta->instance_metaclass))
173 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
174 " is not compatible with the " .
175 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
183 # this should be sufficient, if you have a
184 # use case where it is not, write a test and
186 my $ANON_CLASS_SERIAL = 0;
189 # we need a sufficiently annoying prefix
190 # this should suffice for now, this is
191 # used in a couple of places below, so
192 # need to put it up here for now.
193 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
197 no warnings 'uninitialized';
198 $self->name =~ /^$ANON_CLASS_PREFIX/ ? 1 : 0;
201 sub create_anon_class {
202 my ($class, %options) = @_;
203 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
204 return $class->create($package_name, %options);
208 # this will only get called for
209 # anon-classes, all other calls
210 # are assumed to occur during
211 # global destruction and so don't
212 # really need to be handled explicitly
215 no warnings 'uninitialized';
216 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
217 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
219 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
220 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
222 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
227 # creating classes with MOP ...
231 my $package_name = shift;
233 (defined $package_name && $package_name)
234 || confess "You must pass a package name";
237 || confess "You much pass all parameters as name => value pairs " .
238 "(I found an uneven number of params in \@_)";
242 (ref $options{superclasses} eq 'ARRAY')
243 || confess "You must pass an ARRAY ref of superclasses"
244 if exists $options{superclasses};
246 (ref $options{attributes} eq 'ARRAY')
247 || confess "You must pass an ARRAY ref of attributes"
248 if exists $options{attributes};
250 (ref $options{methods} eq 'HASH')
251 || confess "You must pass an HASH ref of methods"
252 if exists $options{methods};
254 my $code = "package $package_name;";
255 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
256 if exists $options{version};
257 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
258 if exists $options{authority};
261 confess "creation of $package_name failed : $@" if $@;
263 my $meta = $class->initialize($package_name);
265 $meta->add_method('meta' => sub {
266 $class->initialize(blessed($_[0]) || $_[0]);
269 $meta->superclasses(@{$options{superclasses}})
270 if exists $options{superclasses};
272 # process attributes first, so that they can
273 # install accessors, but locally defined methods
274 # can then overwrite them. It is maybe a little odd, but
275 # I think this should be the order of things.
276 if (exists $options{attributes}) {
277 foreach my $attr (@{$options{attributes}}) {
278 $meta->add_attribute($attr);
281 if (exists $options{methods}) {
282 foreach my $method_name (keys %{$options{methods}}) {
283 $meta->add_method($method_name, $options{methods}->{$method_name});
292 # all these attribute readers will be bootstrapped
293 # away in the Class::MOP bootstrap section
295 sub get_attribute_map { $_[0]->{'%!attributes'} }
296 sub attribute_metaclass { $_[0]->{'$!attribute_metaclass'} }
297 sub method_metaclass { $_[0]->{'$!method_metaclass'} }
298 sub instance_metaclass { $_[0]->{'$!instance_metaclass'} }
301 # this is a prime canidate for conversion to XS
305 if (defined $self->{'$!_package_cache_flag'} &&
306 $self->{'$!_package_cache_flag'} == Class::MOP::check_package_cache_flag($self->name)) {
307 return $self->{'%!methods'};
310 my $map = $self->{'%!methods'};
312 my $class_name = $self->name;
313 my $method_metaclass = $self->method_metaclass;
315 foreach my $symbol ($self->list_all_package_symbols('CODE')) {
316 my $code = $self->get_package_symbol('&' . $symbol);
318 next if exists $map->{$symbol} &&
319 defined $map->{$symbol} &&
320 $map->{$symbol}->body == $code;
322 my ($pkg, $name) = Class::MOP::get_code_info($code);
324 next if ($pkg || '') ne $class_name ||
325 (($name || '') ne '__ANON__' && ($pkg || '') ne $class_name);
327 #warn "Checking $pkg against $class_name && $name against __ANON__";
329 $map->{$symbol} = $method_metaclass->wrap($code);
335 # Instance Construction & Cloning
340 # we need to protect the integrity of the
341 # Class::MOP::Class singletons here, so we
342 # delegate this to &construct_class_instance
343 # which will deal with the singletons
344 return $class->construct_class_instance(@_)
345 if $class->name->isa('Class::MOP::Class');
346 return $class->construct_instance(@_);
349 sub construct_instance {
350 my ($class, %params) = @_;
351 my $meta_instance = $class->get_meta_instance();
352 my $instance = $meta_instance->create_instance();
353 foreach my $attr ($class->compute_all_applicable_attributes()) {
354 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
357 # this will only work for a HASH instance type
358 if ($class->is_anon_class) {
359 (reftype($instance) eq 'HASH')
360 || confess "Currently only HASH based instances are supported with instance of anon-classes";
362 # At some point we should make this official
363 # as a reserved slot name, but right now I am
364 # going to keep it here.
