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 = '0.26';
16 our $AUTHORITY = 'cpan:STEVAN';
18 use base 'Class::MOP::Module';
22 sub meta { Class::MOP::Class->initialize(blessed($_[0]) || $_[0]) }
28 my $package_name = shift;
29 (defined $package_name && $package_name && !blessed($package_name))
30 || confess "You must pass a package name and it cannot be blessed";
31 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
34 $class->construct_class_instance('package' => $package_name, @_);
39 my $package_name = shift;
40 (defined $package_name && $package_name && !blessed($package_name))
41 || confess "You must pass a package name and it cannot be blessed";
42 Class::MOP::remove_metaclass_by_name($package_name);
43 $class->construct_class_instance('package' => $package_name, @_);
46 # NOTE: (meta-circularity)
47 # this is a special form of &construct_instance
48 # (see below), which is used to construct class
49 # meta-object instances for any Class::MOP::*
50 # class. All other classes will use the more
51 # normal &construct_instance.
52 sub construct_class_instance {
55 my $package_name = $options{'package'};
56 (defined $package_name && $package_name)
57 || confess "You must pass a package name";
59 # return the metaclass if we have it cached,
60 # and it is still defined (it has not been
61 # reaped by DESTROY yet, which can happen
62 # annoyingly enough during global destruction)
64 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
69 # we need to deal with the possibility
70 # of class immutability here, and then
71 # get the name of the class appropriately
72 $class = (blessed($class)
73 ? ($class->is_immutable
74 ? $class->get_mutable_metaclass_name()
78 # now create the metaclass
80 if ($class eq 'Class::MOP::Class') {
83 # inherited from Class::MOP::Package
84 '$!package' => $package_name,
87 # since the following attributes will
88 # actually be loaded from the symbol
89 # table, and actually bypass the instance
90 # entirely, we can just leave these things
91 # listed here for reference, because they
92 # should not actually have a value associated
94 '%!namespace' => \undef,
95 # inherited from Class::MOP::Module
96 '$!version' => \undef,
97 '$!authority' => \undef,
98 # defined in Class::MOP::Class
99 '@!superclasses' => \undef,
102 '%!attributes' => {},
103 '$!attribute_metaclass' => $options{'attribute_metaclass'} || 'Class::MOP::Attribute',
104 '$!method_metaclass' => $options{'method_metaclass'} || 'Class::MOP::Method',
105 '$!instance_metaclass' => $options{'instance_metaclass'} || 'Class::MOP::Instance',
107 ## uber-private variables
109 # this starts out as undef so that
110 # we can tell the first time the
111 # methods are fetched
113 '$!_package_cache_flag' => undef,
118 # it is safe to use meta here because
119 # class will always be a subclass of
120 # Class::MOP::Class, which defines meta
121 $meta = $class->meta->construct_instance(%options)
124 # and check the metaclass compatibility
125 $meta->check_metaclass_compatability();
127 Class::MOP::store_metaclass_by_name($package_name, $meta);
130 # we need to weaken any anon classes
131 # so that they can call DESTROY properly
132 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
137 sub reset_package_cache_flag { (shift)->{'$!_package_cache_flag'} = undef }
138 sub update_package_cache_flag {
141 # we can manually update the cache number
142 # since we are actually adding the method
143 # to our cache as well. This avoids us
144 # having to regenerate the method_map.
146 $self->{'$!_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
149 sub check_metaclass_compatability {
152 # this is always okay ...
153 return if blessed($self) eq 'Class::MOP::Class' &&
154 $self->instance_metaclass eq 'Class::MOP::Instance';
156 my @class_list = $self->linearized_isa;
157 shift @class_list; # shift off $self->name
159 foreach my $class_name (@class_list) {
160 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
163 # we need to deal with the possibility
164 # of class immutability here, and then
165 # get the name of the class appropriately
166 my $meta_type = ($meta->is_immutable
167 ? $meta->get_mutable_metaclass_name()
170 ($self->isa($meta_type))
171 || confess $self->name . "->meta => (" . (blessed($self)) . ")" .
172 " is not compatible with the " .
173 $class_name . "->meta => (" . ($meta_type) . ")";
175 # we also need to check that instance metaclasses
176 # are compatabile in the same the class.
177 ($self->instance_metaclass->isa($meta->instance_metaclass))
178 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
179 " is not compatible with the " .
180 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
188 # this should be sufficient, if you have a
189 # use case where it is not, write a test and
191 my $ANON_CLASS_SERIAL = 0;
194 # we need a sufficiently annoying prefix
195 # this should suffice for now, this is
196 # used in a couple of places below, so
197 # need to put it up here for now.
198 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
202 no warnings 'uninitialized';
203 $self->name =~ /^$ANON_CLASS_PREFIX/ ? 1 : 0;
206 sub create_anon_class {
207 my ($class, %options) = @_;
208 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
209 return $class->create($package_name, %options);
213 # this will only get called for
214 # anon-classes, all other calls
215 # are assumed to occur during
216 # global destruction and so don't
217 # really need to be handled explicitly
220 no warnings 'uninitialized';
221 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
222 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
224 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
225 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
227 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
232 # creating classes with MOP ...
