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';
13 use Sub::Name 'subname';
15 our $VERSION = '0.31';
16 our $AUTHORITY = 'cpan:STEVAN';
18 use base 'Class::MOP::Module';
24 my $package_name = shift;
25 (defined $package_name && $package_name && !blessed($package_name))
26 || confess "You must pass a package name and it cannot be blessed";
27 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
30 $class->construct_class_instance('package' => $package_name, @_);
35 my $package_name = shift;
36 (defined $package_name && $package_name && !blessed($package_name))
37 || confess "You must pass a package name and it cannot be blessed";
38 Class::MOP::remove_metaclass_by_name($package_name);
39 $class->construct_class_instance('package' => $package_name, @_);
42 # NOTE: (meta-circularity)
43 # this is a special form of &construct_instance
44 # (see below), which is used to construct class
45 # meta-object instances for any Class::MOP::*
46 # class. All other classes will use the more
47 # normal &construct_instance.
48 sub construct_class_instance {
51 my $package_name = $options{'package'};
52 (defined $package_name && $package_name)
53 || confess "You must pass a package name";
55 # return the metaclass if we have it cached,
56 # and it is still defined (it has not been
57 # reaped by DESTROY yet, which can happen
58 # annoyingly enough during global destruction)
60 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
65 # we need to deal with the possibility
66 # of class immutability here, and then
67 # get the name of the class appropriately
68 $class = (blessed($class)
69 ? ($class->is_immutable
70 ? $class->get_mutable_metaclass_name()
74 # now create the metaclass
76 if ($class eq 'Class::MOP::Class') {
79 # inherited from Class::MOP::Package
80 '$!package' => $package_name,
83 # since the following attributes will
84 # actually be loaded from the symbol
85 # table, and actually bypass the instance
86 # entirely, we can just leave these things
87 # listed here for reference, because they
88 # should not actually have a value associated
90 '%!namespace' => \undef,
91 # inherited from Class::MOP::Module
92 '$!version' => \undef,
93 '$!authority' => \undef,
94 # defined in Class::MOP::Class
95 '@!superclasses' => \undef,
99 '$!attribute_metaclass' => $options{'attribute_metaclass'} || 'Class::MOP::Attribute',
100 '$!method_metaclass' => $options{'method_metaclass'} || 'Class::MOP::Method',
101 '$!instance_metaclass' => $options{'instance_metaclass'} || 'Class::MOP::Instance',
103 ## uber-private variables
105 # this starts out as undef so that
106 # we can tell the first time the
107 # methods are fetched
109 '$!_package_cache_flag' => undef,
114 # it is safe to use meta here because
115 # class will always be a subclass of
116 # Class::MOP::Class, which defines meta
117 $meta = $class->meta->construct_instance(%options)
120 # and check the metaclass compatibility
121 $meta->check_metaclass_compatability();
123 Class::MOP::store_metaclass_by_name($package_name, $meta);
126 # we need to weaken any anon classes
127 # so that they can call DESTROY properly
128 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
133 sub reset_package_cache_flag { (shift)->{'$!_package_cache_flag'} = undef }
134 sub update_package_cache_flag {
137 # we can manually update the cache number
138 # since we are actually adding the method
139 # to our cache as well. This avoids us
140 # having to regenerate the method_map.
142 $self->{'$!_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
145 sub check_metaclass_compatability {
148 # this is always okay ...
149 return if blessed($self) eq 'Class::MOP::Class' &&
150 $self->instance_metaclass eq 'Class::MOP::Instance';
152 my @class_list = $self->linearized_isa;
153 shift @class_list; # shift off $self->name
155 foreach my $class_name (@class_list) {
156 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
159 # we need to deal with the possibility
160 # of class immutability here, and then
161 # get the name of the class appropriately
162 my $meta_type = ($meta->is_immutable
163 ? $meta->get_mutable_metaclass_name()
166 ($self->isa($meta_type))
167 || confess $self->name . "->meta => (" . (blessed($self)) . ")" .
168 " is not compatible with the " .
169 $class_name . "->meta => (" . ($meta_type) . ")";
171 # we also need to check that instance metaclasses
172 # are compatabile in the same the class.
173 ($self->instance_metaclass->isa($meta->instance_metaclass))
174 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
175 " is not compatible with the " .
176 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
184 # this should be sufficient, if you have a
185 # use case where it is not, write a test and
187 my $ANON_CLASS_SERIAL = 0;
190 # we need a sufficiently annoying prefix
191 # this should suffice for now, this is
192 # used in a couple of places below, so
193 # need to put it up here for now.
194 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
198 no warnings 'uninitialized';
199 $self->name =~ /^$ANON_CLASS_PREFIX/ ? 1 : 0;
202 sub create_anon_class {
203 my ($class, %options) = @_;
204 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
205 return $class->create($package_name, %options);
209 # this will only get called for
210 # anon-classes, all other calls
211 # are assumed to occur during
212 # global destruction and so don't
213 # really need to be handled explicitly
216 no warnings 'uninitialized';
217 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
218 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
220 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
221 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
223 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
228 # creating classes with MOP ...
232 my $package_name = shift;
234 (defined $package_name && $package_name)
235 || confess "You must pass a package name";
238 || confess "You much pass all parameters as name => value pairs " .