365 # my $RESERVED_MOP_SLOT = '__MOP__';
366 $instance->{'__MOP__'} = $class;
371 sub get_meta_instance {
373 return $class->instance_metaclass->new(
375 $class->compute_all_applicable_attributes()
381 my $instance = shift;
382 (blessed($instance) && $instance->isa($class->name))
383 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
385 # we need to protect the integrity of the
386 # Class::MOP::Class singletons here, they
387 # should not be cloned.
388 return $instance if $instance->isa('Class::MOP::Class');
389 $class->clone_instance($instance, @_);
393 my ($class, $instance, %params) = @_;
395 || confess "You can only clone instances, \$self is not a blessed instance";
396 my $meta_instance = $class->get_meta_instance();
397 my $clone = $meta_instance->clone_instance($instance);
398 foreach my $attr ($class->compute_all_applicable_attributes()) {
399 if ( defined( my $init_arg = $attr->init_arg ) ) {
400 if (exists $params{$init_arg}) {
401 $attr->set_value($clone, $params{$init_arg});
408 sub rebless_instance {
409 my ($self, $instance, %params) = @_;
412 if ($instance->can('meta')) {
413 ($instance->meta->isa('Class::MOP::Class'))
414 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
415 $old_metaclass = $instance->meta;
418 $old_metaclass = $self->initialize(blessed($instance));
421 my $meta_instance = $self->get_meta_instance();
423 $self->name->isa($old_metaclass->name)
424 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
427 $meta_instance->rebless_instance_structure($instance, $self);
429 foreach my $attr ( $self->compute_all_applicable_attributes ) {
430 if ( $attr->has_value($instance) ) {
431 if ( defined( my $init_arg = $attr->init_arg ) ) {
432 $params{$init_arg} = $attr->get_value($instance)
433 unless exists $params{$init_arg};
436 $attr->set_value($instance, $attr->get_value($instance));
441 foreach my $attr ($self->compute_all_applicable_attributes) {
442 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
454 @{$self->get_package_symbol('@ISA')} = @supers;
456 # we need to check the metaclass
457 # compatibility here so that we can
458 # be sure that the superclass is
459 # not potentially creating an issues
460 # we don't know about
461 $self->check_metaclass_compatability();
463 @{$self->get_package_symbol('@ISA')};
469 my $super_class = $self->name;
472 my $find_derived_classes;
473 $find_derived_classes = sub {
474 my ($outer_class) = @_;
476 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
479 for my $symbol ( keys %$symbol_table_hashref ) {
480 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
481 my $inner_class = $1;
483 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
487 ? "${outer_class}::$inner_class"
490 if ( $class->isa($super_class) and $class ne $super_class ) {
491 push @derived_classes, $class;
494 next SYMBOL if $class eq 'main'; # skip 'main::*'
496 $find_derived_classes->($class);
500 my $root_class = q{};
501 $find_derived_classes->($root_class);
503 undef $find_derived_classes;
505 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
507 return @derived_classes;
512 return @{ mro::get_linear_isa( (shift)->name ) };
515 sub class_precedence_list {
517 my $name = $self->name;
519 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
521 # We need to check for circular inheritance here
522 # if we are are not on 5.10, cause 5.8 detects it
523 # late. This will do nothing if all is well, and
524 # blow up otherwise. Yes, it's an ugly hack, better
525 # suggestions are welcome.
527 ($name || return)->isa('This is a test for circular inheritance')
530 # if our mro is c3, we can
531 # just grab the linear_isa
532 if (mro::get_mro($name) eq 'c3') {
533 return @{ mro::get_linear_isa($name) }
537 # we can't grab the linear_isa for dfs
538 # since it has all the duplicates
543 $self->initialize($_)->class_precedence_list()
544 } $self->superclasses()
552 my ($self, $method_name, $method) = @_;
553 (defined $method_name && $method_name)
554 || confess "You must define a method name";
557 if (blessed($method)) {
558 $body = $method->body;
559 if ($method->package_name ne $self->name &&
560 $method->name ne $method_name) {
561 warn "Hello there, got somethig for you."
562 . " Method says " . $method->package_name . " " . $method->name
563 . " Class says " . $self->name . " " . $method_name;
564 $method = $method->clone(
565 package_name => $self->name,
567 ) if $method->can('clone');
572 ('CODE' eq (reftype($body) || ''))
573 || confess "Your code block must be a CODE reference";
574 $method = $self->method_metaclass->wrap(
576 package_name => $self->name,
581 $self->get_method_map->{$method_name} = $method;
583 my $full_method_name = ($self->name . '::' . $method_name);
584 $self->add_package_symbol("&${method_name}" =>
585 Class::MOP::subname($full_method_name => $body)
587 $self->update_package_cache_flag;
591 my $fetch_and_prepare_method = sub {
592 my ($self, $method_name) = @_;
594 my $method = $self->get_method($method_name);
595 # if we dont have local ...