236 my $package_name = shift;
238 (defined $package_name && $package_name)
239 || confess "You must pass a package name";
242 || confess "You much pass all parameters as name => value pairs " .
243 "(I found an uneven number of params in \@_)";
247 my $code = "package $package_name;";
248 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
249 if exists $options{version};
250 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
251 if exists $options{authority};
254 confess "creation of $package_name failed : $@" if $@;
256 my $meta = $class->initialize($package_name);
258 $meta->add_method('meta' => sub {
259 $class->initialize(blessed($_[0]) || $_[0]);
262 $meta->superclasses(@{$options{superclasses}})
263 if exists $options{superclasses};
265 # process attributes first, so that they can
266 # install accessors, but locally defined methods
267 # can then overwrite them. It is maybe a little odd, but
268 # I think this should be the order of things.
269 if (exists $options{attributes}) {
270 foreach my $attr (@{$options{attributes}}) {
271 $meta->add_attribute($attr);
274 if (exists $options{methods}) {
275 foreach my $method_name (keys %{$options{methods}}) {
276 $meta->add_method($method_name, $options{methods}->{$method_name});
285 # all these attribute readers will be bootstrapped
286 # away in the Class::MOP bootstrap section
288 sub get_attribute_map { $_[0]->{'%!attributes'} }
289 sub attribute_metaclass { $_[0]->{'$!attribute_metaclass'} }
290 sub method_metaclass { $_[0]->{'$!method_metaclass'} }
291 sub instance_metaclass { $_[0]->{'$!instance_metaclass'} }
294 # this is a prime canidate for conversion to XS
298 if (defined $self->{'$!_package_cache_flag'} &&
299 $self->{'$!_package_cache_flag'} == Class::MOP::check_package_cache_flag($self->name)) {
300 return $self->{'%!methods'};
303 my $map = $self->{'%!methods'};
305 my $class_name = $self->name;
306 my $method_metaclass = $self->method_metaclass;
308 foreach my $symbol ($self->list_all_package_symbols('CODE')) {
309 my $code = $self->get_package_symbol('&' . $symbol);
311 next if exists $map->{$symbol} &&
312 defined $map->{$symbol} &&
313 $map->{$symbol}->body == $code;
315 my ($pkg, $name) = Class::MOP::get_code_info($code);
316 next if ($pkg || '') ne $class_name &&
317 ($name || '') ne '__ANON__';
319 $map->{$symbol} = $method_metaclass->wrap($code);
325 # Instance Construction & Cloning
330 # we need to protect the integrity of the
331 # Class::MOP::Class singletons here, so we
332 # delegate this to &construct_class_instance
333 # which will deal with the singletons
334 return $class->construct_class_instance(@_)
335 if $class->name->isa('Class::MOP::Class');
336 return $class->construct_instance(@_);
339 sub construct_instance {
340 my ($class, %params) = @_;
341 my $meta_instance = $class->get_meta_instance();
342 my $instance = $meta_instance->create_instance();
343 foreach my $attr ($class->compute_all_applicable_attributes()) {
344 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
347 # this will only work for a HASH instance type
348 if ($class->is_anon_class) {
349 (reftype($instance) eq 'HASH')
350 || confess "Currently only HASH based instances are supported with instance of anon-classes";
352 # At some point we should make this official
353 # as a reserved slot name, but right now I am
354 # going to keep it here.
355 # my $RESERVED_MOP_SLOT = '__MOP__';
356 $instance->{'__MOP__'} = $class;
361 sub get_meta_instance {
363 return $class->instance_metaclass->new(
365 $class->compute_all_applicable_attributes()
371 my $instance = shift;
372 (blessed($instance) && $instance->isa($class->name))
373 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
375 # we need to protect the integrity of the
376 # Class::MOP::Class singletons here, they
377 # should not be cloned.
