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 = '0.32';
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 my $name = $self->name;
156 foreach my $class_name (@class_list) {
157 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
160 # we need to deal with the possibility
161 # of class immutability here, and then
162 # get the name of the class appropriately
163 my $meta_type = ($meta->is_immutable
164 ? $meta->get_mutable_metaclass_name()
167 ($self->isa($meta_type))
168 || confess $name . "->meta => (" . (blessed($self)) . ")" .
169 " is not compatible with the " .
170 $class_name . "->meta => (" . ($meta_type) . ")";
172 # we also need to check that instance metaclasses
173 # are compatabile in the same the class.
174 ($self->instance_metaclass->isa($meta->instance_metaclass))
175 || confess $name . "->meta => (" . ($self->instance_metaclass) . ")" .
176 " is not compatible with the " .
177 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
185 # this should be sufficient, if you have a
186 # use case where it is not, write a test and
188 my $ANON_CLASS_SERIAL = 0;
191 # we need a sufficiently annoying prefix
192 # this should suffice for now, this is
193 # used in a couple of places below, so
194 # need to put it up here for now.
195 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
199 no warnings 'uninitialized';
200 $self->name =~ /^$ANON_CLASS_PREFIX/ ? 1 : 0;
203 sub create_anon_class {
204 my ($class, %options) = @_;
205 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
206 return $class->create($package_name, %options);
210 # this will only get called for
211 # anon-classes, all other calls
212 # are assumed to occur during
213 # global destruction and so don't
214 # really need to be handled explicitly
217 no warnings 'uninitialized';
218 my $name = $self->name;
219 return unless $name =~ /^$ANON_CLASS_PREFIX/;
220 my ($serial_id) = ($name =~ /^$ANON_CLASS_PREFIX(\d+)/);
222 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
223 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
225 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
230 # creating classes with MOP ...
234 my $package_name = shift;
236 (defined $package_name && $package_name)
237 || confess "You must pass a package name";
240 || confess "You much pass all parameters as name => value pairs " .
241 "(I found an uneven number of params in \@_)";
245 (ref $options{superclasses} eq 'ARRAY')
246 || confess "You must pass an ARRAY ref of superclasses"
247 if exists $options{superclasses};
249 (ref $options{attributes} eq 'ARRAY')
250 || confess "You must pass an ARRAY ref of attributes"
251 if exists $options{attributes};
253 (ref $options{methods} eq 'HASH')
254 || confess "You must pass an HASH ref of methods"
255 if exists $options{methods};
257 my $code = "package $package_name;";
258 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
259 if exists $options{version};
260 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
261 if exists $options{authority};
264 confess "creation of $package_name failed : $@" if $@;
266 my $meta = $class->initialize($package_name);
268 $meta->add_method('meta' => sub {
269 $class->initialize(blessed($_[0]) || $_[0]);
272 $meta->superclasses(@{$options{superclasses}})
273 if exists $options{superclasses};
275 # process attributes first, so that they can
276 # install accessors, but locally defined methods
277 # can then overwrite them. It is maybe a little odd, but
278 # I think this should be the order of things.
279 if (exists $options{attributes}) {
280 foreach my $attr (@{$options{attributes}}) {
281 $meta->add_attribute($attr);
284 if (exists $options{methods}) {
285 foreach my $method_name (keys %{$options{methods}}) {
286 $meta->add_method($method_name, $options{methods}->{$method_name});
295 # all these attribute readers will be bootstrapped
296 # away in the Class::MOP bootstrap section
298 sub get_attribute_map { $_[0]->{'%!attributes'} }
299 sub attribute_metaclass { $_[0]->{'$!attribute_metaclass'} }
300 sub method_metaclass { $_[0]->{'$!method_metaclass'} }
301 sub instance_metaclass { $_[0]->{'$!instance_metaclass'} }
304 # this is a prime canidate for conversion to XS
308 if (defined $self->{'$!_package_cache_flag'} &&
309 $self->{'$!_package_cache_flag'} == Class::MOP::check_package_cache_flag($self->name)) {
310 return $self->{'%!methods'};
313 my $map = $self->{'%!methods'};
315 my $class_name = $self->name;
316 my $method_metaclass = $self->method_metaclass;
318 my %all_code = $self->get_all_package_symbols('CODE');
320 foreach my $symbol (keys %all_code) {
321 my $code = $all_code{$symbol};
323 next if exists $map->{$symbol} &&
324 defined $map->{$symbol} &&
325 $map->{$symbol}->body == $code;
327 my ($pkg, $name) = Class::MOP::get_code_info($code);
330 # in 5.10 constant.pm the constants show up
331 # as being in the right package, but in pre-5.10
332 # they show up as constant::__ANON__ so we
333 # make an exception here to be sure that things
334 # work as expected in both.
