2 package Class::MOP::Class;
7 use Class::MOP::Immutable;
8 use Class::MOP::Instance;
9 use Class::MOP::Method::Wrapped;
12 use Scalar::Util 'blessed', 'weaken';
14 our $VERSION = '0.65';
15 our $AUTHORITY = 'cpan:STEVAN';
17 use base 'Class::MOP::Module';
23 my $package_name = shift;
24 (defined $package_name && $package_name && !blessed($package_name))
25 || confess "You must pass a package name and it cannot be blessed";
26 return Class::MOP::get_metaclass_by_name($package_name)
27 || $class->construct_class_instance('package' => $package_name, @_);
32 my $package_name = shift;
33 (defined $package_name && $package_name && !blessed($package_name))
34 || confess "You must pass a package name and it cannot be blessed";
35 Class::MOP::remove_metaclass_by_name($package_name);
36 $class->construct_class_instance('package' => $package_name, @_);
39 # NOTE: (meta-circularity)
40 # this is a special form of &construct_instance
41 # (see below), which is used to construct class
42 # meta-object instances for any Class::MOP::*
43 # class. All other classes will use the more
44 # normal &construct_instance.
45 sub construct_class_instance {
48 my $package_name = $options{'package'};
49 (defined $package_name && $package_name)
50 || confess "You must pass a package name";
52 # return the metaclass if we have it cached,
53 # and it is still defined (it has not been
54 # reaped by DESTROY yet, which can happen
55 # annoyingly enough during global destruction)
57 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
62 # we need to deal with the possibility
63 # of class immutability here, and then
64 # get the name of the class appropriately
65 $class = (blessed($class)
66 ? ($class->is_immutable
67 ? $class->get_mutable_metaclass_name()
71 # now create the metaclass
73 if ($class eq 'Class::MOP::Class') {
76 # inherited from Class::MOP::Package
77 'package' => $package_name,
80 # since the following attributes will
81 # actually be loaded from the symbol
82 # table, and actually bypass the instance
83 # entirely, we can just leave these things
84 # listed here for reference, because they
85 # should not actually have a value associated
87 'namespace' => \undef,
88 # inherited from Class::MOP::Module
90 'authority' => \undef,
91 # defined in Class::MOP::Class
92 'superclasses' => \undef,
96 'attribute_metaclass' => $options{'attribute_metaclass'} || 'Class::MOP::Attribute',
97 'method_metaclass' => $options{'method_metaclass'} || 'Class::MOP::Method',
98 'instance_metaclass' => $options{'instance_metaclass'} || 'Class::MOP::Instance',
100 ## uber-private variables
102 # this starts out as undef so that
103 # we can tell the first time the
104 # methods are fetched
106 '_package_cache_flag' => undef,
107 '_meta_instance' => undef,
112 # it is safe to use meta here because
113 # class will always be a subclass of
114 # Class::MOP::Class, which defines meta
115 $meta = $class->meta->construct_instance(%options)
118 # and check the metaclass compatibility
119 $meta->check_metaclass_compatability();
121 Class::MOP::store_metaclass_by_name($package_name, $meta);
124 # we need to weaken any anon classes
125 # so that they can call DESTROY properly
126 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
131 sub reset_package_cache_flag { (shift)->{'_package_cache_flag'} = undef }
132 sub update_package_cache_flag {
135 # we can manually update the cache number
136 # since we are actually adding the method
137 # to our cache as well. This avoids us
138 # having to regenerate the method_map.
140 $self->{'_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
143 sub check_metaclass_compatability {
146 # this is always okay ...
147 return if blessed($self) eq 'Class::MOP::Class' &&
148 $self->instance_metaclass eq 'Class::MOP::Instance';
150 my @class_list = $self->linearized_isa;
151 shift @class_list; # shift off $self->name
153 foreach my $class_name (@class_list) {
154 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
157 # we need to deal with the possibility
158 # of class immutability here, and then
159 # get the name of the class appropriately
160 my $meta_type = ($meta->is_immutable
161 ? $meta->get_mutable_metaclass_name()
164 ($self->isa($meta_type))
165 || confess $self->name . "->meta => (" . (blessed($self)) . ")" .
166 " is not compatible with the " .
167 $class_name . "->meta => (" . ($meta_type) . ")";
169 # we also need to check that instance metaclasses
170 # are compatabile in the same the class.
171 ($self->instance_metaclass->isa($meta->instance_metaclass))
172 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
173 " is not compatible with the " .
174 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
182 # this should be sufficient, if you have a
183 # use case where it is not, write a test and
185 my $ANON_CLASS_SERIAL = 0;
188 # we need a sufficiently annoying prefix
189 # this should suffice for now, this is
190 # used in a couple of places below, so
191 # need to put it up here for now.