378 return $instance if $instance->isa('Class::MOP::Class');
379 $class->clone_instance($instance, @_);
383 my ($class, $instance, %params) = @_;
385 || confess "You can only clone instances, \$self is not a blessed instance";
386 my $meta_instance = $class->get_meta_instance();
387 my $clone = $meta_instance->clone_instance($instance);
388 foreach my $attr ($class->compute_all_applicable_attributes()) {
389 if (exists $params{$attr->init_arg}) {
390 $meta_instance->set_slot_value($clone, $attr->name, $params{$attr->init_arg});
396 sub rebless_instance {
397 my ($self, $instance, $new_metaclass) = @_;
399 # it's okay (expected, even) to pass in a package name
400 unless (blessed $new_metaclass) {
401 $new_metaclass = $self->initialize($new_metaclass);
404 # make sure we're reblessing into a subclass
406 for my $superclass ($new_metaclass->linearized_isa) {
407 if ($superclass eq $self->name) {
414 || confess "You may rebless only into a subclass. (". $new_metaclass->name .") is not a subclass of (". $self->name .").";
416 my $meta_instance = $self->get_meta_instance();
417 return $meta_instance->rebless_instance_structure($instance, $new_metaclass);
426 @{$self->get_package_symbol('@ISA')} = @supers;
428 # we need to check the metaclass
429 # compatibility here so that we can
430 # be sure that the superclass is
431 # not potentially creating an issues
432 # we don't know about
433 $self->check_metaclass_compatability();
435 @{$self->get_package_symbol('@ISA')};
441 my $super_class = $self->name;
444 my $find_derived_classes;
445 $find_derived_classes = sub {
446 my ($outer_class) = @_;
448 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
451 for my $symbol ( keys %$symbol_table_hashref ) {
452 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
453 my $inner_class = $1;
455 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
459 ? "${outer_class}::$inner_class"
462 if ( $class->isa($super_class) and $class ne $super_class ) {
463 push @derived_classes, $class;
466 next SYMBOL if $class eq 'main'; # skip 'main::*'
468 $find_derived_classes->($class);
472 my $root_class = q{};
473 $find_derived_classes->($root_class);
475 undef $find_derived_classes;
477 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
479 return @derived_classes;
484 if (Class::MOP::IS_RUNNING_ON_5_10()) {
485 return @{ mro::get_linear_isa( (shift)->name ) };
489 return grep { !($seen{$_}++) } (shift)->class_precedence_list;
493 sub class_precedence_list {
496 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
498 # We need to check for circular inheritance here
499 # if we are are not on 5.10, cause 5.8 detects it
500 # late. This will do nothing if all is well, and
501 # blow up otherwise. Yes, it's an ugly hack, better
502 # suggestions are welcome.
504 ($self->name || return)->isa('This is a test for circular inheritance')
510 $self->initialize($_)->class_precedence_list()
511 } $self->superclasses()
518 my ($self, $method_name, $method) = @_;
519 (defined $method_name && $method_name)
520 || confess "You must define a method name";
523 if (blessed($method)) {
524 $body = $method->body;
528 ('CODE' eq (reftype($body) || ''))
529 || confess "Your code block must be a CODE reference";
530 $method = $self->method_metaclass->wrap($body);
532 $self->get_method_map->{$method_name} = $method;
534 my $full_method_name = ($self->name . '::' . $method_name);
535 $self->add_package_symbol("&${method_name}" => subname $full_method_name => $body);
536 $self->update_package_cache_flag;
540 my $fetch_and_prepare_method = sub {
541 my ($self, $method_name) = @_;
543 my $method = $self->get_method($method_name);
544 # if we dont have local ...
546 # try to find the next method
547 $method = $self->find_next_method_by_name($method_name);
548 # die if it does not exist
550 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
551 # and now make sure to wrap it
552 # even if it is already wrapped
553 # because we need a new sub ref
554 $method = Class::MOP::Method::Wrapped->wrap($method);
557 # now make sure we wrap it properly
558 $method = Class::MOP::Method::Wrapped->wrap($method)
559 unless $method->isa('Class::MOP::Method::Wrapped');
561 $self->add_method($method_name => $method);
565 sub add_before_method_modifier {
566 my ($self, $method_name, $method_modifier) = @_;
567 (defined $method_name && $method_name)
568 || confess "You must pass in a method name";
569 my $method = $fetch_and_prepare_method->($self, $method_name);
570 $method->add_before_modifier(subname ':before' => $method_modifier);
573 sub add_after_method_modifier {
574 my ($self, $method_name, $method_modifier) = @_;
575 (defined $method_name && $method_name)
576 || confess "You must pass in a method name";
577 my $method = $fetch_and_prepare_method->($self, $method_name);
578 $method->add_after_modifier(subname ':after' => $method_modifier);
581 sub add_around_method_modifier {
582 my ($self, $method_name, $method_modifier) = @_;
583 (defined $method_name && $method_name)
584 || confess "You must pass in a method name";
585 my $method = $fetch_and_prepare_method->($self, $method_name);
586 $method->add_around_modifier(subname ':around' => $method_modifier);
590 # the methods above used to be named like this:
591 # ${pkg}::${method}:(before|after|around)
592 # but this proved problematic when using one modifier
593 # to wrap multiple methods (something which is likely
594 # to happen pretty regularly IMO). So instead of naming
595 # it like this, I have chosen to just name them purely
596 # with their modifier names, like so:
597 # :(before|after|around)
598 # The fact is that in a stack trace, it will be fairly
599 # evident from the context what method they are attached
600 # to, and so don't need the fully qualified name.