239 "(I found an uneven number of params in \@_)";
243 (ref $options{superclasses} eq 'ARRAY')
244 || confess "You must pass an ARRAY ref of superclasses"
245 if exists $options{superclasses};
247 (ref $options{attributes} eq 'ARRAY')
248 || confess "You must pass an ARRAY ref of attributes"
249 if exists $options{attributes};
251 (ref $options{methods} eq 'HASH')
252 || confess "You must pass an HASH ref of methods"
253 if exists $options{methods};
255 my $code = "package $package_name;";
256 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
257 if exists $options{version};
258 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
259 if exists $options{authority};
262 confess "creation of $package_name failed : $@" if $@;
264 my $meta = $class->initialize($package_name);
266 $meta->add_method('meta' => sub {
267 $class->initialize(blessed($_[0]) || $_[0]);
270 $meta->superclasses(@{$options{superclasses}})
271 if exists $options{superclasses};
273 # process attributes first, so that they can
274 # install accessors, but locally defined methods
275 # can then overwrite them. It is maybe a little odd, but
276 # I think this should be the order of things.
277 if (exists $options{attributes}) {
278 foreach my $attr (@{$options{attributes}}) {
279 $meta->add_attribute($attr);
282 if (exists $options{methods}) {
283 foreach my $method_name (keys %{$options{methods}}) {
284 $meta->add_method($method_name, $options{methods}->{$method_name});
293 # all these attribute readers will be bootstrapped
294 # away in the Class::MOP bootstrap section
296 sub get_attribute_map { $_[0]->{'%!attributes'} }
297 sub attribute_metaclass { $_[0]->{'$!attribute_metaclass'} }
298 sub method_metaclass { $_[0]->{'$!method_metaclass'} }
299 sub instance_metaclass { $_[0]->{'$!instance_metaclass'} }
302 # this is a prime canidate for conversion to XS
306 if (defined $self->{'$!_package_cache_flag'} &&
307 $self->{'$!_package_cache_flag'} == Class::MOP::check_package_cache_flag($self->name)) {
308 return $self->{'%!methods'};
311 my $map = $self->{'%!methods'};
313 my $class_name = $self->name;
314 my $method_metaclass = $self->method_metaclass;
316 foreach my $symbol ($self->list_all_package_symbols('CODE')) {
317 my $code = $self->get_package_symbol('&' . $symbol);
319 next if exists $map->{$symbol} &&
320 defined $map->{$symbol} &&
321 $map->{$symbol}->body == $code;
323 my ($pkg, $name) = Class::MOP::get_code_info($code);
324 next if ($pkg || '') ne $class_name &&
325 ($name || '') ne '__ANON__';
327 $map->{$symbol} = $method_metaclass->wrap($code);
333 # Instance Construction & Cloning
338 # we need to protect the integrity of the
339 # Class::MOP::Class singletons here, so we
340 # delegate this to &construct_class_instance
341 # which will deal with the singletons
342 return $class->construct_class_instance(@_)
343 if $class->name->isa('Class::MOP::Class');
344 return $class->construct_instance(@_);
347 sub construct_instance {
348 my ($class, %params) = @_;
349 my $meta_instance = $class->get_meta_instance();
350 my $instance = $meta_instance->create_instance();
351 foreach my $attr ($class->compute_all_applicable_attributes()) {
352 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
355 # this will only work for a HASH instance type
356 if ($class->is_anon_class) {
357 (reftype($instance) eq 'HASH')
358 || confess "Currently only HASH based instances are supported with instance of anon-classes";
360 # At some point we should make this official
361 # as a reserved slot name, but right now I am
362 # going to keep it here.
363 # my $RESERVED_MOP_SLOT = '__MOP__';
364 $instance->{'__MOP__'} = $class;
369 sub get_meta_instance {
371 return $class->instance_metaclass->new(
373 $class->compute_all_applicable_attributes()
379 my $instance = shift;
380 (blessed($instance) && $instance->isa($class->name))
381 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
383 # we need to protect the integrity of the
384 # Class::MOP::Class singletons here, they
385 # should not be cloned.