192 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
196 no warnings 'uninitialized';
197 $self->name =~ /^$ANON_CLASS_PREFIX/ ? 1 : 0;
200 sub create_anon_class {
201 my ($class, %options) = @_;
202 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
203 return $class->create($package_name, %options);
207 # this will only get called for
208 # anon-classes, all other calls
209 # are assumed to occur during
210 # global destruction and so don't
211 # really need to be handled explicitly
214 no warnings 'uninitialized';
215 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
216 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
218 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
219 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
221 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
226 # creating classes with MOP ...
230 my $package_name = shift;
232 (defined $package_name && $package_name)
233 || confess "You must pass a package name";
236 || confess "You much pass all parameters as name => value pairs " .
237 "(I found an uneven number of params in \@_)";
241 (ref $options{superclasses} eq 'ARRAY')
242 || confess "You must pass an ARRAY ref of superclasses"
243 if exists $options{superclasses};
245 (ref $options{attributes} eq 'ARRAY')
246 || confess "You must pass an ARRAY ref of attributes"
247 if exists $options{attributes};
249 (ref $options{methods} eq 'HASH')
250 || confess "You must pass an HASH ref of methods"
251 if exists $options{methods};
253 my $code = "package $package_name;";
254 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
255 if exists $options{version};
256 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
257 if exists $options{authority};
260 confess "creation of $package_name failed : $@" if $@;
262 my $meta = $class->initialize($package_name);
264 $meta->add_method('meta' => sub {
265 $class->initialize(blessed($_[0]) || $_[0]);
268 $meta->superclasses(@{$options{superclasses}})
269 if exists $options{superclasses};
271 # process attributes first, so that they can
272 # install accessors, but locally defined methods
273 # can then overwrite them. It is maybe a little odd, but
274 # I think this should be the order of things.
275 if (exists $options{attributes}) {
276 foreach my $attr (@{$options{attributes}}) {
277 $meta->add_attribute($attr);
280 if (exists $options{methods}) {
281 foreach my $method_name (keys %{$options{methods}}) {
282 $meta->add_method($method_name, $options{methods}->{$method_name});
291 # all these attribute readers will be bootstrapped
292 # away in the Class::MOP bootstrap section
294 sub get_attribute_map { $_[0]->{'attributes'} }
295 sub attribute_metaclass { $_[0]->{'attribute_metaclass'} }
296 sub method_metaclass { $_[0]->{'method_metaclass'} }
297 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
300 # this is a prime canidate for conversion to XS
304 if (defined $self->{'_package_cache_flag'} &&
305 $self->{'_package_cache_flag'} == Class::MOP::check_package_cache_flag($self->name)) {
306 return $self->{'methods'};
309 my $map = $self->{'methods'};
311 my $class_name = $self->name;
312 my $method_metaclass = $self->method_metaclass;
314 my %all_code = $self->get_all_package_symbols('CODE');
316 foreach my $symbol (keys %all_code) {
317 my $code = $all_code{$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);
326 # in 5.10 constant.pm the constants show up
327 # as being in the right package, but in pre-5.10
328 # they show up as constant::__ANON__ so we
329 # make an exception here to be sure that things
330 # work as expected in both.
332 unless ($pkg eq 'constant' && $name eq '__ANON__') {
333 next if ($pkg || '') ne $class_name ||
334 (($name || '') ne '__ANON__' && ($pkg || '') ne $class_name);
337 $map->{$symbol} = $method_metaclass->wrap(
339 package_name => $class_name,
347 # Instance Construction & Cloning
353 # we need to protect the integrity of the
354 # Class::MOP::Class singletons here, so we
355 # delegate this to &construct_class_instance
356 # which will deal with the singletons
357 return $class->construct_class_instance(@_)
358 if $class->name->isa('Class::MOP::Class');
359 return $class->construct_instance(@_);
362 sub construct_instance {
363 my ($class, %params) = @_;
364 my $meta_instance = $class->get_meta_instance();
365 my $instance = $meta_instance->create_instance();
366 foreach my $attr ($class->compute_all_applicable_attributes()) {
367 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
370 # this will only work for a HASH instance type
371 if ($class->is_anon_class) {
372 (Scalar::Util::reftype($instance) eq 'HASH')
373 || confess "Currently only HASH based instances are supported with instance of anon-classes";
375 # At some point we should make this official
376 # as a reserved slot name, but right now I am
377 # going to keep it here.