597 # try to find the next method
598 $method = $self->find_next_method_by_name($method_name);
599 # die if it does not exist
601 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
602 # and now make sure to wrap it
603 # even if it is already wrapped
604 # because we need a new sub ref
605 $method = Class::MOP::Method::Wrapped->wrap($method);
608 # now make sure we wrap it properly
609 $method = Class::MOP::Method::Wrapped->wrap($method)
610 unless $method->isa('Class::MOP::Method::Wrapped');
612 $self->add_method($method_name => $method);
616 sub add_before_method_modifier {
617 my ($self, $method_name, $method_modifier) = @_;
618 (defined $method_name && $method_name)
619 || confess "You must pass in a method name";
620 my $method = $fetch_and_prepare_method->($self, $method_name);
621 $method->add_before_modifier(
622 Class::MOP::subname(':before' => $method_modifier)
626 sub add_after_method_modifier {
627 my ($self, $method_name, $method_modifier) = @_;
628 (defined $method_name && $method_name)
629 || confess "You must pass in a method name";
630 my $method = $fetch_and_prepare_method->($self, $method_name);
631 $method->add_after_modifier(
632 Class::MOP::subname(':after' => $method_modifier)
636 sub add_around_method_modifier {
637 my ($self, $method_name, $method_modifier) = @_;
638 (defined $method_name && $method_name)
639 || confess "You must pass in a method name";
640 my $method = $fetch_and_prepare_method->($self, $method_name);
641 $method->add_around_modifier(
642 Class::MOP::subname(':around' => $method_modifier)
647 # the methods above used to be named like this:
648 # ${pkg}::${method}:(before|after|around)
649 # but this proved problematic when using one modifier
650 # to wrap multiple methods (something which is likely
651 # to happen pretty regularly IMO). So instead of naming
652 # it like this, I have chosen to just name them purely
653 # with their modifier names, like so:
654 # :(before|after|around)
655 # The fact is that in a stack trace, it will be fairly
656 # evident from the context what method they are attached
657 # to, and so don't need the fully qualified name.
661 my ($self, $method_name, $method) = @_;
662 (defined $method_name && $method_name)
663 || confess "You must define a method name";
665 my $body = (blessed($method) ? $method->body : $method);
666 ('CODE' eq (reftype($body) || ''))
667 || confess "Your code block must be a CODE reference";
669 $self->add_package_symbol("&${method_name}" => $body);
670 $self->update_package_cache_flag;
674 my ($self, $method_name) = @_;
675 (defined $method_name && $method_name)
676 || confess "You must define a method name";
678 return 0 unless exists $self->get_method_map->{$method_name};
683 my ($self, $method_name) = @_;
684 (defined $method_name && $method_name)
685 || confess "You must define a method name";
688 # I don't really need this here, because
689 # if the method_map is missing a key it
690 # will just return undef for me now
691 # return unless $self->has_method($method_name);
693 return $self->get_method_map->{$method_name};
697 my ($self, $method_name) = @_;
698 (defined $method_name && $method_name)
699 || confess "You must define a method name";
701 my $removed_method = delete $self->get_method_map->{$method_name};
703 $self->remove_package_symbol("&${method_name}");
705 $self->update_package_cache_flag;
707 return $removed_method;
710 sub get_method_list {
712 keys %{$self->get_method_map};
715 sub find_method_by_name {
716 my ($self, $method_name) = @_;
717 (defined $method_name && $method_name)
718 || confess "You must define a method name to find";
719 foreach my $class ($self->linearized_isa) {
720 # fetch the meta-class ...
721 my $meta = $self->initialize($class);
722 return $meta->get_method($method_name)
723 if $meta->has_method($method_name);
728 sub compute_all_applicable_methods {
730 my (@methods, %seen_method);
731 foreach my $class ($self->linearized_isa) {
732 # fetch the meta-class ...
733 my $meta = $self->initialize($class);
734 foreach my $method_name ($meta->get_method_list()) {
735 next if exists $seen_method{$method_name};
736 $seen_method{$method_name}++;
738 name => $method_name,
740 code => $meta->get_method($method_name)
747 sub find_all_methods_by_name {
748 my ($self, $method_name) = @_;
749 (defined $method_name && $method_name)
750 || confess "You must define a method name to find";
752 foreach my $class ($self->linearized_isa) {
753 # fetch the meta-class ...