336 unless ($pkg eq 'constant' && $name eq '__ANON__') {
337 next if ($pkg || '') ne $class_name ||
338 (($name || '') ne '__ANON__' && ($pkg || '') ne $class_name);
341 $map->{$symbol} = $method_metaclass->wrap(
343 package_name => $class_name,
351 # Instance Construction & Cloning
356 # we need to protect the integrity of the
357 # Class::MOP::Class singletons here, so we
358 # delegate this to &construct_class_instance
359 # which will deal with the singletons
360 return $class->construct_class_instance(@_)
361 if $class->name->isa('Class::MOP::Class');
362 return $class->construct_instance(@_);
365 sub construct_instance {
366 my ($class, %params) = @_;
367 my $meta_instance = $class->get_meta_instance();
368 my $instance = $meta_instance->create_instance();
369 foreach my $attr ($class->compute_all_applicable_attributes()) {
370 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
373 # this will only work for a HASH instance type
374 if ($class->is_anon_class) {
375 (reftype($instance) eq 'HASH')
376 || confess "Currently only HASH based instances are supported with instance of anon-classes";
378 # At some point we should make this official
379 # as a reserved slot name, but right now I am
380 # going to keep it here.
381 # my $RESERVED_MOP_SLOT = '__MOP__';
382 $instance->{'__MOP__'} = $class;
387 sub get_meta_instance {
389 return $class->instance_metaclass->new(
391 $class->compute_all_applicable_attributes()
397 my $instance = shift;
399 my $name = $class->name;
401 (blessed($instance) && $instance->isa($name))
402 || confess "You must pass an instance ($instance) of the metaclass (" . $name . ")";
404 # we need to protect the integrity of the
405 # Class::MOP::Class singletons here, they
406 # should not be cloned.
407 return $instance if $instance->isa('Class::MOP::Class');
408 $class->clone_instance($instance, @_);
412 my ($class, $instance, %params) = @_;
414 || confess "You can only clone instances, \$self is not a blessed instance";
415 my $meta_instance = $class->get_meta_instance();
416 my $clone = $meta_instance->clone_instance($instance);
417 foreach my $attr ($class->compute_all_applicable_attributes()) {
418 if ( defined( my $init_arg = $attr->init_arg ) ) {
419 if (exists $params{$init_arg}) {
420 $attr->set_value($clone, $params{$init_arg});
427 sub rebless_instance {
428 my ($self, $instance, %params) = @_;
432 if ($instance->can('meta')) {
433 ($instance->meta->isa('Class::MOP::Class'))
434 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
435 $old_metaclass = $instance->meta;
438 $old_metaclass = $self->initialize(blessed($instance));
441 my $meta_instance = $self->get_meta_instance();
442 my $name = $self->name;
443 my $old_name = $old_metaclass->name;
445 $name->isa($old_name)
446 || confess "You may rebless only into a subclass of (". $old_name ."), of which (". $name .") isn't.";
449 $meta_instance->rebless_instance_structure($instance, $self);
451 foreach my $attr ( $self->compute_all_applicable_attributes ) {
452 if ( $attr->has_value($instance) ) {
453 if ( defined( my $init_arg = $attr->init_arg ) ) {
454 $params{$init_arg} = $attr->get_value($instance)
455 unless exists $params{$init_arg};
458 $attr->set_value($instance, $attr->get_value($instance));
463 foreach my $attr ($self->compute_all_applicable_attributes) {
464 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
476 @{$self->get_package_symbol('@ISA')} = @supers;
478 # we need to check the metaclass
479 # compatibility here so that we can
480 # be sure that the superclass is
481 # not potentially creating an issues
482 # we don't know about
483 $self->check_metaclass_compatability();
485 @{$self->get_package_symbol('@ISA')};
491 my $super_class = $self->name;
494 my $find_derived_classes;
495 $find_derived_classes = sub {
496 my ($outer_class) = @_;
498 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
501 for my $symbol ( keys %$symbol_table_hashref ) {
502 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
503 my $inner_class = $1;
505 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
509 ? "${outer_class}::$inner_class"
512 if ( $class->isa($super_class) and $class ne $super_class ) {
513 push @derived_classes, $class;
516 next SYMBOL if $class eq 'main'; # skip 'main::*'
518 $find_derived_classes->($class);
522 my $root_class = q{};
523 $find_derived_classes->($root_class);
525 undef $find_derived_classes;
527 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
529 return @derived_classes;
534 return @{ mro::get_linear_isa( (shift)->name ) };
537 sub class_precedence_list {
539 my $name = $self->name;
541 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
543 # We need to check for circular inheritance here
544 # if we are are not on 5.10, cause 5.8 detects it
545 # late. This will do nothing if all is well, and
546 # blow up otherwise. Yes, it's an ugly hack, better
547 # suggestions are welcome.