378 # my $RESERVED_MOP_SLOT = '__MOP__';
379 $instance->{'__MOP__'} = $class;
385 sub get_meta_instance {
388 # just about any fiddling with @ISA or
389 # any fiddling with attributes will
390 # also fiddle with the symbol table
391 # and therefore invalidate the package
392 # cache, in which case we should blow
393 # away the meta-instance cache. Of course
394 # this will invalidate it more often then
395 # is probably needed, but better safe
398 $self->{'_meta_instance'} = undef
399 if defined $self->{'_package_cache_flag'} &&
400 $self->{'_package_cache_flag'} == Class::MOP::check_package_cache_flag($self->name);
401 $self->{'_meta_instance'} ||= $self->instance_metaclass->new(
403 $self->compute_all_applicable_attributes()
409 my $instance = shift;
410 (blessed($instance) && $instance->isa($class->name))
411 || confess "You must pass an instance of the metaclass (" . $class->name . "), not ($instance)";
414 # we need to protect the integrity of the
415 # Class::MOP::Class singletons here, they
416 # should not be cloned.
417 return $instance if $instance->isa('Class::MOP::Class');
418 $class->clone_instance($instance, @_);
422 my ($class, $instance, %params) = @_;
424 || confess "You can only clone instances, ($instance) is not a blessed instance";
425 my $meta_instance = $class->get_meta_instance();
426 my $clone = $meta_instance->clone_instance($instance);
427 foreach my $attr ($class->compute_all_applicable_attributes()) {
428 if ( defined( my $init_arg = $attr->init_arg ) ) {
429 if (exists $params{$init_arg}) {
430 $attr->set_value($clone, $params{$init_arg});
437 sub rebless_instance {
438 my ($self, $instance, %params) = @_;
441 if ($instance->can('meta')) {
442 ($instance->meta->isa('Class::MOP::Class'))
443 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
444 $old_metaclass = $instance->meta;
447 $old_metaclass = $self->initialize(blessed($instance));
450 my $meta_instance = $self->get_meta_instance();
452 $self->name->isa($old_metaclass->name)
453 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
456 $meta_instance->rebless_instance_structure($instance, $self);
458 foreach my $attr ( $self->compute_all_applicable_attributes ) {
459 if ( $attr->has_value($instance) ) {
460 if ( defined( my $init_arg = $attr->init_arg ) ) {
461 $params{$init_arg} = $attr->get_value($instance)
462 unless exists $params{$init_arg};
465 $attr->set_value($instance, $attr->get_value($instance));
470 foreach my $attr ($self->compute_all_applicable_attributes) {
471 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
481 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
484 @{$self->get_package_symbol($var_spec)} = @supers;
486 # we need to check the metaclass
487 # compatibility here so that we can
488 # be sure that the superclass is
489 # not potentially creating an issues
490 # we don't know about
491 $self->check_metaclass_compatability();
493 @{$self->get_package_symbol($var_spec)};
499 my $super_class = $self->name;
502 my $find_derived_classes;
503 $find_derived_classes = sub {
504 my ($outer_class) = @_;
506 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
509 for my $symbol ( keys %$symbol_table_hashref ) {
510 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
511 my $inner_class = $1;
513 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
517 ? "${outer_class}::$inner_class"
520 if ( $class->isa($super_class) and $class ne $super_class ) {
521 push @derived_classes, $class;
524 next SYMBOL if $class eq 'main'; # skip 'main::*'
526 $find_derived_classes->($class);
530 my $root_class = q{};
531 $find_derived_classes->($root_class);
533 undef $find_derived_classes;
535 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
537 return @derived_classes;
542 return @{ mro::get_linear_isa( (shift)->name ) };
545 sub class_precedence_list {
547 my $name = $self->name;
549 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
551 # We need to check for circular inheritance here
552 # if we are are not on 5.10, cause 5.8 detects it
553 # late. This will do nothing if all is well, and
554 # blow up otherwise. Yes, it's an ugly hack, better
555 # suggestions are welcome.
557 ($name || return)->isa('This is a test for circular inheritance')
560 # if our mro is c3, we can
561 # just grab the linear_isa
562 if (mro::get_mro($name) eq 'c3') {
563 return @{ mro::get_linear_isa($name) }
567 # we can't grab the linear_isa for dfs
568 # since it has all the duplicates
573 $self->initialize($_)->class_precedence_list()
574 } $self->superclasses()
582 my ($self, $method_name, $method) = @_;
583 (defined $method_name && $method_name)
584 || confess "You must define a method name";
587 if (blessed($method)) {
588 $body = $method->body;
589 if ($method->package_name ne $self->name &&
590 $method->name ne $method_name) {
591 warn "Hello there, got something for you."