754 my $meta = $self->initialize($class);
756 name => $method_name,
758 code => $meta->get_method($method_name)
759 } if $meta->has_method($method_name);
764 sub find_next_method_by_name {
765 my ($self, $method_name) = @_;
766 (defined $method_name && $method_name)
767 || confess "You must define a method name to find";
768 my @cpl = $self->linearized_isa;
769 shift @cpl; # discard ourselves
770 foreach my $class (@cpl) {
771 # fetch the meta-class ...
772 my $meta = $self->initialize($class);
773 return $meta->get_method($method_name)
774 if $meta->has_method($method_name);
783 # either we have an attribute object already
784 # or we need to create one from the args provided
785 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
786 # make sure it is derived from the correct type though
787 ($attribute->isa('Class::MOP::Attribute'))
788 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
790 # first we attach our new attribute
791 # because it might need certain information
792 # about the class which it is attached to
793 $attribute->attach_to_class($self);
795 # then we remove attributes of a conflicting
796 # name here so that we can properly detach
797 # the old attr object, and remove any
798 # accessors it would have generated
799 $self->remove_attribute($attribute->name)
800 if $self->has_attribute($attribute->name);
802 # then onto installing the new accessors
803 $attribute->install_accessors();
804 $self->get_attribute_map->{$attribute->name} = $attribute;
808 my ($self, $attribute_name) = @_;
809 (defined $attribute_name && $attribute_name)
810 || confess "You must define an attribute name";
811 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
815 my ($self, $attribute_name) = @_;
816 (defined $attribute_name && $attribute_name)
817 || confess "You must define an attribute name";
818 return $self->get_attribute_map->{$attribute_name}
820 # this will return undef anyway, so no need ...
821 # if $self->has_attribute($attribute_name);
825 sub remove_attribute {
826 my ($self, $attribute_name) = @_;
827 (defined $attribute_name && $attribute_name)
828 || confess "You must define an attribute name";
829 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
830 return unless defined $removed_attribute;
831 delete $self->get_attribute_map->{$attribute_name};
832 $removed_attribute->remove_accessors();
833 $removed_attribute->detach_from_class();
834 return $removed_attribute;
837 sub get_attribute_list {
839 keys %{$self->get_attribute_map};
842 sub compute_all_applicable_attributes {
844 my (@attrs, %seen_attr);
845 foreach my $class ($self->linearized_isa) {
846 # fetch the meta-class ...
847 my $meta = $self->initialize($class);
848 foreach my $attr_name ($meta->get_attribute_list()) {
849 next if exists $seen_attr{$attr_name};
850 $seen_attr{$attr_name}++;
851 push @attrs => $meta->get_attribute($attr_name);
857 sub find_attribute_by_name {
858 my ($self, $attr_name) = @_;
859 foreach my $class ($self->linearized_isa) {
860 # fetch the meta-class ...
861 my $meta = $self->initialize($class);
862 return $meta->get_attribute($attr_name)
863 if $meta->has_attribute($attr_name);
871 sub is_immutable { 0 }
874 # Why I changed this (groditi)
875 # - One Metaclass may have many Classes through many Metaclass instances
876 # - One Metaclass should only have one Immutable Transformer instance
877 # - Each Class may have different Immutabilizing options
878 # - Therefore each Metaclass instance may have different Immutabilizing options
879 # - We need to store one Immutable Transformer instance per Metaclass
880 # - We need to store one set of Immutable Transformer options per Class
881 # - Upon make_mutable we may delete the Immutabilizing options
882 # - We could clean the immutable Transformer instance when there is no more
883 # immutable Classes of that type, but we can also keep it in case
884 # another class with this same Metaclass becomes immutable. It is a case
885 # of trading of storing an instance to avoid unnecessary instantiations of
886 # Immutable Transformers. You may view this as a memory leak, however
887 # Because we have few Metaclasses, in practice it seems acceptable
888 # - To allow Immutable Transformers instances to be cleaned up we could weaken
889 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
892 my %IMMUTABLE_TRANSFORMERS;
893 my %IMMUTABLE_OPTIONS;
897 my $class = blessed $self || $self;
899 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
900 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
902 $transformer->make_metaclass_immutable($self, \%options);
903 $IMMUTABLE_OPTIONS{$self->name} =
904 { %options, IMMUTABLE_TRANSFORMER => $transformer };
906 if( exists $options{debug} && $options{debug} ){
907 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
908 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
916 return if $self->is_mutable;
917 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
918 confess "unable to find immutabilizing options" unless ref $options;
919 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
920 $transformer->make_metaclass_mutable($self, $options);
925 sub create_immutable_transformer {
927 my $class = Class::MOP::Immutable->new($self, {
928 read_only => [qw/superclasses/],
935 remove_package_symbol
938 class_precedence_list => 'ARRAY',
939 linearized_isa => 'ARRAY',
940 compute_all_applicable_attributes => 'ARRAY',
941 get_meta_instance => 'SCALAR',
942 get_method_map => 'SCALAR',
945 # this is ugly, but so are typeglobs,
946 # so whattayahgonnadoboutit
949 add_package_symbol => sub {
950 my $original = shift;
951 confess "Cannot add package symbols to an immutable metaclass"
952 unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
953 goto $original->body;
968 Class::MOP::Class - Class Meta Object
972 # assuming that class Foo
973 # has been defined, you can
975 # use this for introspection ...