386 return $instance if $instance->isa('Class::MOP::Class');
387 $class->clone_instance($instance, @_);
391 my ($class, $instance, %params) = @_;
393 || confess "You can only clone instances, \$self is not a blessed instance";
394 my $meta_instance = $class->get_meta_instance();
395 my $clone = $meta_instance->clone_instance($instance);
396 foreach my $attr ($class->compute_all_applicable_attributes()) {
397 if ( defined( my $init_arg = $attr->init_arg ) ) {
398 if (exists $params{$init_arg}) {
399 $attr->set_value($clone, $params{$init_arg});
406 sub rebless_instance {
407 my ($self, $instance, %params) = @_;
410 if ($instance->can('meta')) {
411 ($instance->meta->isa('Class::MOP::Class'))
412 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
413 $old_metaclass = $instance->meta;
416 $old_metaclass = $self->initialize(blessed($instance));
419 my $meta_instance = $self->get_meta_instance();
421 $self->name->isa($old_metaclass->name)
422 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
425 $meta_instance->rebless_instance_structure($instance, $self);
427 foreach my $attr ( $self->compute_all_applicable_attributes ) {
428 if ( $attr->has_value($instance) ) {
429 if ( defined( my $init_arg = $attr->init_arg ) ) {
430 $params{$init_arg} = $attr->get_value($instance)
431 unless exists $params{$init_arg};
434 $attr->set_value($instance, $attr->get_value($instance));
439 foreach my $attr ($self->compute_all_applicable_attributes) {
440 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
452 @{$self->get_package_symbol('@ISA')} = @supers;
454 # we need to check the metaclass
455 # compatibility here so that we can
456 # be sure that the superclass is
457 # not potentially creating an issues
458 # we don't know about
459 $self->check_metaclass_compatability();
461 @{$self->get_package_symbol('@ISA')};
467 my $super_class = $self->name;
470 my $find_derived_classes;
471 $find_derived_classes = sub {
472 my ($outer_class) = @_;
474 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
477 for my $symbol ( keys %$symbol_table_hashref ) {
478 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
479 my $inner_class = $1;
481 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
485 ? "${outer_class}::$inner_class"
488 if ( $class->isa($super_class) and $class ne $super_class ) {
489 push @derived_classes, $class;
492 next SYMBOL if $class eq 'main'; # skip 'main::*'
494 $find_derived_classes->($class);
498 my $root_class = q{};
499 $find_derived_classes->($root_class);
501 undef $find_derived_classes;
503 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
505 return @derived_classes;
510 return @{ mro::get_linear_isa( (shift)->name ) };
513 sub class_precedence_list {
515 my $name = $self->name;
517 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
519 # We need to check for circular inheritance here
520 # if we are are not on 5.10, cause 5.8 detects it
521 # late. This will do nothing if all is well, and
522 # blow up otherwise. Yes, it's an ugly hack, better
523 # suggestions are welcome.
525 ($name || return)->isa('This is a test for circular inheritance')
528 # if our mro is c3, we can
529 # just grab the linear_isa
530 if (mro::get_mro($name) eq 'c3') {
531 return @{ mro::get_linear_isa($name) }
535 # we can't grab the linear_isa for dfs
536 # since it has all the duplicates
541 $self->initialize($_)->class_precedence_list()
542 } $self->superclasses()
550 my ($self, $method_name, $method) = @_;
551 (defined $method_name && $method_name)
552 || confess "You must define a method name";
555 if (blessed($method)) {
556 $body = $method->body;
560 ('CODE' eq (reftype($body) || ''))
561 || confess "Your code block must be a CODE reference";
562 $method = $self->method_metaclass->wrap($body);
564 $self->get_method_map->{$method_name} = $method;
566 my $full_method_name = ($self->name . '::' . $method_name);
567 $self->add_package_symbol("&${method_name}" => subname $full_method_name => $body);
568 $self->update_package_cache_flag;
572 my $fetch_and_prepare_method = sub {
573 my ($self, $method_name) = @_;
575 my $method = $self->get_method($method_name);
576 # if we dont have local ...
578 # try to find the next method
579 $method = $self->find_next_method_by_name($method_name);
580 # die if it does not exist
582 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
583 # and now make sure to wrap it
584 # even if it is already wrapped
585 # because we need a new sub ref
586 $method = Class::MOP::Method::Wrapped->wrap($method);
589 # now make sure we wrap it properly
590 $method = Class::MOP::Method::Wrapped->wrap($method)
591 unless $method->isa('Class::MOP::Method::Wrapped');
593 $self->add_method($method_name => $method);
597 sub add_before_method_modifier {
598 my ($self, $method_name, $method_modifier) = @_;
599 (defined $method_name && $method_name)
600 || confess "You must pass in a method name";
601 my $method = $fetch_and_prepare_method->($self, $method_name);
602 $method->add_before_modifier(subname ':before' => $method_modifier);
605 sub add_after_method_modifier {
606 my ($self, $method_name, $method_modifier) = @_;
607 (defined $method_name && $method_name)
608 || confess "You must pass in a method name";
609 my $method = $fetch_and_prepare_method->($self, $method_name);
610 $method->add_after_modifier(subname ':after' => $method_modifier);
613 sub add_around_method_modifier {
614 my ($self, $method_name, $method_modifier) = @_;
615 (defined $method_name && $method_name)
616 || confess "You must pass in a method name";
617 my $method = $fetch_and_prepare_method->($self, $method_name);
618 $method->add_around_modifier(subname ':around' => $method_modifier);
622 # the methods above used to be named like this:
623 # ${pkg}::${method}:(before|after|around)
624 # but this proved problematic when using one modifier
625 # to wrap multiple methods (something which is likely
626 # to happen pretty regularly IMO). So instead of naming
627 # it like this, I have chosen to just name them purely
628 # with their modifier names, like so:
629 # :(before|after|around)
630 # The fact is that in a stack trace, it will be fairly
631 # evident from the context what method they are attached
632 # to, and so don't need the fully qualified name.