592 . " Method says " . $method->package_name . " " . $method->name
593 . " Class says " . $self->name . " " . $method_name;
594 $method = $method->clone(
595 package_name => $self->name,
597 ) if $method->can('clone');
602 ('CODE' eq ref($body))
603 || confess "Your code block must be a CODE reference";
604 $method = $self->method_metaclass->wrap(
606 package_name => $self->name,
611 $self->get_method_map->{$method_name} = $method;
613 my $full_method_name = ($self->name . '::' . $method_name);
614 $self->add_package_symbol(
615 { sigil => '&', type => 'CODE', name => $method_name },
616 Class::MOP::subname($full_method_name => $body)
618 $self->update_package_cache_flag;
622 my $fetch_and_prepare_method = sub {
623 my ($self, $method_name) = @_;
625 my $method = $self->get_method($method_name);
626 # if we dont have local ...
628 # try to find the next method
629 $method = $self->find_next_method_by_name($method_name);
630 # die if it does not exist
632 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
633 # and now make sure to wrap it
634 # even if it is already wrapped
635 # because we need a new sub ref
636 $method = Class::MOP::Method::Wrapped->wrap($method);
639 # now make sure we wrap it properly
640 $method = Class::MOP::Method::Wrapped->wrap($method)
641 unless $method->isa('Class::MOP::Method::Wrapped');
643 $self->add_method($method_name => $method);
647 sub add_before_method_modifier {
648 my ($self, $method_name, $method_modifier) = @_;
649 (defined $method_name && $method_name)
650 || confess "You must pass in a method name";
651 my $method = $fetch_and_prepare_method->($self, $method_name);
652 $method->add_before_modifier(
653 Class::MOP::subname(':before' => $method_modifier)
657 sub add_after_method_modifier {
658 my ($self, $method_name, $method_modifier) = @_;
659 (defined $method_name && $method_name)
660 || confess "You must pass in a method name";
661 my $method = $fetch_and_prepare_method->($self, $method_name);
662 $method->add_after_modifier(
663 Class::MOP::subname(':after' => $method_modifier)
667 sub add_around_method_modifier {
668 my ($self, $method_name, $method_modifier) = @_;
669 (defined $method_name && $method_name)
670 || confess "You must pass in a method name";
671 my $method = $fetch_and_prepare_method->($self, $method_name);
672 $method->add_around_modifier(
673 Class::MOP::subname(':around' => $method_modifier)
678 # the methods above used to be named like this:
679 # ${pkg}::${method}:(before|after|around)
680 # but this proved problematic when using one modifier
681 # to wrap multiple methods (something which is likely
682 # to happen pretty regularly IMO). So instead of naming
683 # it like this, I have chosen to just name them purely
684 # with their modifier names, like so:
685 # :(before|after|around)
686 # The fact is that in a stack trace, it will be fairly
687 # evident from the context what method they are attached
688 # to, and so don't need the fully qualified name.
692 my ($self, $method_name, $method) = @_;
693 (defined $method_name && $method_name)
694 || confess "You must define a method name";
696 my $body = (blessed($method) ? $method->body : $method);
697 ('CODE' eq ref($body))
698 || confess "Your code block must be a CODE reference";
700 $self->add_package_symbol(
701 { sigil => '&', type => 'CODE', name => $method_name } => $body
703 $self->update_package_cache_flag;
707 my ($self, $method_name) = @_;
708 (defined $method_name && $method_name)
709 || confess "You must define a method name";
711 return 0 unless exists $self->get_method_map->{$method_name};
716 my ($self, $method_name) = @_;
717 (defined $method_name && $method_name)
718 || confess "You must define a method name";
721 # I don't really need this here, because
722 # if the method_map is missing a key it
723 # will just return undef for me now
724 # return unless $self->has_method($method_name);
726 return $self->get_method_map->{$method_name};
730 my ($self, $method_name) = @_;
731 (defined $method_name && $method_name)
732 || confess "You must define a method name";
734 my $removed_method = delete $self->get_method_map->{$method_name};
736 $self->remove_package_symbol(
737 { sigil => '&', type => 'CODE', name => $method_name }
740 $self->update_package_cache_flag;
742 return $removed_method;
745 sub get_method_list {
747 keys %{$self->get_method_map};
750 sub find_method_by_name {
751 my ($self, $method_name) = @_;
752 (defined $method_name && $method_name)
753 || confess "You must define a method name to find";
754 foreach my $class ($self->linearized_isa) {
755 # fetch the meta-class ...
756 my $meta = $self->initialize($class);
757 return $meta->get_method($method_name)
758 if $meta->has_method($method_name);
763 sub compute_all_applicable_methods {
765 my (@methods, %seen_method);
766 foreach my $class ($self->linearized_isa) {
767 # fetch the meta-class ...
768 my $meta = $self->initialize($class);
769 foreach my $method_name ($meta->get_method_list()) {
770 next if exists $seen_method{$method_name};
771 $seen_method{$method_name}++;
773 name => $method_name,
775 code => $meta->get_method($method_name)
782 sub find_all_methods_by_name {
783 my ($self, $method_name) = @_;
784 (defined $method_name && $method_name)
785 || confess "You must define a method name to find";
787 foreach my $class ($self->linearized_isa) {
788 # fetch the meta-class ...