604 my ($self, $method_name, $method) = @_;
605 (defined $method_name && $method_name)
606 || confess "You must define a method name";
608 my $body = (blessed($method) ? $method->body : $method);
609 ('CODE' eq (reftype($body) || ''))
610 || confess "Your code block must be a CODE reference";
612 $self->add_package_symbol("&${method_name}" => $body);
613 $self->update_package_cache_flag;
617 my ($self, $method_name) = @_;
618 (defined $method_name && $method_name)
619 || confess "You must define a method name";
621 return 0 unless exists $self->get_method_map->{$method_name};
626 my ($self, $method_name) = @_;
627 (defined $method_name && $method_name)
628 || confess "You must define a method name";
631 # I don't really need this here, because
632 # if the method_map is missing a key it
633 # will just return undef for me now
634 # return unless $self->has_method($method_name);
636 return $self->get_method_map->{$method_name};
640 my ($self, $method_name) = @_;
641 (defined $method_name && $method_name)
642 || confess "You must define a method name";
644 my $removed_method = delete $self->get_method_map->{$method_name};
646 $self->remove_package_symbol("&${method_name}");
648 $self->update_package_cache_flag;
650 return $removed_method;
653 sub get_method_list {
655 keys %{$self->get_method_map};
658 sub find_method_by_name {
659 my ($self, $method_name) = @_;
660 (defined $method_name && $method_name)
661 || confess "You must define a method name to find";
662 foreach my $class ($self->linearized_isa) {
663 # fetch the meta-class ...
664 my $meta = $self->initialize($class);
665 return $meta->get_method($method_name)
666 if $meta->has_method($method_name);
671 sub compute_all_applicable_methods {
673 my (@methods, %seen_method);
674 foreach my $class ($self->linearized_isa) {
675 # fetch the meta-class ...
676 my $meta = $self->initialize($class);
677 foreach my $method_name ($meta->get_method_list()) {
678 next if exists $seen_method{$method_name};
679 $seen_method{$method_name}++;
681 name => $method_name,
683 code => $meta->get_method($method_name)
690 sub find_all_methods_by_name {
691 my ($self, $method_name) = @_;
692 (defined $method_name && $method_name)
693 || confess "You must define a method name to find";
695 foreach my $class ($self->linearized_isa) {
696 # fetch the meta-class ...
697 my $meta = $self->initialize($class);
699 name => $method_name,
701 code => $meta->get_method($method_name)
702 } if $meta->has_method($method_name);
707 sub find_next_method_by_name {
708 my ($self, $method_name) = @_;
709 (defined $method_name && $method_name)
710 || confess "You must define a method name to find";
711 my @cpl = $self->linearized_isa;
712 shift @cpl; # discard ourselves
713 foreach my $class (@cpl) {
714 # fetch the meta-class ...
715 my $meta = $self->initialize($class);
716 return $meta->get_method($method_name)
717 if $meta->has_method($method_name);
726 # either we have an attribute object already
727 # or we need to create one from the args provided
728 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
729 # make sure it is derived from the correct type though
730 ($attribute->isa('Class::MOP::Attribute'))
731 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
733 # first we attach our new attribute
734 # because it might need certain information
735 # about the class which it is attached to
736 $attribute->attach_to_class($self);
738 # then we remove attributes of a conflicting
739 # name here so that we can properly detach
740 # the old attr object, and remove any
741 # accessors it would have generated
742 $self->remove_attribute($attribute->name)
743 if $self->has_attribute($attribute->name);
745 # then onto installing the new accessors
746 $attribute->install_accessors();
747 $self->get_attribute_map->{$attribute->name} = $attribute;
751 my ($self, $attribute_name) = @_;
752 (defined $attribute_name && $attribute_name)
753 || confess "You must define an attribute name";
754 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
758 my ($self, $attribute_name) = @_;
759 (defined $attribute_name && $attribute_name)
760 || confess "You must define an attribute name";
761 return $self->get_attribute_map->{$attribute_name}
763 # this will return undef anyway, so no need ...
764 # if $self->has_attribute($attribute_name);
768 sub remove_attribute {
769 my ($self, $attribute_name) = @_;
770 (defined $attribute_name && $attribute_name)
771 || confess "You must define an attribute name";
772 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
773 return unless defined $removed_attribute;
774 delete $self->get_attribute_map->{$attribute_name};
775 $removed_attribute->remove_accessors();
776 $removed_attribute->detach_from_class();
777 return $removed_attribute;
780 sub get_attribute_list {
782 keys %{$self->get_attribute_map};
785 sub compute_all_applicable_attributes {
787 my (@attrs, %seen_attr);
788 foreach my $class ($self->linearized_isa) {
789 # fetch the meta-class ...
790 my $meta = $self->initialize($class);
791 foreach my $attr_name ($meta->get_attribute_list()) {
792 next if exists $seen_attr{$attr_name};
793 $seen_attr{$attr_name}++;
794 push @attrs => $meta->get_attribute($attr_name);
800 sub find_attribute_by_name {
801 my ($self, $attr_name) = @_;
802 foreach my $class ($self->linearized_isa) {
803 # fetch the meta-class ...