636 my ($self, $method_name, $method) = @_;
637 (defined $method_name && $method_name)
638 || confess "You must define a method name";
640 my $body = (blessed($method) ? $method->body : $method);
641 ('CODE' eq (reftype($body) || ''))
642 || confess "Your code block must be a CODE reference";
644 $self->add_package_symbol("&${method_name}" => $body);
645 $self->update_package_cache_flag;
649 my ($self, $method_name) = @_;
650 (defined $method_name && $method_name)
651 || confess "You must define a method name";
653 return 0 unless exists $self->get_method_map->{$method_name};
658 my ($self, $method_name) = @_;
659 (defined $method_name && $method_name)
660 || confess "You must define a method name";
663 # I don't really need this here, because
664 # if the method_map is missing a key it
665 # will just return undef for me now
666 # return unless $self->has_method($method_name);
668 return $self->get_method_map->{$method_name};
672 my ($self, $method_name) = @_;
673 (defined $method_name && $method_name)
674 || confess "You must define a method name";
676 my $removed_method = delete $self->get_method_map->{$method_name};
678 $self->remove_package_symbol("&${method_name}");
680 $self->update_package_cache_flag;
682 return $removed_method;
685 sub get_method_list {
687 keys %{$self->get_method_map};
690 sub find_method_by_name {
691 my ($self, $method_name) = @_;
692 (defined $method_name && $method_name)
693 || confess "You must define a method name to find";
694 foreach my $class ($self->linearized_isa) {
695 # fetch the meta-class ...
696 my $meta = $self->initialize($class);
697 return $meta->get_method($method_name)
698 if $meta->has_method($method_name);
703 sub compute_all_applicable_methods {
705 my (@methods, %seen_method);
706 foreach my $class ($self->linearized_isa) {
707 # fetch the meta-class ...
708 my $meta = $self->initialize($class);
709 foreach my $method_name ($meta->get_method_list()) {
710 next if exists $seen_method{$method_name};
711 $seen_method{$method_name}++;
713 name => $method_name,
715 code => $meta->get_method($method_name)
722 sub find_all_methods_by_name {
723 my ($self, $method_name) = @_;
724 (defined $method_name && $method_name)
725 || confess "You must define a method name to find";
727 foreach my $class ($self->linearized_isa) {
728 # fetch the meta-class ...
729 my $meta = $self->initialize($class);
731 name => $method_name,
733 code => $meta->get_method($method_name)
734 } if $meta->has_method($method_name);
739 sub find_next_method_by_name {
740 my ($self, $method_name) = @_;
741 (defined $method_name && $method_name)
742 || confess "You must define a method name to find";
743 my @cpl = $self->linearized_isa;
744 shift @cpl; # discard ourselves
745 foreach my $class (@cpl) {
746 # fetch the meta-class ...
747 my $meta = $self->initialize($class);
748 return $meta->get_method($method_name)
749 if $meta->has_method($method_name);
758 # either we have an attribute object already
759 # or we need to create one from the args provided
760 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
761 # make sure it is derived from the correct type though
762 ($attribute->isa('Class::MOP::Attribute'))
763 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
765 # first we attach our new attribute
766 # because it might need certain information
767 # about the class which it is attached to
768 $attribute->attach_to_class($self);
770 # then we remove attributes of a conflicting
771 # name here so that we can properly detach
772 # the old attr object, and remove any
773 # accessors it would have generated
774 $self->remove_attribute($attribute->name)
775 if $self->has_attribute($attribute->name);
777 # then onto installing the new accessors
778 $attribute->install_accessors();
779 $self->get_attribute_map->{$attribute->name} = $attribute;
783 my ($self, $attribute_name) = @_;
784 (defined $attribute_name && $attribute_name)
785 || confess "You must define an attribute name";
786 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
790 my ($self, $attribute_name) = @_;
791 (defined $attribute_name && $attribute_name)
792 || confess "You must define an attribute name";
793 return $self->get_attribute_map->{$attribute_name}
795 # this will return undef anyway, so no need ...
796 # if $self->has_attribute($attribute_name);
800 sub remove_attribute {
801 my ($self, $attribute_name) = @_;
802 (defined $attribute_name && $attribute_name)
803 || confess "You must define an attribute name";
804 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
805 return unless defined $removed_attribute;
806 delete $self->get_attribute_map->{$attribute_name};
807 $removed_attribute->remove_accessors();
808 $removed_attribute->detach_from_class();
809 return $removed_attribute;
812 sub get_attribute_list {
814 keys %{$self->get_attribute_map};
817 sub compute_all_applicable_attributes {
819 my (@attrs, %seen_attr);
820 foreach my $class ($self->linearized_isa) {
821 # fetch the meta-class ...
822 my $meta = $self->initialize($class);
823 foreach my $attr_name ($meta->get_attribute_list()) {
824 next if exists $seen_attr{$attr_name};
825 $seen_attr{$attr_name}++;
826 push @attrs => $meta->get_attribute($attr_name);
832 sub find_attribute_by_name {
833 my ($self, $attr_name) = @_;
834 foreach my $class ($self->linearized_isa) {
835 # fetch the meta-class ...