789 my $meta = $self->initialize($class);
791 name => $method_name,
793 code => $meta->get_method($method_name)
794 } if $meta->has_method($method_name);
799 sub find_next_method_by_name {
800 my ($self, $method_name) = @_;
801 (defined $method_name && $method_name)
802 || confess "You must define a method name to find";
803 my @cpl = $self->linearized_isa;
804 shift @cpl; # discard ourselves
805 foreach my $class (@cpl) {
806 # fetch the meta-class ...
807 my $meta = $self->initialize($class);
808 return $meta->get_method($method_name)
809 if $meta->has_method($method_name);
818 # either we have an attribute object already
819 # or we need to create one from the args provided
820 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
821 # make sure it is derived from the correct type though
822 ($attribute->isa('Class::MOP::Attribute'))
823 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
825 # first we attach our new attribute
826 # because it might need certain information
827 # about the class which it is attached to
828 $attribute->attach_to_class($self);
830 # then we remove attributes of a conflicting
831 # name here so that we can properly detach
832 # the old attr object, and remove any
833 # accessors it would have generated
834 $self->remove_attribute($attribute->name)
835 if $self->has_attribute($attribute->name);
837 # then onto installing the new accessors
838 $attribute->install_accessors();
839 $self->get_attribute_map->{$attribute->name} = $attribute;
843 my ($self, $attribute_name) = @_;
844 (defined $attribute_name && $attribute_name)
845 || confess "You must define an attribute name";
846 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
850 my ($self, $attribute_name) = @_;
851 (defined $attribute_name && $attribute_name)
852 || confess "You must define an attribute name";
853 return $self->get_attribute_map->{$attribute_name}
855 # this will return undef anyway, so no need ...
856 # if $self->has_attribute($attribute_name);
860 sub remove_attribute {
861 my ($self, $attribute_name) = @_;
862 (defined $attribute_name && $attribute_name)
863 || confess "You must define an attribute name";
864 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
865 return unless defined $removed_attribute;
866 delete $self->get_attribute_map->{$attribute_name};
867 $removed_attribute->remove_accessors();
868 $removed_attribute->detach_from_class();
869 return $removed_attribute;
872 sub get_attribute_list {
874 keys %{$self->get_attribute_map};
877 sub compute_all_applicable_attributes {
879 my (@attrs, %seen_attr);
880 foreach my $class ($self->linearized_isa) {
881 # fetch the meta-class ...
882 my $meta = $self->initialize($class);
883 foreach my $attr_name ($meta->get_attribute_list()) {
884 next if exists $seen_attr{$attr_name};
885 $seen_attr{$attr_name}++;
886 push @attrs => $meta->get_attribute($attr_name);
892 sub find_attribute_by_name {
893 my ($self, $attr_name) = @_;
894 foreach my $class ($self->linearized_isa) {
895 # fetch the meta-class ...
896 my $meta = $self->initialize($class);
897 return $meta->get_attribute($attr_name)
898 if $meta->has_attribute($attr_name);
906 sub is_immutable { 0 }
909 # Why I changed this (groditi)
910 # - One Metaclass may have many Classes through many Metaclass instances
911 # - One Metaclass should only have one Immutable Transformer instance
912 # - Each Class may have different Immutabilizing options
913 # - Therefore each Metaclass instance may have different Immutabilizing options
914 # - We need to store one Immutable Transformer instance per Metaclass
915 # - We need to store one set of Immutable Transformer options per Class
916 # - Upon make_mutable we may delete the Immutabilizing options
917 # - We could clean the immutable Transformer instance when there is no more
918 # immutable Classes of that type, but we can also keep it in case
919 # another class with this same Metaclass becomes immutable. It is a case
920 # of trading of storing an instance to avoid unnecessary instantiations of
921 # Immutable Transformers. You may view this as a memory leak, however
922 # Because we have few Metaclasses, in practice it seems acceptable
923 # - To allow Immutable Transformers instances to be cleaned up we could weaken
924 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
928 my %IMMUTABLE_TRANSFORMERS;
929 my %IMMUTABLE_OPTIONS;
931 sub get_immutable_options {
933 return if $self->is_mutable;
934 confess "unable to find immutabilizing options"
935 unless exists $IMMUTABLE_OPTIONS{$self->name};
936 my %options = %{$IMMUTABLE_OPTIONS{$self->name}};
937 delete $options{IMMUTABLE_TRANSFORMER};
941 sub get_immutable_transformer {
943 if( $self->is_mutable ){
944 my $class = blessed $self || $self;
945 return $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
947 confess "unable to find transformer for immutable class"
948 unless exists $IMMUTABLE_OPTIONS{$self->name};