804 my $meta = $self->initialize($class);
805 return $meta->get_attribute($attr_name)
806 if $meta->has_attribute($attr_name);
814 sub is_immutable { 0 }
817 # Why I changed this (groditi)
818 # - One Metaclass may have many Classes through many Metaclass instances
819 # - One Metaclass should only have one Immutable Transformer instance
820 # - Each Class may have different Immutabilizing options
821 # - Therefore each Metaclass instance may have different Immutabilizing options
822 # - We need to store one Immutable Transformer instance per Metaclass
823 # - We need to store one set of Immutable Transformer options per Class
824 # - Upon make_mutable we may delete the Immutabilizing options
825 # - We could clean the immutable Transformer instance when there is no more
826 # immutable Classes of that type, but we can also keep it in case
827 # another class with this same Metaclass becomes immutable. It is a case
828 # of trading of storing an instance to avoid unnecessary instantiations of
829 # Immutable Transformers. You may view this as a memory leak, however
830 # Because we have few Metaclasses, in practice it seems acceptable
831 # - To allow Immutable Transformers instances to be cleaned up we could weaken
832 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
835 my %IMMUTABLE_TRANSFORMERS;
836 my %IMMUTABLE_OPTIONS;
840 my $class = blessed $self || $self;
842 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
843 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
845 $transformer->make_metaclass_immutable($self, \%options);
846 $IMMUTABLE_OPTIONS{$self->name} =
847 { %options, IMMUTABLE_TRANSFORMER => $transformer };
849 if( exists $options{debug} && $options{debug} ){
850 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
851 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
857 return if $self->is_mutable;
858 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
859 confess "unable to find immutabilizing options" unless ref $options;
860 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
861 $transformer->make_metaclass_mutable($self, $options);
865 sub create_immutable_transformer {
867 my $class = Class::MOP::Immutable->new($self, {
868 read_only => [qw/superclasses/],
876 remove_package_symbol
879 class_precedence_list => 'ARRAY',
880 linearized_isa => 'ARRAY',
881 compute_all_applicable_attributes => 'ARRAY',
882 get_meta_instance => 'SCALAR',
883 get_method_map => 'SCALAR',
897 Class::MOP::Class - Class Meta Object
901 # assuming that class Foo
902 # has been defined, you can
904 # use this for introspection ...
906 # add a method to Foo ...
907 Foo->meta->add_method('bar' => sub { ... })
909 # get a list of all the classes searched
910 # the method dispatcher in the correct order
911 Foo->meta->class_precedence_list()
913 # remove a method from Foo
914 Foo->meta->remove_method('bar');
916 # or use this to actually create classes ...
918 Class::MOP::Class->create('Bar' => (
920 superclasses => [ 'Foo' ],
922 Class::MOP:::Attribute->new('$bar'),
923 Class::MOP:::Attribute->new('$baz'),
926 calculate_bar => sub { ... },
927 construct_baz => sub { ... }
933 This is the largest and currently most complex part of the Perl 5
934 meta-object protocol. It controls the introspection and
935 manipulation of Perl 5 classes (and it can create them too). The
936 best way to understand what this module can do, is to read the
937 documentation for each of it's methods.
941 =head2 Self Introspection
947 This will return a B<Class::MOP::Class> instance which is related
948 to this class. Thereby allowing B<Class::MOP::Class> to actually
951 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
952 bootstrap this module by installing a number of attribute meta-objects
953 into it's metaclass. This will allow this class to reap all the benifits
954 of the MOP when subclassing it.
958 =head2 Class construction
960 These methods will handle creating B<Class::MOP::Class> objects,
961 which can be used to both create new classes, and analyze
962 pre-existing classes.
964 This module will internally store references to all the instances
965 you create with these methods, so that they do not need to be
966 created any more than nessecary. Basically, they are singletons.
970 =item B<create ($package_name,
971 version =E<gt> ?$version,
972 authority =E<gt> ?$authority,
973 superclasses =E<gt> ?@superclasses,
974 methods =E<gt> ?%methods,
975 attributes =E<gt> ?%attributes)>
977 This returns a B<Class::MOP::Class> object, bringing the specified
978 C<$package_name> into existence and adding any of the C<$version>,
979 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
982 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
983 methods =E<gt> ?%methods,
984 attributes =E<gt> ?%attributes)>
986 This will create an anonymous class, it works much like C<create> but
987 it does not need a C<$package_name>. Instead it will create a suitably
988 unique package name for you to stash things into.
990 On very important distinction is that anon classes are destroyed once
991 the metaclass they are attached to goes out of scope. In the DESTROY
992 method, the created package will be removed from the symbol table.
994 It is also worth noting that any instances created with an anon-class
995 will keep a special reference to the anon-meta which will prevent the
996 anon-class from going out of scope until all instances of it have also
997 been destroyed. This however only works for HASH based instance types,
998 as we use a special reserved slot (C<__MOP__>) to store this.
1000 =item B<initialize ($package_name, %options)>
1002 This initializes and returns returns a B<Class::MOP::Class> object
1003 for a given a C<$package_name>.
1005 =item B<reinitialize ($package_name, %options)>
1007 This removes the old metaclass, and creates a new one in it's place.
1008 Do B<not> use this unless you really know what you are doing, it could
1009 very easily make a very large mess of your program.
1011 =item B<construct_class_instance (%options)>
1013 This will construct an instance of B<Class::MOP::Class>, it is
1014 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1015 to use C<construct_instance> once all the bootstrapping is done. This
1016 method is used internally by C<initialize> and should never be called
1017 from outside of that method really.