836 my $meta = $self->initialize($class);
837 return $meta->get_attribute($attr_name)
838 if $meta->has_attribute($attr_name);
846 sub is_immutable { 0 }
849 # Why I changed this (groditi)
850 # - One Metaclass may have many Classes through many Metaclass instances
851 # - One Metaclass should only have one Immutable Transformer instance
852 # - Each Class may have different Immutabilizing options
853 # - Therefore each Metaclass instance may have different Immutabilizing options
854 # - We need to store one Immutable Transformer instance per Metaclass
855 # - We need to store one set of Immutable Transformer options per Class
856 # - Upon make_mutable we may delete the Immutabilizing options
857 # - We could clean the immutable Transformer instance when there is no more
858 # immutable Classes of that type, but we can also keep it in case
859 # another class with this same Metaclass becomes immutable. It is a case
860 # of trading of storing an instance to avoid unnecessary instantiations of
861 # Immutable Transformers. You may view this as a memory leak, however
862 # Because we have few Metaclasses, in practice it seems acceptable
863 # - To allow Immutable Transformers instances to be cleaned up we could weaken
864 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
867 my %IMMUTABLE_TRANSFORMERS;
868 my %IMMUTABLE_OPTIONS;
872 my $class = blessed $self || $self;
874 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
875 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
877 $transformer->make_metaclass_immutable($self, \%options);
878 $IMMUTABLE_OPTIONS{$self->name} =
879 { %options, IMMUTABLE_TRANSFORMER => $transformer };
881 if( exists $options{debug} && $options{debug} ){
882 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
883 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
891 return if $self->is_mutable;
892 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
893 confess "unable to find immutabilizing options" unless ref $options;
894 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
895 $transformer->make_metaclass_mutable($self, $options);
900 sub create_immutable_transformer {
902 my $class = Class::MOP::Immutable->new($self, {
903 read_only => [qw/superclasses/],
910 remove_package_symbol
913 class_precedence_list => 'ARRAY',
914 linearized_isa => 'ARRAY',
915 compute_all_applicable_attributes => 'ARRAY',
916 get_meta_instance => 'SCALAR',
917 get_method_map => 'SCALAR',
920 # this is ugly, but so are typeglobs,
921 # so whattayahgonnadoboutit
924 add_package_symbol => sub {
925 my $original = shift;
926 confess "Cannot add package symbols to an immutable metaclass"
927 unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
928 goto $original->body;
943 Class::MOP::Class - Class Meta Object
947 # assuming that class Foo
948 # has been defined, you can
950 # use this for introspection ...
952 # add a method to Foo ...
953 Foo->meta->add_method('bar' => sub { ... })
955 # get a list of all the classes searched
956 # the method dispatcher in the correct order
957 Foo->meta->class_precedence_list()
959 # remove a method from Foo
960 Foo->meta->remove_method('bar');
962 # or use this to actually create classes ...
964 Class::MOP::Class->create('Bar' => (
966 superclasses => [ 'Foo' ],
968 Class::MOP:::Attribute->new('$bar'),
969 Class::MOP:::Attribute->new('$baz'),
972 calculate_bar => sub { ... },
973 construct_baz => sub { ... }
979 This is the largest and currently most complex part of the Perl 5
980 meta-object protocol. It controls the introspection and
981 manipulation of Perl 5 classes (and it can create them too). The
982 best way to understand what this module can do, is to read the
983 documentation for each of it's methods.
987 =head2 Self Introspection
993 This will return a B<Class::MOP::Class> instance which is related
994 to this class. Thereby allowing B<Class::MOP::Class> to actually
997 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
998 bootstrap this module by installing a number of attribute meta-objects
999 into it's metaclass. This will allow this class to reap all the benifits
1000 of the MOP when subclassing it.
1004 =head2 Class construction
1006 These methods will handle creating B<Class::MOP::Class> objects,
1007 which can be used to both create new classes, and analyze
1008 pre-existing classes.
1010 This module will internally store references to all the instances
1011 you create with these methods, so that they do not need to be
1012 created any more than nessecary. Basically, they are singletons.
1016 =item B<create ($package_name,
1017 version =E<gt> ?$version,
1018 authority =E<gt> ?$authority,
1019 superclasses =E<gt> ?@superclasses,
1020 methods =E<gt> ?%methods,
1021 attributes =E<gt> ?%attributes)>
1023 This returns a B<Class::MOP::Class> object, bringing the specified
1024 C<$package_name> into existence and adding any of the C<$version>,
1025 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1028 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1029 methods =E<gt> ?%methods,
1030 attributes =E<gt> ?%attributes)>
1032 This will create an anonymous class, it works much like C<create> but
1033 it does not need a C<$package_name>. Instead it will create a suitably
1034 unique package name for you to stash things into.
1036 On very important distinction is that anon classes are destroyed once
1037 the metaclass they are attached to goes out of scope. In the DESTROY
1038 method, the created package will be removed from the symbol table.
1040 It is also worth noting that any instances created with an anon-class
1041 will keep a special reference to the anon-meta which will prevent the
1042 anon-class from going out of scope until all instances of it have also
1043 been destroyed. This however only works for HASH based instance types,
1044 as we use a special reserved slot (C<__MOP__>) to store this.
1046 =item B<initialize ($package_name, %options)>
1048 This initializes and returns returns a B<Class::MOP::Class> object
1049 for a given a C<$package_name>.