977 # add a method to Foo ...
978 Foo->meta->add_method('bar' => sub { ... })
980 # get a list of all the classes searched
981 # the method dispatcher in the correct order
982 Foo->meta->class_precedence_list()
984 # remove a method from Foo
985 Foo->meta->remove_method('bar');
987 # or use this to actually create classes ...
989 Class::MOP::Class->create('Bar' => (
991 superclasses => [ 'Foo' ],
993 Class::MOP:::Attribute->new('$bar'),
994 Class::MOP:::Attribute->new('$baz'),
997 calculate_bar => sub { ... },
998 construct_baz => sub { ... }
1004 This is the largest and currently most complex part of the Perl 5
1005 meta-object protocol. It controls the introspection and
1006 manipulation of Perl 5 classes (and it can create them too). The
1007 best way to understand what this module can do, is to read the
1008 documentation for each of it's methods.
1012 =head2 Self Introspection
1018 This will return a B<Class::MOP::Class> instance which is related
1019 to this class. Thereby allowing B<Class::MOP::Class> to actually
1022 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
1023 bootstrap this module by installing a number of attribute meta-objects
1024 into it's metaclass. This will allow this class to reap all the benifits
1025 of the MOP when subclassing it.
1029 =head2 Class construction
1031 These methods will handle creating B<Class::MOP::Class> objects,
1032 which can be used to both create new classes, and analyze
1033 pre-existing classes.
1035 This module will internally store references to all the instances
1036 you create with these methods, so that they do not need to be
1037 created any more than nessecary. Basically, they are singletons.
1041 =item B<create ($package_name,
1042 version =E<gt> ?$version,
1043 authority =E<gt> ?$authority,
1044 superclasses =E<gt> ?@superclasses,
1045 methods =E<gt> ?%methods,
1046 attributes =E<gt> ?%attributes)>
1048 This returns a B<Class::MOP::Class> object, bringing the specified
1049 C<$package_name> into existence and adding any of the C<$version>,
1050 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1053 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1054 methods =E<gt> ?%methods,
1055 attributes =E<gt> ?%attributes)>
1057 This will create an anonymous class, it works much like C<create> but
1058 it does not need a C<$package_name>. Instead it will create a suitably
1059 unique package name for you to stash things into.
1061 On very important distinction is that anon classes are destroyed once
1062 the metaclass they are attached to goes out of scope. In the DESTROY
1063 method, the created package will be removed from the symbol table.
1065 It is also worth noting that any instances created with an anon-class
1066 will keep a special reference to the anon-meta which will prevent the
1067 anon-class from going out of scope until all instances of it have also
1068 been destroyed. This however only works for HASH based instance types,
1069 as we use a special reserved slot (C<__MOP__>) to store this.
1071 =item B<initialize ($package_name, %options)>
1073 This initializes and returns returns a B<Class::MOP::Class> object
1074 for a given a C<$package_name>.
1076 =item B<reinitialize ($package_name, %options)>
1078 This removes the old metaclass, and creates a new one in it's place.
1079 Do B<not> use this unless you really know what you are doing, it could
1080 very easily make a very large mess of your program.
1082 =item B<construct_class_instance (%options)>
1084 This will construct an instance of B<Class::MOP::Class>, it is
1085 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1086 to use C<construct_instance> once all the bootstrapping is done. This
1087 method is used internally by C<initialize> and should never be called
1088 from outside of that method really.
1090 =item B<check_metaclass_compatability>
1092 This method is called as the very last thing in the
1093 C<construct_class_instance> method. This will check that the
1094 metaclass you are creating is compatible with the metaclasses of all
1095 your ancestors. For more inforamtion about metaclass compatibility
1096 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1098 =item B<update_package_cache_flag>
1100 This will reset the package cache flag for this particular metaclass
1101 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1102 function. This is very rarely needed from outside of C<Class::MOP::Class>
1103 but in some cases you might want to use it, so it is here.
1105 =item B<reset_package_cache_flag>
1107 Clears the package cache flag to announce to the internals that we need
1108 to rebuild the method map.
1112 =head2 Object instance construction and cloning
1114 These methods are B<entirely optional>, it is up to you whether you want
1119 =item B<instance_metaclass>
1121 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1122 for more information on the instance metaclasses.
1124 =item B<get_meta_instance>
1126 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1127 of a new instance of the class.