549 ($name || return)->isa('This is a test for circular inheritance')
552 # if our mro is c3, we can
553 # just grab the linear_isa
554 if (mro::get_mro($name) eq 'c3') {
555 return @{ mro::get_linear_isa($name) }
559 # we can't grab the linear_isa for dfs
560 # since it has all the duplicates
565 $self->initialize($_)->class_precedence_list()
566 } $self->superclasses()
574 my ($self, $method_name, $method) = @_;
575 (defined $method_name && $method_name)
576 || confess "You must define a method name";
578 my $name = $self->name;
580 if (blessed($method)) {
581 $body = $method->body;
582 if ($method->package_name ne $name &&
583 $method->name ne $method_name) {
584 warn "Hello there, got somethig for you."
585 . " Method says " . $method->package_name . " " . $method->name
586 . " Class says " . $name . " " . $method_name;
587 $method = $method->clone(
588 package_name => $name,
590 ) if $method->can('clone');
595 ('CODE' eq (reftype($body) || ''))
596 || confess "Your code block must be a CODE reference";
597 $method = $self->method_metaclass->wrap(
599 package_name => $name,
604 $self->get_method_map->{$method_name} = $method;
606 my $full_method_name = ($name . '::' . $method_name);
607 $self->add_package_symbol("&${method_name}" =>
608 Class::MOP::subname($full_method_name => $body)
610 $self->update_package_cache_flag;
614 my $fetch_and_prepare_method = sub {
615 my ($self, $method_name) = @_;
617 my $method = $self->get_method($method_name);
618 # if we dont have local ...
620 # try to find the next method
621 $method = $self->find_next_method_by_name($method_name);
622 # die if it does not exist
624 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
625 # and now make sure to wrap it
626 # even if it is already wrapped
627 # because we need a new sub ref
628 $method = Class::MOP::Method::Wrapped->wrap($method);
631 # now make sure we wrap it properly
632 $method = Class::MOP::Method::Wrapped->wrap($method)
633 unless $method->isa('Class::MOP::Method::Wrapped');
635 $self->add_method($method_name => $method);
639 sub add_before_method_modifier {
640 my ($self, $method_name, $method_modifier) = @_;
641 (defined $method_name && $method_name)
642 || confess "You must pass in a method name";
643 my $method = $fetch_and_prepare_method->($self, $method_name);
644 $method->add_before_modifier(
645 Class::MOP::subname(':before' => $method_modifier)
649 sub add_after_method_modifier {
650 my ($self, $method_name, $method_modifier) = @_;
651 (defined $method_name && $method_name)
652 || confess "You must pass in a method name";
653 my $method = $fetch_and_prepare_method->($self, $method_name);
654 $method->add_after_modifier(
655 Class::MOP::subname(':after' => $method_modifier)
659 sub add_around_method_modifier {
660 my ($self, $method_name, $method_modifier) = @_;
661 (defined $method_name && $method_name)
662 || confess "You must pass in a method name";
663 my $method = $fetch_and_prepare_method->($self, $method_name);
664 $method->add_around_modifier(
665 Class::MOP::subname(':around' => $method_modifier)
670 # the methods above used to be named like this:
671 # ${pkg}::${method}:(before|after|around)
672 # but this proved problematic when using one modifier
673 # to wrap multiple methods (something which is likely
674 # to happen pretty regularly IMO). So instead of naming
675 # it like this, I have chosen to just name them purely
676 # with their modifier names, like so:
677 # :(before|after|around)
678 # The fact is that in a stack trace, it will be fairly
679 # evident from the context what method they are attached
680 # to, and so don't need the fully qualified name.
684 my ($self, $method_name, $method) = @_;
685 (defined $method_name && $method_name)
686 || confess "You must define a method name";
688 my $body = (blessed($method) ? $method->body : $method);
689 ('CODE' eq (reftype($body) || ''))
690 || confess "Your code block must be a CODE reference";
692 $self->add_package_symbol("&${method_name}" => $body);
693 $self->update_package_cache_flag;
697 my ($self, $method_name) = @_;
698 (defined $method_name && $method_name)
699 || confess "You must define a method name";
701 return 0 unless exists $self->get_method_map->{$method_name};
706 my ($self, $method_name) = @_;
707 (defined $method_name && $method_name)
708 || confess "You must define a method name";
711 # I don't really need this here, because
712 # if the method_map is missing a key it
713 # will just return undef for me now
714 # return unless $self->has_method($method_name);
716 return $self->get_method_map->{$method_name};
720 my ($self, $method_name) = @_;
721 (defined $method_name && $method_name)
722 || confess "You must define a method name";
724 my $removed_method = delete $self->get_method_map->{$method_name};
726 $self->remove_package_symbol("&${method_name}");
728 $self->update_package_cache_flag;
730 return $removed_method;
733 sub get_method_list {
735 keys %{$self->get_method_map};
738 sub find_method_by_name {
739 my ($self, $method_name) = @_;
740 (defined $method_name && $method_name)
741 || confess "You must define a method name to find";
742 foreach my $class ($self->linearized_isa) {
743 # fetch the meta-class ...