949 return $IMMUTABLE_OPTIONS{$self->name}->{IMMUTABLE_TRANSFORMER};
956 my $transformer = $self->get_immutable_transformer;
957 $transformer->make_metaclass_immutable($self, \%options);
958 $IMMUTABLE_OPTIONS{$self->name} =
959 { %options, IMMUTABLE_TRANSFORMER => $transformer };
961 if( exists $options{debug} && $options{debug} ){
962 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
963 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
971 return if $self->is_mutable;
972 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
973 confess "unable to find immutabilizing options" unless ref $options;
974 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
975 $transformer->make_metaclass_mutable($self, $options);
980 sub create_immutable_transformer {
982 my $class = Class::MOP::Immutable->new($self, {
983 read_only => [qw/superclasses/],
990 remove_package_symbol
993 class_precedence_list => 'ARRAY',
994 linearized_isa => 'ARRAY',
995 compute_all_applicable_attributes => 'ARRAY',
996 get_meta_instance => 'SCALAR',
997 get_method_map => 'SCALAR',
1000 # this is ugly, but so are typeglobs,
1001 # so whattayahgonnadoboutit
1004 add_package_symbol => sub {
1005 my $original = shift;
1006 confess "Cannot add package symbols to an immutable metaclass"
1007 unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
1008 goto $original->body;
1023 Class::MOP::Class - Class Meta Object
1027 # assuming that class Foo
1028 # has been defined, you can
1030 # use this for introspection ...
1032 # add a method to Foo ...
1033 Foo->meta->add_method('bar' => sub { ... })
1035 # get a list of all the classes searched
1036 # the method dispatcher in the correct order
1037 Foo->meta->class_precedence_list()
1039 # remove a method from Foo
1040 Foo->meta->remove_method('bar');
1042 # or use this to actually create classes ...
1044 Class::MOP::Class->create('Bar' => (
1046 superclasses => [ 'Foo' ],
1048 Class::MOP:::Attribute->new('$bar'),
1049 Class::MOP:::Attribute->new('$baz'),
1052 calculate_bar => sub { ... },
1053 construct_baz => sub { ... }
1059 This is the largest and currently most complex part of the Perl 5
1060 meta-object protocol. It controls the introspection and
1061 manipulation of Perl 5 classes (and it can create them too). The
1062 best way to understand what this module can do, is to read the
1063 documentation for each of it's methods.
1067 =head2 Self Introspection
1073 This will return a B<Class::MOP::Class> instance which is related
1074 to this class. Thereby allowing B<Class::MOP::Class> to actually
1077 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
1078 bootstrap this module by installing a number of attribute meta-objects
1079 into it's metaclass. This will allow this class to reap all the benifits
1080 of the MOP when subclassing it.
1084 =head2 Class construction
1086 These methods will handle creating B<Class::MOP::Class> objects,
1087 which can be used to both create new classes, and analyze
1088 pre-existing classes.
1090 This module will internally store references to all the instances
1091 you create with these methods, so that they do not need to be
1092 created any more than nessecary. Basically, they are singletons.
1096 =item B<create ($package_name,
1097 version =E<gt> ?$version,
1098 authority =E<gt> ?$authority,
1099 superclasses =E<gt> ?@superclasses,
1100 methods =E<gt> ?%methods,
1101 attributes =E<gt> ?%attributes)>
1103 This returns a B<Class::MOP::Class> object, bringing the specified
1104 C<$package_name> into existence and adding any of the C<$version>,
1105 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1108 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1109 methods =E<gt> ?%methods,
1110 attributes =E<gt> ?%attributes)>
1112 This will create an anonymous class, it works much like C<create> but
1113 it does not need a C<$package_name>. Instead it will create a suitably
1114 unique package name for you to stash things into.
1116 On very important distinction is that anon classes are destroyed once
1117 the metaclass they are attached to goes out of scope. In the DESTROY
1118 method, the created package will be removed from the symbol table.
1120 It is also worth noting that any instances created with an anon-class
1121 will keep a special reference to the anon-meta which will prevent the
1122 anon-class from going out of scope until all instances of it have also
1123 been destroyed. This however only works for HASH based instance types,
1124 as we use a special reserved slot (C<__MOP__>) to store this.
1126 =item B<initialize ($package_name, %options)>
1128 This initializes and returns returns a B<Class::MOP::Class> object
1129 for a given a C<$package_name>.
1131 =item B<reinitialize ($package_name, %options)>
1133 This removes the old metaclass, and creates a new one in it's place.
1134 Do B<not> use this unless you really know what you are doing, it could
1135 very easily make a very large mess of your program.