1129 =item B<new_object (%params)>
1131 This is a convience method for creating a new object of the class, and
1132 blessing it into the appropriate package as well. Ideally your class
1133 would call a C<new> this method like so:
1136 my ($class, %param) = @_;
1137 $class->meta->new_object(%params);
1140 =item B<construct_instance (%params)>
1142 This method is used to construct an instance structure suitable for
1143 C<bless>-ing into your package of choice. It works in conjunction
1144 with the Attribute protocol to collect all applicable attributes.
1146 This will construct and instance using a HASH ref as storage
1147 (currently only HASH references are supported). This will collect all
1148 the applicable attributes and layout out the fields in the HASH ref,
1149 it will then initialize them using either use the corresponding key
1150 in C<%params> or any default value or initializer found in the
1151 attribute meta-object.
1153 =item B<clone_object ($instance, %params)>
1155 This is a convience method for cloning an object instance, then
1156 blessing it into the appropriate package. This method will call
1157 C<clone_instance>, which performs a shallow copy of the object,
1158 see that methods documentation for more details. Ideally your
1159 class would call a C<clone> this method like so:
1161 sub MyClass::clone {
1162 my ($self, %param) = @_;
1163 $self->meta->clone_object($self, %params);
1166 =item B<clone_instance($instance, %params)>
1168 This method is a compliment of C<construct_instance> (which means if
1169 you override C<construct_instance>, you need to override this one too),
1170 and clones the instance shallowly.
1172 The cloned structure returned is (like with C<construct_instance>) an
1173 unC<bless>ed HASH reference, it is your responsibility to then bless
1174 this cloned structure into the right class (which C<clone_object> will
1177 As of 0.11, this method will clone the C<$instance> structure shallowly,
1178 as opposed to the deep cloning implemented in prior versions. After much
1179 thought, research and discussion, I have decided that anything but basic
1180 shallow cloning is outside the scope of the meta-object protocol. I
1181 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1182 is too I<context-specific> to be part of the MOP.
1184 =item B<rebless_instance($instance, ?%params)>
1186 This will change the class of C<$instance> to the class of the invoking
1187 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1188 itself. You may pass in optional C<%params> which are like constructor
1189 params and will override anything already defined in the instance.
1193 =head2 Informational
1195 These are a few predicate methods for asking information about the class.
1199 =item B<is_anon_class>
1201 This returns true if the class is a C<Class::MOP::Class> created anon class.
1205 This returns true if the class is still mutable.
1207 =item B<is_immutable>
1209 This returns true if the class has been made immutable.
1213 =head2 Inheritance Relationships
1217 =item B<superclasses (?@superclasses)>
1219 This is a read-write attribute which represents the superclass
1220 relationships of the class the B<Class::MOP::Class> instance is
1221 associated with. Basically, it can get and set the C<@ISA> for you.
1223 =item B<class_precedence_list>
1225 This computes the a list of all the class's ancestors in the same order
1226 in which method dispatch will be done. This is similair to what
1227 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1229 =item B<linearized_isa>
1231 This returns a list based on C<class_precedence_list> but with all
1236 This returns a list of subclasses for this class.
1244 =item B<get_method_map>
1246 Returns a HASH ref of name to CODE reference mapping for this class.
1248 =item B<method_metaclass>
1250 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1251 for more information on the method metaclasses.
1253 =item B<add_method ($method_name, $method)>
1255 This will take a C<$method_name> and CODE reference to that
1256 C<$method> and install it into the class's package.
1259 This does absolutely nothing special to C<$method>
1260 other than use B<Sub::Name> to make sure it is tagged with the
1261 correct name, and therefore show up correctly in stack traces and
1264 =item B<alias_method ($method_name, $method)>
1266 This will take a C<$method_name> and CODE reference to that
1267 C<$method> and alias the method into the class's package.
1270 Unlike C<add_method>, this will B<not> try to name the
1271 C<$method> using B<Sub::Name>, it only aliases the method in
1272 the class's package.
1274 =item B<has_method ($method_name)>
1276 This just provides a simple way to check if the class implements
1277 a specific C<$method_name>. It will I<not> however, attempt to check
1278 if the class inherits the method (use C<UNIVERSAL::can> for that).
1280 This will correctly handle functions defined outside of the package
1281 that use a fully qualified name (C<sub Package::name { ... }>).
1283 This will correctly handle functions renamed with B<Sub::Name> and
1284 installed using the symbol tables. However, if you are naming the
1285 subroutine outside of the package scope, you must use the fully
1286 qualified name, including the package name, for C<has_method> to
1287 correctly identify it.
1289 This will attempt to correctly ignore functions imported from other
1290 packages using B<Exporter>. It breaks down if the function imported
1291 is an C<__ANON__> sub (such as with C<use constant>), which very well
1292 may be a valid method being applied to the class.