744 my $meta = $self->initialize($class);
745 return $meta->get_method($method_name)
746 if $meta->has_method($method_name);
751 sub compute_all_applicable_methods {
753 my (@methods, %seen_method);
754 foreach my $class ($self->linearized_isa) {
755 # fetch the meta-class ...
756 my $meta = $self->initialize($class);
757 foreach my $method_name ($meta->get_method_list()) {
758 next if exists $seen_method{$method_name};
759 $seen_method{$method_name}++;
761 name => $method_name,
763 code => $meta->get_method($method_name)
770 sub find_all_methods_by_name {
771 my ($self, $method_name) = @_;
772 (defined $method_name && $method_name)
773 || confess "You must define a method name to find";
775 foreach my $class ($self->linearized_isa) {
776 # fetch the meta-class ...
777 my $meta = $self->initialize($class);
779 name => $method_name,
781 code => $meta->get_method($method_name)
782 } if $meta->has_method($method_name);
787 sub find_next_method_by_name {
788 my ($self, $method_name) = @_;
789 (defined $method_name && $method_name)
790 || confess "You must define a method name to find";
791 my @cpl = $self->linearized_isa;
792 shift @cpl; # discard ourselves
793 foreach my $class (@cpl) {
794 # fetch the meta-class ...
795 my $meta = $self->initialize($class);
796 return $meta->get_method($method_name)
797 if $meta->has_method($method_name);
806 # either we have an attribute object already
807 # or we need to create one from the args provided
808 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
809 # make sure it is derived from the correct type though
810 ($attribute->isa('Class::MOP::Attribute'))
811 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
813 # first we attach our new attribute
814 # because it might need certain information
815 # about the class which it is attached to
816 $attribute->attach_to_class($self);
818 # then we remove attributes of a conflicting
819 # name here so that we can properly detach
820 # the old attr object, and remove any
821 # accessors it would have generated
822 my $attr_name = $attribute->name;
823 $self->remove_attribute($attr_name)
824 if $self->has_attribute($attr_name);
826 # then onto installing the new accessors
827 $attribute->install_accessors();
828 $self->get_attribute_map->{$attr_name} = $attribute;
832 my ($self, $attribute_name) = @_;
833 (defined $attribute_name && $attribute_name)
834 || confess "You must define an attribute name";
835 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
839 my ($self, $attribute_name) = @_;
840 (defined $attribute_name && $attribute_name)
841 || confess "You must define an attribute name";
842 return $self->get_attribute_map->{$attribute_name}
844 # this will return undef anyway, so no need ...
845 # if $self->has_attribute($attribute_name);
849 sub remove_attribute {
850 my ($self, $attribute_name) = @_;
851 (defined $attribute_name && $attribute_name)
852 || confess "You must define an attribute name";
853 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
854 return unless defined $removed_attribute;
855 delete $self->get_attribute_map->{$attribute_name};
856 $removed_attribute->remove_accessors();
857 $removed_attribute->detach_from_class();
858 return $removed_attribute;
861 sub get_attribute_list {
863 keys %{$self->get_attribute_map};
866 sub compute_all_applicable_attributes {
868 my (@attrs, %seen_attr);
869 foreach my $class ($self->linearized_isa) {
870 # fetch the meta-class ...
871 my $meta = $self->initialize($class);
872 foreach my $attr_name ($meta->get_attribute_list()) {
873 next if exists $seen_attr{$attr_name};
874 $seen_attr{$attr_name}++;
875 push @attrs => $meta->get_attribute($attr_name);
881 sub find_attribute_by_name {
882 my ($self, $attr_name) = @_;
883 foreach my $class ($self->linearized_isa) {
884 # fetch the meta-class ...
885 my $meta = $self->initialize($class);
886 return $meta->get_attribute($attr_name)
887 if $meta->has_attribute($attr_name);
895 sub is_immutable { 0 }
898 # Why I changed this (groditi)
899 # - One Metaclass may have many Classes through many Metaclass instances
900 # - One Metaclass should only have one Immutable Transformer instance
901 # - Each Class may have different Immutabilizing options
902 # - Therefore each Metaclass instance may have different Immutabilizing options
903 # - We need to store one Immutable Transformer instance per Metaclass
904 # - We need to store one set of Immutable Transformer options per Class
905 # - Upon make_mutable we may delete the Immutabilizing options
906 # - We could clean the immutable Transformer instance when there is no more
907 # immutable Classes of that type, but we can also keep it in case
908 # another class with this same Metaclass becomes immutable. It is a case
909 # of trading of storing an instance to avoid unnecessary instantiations of
910 # Immutable Transformers. You may view this as a memory leak, however
911 # Because we have few Metaclasses, in practice it seems acceptable
912 # - To allow Immutable Transformers instances to be cleaned up we could weaken
913 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
916 my %IMMUTABLE_TRANSFORMERS;
917 my %IMMUTABLE_OPTIONS;
921 my $class = blessed $self || $self;
923 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
924 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
926 $transformer->make_metaclass_immutable($self, \%options);
927 $IMMUTABLE_OPTIONS{$self->name} =
928 { %options, IMMUTABLE_TRANSFORMER => $transformer };
930 if( exists $options{debug} && $options{debug} ){
931 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
932 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
940 return if $self->is_mutable;
941 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
942 confess "unable to find immutabilizing options" unless ref $options;
943 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
944 $transformer->make_metaclass_mutable($self, $options);
949 sub create_immutable_transformer {
951 my $class = Class::MOP::Immutable->new($self, {
952 read_only => [qw/superclasses/],
959 remove_package_symbol
962 class_precedence_list => 'ARRAY',
963 linearized_isa => 'ARRAY',
964 compute_all_applicable_attributes => 'ARRAY',
965 get_meta_instance => 'SCALAR',
966 get_method_map => 'SCALAR',
969 # this is ugly, but so are typeglobs,
970 # so whattayahgonnadoboutit
973 add_package_symbol => sub {
974 my $original = shift;
975 confess "Cannot add package symbols to an immutable metaclass"
976 unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
977 goto $original->body;
992 Class::MOP::Class - Class Meta Object
996 # assuming that class Foo
997 # has been defined, you can
999 # use this for introspection ...