1137 =item B<construct_class_instance (%options)>
1139 This will construct an instance of B<Class::MOP::Class>, it is
1140 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1141 to use C<construct_instance> once all the bootstrapping is done. This
1142 method is used internally by C<initialize> and should never be called
1143 from outside of that method really.
1145 =item B<check_metaclass_compatability>
1147 This method is called as the very last thing in the
1148 C<construct_class_instance> method. This will check that the
1149 metaclass you are creating is compatible with the metaclasses of all
1150 your ancestors. For more inforamtion about metaclass compatibility
1151 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1153 =item B<update_package_cache_flag>
1155 This will reset the package cache flag for this particular metaclass
1156 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1157 function. This is very rarely needed from outside of C<Class::MOP::Class>
1158 but in some cases you might want to use it, so it is here.
1160 =item B<reset_package_cache_flag>
1162 Clears the package cache flag to announce to the internals that we need
1163 to rebuild the method map.
1167 =head2 Object instance construction and cloning
1169 These methods are B<entirely optional>, it is up to you whether you want
1174 =item B<instance_metaclass>
1176 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1177 for more information on the instance metaclasses.
1179 =item B<get_meta_instance>
1181 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1182 of a new instance of the class.
1184 =item B<new_object (%params)>
1186 This is a convience method for creating a new object of the class, and
1187 blessing it into the appropriate package as well. Ideally your class
1188 would call a C<new> this method like so:
1191 my ($class, %param) = @_;
1192 $class->meta->new_object(%params);
1195 =item B<construct_instance (%params)>
1197 This method is used to construct an instance structure suitable for
1198 C<bless>-ing into your package of choice. It works in conjunction
1199 with the Attribute protocol to collect all applicable attributes.
1201 This will construct and instance using a HASH ref as storage
1202 (currently only HASH references are supported). This will collect all
1203 the applicable attributes and layout out the fields in the HASH ref,
1204 it will then initialize them using either use the corresponding key
1205 in C<%params> or any default value or initializer found in the
1206 attribute meta-object.
1208 =item B<clone_object ($instance, %params)>
1210 This is a convience method for cloning an object instance, then
1211 blessing it into the appropriate package. This method will call
1212 C<clone_instance>, which performs a shallow copy of the object,
1213 see that methods documentation for more details. Ideally your
1214 class would call a C<clone> this method like so:
1216 sub MyClass::clone {
1217 my ($self, %param) = @_;
1218 $self->meta->clone_object($self, %params);
1221 =item B<clone_instance($instance, %params)>
1223 This method is a compliment of C<construct_instance> (which means if
1224 you override C<construct_instance>, you need to override this one too),
1225 and clones the instance shallowly.
1227 The cloned structure returned is (like with C<construct_instance>) an
1228 unC<bless>ed HASH reference, it is your responsibility to then bless
1229 this cloned structure into the right class (which C<clone_object> will
1232 As of 0.11, this method will clone the C<$instance> structure shallowly,
1233 as opposed to the deep cloning implemented in prior versions. After much
1234 thought, research and discussion, I have decided that anything but basic
1235 shallow cloning is outside the scope of the meta-object protocol. I
1236 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1237 is too I<context-specific> to be part of the MOP.
1239 =item B<rebless_instance($instance, ?%params)>
1241 This will change the class of C<$instance> to the class of the invoking
1242 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1243 itself. You may pass in optional C<%params> which are like constructor
1244 params and will override anything already defined in the instance.
1248 =head2 Informational
1250 These are a few predicate methods for asking information about the class.
1254 =item B<is_anon_class>
1256 This returns true if the class is a C<Class::MOP::Class> created anon class.
1260 This returns true if the class is still mutable.
1262 =item B<is_immutable>
1264 This returns true if the class has been made immutable.
1268 =head2 Inheritance Relationships
1272 =item B<superclasses (?@superclasses)>
1274 This is a read-write attribute which represents the superclass
1275 relationships of the class the B<Class::MOP::Class> instance is
1276 associated with. Basically, it can get and set the C<@ISA> for you.
1278 =item B<class_precedence_list>
1280 This computes the a list of all the class's ancestors in the same order
1281 in which method dispatch will be done. This is similair to what
1282 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1284 =item B<linearized_isa>
1286 This returns a list based on C<class_precedence_list> but with all
1291 This returns a list of subclasses for this class.
1299 =item B<get_method_map>
1301 Returns a HASH ref of name to CODE reference mapping for this class.
1303 =item B<method_metaclass>
1305 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1306 for more information on the method metaclasses.