1051 =item B<reinitialize ($package_name, %options)>
1053 This removes the old metaclass, and creates a new one in it's place.
1054 Do B<not> use this unless you really know what you are doing, it could
1055 very easily make a very large mess of your program.
1057 =item B<construct_class_instance (%options)>
1059 This will construct an instance of B<Class::MOP::Class>, it is
1060 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1061 to use C<construct_instance> once all the bootstrapping is done. This
1062 method is used internally by C<initialize> and should never be called
1063 from outside of that method really.
1065 =item B<check_metaclass_compatability>
1067 This method is called as the very last thing in the
1068 C<construct_class_instance> method. This will check that the
1069 metaclass you are creating is compatible with the metaclasses of all
1070 your ancestors. For more inforamtion about metaclass compatibility
1071 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1073 =item B<update_package_cache_flag>
1075 This will reset the package cache flag for this particular metaclass
1076 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1077 function. This is very rarely needed from outside of C<Class::MOP::Class>
1078 but in some cases you might want to use it, so it is here.
1080 =item B<reset_package_cache_flag>
1082 Clears the package cache flag to announce to the internals that we need
1083 to rebuild the method map.
1087 =head2 Object instance construction and cloning
1089 These methods are B<entirely optional>, it is up to you whether you want
1094 =item B<instance_metaclass>
1096 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1097 for more information on the instance metaclasses.
1099 =item B<get_meta_instance>
1101 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1102 of a new instance of the class.
1104 =item B<new_object (%params)>
1106 This is a convience method for creating a new object of the class, and
1107 blessing it into the appropriate package as well. Ideally your class
1108 would call a C<new> this method like so:
1111 my ($class, %param) = @_;
1112 $class->meta->new_object(%params);
1115 =item B<construct_instance (%params)>
1117 This method is used to construct an instance structure suitable for
1118 C<bless>-ing into your package of choice. It works in conjunction
1119 with the Attribute protocol to collect all applicable attributes.
1121 This will construct and instance using a HASH ref as storage
1122 (currently only HASH references are supported). This will collect all
1123 the applicable attributes and layout out the fields in the HASH ref,
1124 it will then initialize them using either use the corresponding key
1125 in C<%params> or any default value or initializer found in the
1126 attribute meta-object.
1128 =item B<clone_object ($instance, %params)>
1130 This is a convience method for cloning an object instance, then
1131 blessing it into the appropriate package. This method will call
1132 C<clone_instance>, which performs a shallow copy of the object,
1133 see that methods documentation for more details. Ideally your
1134 class would call a C<clone> this method like so:
1136 sub MyClass::clone {
1137 my ($self, %param) = @_;
1138 $self->meta->clone_object($self, %params);
1141 =item B<clone_instance($instance, %params)>
1143 This method is a compliment of C<construct_instance> (which means if
1144 you override C<construct_instance>, you need to override this one too),
1145 and clones the instance shallowly.
1147 The cloned structure returned is (like with C<construct_instance>) an
1148 unC<bless>ed HASH reference, it is your responsibility to then bless
1149 this cloned structure into the right class (which C<clone_object> will
1152 As of 0.11, this method will clone the C<$instance> structure shallowly,
1153 as opposed to the deep cloning implemented in prior versions. After much
1154 thought, research and discussion, I have decided that anything but basic
1155 shallow cloning is outside the scope of the meta-object protocol. I
1156 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1157 is too I<context-specific> to be part of the MOP.
1159 =item B<rebless_instance($instance, ?%params)>
1161 This will change the class of C<$instance> to the class of the invoking
1162 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1163 itself. You may pass in optional C<%params> which are like constructor
1164 params and will override anything already defined in the instance.
1168 =head2 Informational
1170 These are a few predicate methods for asking information about the class.
1174 =item B<is_anon_class>
1176 This returns true if the class is a C<Class::MOP::Class> created anon class.
1180 This returns true if the class is still mutable.
1182 =item B<is_immutable>
1184 This returns true if the class has been made immutable.
1188 =head2 Inheritance Relationships
1192 =item B<superclasses (?@superclasses)>
1194 This is a read-write attribute which represents the superclass
1195 relationships of the class the B<Class::MOP::Class> instance is
1196 associated with. Basically, it can get and set the C<@ISA> for you.
1198 =item B<class_precedence_list>
1200 This computes the a list of all the class's ancestors in the same order
1201 in which method dispatch will be done. This is similair to what
1202 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1204 =item B<linearized_isa>
1206 This returns a list based on C<class_precedence_list> but with all
1211 This returns a list of subclasses for this class.
1219 =item B<get_method_map>
1221 Returns a HASH ref of name to CODE reference mapping for this class.
1223 =item B<method_metaclass>
1225 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1226 for more information on the method metaclasses.
1228 =item B<add_method ($method_name, $method)>
1230 This will take a C<$method_name> and CODE reference to that
1231 C<$method> and install it into the class's package.
1234 This does absolutely nothing special to C<$method>
1235 other than use B<Sub::Name> to make sure it is tagged with the
1236 correct name, and therefore show up correctly in stack traces and
1239 =item B<alias_method ($method_name, $method)>
1241 This will take a C<$method_name> and CODE reference to that
1242 C<$method> and alias the method into the class's package.
1245 Unlike C<add_method>, this will B<not> try to name the
1246 C<$method> using B<Sub::Name>, it only aliases the method in
1247 the class's package.