1019 =item B<check_metaclass_compatability>
1021 This method is called as the very last thing in the
1022 C<construct_class_instance> method. This will check that the
1023 metaclass you are creating is compatible with the metaclasses of all
1024 your ancestors. For more inforamtion about metaclass compatibility
1025 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1027 =item B<update_package_cache_flag>
1029 This will reset the package cache flag for this particular metaclass
1030 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1031 function. This is very rarely needed from outside of C<Class::MOP::Class>
1032 but in some cases you might want to use it, so it is here.
1034 =item B<reset_package_cache_flag>
1036 Clear this flag, used in Moose.
1040 =head2 Object instance construction and cloning
1042 These methods are B<entirely optional>, it is up to you whether you want
1047 =item B<instance_metaclass>
1049 =item B<get_meta_instance>
1051 =item B<new_object (%params)>
1053 This is a convience method for creating a new object of the class, and
1054 blessing it into the appropriate package as well. Ideally your class
1055 would call a C<new> this method like so:
1058 my ($class, %param) = @_;
1059 $class->meta->new_object(%params);
1062 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1063 but that is considered bad style, so we do not do that.
1065 =item B<construct_instance (%params)>
1067 This method is used to construct an instace structure suitable for
1068 C<bless>-ing into your package of choice. It works in conjunction
1069 with the Attribute protocol to collect all applicable attributes.
1071 This will construct and instance using a HASH ref as storage
1072 (currently only HASH references are supported). This will collect all
1073 the applicable attributes and layout out the fields in the HASH ref,
1074 it will then initialize them using either use the corresponding key
1075 in C<%params> or any default value or initializer found in the
1076 attribute meta-object.
1078 =item B<clone_object ($instance, %params)>
1080 This is a convience method for cloning an object instance, then
1081 blessing it into the appropriate package. This method will call
1082 C<clone_instance>, which performs a shallow copy of the object,
1083 see that methods documentation for more details. Ideally your
1084 class would call a C<clone> this method like so:
1086 sub MyClass::clone {
1087 my ($self, %param) = @_;
1088 $self->meta->clone_object($self, %params);
1091 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1092 but that is considered bad style, so we do not do that.
1094 =item B<clone_instance($instance, %params)>
1096 This method is a compliment of C<construct_instance> (which means if
1097 you override C<construct_instance>, you need to override this one too),
1098 and clones the instance shallowly.
1100 The cloned structure returned is (like with C<construct_instance>) an
1101 unC<bless>ed HASH reference, it is your responsibility to then bless
1102 this cloned structure into the right class (which C<clone_object> will
1105 As of 0.11, this method will clone the C<$instance> structure shallowly,
1106 as opposed to the deep cloning implemented in prior versions. After much
1107 thought, research and discussion, I have decided that anything but basic
1108 shallow cloning is outside the scope of the meta-object protocol. I
1109 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1110 is too I<context-specific> to be part of the MOP.
1114 =head2 Informational
1116 These are a few predicate methods for asking information about the class.
1120 =item B<is_anon_class>
1122 This returns true if the class is a C<Class::MOP::Class> created anon class.
1126 This returns true if the class is still mutable.
1128 =item B<is_immutable>
1130 This returns true if the class has been made immutable.
1134 =head2 Inheritance Relationships
1138 =item B<superclasses (?@superclasses)>
1140 This is a read-write attribute which represents the superclass
1141 relationships of the class the B<Class::MOP::Class> instance is
1142 associated with. Basically, it can get and set the C<@ISA> for you.
1145 Perl will occasionally perform some C<@ISA> and method caching, if
1146 you decide to change your superclass relationship at runtime (which
1147 is quite insane and very much not recommened), then you should be
1148 aware of this and the fact that this module does not make any
1149 attempt to address this issue.
1151 =item B<class_precedence_list>
1153 This computes the a list of all the class's ancestors in the same order
1154 in which method dispatch will be done. This is similair to
1155 what B<Class::ISA::super_path> does, but we don't remove duplicate names.
1157 =item B<linearized_isa>
1159 This returns a list based on C<class_precedence_list> but with all
1164 This returns a list of subclasses for this class.
1172 =item B<get_method_map>
1174 =item B<method_metaclass>
1176 =item B<add_method ($method_name, $method)>
1178 This will take a C<$method_name> and CODE reference to that
1179 C<$method> and install it into the class's package.
1182 This does absolutely nothing special to C<$method>
1183 other than use B<Sub::Name> to make sure it is tagged with the
1184 correct name, and therefore show up correctly in stack traces and
1187 =item B<alias_method ($method_name, $method)>
1189 This will take a C<$method_name> and CODE reference to that
1190 C<$method> and alias the method into the class's package.
1193 Unlike C<add_method>, this will B<not> try to name the
1194 C<$method> using B<Sub::Name>, it only aliases the method in
1195 the class's package.
1197 =item B<has_method ($method_name)>
1199 This just provides a simple way to check if the class implements
1200 a specific C<$method_name>. It will I<not> however, attempt to check
1201 if the class inherits the method (use C<UNIVERSAL::can> for that).