1001 # add a method to Foo ...
1002 Foo->meta->add_method('bar' => sub { ... })
1004 # get a list of all the classes searched
1005 # the method dispatcher in the correct order
1006 Foo->meta->class_precedence_list()
1008 # remove a method from Foo
1009 Foo->meta->remove_method('bar');
1011 # or use this to actually create classes ...
1013 Class::MOP::Class->create('Bar' => (
1015 superclasses => [ 'Foo' ],
1017 Class::MOP:::Attribute->new('$bar'),
1018 Class::MOP:::Attribute->new('$baz'),
1021 calculate_bar => sub { ... },
1022 construct_baz => sub { ... }
1028 This is the largest and currently most complex part of the Perl 5
1029 meta-object protocol. It controls the introspection and
1030 manipulation of Perl 5 classes (and it can create them too). The
1031 best way to understand what this module can do, is to read the
1032 documentation for each of it's methods.
1036 =head2 Self Introspection
1042 This will return a B<Class::MOP::Class> instance which is related
1043 to this class. Thereby allowing B<Class::MOP::Class> to actually
1046 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
1047 bootstrap this module by installing a number of attribute meta-objects
1048 into it's metaclass. This will allow this class to reap all the benifits
1049 of the MOP when subclassing it.
1053 =head2 Class construction
1055 These methods will handle creating B<Class::MOP::Class> objects,
1056 which can be used to both create new classes, and analyze
1057 pre-existing classes.
1059 This module will internally store references to all the instances
1060 you create with these methods, so that they do not need to be
1061 created any more than nessecary. Basically, they are singletons.
1065 =item B<create ($package_name,
1066 version =E<gt> ?$version,
1067 authority =E<gt> ?$authority,
1068 superclasses =E<gt> ?@superclasses,
1069 methods =E<gt> ?%methods,
1070 attributes =E<gt> ?%attributes)>
1072 This returns a B<Class::MOP::Class> object, bringing the specified
1073 C<$package_name> into existence and adding any of the C<$version>,
1074 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1077 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1078 methods =E<gt> ?%methods,
1079 attributes =E<gt> ?%attributes)>
1081 This will create an anonymous class, it works much like C<create> but
1082 it does not need a C<$package_name>. Instead it will create a suitably
1083 unique package name for you to stash things into.
1085 On very important distinction is that anon classes are destroyed once
1086 the metaclass they are attached to goes out of scope. In the DESTROY
1087 method, the created package will be removed from the symbol table.
1089 It is also worth noting that any instances created with an anon-class
1090 will keep a special reference to the anon-meta which will prevent the
1091 anon-class from going out of scope until all instances of it have also
1092 been destroyed. This however only works for HASH based instance types,
1093 as we use a special reserved slot (C<__MOP__>) to store this.
1095 =item B<initialize ($package_name, %options)>
1097 This initializes and returns returns a B<Class::MOP::Class> object
1098 for a given a C<$package_name>.
1100 =item B<reinitialize ($package_name, %options)>
1102 This removes the old metaclass, and creates a new one in it's place.
1103 Do B<not> use this unless you really know what you are doing, it could
1104 very easily make a very large mess of your program.
1106 =item B<construct_class_instance (%options)>
1108 This will construct an instance of B<Class::MOP::Class>, it is
1109 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1110 to use C<construct_instance> once all the bootstrapping is done. This
1111 method is used internally by C<initialize> and should never be called
1112 from outside of that method really.
1114 =item B<check_metaclass_compatability>
1116 This method is called as the very last thing in the
1117 C<construct_class_instance> method. This will check that the
1118 metaclass you are creating is compatible with the metaclasses of all
1119 your ancestors. For more inforamtion about metaclass compatibility
1120 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1122 =item B<update_package_cache_flag>
1124 This will reset the package cache flag for this particular metaclass
1125 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1126 function. This is very rarely needed from outside of C<Class::MOP::Class>
1127 but in some cases you might want to use it, so it is here.