1249 =item B<has_method ($method_name)>
1251 This just provides a simple way to check if the class implements
1252 a specific C<$method_name>. It will I<not> however, attempt to check
1253 if the class inherits the method (use C<UNIVERSAL::can> for that).
1255 This will correctly handle functions defined outside of the package
1256 that use a fully qualified name (C<sub Package::name { ... }>).
1258 This will correctly handle functions renamed with B<Sub::Name> and
1259 installed using the symbol tables. However, if you are naming the
1260 subroutine outside of the package scope, you must use the fully
1261 qualified name, including the package name, for C<has_method> to
1262 correctly identify it.
1264 This will attempt to correctly ignore functions imported from other
1265 packages using B<Exporter>. It breaks down if the function imported
1266 is an C<__ANON__> sub (such as with C<use constant>), which very well
1267 may be a valid method being applied to the class.
1269 In short, this method cannot always be trusted to determine if the
1270 C<$method_name> is actually a method. However, it will DWIM about
1271 90% of the time, so it's a small trade off I think.
1273 =item B<get_method ($method_name)>
1275 This will return a Class::MOP::Method instance related to the specified
1276 C<$method_name>, or return undef if that method does not exist.
1278 The Class::MOP::Method is codifiable, so you can use it like a normal
1279 CODE reference, see L<Class::MOP::Method> for more information.
1281 =item B<find_method_by_name ($method_name)>
1283 This will return a CODE reference of the specified C<$method_name>,
1284 or return undef if that method does not exist.
1286 Unlike C<get_method> this will also look in the superclasses.
1288 =item B<remove_method ($method_name)>
1290 This will attempt to remove a given C<$method_name> from the class.
1291 It will return the CODE reference that it has removed, and will
1292 attempt to use B<Sub::Name> to clear the methods associated name.
1294 =item B<get_method_list>
1296 This will return a list of method names for all I<locally> defined
1297 methods. It does B<not> provide a list of all applicable methods,
1298 including any inherited ones. If you want a list of all applicable
1299 methods, use the C<compute_all_applicable_methods> method.
1301 =item B<compute_all_applicable_methods>
1303 This will return a list of all the methods names this class will
1304 respond to, taking into account inheritance. The list will be a list of
1305 HASH references, each one containing the following information; method
1306 name, the name of the class in which the method lives and a CODE
1307 reference for the actual method.
1309 =item B<find_all_methods_by_name ($method_name)>
1311 This will traverse the inheritence hierarchy and locate all methods
1312 with a given C<$method_name>. Similar to
1313 C<compute_all_applicable_methods> it returns a list of HASH references
1314 with the following information; method name (which will always be the
1315 same as C<$method_name>), the name of the class in which the method
1316 lives and a CODE reference for the actual method.
1318 The list of methods produced is a distinct list, meaning there are no
1319 duplicates in it. This is especially useful for things like object
1320 initialization and destruction where you only want the method called
1321 once, and in the correct order.
1323 =item B<find_next_method_by_name ($method_name)>
1325 This will return the first method to match a given C<$method_name> in
1326 the superclasses, this is basically equivalent to calling
1327 C<SUPER::$method_name>, but it can be dispatched at runtime.
1331 =head2 Method Modifiers
1333 Method modifiers are a concept borrowed from CLOS, in which a method
1334 can be wrapped with I<before>, I<after> and I<around> method modifiers
1335 that will be called everytime the method is called.
1337 =head3 How method modifiers work?
1339 Method modifiers work by wrapping the original method and then replacing
1340 it in the classes symbol table. The wrappers will handle calling all the
1341 modifiers in the appropariate orders and preserving the calling context
1342 for the original method.
1344 Each method modifier serves a particular purpose, which may not be
1345 obvious to users of other method wrapping modules. To start with, the
1346 return values of I<before> and I<after> modifiers are ignored. This is
1347 because thier purpose is B<not> to filter the input and output of the
1348 primary method (this is done with an I<around> modifier). This may seem
1349 like an odd restriction to some, but doing this allows for simple code
1350 to be added at the begining or end of a method call without jeapordizing
1351 the normal functioning of the primary method or placing any extra
1352 responsibility on the code of the modifier. Of course if you have more
1353 complex needs, then use the I<around> modifier, which uses a variation
1354 of continutation passing style to allow for a high degree of flexibility.
1356 Before and around modifiers are called in last-defined-first-called order,
1357 while after modifiers are called in first-defined-first-called order. So
1358 the call tree might looks something like this:
1368 To see examples of using method modifiers, see the following examples
1369 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1370 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1371 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1373 =head3 What is the performance impact?
1375 Of course there is a performance cost associated with method modifiers,
1376 but we have made every effort to make that cost be directly proportional
1377 to the amount of modifier features you utilize.
1379 The wrapping method does it's best to B<only> do as much work as it
1380 absolutely needs to. In order to do this we have moved some of the
1381 performance costs to set-up time, where they are easier to amortize.