1203 This will correctly handle functions defined outside of the package
1204 that use a fully qualified name (C<sub Package::name { ... }>).
1206 This will correctly handle functions renamed with B<Sub::Name> and
1207 installed using the symbol tables. However, if you are naming the
1208 subroutine outside of the package scope, you must use the fully
1209 qualified name, including the package name, for C<has_method> to
1210 correctly identify it.
1212 This will attempt to correctly ignore functions imported from other
1213 packages using B<Exporter>. It breaks down if the function imported
1214 is an C<__ANON__> sub (such as with C<use constant>), which very well
1215 may be a valid method being applied to the class.
1217 In short, this method cannot always be trusted to determine if the
1218 C<$method_name> is actually a method. However, it will DWIM about
1219 90% of the time, so it's a small trade off I think.
1221 =item B<get_method ($method_name)>
1223 This will return a Class::MOP::Method instance related to the specified
1224 C<$method_name>, or return undef if that method does not exist.
1226 The Class::MOP::Method is codifiable, so you can use it like a normal
1227 CODE reference, see L<Class::MOP::Method> for more information.
1229 =item B<find_method_by_name ($method_name>
1231 This will return a CODE reference of the specified C<$method_name>,
1232 or return undef if that method does not exist.
1234 Unlike C<get_method> this will also look in the superclasses.
1236 =item B<remove_method ($method_name)>
1238 This will attempt to remove a given C<$method_name> from the class.
1239 It will return the CODE reference that it has removed, and will
1240 attempt to use B<Sub::Name> to clear the methods associated name.
1242 =item B<get_method_list>
1244 This will return a list of method names for all I<locally> defined
1245 methods. It does B<not> provide a list of all applicable methods,
1246 including any inherited ones. If you want a list of all applicable
1247 methods, use the C<compute_all_applicable_methods> method.
1249 =item B<compute_all_applicable_methods>
1251 This will return a list of all the methods names this class will
1252 respond to, taking into account inheritance. The list will be a list of
1253 HASH references, each one containing the following information; method
1254 name, the name of the class in which the method lives and a CODE
1255 reference for the actual method.
1257 =item B<find_all_methods_by_name ($method_name)>
1259 This will traverse the inheritence hierarchy and locate all methods
1260 with a given C<$method_name>. Similar to
1261 C<compute_all_applicable_methods> it returns a list of HASH references
1262 with the following information; method name (which will always be the
1263 same as C<$method_name>), the name of the class in which the method
1264 lives and a CODE reference for the actual method.
1266 The list of methods produced is a distinct list, meaning there are no
1267 duplicates in it. This is especially useful for things like object
1268 initialization and destruction where you only want the method called
1269 once, and in the correct order.
1271 =item B<find_next_method_by_name ($method_name)>
1273 This will return the first method to match a given C<$method_name> in
1274 the superclasses, this is basically equivalent to calling
1275 C<SUPER::$method_name>, but it can be dispatched at runtime.
1279 =head2 Method Modifiers
1281 Method modifiers are a concept borrowed from CLOS, in which a method
1282 can be wrapped with I<before>, I<after> and I<around> method modifiers
1283 that will be called everytime the method is called.
1285 =head3 How method modifiers work?
1287 Method modifiers work by wrapping the original method and then replacing
1288 it in the classes symbol table. The wrappers will handle calling all the
1289 modifiers in the appropariate orders and preserving the calling context
1290 for the original method.
1292 Each method modifier serves a particular purpose, which may not be
1293 obvious to users of other method wrapping modules. To start with, the
1294 return values of I<before> and I<after> modifiers are ignored. This is
1295 because thier purpose is B<not> to filter the input and output of the
1296 primary method (this is done with an I<around> modifier). This may seem
1297 like an odd restriction to some, but doing this allows for simple code
1298 to be added at the begining or end of a method call without jeapordizing
1299 the normal functioning of the primary method or placing any extra
1300 responsibility on the code of the modifier. Of course if you have more
1301 complex needs, then use the I<around> modifier, which uses a variation
1302 of continutation passing style to allow for a high degree of flexibility.
1304 Before and around modifiers are called in last-defined-first-called order,
1305 while after modifiers are called in first-defined-first-called order. So
1306 the call tree might looks something like this:
1316 To see examples of using method modifiers, see the following examples
1317 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1318 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1319 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1321 =head3 What is the performance impact?
1323 Of course there is a performance cost associated with method modifiers,
1324 but we have made every effort to make that cost be directly proportional
1325 to the amount of modifier features you utilize.
1327 The wrapping method does it's best to B<only> do as much work as it
1328 absolutely needs to. In order to do this we have moved some of the
1329 performance costs to set-up time, where they are easier to amortize.