1129 =item B<reset_package_cache_flag>
1131 Clears the package cache flag to announce to the internals that we need
1132 to rebuild the method map.
1136 =head2 Object instance construction and cloning
1138 These methods are B<entirely optional>, it is up to you whether you want
1143 =item B<instance_metaclass>
1145 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1146 for more information on the instance metaclasses.
1148 =item B<get_meta_instance>
1150 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1151 of a new instance of the class.
1153 =item B<new_object (%params)>
1155 This is a convience method for creating a new object of the class, and
1156 blessing it into the appropriate package as well. Ideally your class
1157 would call a C<new> this method like so:
1160 my ($class, %param) = @_;
1161 $class->meta->new_object(%params);
1164 =item B<construct_instance (%params)>
1166 This method is used to construct an instance structure suitable for
1167 C<bless>-ing into your package of choice. It works in conjunction
1168 with the Attribute protocol to collect all applicable attributes.
1170 This will construct and instance using a HASH ref as storage
1171 (currently only HASH references are supported). This will collect all
1172 the applicable attributes and layout out the fields in the HASH ref,
1173 it will then initialize them using either use the corresponding key
1174 in C<%params> or any default value or initializer found in the
1175 attribute meta-object.
1177 =item B<clone_object ($instance, %params)>
1179 This is a convience method for cloning an object instance, then
1180 blessing it into the appropriate package. This method will call
1181 C<clone_instance>, which performs a shallow copy of the object,
1182 see that methods documentation for more details. Ideally your
1183 class would call a C<clone> this method like so:
1185 sub MyClass::clone {
1186 my ($self, %param) = @_;
1187 $self->meta->clone_object($self, %params);
1190 =item B<clone_instance($instance, %params)>
1192 This method is a compliment of C<construct_instance> (which means if
1193 you override C<construct_instance>, you need to override this one too),
1194 and clones the instance shallowly.
1196 The cloned structure returned is (like with C<construct_instance>) an
1197 unC<bless>ed HASH reference, it is your responsibility to then bless
1198 this cloned structure into the right class (which C<clone_object> will
1201 As of 0.11, this method will clone the C<$instance> structure shallowly,
1202 as opposed to the deep cloning implemented in prior versions. After much
1203 thought, research and discussion, I have decided that anything but basic
1204 shallow cloning is outside the scope of the meta-object protocol. I
1205 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1206 is too I<context-specific> to be part of the MOP.
1208 =item B<rebless_instance($instance, ?%params)>
1210 This will change the class of C<$instance> to the class of the invoking
1211 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1212 itself. You may pass in optional C<%params> which are like constructor
1213 params and will override anything already defined in the instance.
1217 =head2 Informational
1219 These are a few predicate methods for asking information about the class.
1223 =item B<is_anon_class>
1225 This returns true if the class is a C<Class::MOP::Class> created anon class.
1229 This returns true if the class is still mutable.
1231 =item B<is_immutable>
1233 This returns true if the class has been made immutable.
1237 =head2 Inheritance Relationships
1241 =item B<superclasses (?@superclasses)>
1243 This is a read-write attribute which represents the superclass
1244 relationships of the class the B<Class::MOP::Class> instance is
1245 associated with. Basically, it can get and set the C<@ISA> for you.
1247 =item B<class_precedence_list>
1249 This computes the a list of all the class's ancestors in the same order
1250 in which method dispatch will be done. This is similair to what
1251 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1253 =item B<linearized_isa>
1255 This returns a list based on C<class_precedence_list> but with all
1260 This returns a list of subclasses for this class.
1268 =item B<get_method_map>
1270 Returns a HASH ref of name to CODE reference mapping for this class.
1272 =item B<method_metaclass>
1274 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1275 for more information on the method metaclasses.
1277 =item B<add_method ($method_name, $method)>
1279 This will take a C<$method_name> and CODE reference to that
1280 C<$method> and install it into the class's package.
1283 This does absolutely nothing special to C<$method>
1284 other than use B<Sub::Name> to make sure it is tagged with the
1285 correct name, and therefore show up correctly in stack traces and
1288 =item B<alias_method ($method_name, $method)>
1290 This will take a C<$method_name> and CODE reference to that
1291 C<$method> and alias the method into the class's package.
1294 Unlike C<add_method>, this will B<not> try to name the
1295 C<$method> using B<Sub::Name>, it only aliases the method in
1296 the class's package.
1298 =item B<has_method ($method_name)>
1300 This just provides a simple way to check if the class implements
1301 a specific C<$method_name>. It will I<not> however, attempt to check
1302 if the class inherits the method (use C<UNIVERSAL::can> for that).
1304 This will correctly handle functions defined outside of the package
1305 that use a fully qualified name (C<sub Package::name { ... }>).