1383 All this said, my benchmarks have indicated the following:
1385 simple wrapper with no modifiers 100% slower
1386 simple wrapper with simple before modifier 400% slower
1387 simple wrapper with simple after modifier 450% slower
1388 simple wrapper with simple around modifier 500-550% slower
1389 simple wrapper with all 3 modifiers 1100% slower
1391 These numbers may seem daunting, but you must remember, every feature
1392 comes with some cost. To put things in perspective, just doing a simple
1393 C<AUTOLOAD> which does nothing but extract the name of the method called
1394 and return it costs about 400% over a normal method call.
1398 =item B<add_before_method_modifier ($method_name, $code)>
1400 This will wrap the method at C<$method_name> and the supplied C<$code>
1401 will be passed the C<@_> arguments, and called before the original
1402 method is called. As specified above, the return value of the I<before>
1403 method modifiers is ignored, and it's ability to modify C<@_> is
1404 fairly limited. If you need to do either of these things, use an
1405 C<around> method modifier.
1407 =item B<add_after_method_modifier ($method_name, $code)>
1409 This will wrap the method at C<$method_name> so that the original
1410 method will be called, it's return values stashed, and then the
1411 supplied C<$code> will be passed the C<@_> arguments, and called.
1412 As specified above, the return value of the I<after> method
1413 modifiers is ignored, and it cannot modify the return values of
1414 the original method. If you need to do either of these things, use an
1415 C<around> method modifier.
1417 =item B<add_around_method_modifier ($method_name, $code)>
1419 This will wrap the method at C<$method_name> so that C<$code>
1420 will be called and passed the original method as an extra argument
1421 at the begining of the C<@_> argument list. This is a variation of
1422 continuation passing style, where the function prepended to C<@_>
1423 can be considered a continuation. It is up to C<$code> if it calls
1424 the original method or not, there is no restriction on what the
1425 C<$code> can or cannot do.
1431 It should be noted that since there is no one consistent way to define
1432 the attributes of a class in Perl 5. These methods can only work with
1433 the information given, and can not easily discover information on
1434 their own. See L<Class::MOP::Attribute> for more details.
1438 =item B<attribute_metaclass>
1440 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1441 for more information on the attribute metaclasses.
1443 =item B<get_attribute_map>
1445 This returns a HASH ref of name to attribute meta-object mapping.
1447 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1449 This stores the C<$attribute_meta_object> (or creates one from the
1450 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1451 instance associated with the given class. Unlike methods, attributes
1452 within the MOP are stored as meta-information only. They will be used
1453 later to construct instances from (see C<construct_instance> above).
1454 More details about the attribute meta-objects can be found in the
1455 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1458 It should be noted that any accessor, reader/writer or predicate
1459 methods which the C<$attribute_meta_object> has will be installed
1460 into the class at this time.
1463 If an attribute already exists for C<$attribute_name>, the old one
1464 will be removed (as well as removing all it's accessors), and then
1467 =item B<has_attribute ($attribute_name)>
1469 Checks to see if this class has an attribute by the name of
1470 C<$attribute_name> and returns a boolean.
1472 =item B<get_attribute ($attribute_name)>
1474 Returns the attribute meta-object associated with C<$attribute_name>,
1475 if none is found, it will return undef.
1477 =item B<remove_attribute ($attribute_name)>
1479 This will remove the attribute meta-object stored at
1480 C<$attribute_name>, then return the removed attribute meta-object.
1483 Removing an attribute will only affect future instances of
1484 the class, it will not make any attempt to remove the attribute from
1485 any existing instances of the class.
1487 It should be noted that any accessor, reader/writer or predicate
1488 methods which the attribute meta-object stored at C<$attribute_name>
1489 has will be removed from the class at this time. This B<will> make
1490 these attributes somewhat inaccessable in previously created
1491 instances. But if you are crazy enough to do this at runtime, then
1492 you are crazy enough to deal with something like this :).
1494 =item B<get_attribute_list>
1496 This returns a list of attribute names which are defined in the local
1497 class. If you want a list of all applicable attributes for a class,
1498 use the C<compute_all_applicable_attributes> method.
1500 =item B<compute_all_applicable_attributes>
1502 This will traverse the inheritance heirachy and return a list of all
1503 the applicable attributes for this class. It does not construct a
1504 HASH reference like C<compute_all_applicable_methods> because all
1505 that same information is discoverable through the attribute
1508 =item B<find_attribute_by_name ($attr_name)>
1510 This method will traverse the inheritance heirachy and find the
1511 first attribute whose name matches C<$attr_name>, then return it.
1512 It will return undef if nothing is found.
1516 =head2 Class Immutability
1520 =item B<make_immutable (%options)>
1522 This method will invoke a tranforamtion upon the class which will
1523 make it immutable. Details of this transformation can be found in
1524 the L<Class::MOP::Immutable> documentation.
1526 =item B<make_mutable>
1528 This method will reverse tranforamtion upon the class which
1531 =item B<create_immutable_transformer>
1533 Create a transformer suitable for making this class immutable
1539 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1541 =head1 COPYRIGHT AND LICENSE
1543 Copyright 2006-2008 by Infinity Interactive, Inc.
1545 L<http://www.iinteractive.com>
1547 This library is free software; you can redistribute it and/or modify
1548 it under the same terms as Perl itself.