1294 In short, this method cannot always be trusted to determine if the
1295 C<$method_name> is actually a method. However, it will DWIM about
1296 90% of the time, so it's a small trade off I think.
1298 =item B<get_method ($method_name)>
1300 This will return a Class::MOP::Method instance related to the specified
1301 C<$method_name>, or return undef if that method does not exist.
1303 The Class::MOP::Method is codifiable, so you can use it like a normal
1304 CODE reference, see L<Class::MOP::Method> for more information.
1306 =item B<find_method_by_name ($method_name)>
1308 This will return a CODE reference of the specified C<$method_name>,
1309 or return undef if that method does not exist.
1311 Unlike C<get_method> this will also look in the superclasses.
1313 =item B<remove_method ($method_name)>
1315 This will attempt to remove a given C<$method_name> from the class.
1316 It will return the CODE reference that it has removed, and will
1317 attempt to use B<Sub::Name> to clear the methods associated name.
1319 =item B<get_method_list>
1321 This will return a list of method names for all I<locally> defined
1322 methods. It does B<not> provide a list of all applicable methods,
1323 including any inherited ones. If you want a list of all applicable
1324 methods, use the C<compute_all_applicable_methods> method.
1326 =item B<compute_all_applicable_methods>
1328 This will return a list of all the methods names this class will
1329 respond to, taking into account inheritance. The list will be a list of
1330 HASH references, each one containing the following information; method
1331 name, the name of the class in which the method lives and a CODE
1332 reference for the actual method.
1334 =item B<find_all_methods_by_name ($method_name)>
1336 This will traverse the inheritence hierarchy and locate all methods
1337 with a given C<$method_name>. Similar to
1338 C<compute_all_applicable_methods> it returns a list of HASH references
1339 with the following information; method name (which will always be the
1340 same as C<$method_name>), the name of the class in which the method
1341 lives and a CODE reference for the actual method.
1343 The list of methods produced is a distinct list, meaning there are no
1344 duplicates in it. This is especially useful for things like object
1345 initialization and destruction where you only want the method called
1346 once, and in the correct order.
1348 =item B<find_next_method_by_name ($method_name)>
1350 This will return the first method to match a given C<$method_name> in
1351 the superclasses, this is basically equivalent to calling
1352 C<SUPER::$method_name>, but it can be dispatched at runtime.
1356 =head2 Method Modifiers
1358 Method modifiers are a concept borrowed from CLOS, in which a method
1359 can be wrapped with I<before>, I<after> and I<around> method modifiers
1360 that will be called everytime the method is called.
1362 =head3 How method modifiers work?
1364 Method modifiers work by wrapping the original method and then replacing
1365 it in the classes symbol table. The wrappers will handle calling all the
1366 modifiers in the appropariate orders and preserving the calling context
1367 for the original method.
1369 Each method modifier serves a particular purpose, which may not be
1370 obvious to users of other method wrapping modules. To start with, the
1371 return values of I<before> and I<after> modifiers are ignored. This is
1372 because thier purpose is B<not> to filter the input and output of the
1373 primary method (this is done with an I<around> modifier). This may seem
1374 like an odd restriction to some, but doing this allows for simple code
1375 to be added at the begining or end of a method call without jeapordizing
1376 the normal functioning of the primary method or placing any extra
1377 responsibility on the code of the modifier. Of course if you have more
1378 complex needs, then use the I<around> modifier, which uses a variation
1379 of continutation passing style to allow for a high degree of flexibility.
1381 Before and around modifiers are called in last-defined-first-called order,
1382 while after modifiers are called in first-defined-first-called order. So
1383 the call tree might looks something like this:
1393 To see examples of using method modifiers, see the following examples
1394 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1395 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1396 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1398 =head3 What is the performance impact?
1400 Of course there is a performance cost associated with method modifiers,
1401 but we have made every effort to make that cost be directly proportional
1402 to the amount of modifier features you utilize.
1404 The wrapping method does it's best to B<only> do as much work as it
1405 absolutely needs to. In order to do this we have moved some of the
1406 performance costs to set-up time, where they are easier to amortize.
1408 All this said, my benchmarks have indicated the following:
1410 simple wrapper with no modifiers 100% slower
1411 simple wrapper with simple before modifier 400% slower
1412 simple wrapper with simple after modifier 450% slower
1413 simple wrapper with simple around modifier 500-550% slower
1414 simple wrapper with all 3 modifiers 1100% slower
1416 These numbers may seem daunting, but you must remember, every feature
1417 comes with some cost. To put things in perspective, just doing a simple
1418 C<AUTOLOAD> which does nothing but extract the name of the method called
1419 and return it costs about 400% over a normal method call.