1331 All this said, my benchmarks have indicated the following:
1333 simple wrapper with no modifiers 100% slower
1334 simple wrapper with simple before modifier 400% slower
1335 simple wrapper with simple after modifier 450% slower
1336 simple wrapper with simple around modifier 500-550% slower
1337 simple wrapper with all 3 modifiers 1100% slower
1339 These numbers may seem daunting, but you must remember, every feature
1340 comes with some cost. To put things in perspective, just doing a simple
1341 C<AUTOLOAD> which does nothing but extract the name of the method called
1342 and return it costs about 400% over a normal method call.
1346 =item B<add_before_method_modifier ($method_name, $code)>
1348 This will wrap the method at C<$method_name> and the supplied C<$code>
1349 will be passed the C<@_> arguments, and called before the original
1350 method is called. As specified above, the return value of the I<before>
1351 method modifiers is ignored, and it's ability to modify C<@_> is
1352 fairly limited. If you need to do either of these things, use an
1353 C<around> method modifier.
1355 =item B<add_after_method_modifier ($method_name, $code)>
1357 This will wrap the method at C<$method_name> so that the original
1358 method will be called, it's return values stashed, and then the
1359 supplied C<$code> will be passed the C<@_> arguments, and called.
1360 As specified above, the return value of the I<after> method
1361 modifiers is ignored, and it cannot modify the return values of
1362 the original method. If you need to do either of these things, use an
1363 C<around> method modifier.
1365 =item B<add_around_method_modifier ($method_name, $code)>
1367 This will wrap the method at C<$method_name> so that C<$code>
1368 will be called and passed the original method as an extra argument
1369 at the begining of the C<@_> argument list. This is a variation of
1370 continuation passing style, where the function prepended to C<@_>
1371 can be considered a continuation. It is up to C<$code> if it calls
1372 the original method or not, there is no restriction on what the
1373 C<$code> can or cannot do.
1379 It should be noted that since there is no one consistent way to define
1380 the attributes of a class in Perl 5. These methods can only work with
1381 the information given, and can not easily discover information on
1382 their own. See L<Class::MOP::Attribute> for more details.
1386 =item B<attribute_metaclass>
1388 =item B<get_attribute_map>
1390 =item B<add_attribute ($attribute_meta_object | $attribute_name, %attribute_spec)>
1392 This stores the C<$attribute_meta_object> (or creates one from the
1393 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1394 instance associated with the given class. Unlike methods, attributes
1395 within the MOP are stored as meta-information only. They will be used
1396 later to construct instances from (see C<construct_instance> above).
1397 More details about the attribute meta-objects can be found in the
1398 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1401 It should be noted that any accessor, reader/writer or predicate
1402 methods which the C<$attribute_meta_object> has will be installed
1403 into the class at this time.
1406 If an attribute already exists for C<$attribute_name>, the old one
1407 will be removed (as well as removing all it's accessors), and then
1410 =item B<has_attribute ($attribute_name)>
1412 Checks to see if this class has an attribute by the name of
1413 C<$attribute_name> and returns a boolean.
1415 =item B<get_attribute ($attribute_name)>
1417 Returns the attribute meta-object associated with C<$attribute_name>,
1418 if none is found, it will return undef.
1420 =item B<remove_attribute ($attribute_name)>
1422 This will remove the attribute meta-object stored at
1423 C<$attribute_name>, then return the removed attribute meta-object.
1426 Removing an attribute will only affect future instances of
1427 the class, it will not make any attempt to remove the attribute from
1428 any existing instances of the class.
1430 It should be noted that any accessor, reader/writer or predicate
1431 methods which the attribute meta-object stored at C<$attribute_name>
1432 has will be removed from the class at this time. This B<will> make
1433 these attributes somewhat inaccessable in previously created
1434 instances. But if you are crazy enough to do this at runtime, then
1435 you are crazy enough to deal with something like this :).
1437 =item B<get_attribute_list>
1439 This returns a list of attribute names which are defined in the local
1440 class. If you want a list of all applicable attributes for a class,
1441 use the C<compute_all_applicable_attributes> method.
1443 =item B<compute_all_applicable_attributes>
1445 This will traverse the inheritance heirachy and return a list of all
1446 the applicable attributes for this class. It does not construct a
1447 HASH reference like C<compute_all_applicable_methods> because all
1448 that same information is discoverable through the attribute
1451 =item B<find_attribute_by_name ($attr_name)>
1453 This method will traverse the inheritance heirachy and find the
1454 first attribute whose name matches C<$attr_name>, then return it.
1455 It will return undef if nothing is found.
1459 =head2 Class Immutability
1463 =item B<make_immutable (%options)>
1465 This method will invoke a tranforamtion upon the class which will
1466 make it immutable. Details of this transformation can be found in
1467 the L<Class::MOP::Immutable> documentation.
1469 =item B<make_mutable>
1471 This method will reverse tranforamtion upon the class which
1474 =item B<create_immutable_transformer>
1476 Create a transformer suitable for making this class immutable
1482 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1484 =head1 COPYRIGHT AND LICENSE
1486 Copyright 2006-2008 by Infinity Interactive, Inc.
1488 L<http://www.iinteractive.com>
1490 This library is free software; you can redistribute it and/or modify
1491 it under the same terms as Perl itself.