1307 This will correctly handle functions renamed with B<Sub::Name> and
1308 installed using the symbol tables. However, if you are naming the
1309 subroutine outside of the package scope, you must use the fully
1310 qualified name, including the package name, for C<has_method> to
1311 correctly identify it.
1313 This will attempt to correctly ignore functions imported from other
1314 packages using B<Exporter>. It breaks down if the function imported
1315 is an C<__ANON__> sub (such as with C<use constant>), which very well
1316 may be a valid method being applied to the class.
1318 In short, this method cannot always be trusted to determine if the
1319 C<$method_name> is actually a method. However, it will DWIM about
1320 90% of the time, so it's a small trade off I think.
1322 =item B<get_method ($method_name)>
1324 This will return a Class::MOP::Method instance related to the specified
1325 C<$method_name>, or return undef if that method does not exist.
1327 The Class::MOP::Method is codifiable, so you can use it like a normal
1328 CODE reference, see L<Class::MOP::Method> for more information.
1330 =item B<find_method_by_name ($method_name)>
1332 This will return a CODE reference of the specified C<$method_name>,
1333 or return undef if that method does not exist.
1335 Unlike C<get_method> this will also look in the superclasses.
1337 =item B<remove_method ($method_name)>
1339 This will attempt to remove a given C<$method_name> from the class.
1340 It will return the CODE reference that it has removed, and will
1341 attempt to use B<Sub::Name> to clear the methods associated name.
1343 =item B<get_method_list>
1345 This will return a list of method names for all I<locally> defined
1346 methods. It does B<not> provide a list of all applicable methods,
1347 including any inherited ones. If you want a list of all applicable
1348 methods, use the C<compute_all_applicable_methods> method.
1350 =item B<compute_all_applicable_methods>
1352 This will return a list of all the methods names this class will
1353 respond to, taking into account inheritance. The list will be a list of
1354 HASH references, each one containing the following information; method
1355 name, the name of the class in which the method lives and a CODE
1356 reference for the actual method.
1358 =item B<find_all_methods_by_name ($method_name)>
1360 This will traverse the inheritence hierarchy and locate all methods
1361 with a given C<$method_name>. Similar to
1362 C<compute_all_applicable_methods> it returns a list of HASH references
1363 with the following information; method name (which will always be the
1364 same as C<$method_name>), the name of the class in which the method
1365 lives and a CODE reference for the actual method.
1367 The list of methods produced is a distinct list, meaning there are no
1368 duplicates in it. This is especially useful for things like object
1369 initialization and destruction where you only want the method called
1370 once, and in the correct order.
1372 =item B<find_next_method_by_name ($method_name)>
1374 This will return the first method to match a given C<$method_name> in
1375 the superclasses, this is basically equivalent to calling
1376 C<SUPER::$method_name>, but it can be dispatched at runtime.
1380 =head2 Method Modifiers
1382 Method modifiers are a concept borrowed from CLOS, in which a method
1383 can be wrapped with I<before>, I<after> and I<around> method modifiers
1384 that will be called everytime the method is called.
1386 =head3 How method modifiers work?
1388 Method modifiers work by wrapping the original method and then replacing
1389 it in the classes symbol table. The wrappers will handle calling all the
1390 modifiers in the appropariate orders and preserving the calling context
1391 for the original method.
1393 Each method modifier serves a particular purpose, which may not be
1394 obvious to users of other method wrapping modules. To start with, the
1395 return values of I<before> and I<after> modifiers are ignored. This is
1396 because thier purpose is B<not> to filter the input and output of the
1397 primary method (this is done with an I<around> modifier). This may seem
1398 like an odd restriction to some, but doing this allows for simple code
1399 to be added at the begining or end of a method call without jeapordizing
1400 the normal functioning of the primary method or placing any extra
1401 responsibility on the code of the modifier. Of course if you have more
1402 complex needs, then use the I<around> modifier, which uses a variation
1403 of continutation passing style to allow for a high degree of flexibility.
1405 Before and around modifiers are called in last-defined-first-called order,
1406 while after modifiers are called in first-defined-first-called order. So
1407 the call tree might looks something like this:
1417 To see examples of using method modifiers, see the following examples
1418 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1419 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1420 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1422 =head3 What is the performance impact?
1424 Of course there is a performance cost associated with method modifiers,
1425 but we have made every effort to make that cost be directly proportional
1426 to the amount of modifier features you utilize.
1428 The wrapping method does it's best to B<only> do as much work as it
1429 absolutely needs to. In order to do this we have moved some of the
1430 performance costs to set-up time, where they are easier to amortize.
1432 All this said, my benchmarks have indicated the following:
1434 simple wrapper with no modifiers 100% slower
1435 simple wrapper with simple before modifier 400% slower
1436 simple wrapper with simple after modifier 450% slower
1437 simple wrapper with simple around modifier 500-550% slower
1438 simple wrapper with all 3 modifiers 1100% slower
1440 These numbers may seem daunting, but you must remember, every feature
1441 comes with some cost. To put things in perspective, just doing a simple
1442 C<AUTOLOAD> which does nothing but extract the name of the method called
1443 and return it costs about 400% over a normal method call.