1423 =item B<add_before_method_modifier ($method_name, $code)>
1425 This will wrap the method at C<$method_name> and the supplied C<$code>
1426 will be passed the C<@_> arguments, and called before the original
1427 method is called. As specified above, the return value of the I<before>
1428 method modifiers is ignored, and it's ability to modify C<@_> is
1429 fairly limited. If you need to do either of these things, use an
1430 C<around> method modifier.
1432 =item B<add_after_method_modifier ($method_name, $code)>
1434 This will wrap the method at C<$method_name> so that the original
1435 method will be called, it's return values stashed, and then the
1436 supplied C<$code> will be passed the C<@_> arguments, and called.
1437 As specified above, the return value of the I<after> method
1438 modifiers is ignored, and it cannot modify the return values of
1439 the original method. If you need to do either of these things, use an
1440 C<around> method modifier.
1442 =item B<add_around_method_modifier ($method_name, $code)>
1444 This will wrap the method at C<$method_name> so that C<$code>
1445 will be called and passed the original method as an extra argument
1446 at the begining of the C<@_> argument list. This is a variation of
1447 continuation passing style, where the function prepended to C<@_>
1448 can be considered a continuation. It is up to C<$code> if it calls
1449 the original method or not, there is no restriction on what the
1450 C<$code> can or cannot do.
1456 It should be noted that since there is no one consistent way to define
1457 the attributes of a class in Perl 5. These methods can only work with
1458 the information given, and can not easily discover information on
1459 their own. See L<Class::MOP::Attribute> for more details.
1463 =item B<attribute_metaclass>
1465 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1466 for more information on the attribute metaclasses.
1468 =item B<get_attribute_map>
1470 This returns a HASH ref of name to attribute meta-object mapping.
1472 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1474 This stores the C<$attribute_meta_object> (or creates one from the
1475 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1476 instance associated with the given class. Unlike methods, attributes
1477 within the MOP are stored as meta-information only. They will be used
1478 later to construct instances from (see C<construct_instance> above).
1479 More details about the attribute meta-objects can be found in the
1480 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1483 It should be noted that any accessor, reader/writer or predicate
1484 methods which the C<$attribute_meta_object> has will be installed
1485 into the class at this time.
1488 If an attribute already exists for C<$attribute_name>, the old one
1489 will be removed (as well as removing all it's accessors), and then
1492 =item B<has_attribute ($attribute_name)>
1494 Checks to see if this class has an attribute by the name of
1495 C<$attribute_name> and returns a boolean.
1497 =item B<get_attribute ($attribute_name)>
1499 Returns the attribute meta-object associated with C<$attribute_name>,
1500 if none is found, it will return undef.
1502 =item B<remove_attribute ($attribute_name)>
1504 This will remove the attribute meta-object stored at
1505 C<$attribute_name>, then return the removed attribute meta-object.
1508 Removing an attribute will only affect future instances of
1509 the class, it will not make any attempt to remove the attribute from
1510 any existing instances of the class.
1512 It should be noted that any accessor, reader/writer or predicate
1513 methods which the attribute meta-object stored at C<$attribute_name>
1514 has will be removed from the class at this time. This B<will> make
1515 these attributes somewhat inaccessable in previously created
1516 instances. But if you are crazy enough to do this at runtime, then
1517 you are crazy enough to deal with something like this :).
1519 =item B<get_attribute_list>
1521 This returns a list of attribute names which are defined in the local
1522 class. If you want a list of all applicable attributes for a class,
1523 use the C<compute_all_applicable_attributes> method.
1525 =item B<compute_all_applicable_attributes>
1527 This will traverse the inheritance heirachy and return a list of all
1528 the applicable attributes for this class. It does not construct a
1529 HASH reference like C<compute_all_applicable_methods> because all
1530 that same information is discoverable through the attribute
1533 =item B<find_attribute_by_name ($attr_name)>
1535 This method will traverse the inheritance heirachy and find the
1536 first attribute whose name matches C<$attr_name>, then return it.
1537 It will return undef if nothing is found.
1541 =head2 Class Immutability
1545 =item B<make_immutable (%options)>
1547 This method will invoke a tranforamtion upon the class which will
1548 make it immutable. Details of this transformation can be found in
1549 the L<Class::MOP::Immutable> documentation.
1551 =item B<make_mutable>
1553 This method will reverse tranforamtion upon the class which
1556 =item B<create_immutable_transformer>
1558 Create a transformer suitable for making this class immutable
1564 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1566 =head1 COPYRIGHT AND LICENSE
1568 Copyright 2006-2008 by Infinity Interactive, Inc.
1570 L<http://www.iinteractive.com>
1572 This library is free software; you can redistribute it and/or modify
1573 it under the same terms as Perl itself.