1447 =item B<add_before_method_modifier ($method_name, $code)>
1449 This will wrap the method at C<$method_name> and the supplied C<$code>
1450 will be passed the C<@_> arguments, and called before the original
1451 method is called. As specified above, the return value of the I<before>
1452 method modifiers is ignored, and it's ability to modify C<@_> is
1453 fairly limited. If you need to do either of these things, use an
1454 C<around> method modifier.
1456 =item B<add_after_method_modifier ($method_name, $code)>
1458 This will wrap the method at C<$method_name> so that the original
1459 method will be called, it's return values stashed, and then the
1460 supplied C<$code> will be passed the C<@_> arguments, and called.
1461 As specified above, the return value of the I<after> method
1462 modifiers is ignored, and it cannot modify the return values of
1463 the original method. If you need to do either of these things, use an
1464 C<around> method modifier.
1466 =item B<add_around_method_modifier ($method_name, $code)>
1468 This will wrap the method at C<$method_name> so that C<$code>
1469 will be called and passed the original method as an extra argument
1470 at the begining of the C<@_> argument list. This is a variation of
1471 continuation passing style, where the function prepended to C<@_>
1472 can be considered a continuation. It is up to C<$code> if it calls
1473 the original method or not, there is no restriction on what the
1474 C<$code> can or cannot do.
1480 It should be noted that since there is no one consistent way to define
1481 the attributes of a class in Perl 5. These methods can only work with
1482 the information given, and can not easily discover information on
1483 their own. See L<Class::MOP::Attribute> for more details.
1487 =item B<attribute_metaclass>
1489 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1490 for more information on the attribute metaclasses.
1492 =item B<get_attribute_map>
1494 This returns a HASH ref of name to attribute meta-object mapping.
1496 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1498 This stores the C<$attribute_meta_object> (or creates one from the
1499 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1500 instance associated with the given class. Unlike methods, attributes
1501 within the MOP are stored as meta-information only. They will be used
1502 later to construct instances from (see C<construct_instance> above).
1503 More details about the attribute meta-objects can be found in the
1504 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1507 It should be noted that any accessor, reader/writer or predicate
1508 methods which the C<$attribute_meta_object> has will be installed
1509 into the class at this time.
1512 If an attribute already exists for C<$attribute_name>, the old one
1513 will be removed (as well as removing all it's accessors), and then
1516 =item B<has_attribute ($attribute_name)>
1518 Checks to see if this class has an attribute by the name of
1519 C<$attribute_name> and returns a boolean.
1521 =item B<get_attribute ($attribute_name)>
1523 Returns the attribute meta-object associated with C<$attribute_name>,
1524 if none is found, it will return undef.
1526 =item B<remove_attribute ($attribute_name)>
1528 This will remove the attribute meta-object stored at
1529 C<$attribute_name>, then return the removed attribute meta-object.
1532 Removing an attribute will only affect future instances of
1533 the class, it will not make any attempt to remove the attribute from
1534 any existing instances of the class.
1536 It should be noted that any accessor, reader/writer or predicate
1537 methods which the attribute meta-object stored at C<$attribute_name>
1538 has will be removed from the class at this time. This B<will> make
1539 these attributes somewhat inaccessable in previously created
1540 instances. But if you are crazy enough to do this at runtime, then
1541 you are crazy enough to deal with something like this :).
1543 =item B<get_attribute_list>
1545 This returns a list of attribute names which are defined in the local
1546 class. If you want a list of all applicable attributes for a class,
1547 use the C<compute_all_applicable_attributes> method.
1549 =item B<compute_all_applicable_attributes>
1551 This will traverse the inheritance heirachy and return a list of all
1552 the applicable attributes for this class. It does not construct a
1553 HASH reference like C<compute_all_applicable_methods> because all
1554 that same information is discoverable through the attribute
1557 =item B<find_attribute_by_name ($attr_name)>
1559 This method will traverse the inheritance heirachy and find the
1560 first attribute whose name matches C<$attr_name>, then return it.
1561 It will return undef if nothing is found.
1565 =head2 Class Immutability
1569 =item B<make_immutable (%options)>
1571 This method will invoke a tranforamtion upon the class which will
1572 make it immutable. Details of this transformation can be found in
1573 the L<Class::MOP::Immutable> documentation.
1575 =item B<make_mutable>
1577 This method will reverse tranforamtion upon the class which
1580 =item B<create_immutable_transformer>
1582 Create a transformer suitable for making this class immutable
1588 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1590 =head1 COPYRIGHT AND LICENSE
1592 Copyright 2006-2008 by Infinity Interactive, Inc.
1594 L<http://www.iinteractive.com>
1596 This library is free software; you can redistribute it and/or modify
1597 it under the same terms as Perl itself.