1308 =item B<add_method ($method_name, $method)>
1310 This will take a C<$method_name> and CODE reference to that
1311 C<$method> and install it into the class's package.
1314 This does absolutely nothing special to C<$method>
1315 other than use B<Sub::Name> to make sure it is tagged with the
1316 correct name, and therefore show up correctly in stack traces and
1319 =item B<alias_method ($method_name, $method)>
1321 This will take a C<$method_name> and CODE reference to that
1322 C<$method> and alias the method into the class's package.
1325 Unlike C<add_method>, this will B<not> try to name the
1326 C<$method> using B<Sub::Name>, it only aliases the method in
1327 the class's package.
1329 =item B<has_method ($method_name)>
1331 This just provides a simple way to check if the class implements
1332 a specific C<$method_name>. It will I<not> however, attempt to check
1333 if the class inherits the method (use C<UNIVERSAL::can> for that).
1335 This will correctly handle functions defined outside of the package
1336 that use a fully qualified name (C<sub Package::name { ... }>).
1338 This will correctly handle functions renamed with B<Sub::Name> and
1339 installed using the symbol tables. However, if you are naming the
1340 subroutine outside of the package scope, you must use the fully
1341 qualified name, including the package name, for C<has_method> to
1342 correctly identify it.
1344 This will attempt to correctly ignore functions imported from other
1345 packages using B<Exporter>. It breaks down if the function imported
1346 is an C<__ANON__> sub (such as with C<use constant>), which very well
1347 may be a valid method being applied to the class.
1349 In short, this method cannot always be trusted to determine if the
1350 C<$method_name> is actually a method. However, it will DWIM about
1351 90% of the time, so it's a small trade off I think.
1353 =item B<get_method ($method_name)>
1355 This will return a Class::MOP::Method instance related to the specified
1356 C<$method_name>, or return undef if that method does not exist.
1358 The Class::MOP::Method is codifiable, so you can use it like a normal
1359 CODE reference, see L<Class::MOP::Method> for more information.
1361 =item B<find_method_by_name ($method_name)>
1363 This will return a CODE reference of the specified C<$method_name>,
1364 or return undef if that method does not exist.
1366 Unlike C<get_method> this will also look in the superclasses.
1368 =item B<remove_method ($method_name)>
1370 This will attempt to remove a given C<$method_name> from the class.
1371 It will return the CODE reference that it has removed, and will
1372 attempt to use B<Sub::Name> to clear the methods associated name.
1374 =item B<get_method_list>
1376 This will return a list of method names for all I<locally> defined
1377 methods. It does B<not> provide a list of all applicable methods,
1378 including any inherited ones. If you want a list of all applicable
1379 methods, use the C<compute_all_applicable_methods> method.
1381 =item B<compute_all_applicable_methods>
1383 This will return a list of all the methods names this class will
1384 respond to, taking into account inheritance. The list will be a list of
1385 HASH references, each one containing the following information; method
1386 name, the name of the class in which the method lives and a CODE
1387 reference for the actual method.
1389 =item B<find_all_methods_by_name ($method_name)>
1391 This will traverse the inheritence hierarchy and locate all methods
1392 with a given C<$method_name>. Similar to
1393 C<compute_all_applicable_methods> it returns a list of HASH references
1394 with the following information; method name (which will always be the
1395 same as C<$method_name>), the name of the class in which the method
1396 lives and a CODE reference for the actual method.
1398 The list of methods produced is a distinct list, meaning there are no
1399 duplicates in it. This is especially useful for things like object
1400 initialization and destruction where you only want the method called
1401 once, and in the correct order.
1403 =item B<find_next_method_by_name ($method_name)>
1405 This will return the first method to match a given C<$method_name> in
1406 the superclasses, this is basically equivalent to calling
1407 C<SUPER::$method_name>, but it can be dispatched at runtime.
1411 =head2 Method Modifiers
1413 Method modifiers are a concept borrowed from CLOS, in which a method
1414 can be wrapped with I<before>, I<after> and I<around> method modifiers
1415 that will be called everytime the method is called.
1417 =head3 How method modifiers work?
1419 Method modifiers work by wrapping the original method and then replacing
1420 it in the classes symbol table. The wrappers will handle calling all the
1421 modifiers in the appropariate orders and preserving the calling context
1422 for the original method.
1424 Each method modifier serves a particular purpose, which may not be
1425 obvious to users of other method wrapping modules. To start with, the
1426 return values of I<before> and I<after> modifiers are ignored. This is
1427 because thier purpose is B<not> to filter the input and output of the
1428 primary method (this is done with an I<around> modifier). This may seem
1429 like an odd restriction to some, but doing this allows for simple code
1430 to be added at the begining or end of a method call without jeapordizing
1431 the normal functioning of the primary method or placing any extra
1432 responsibility on the code of the modifier. Of course if you have more
1433 complex needs, then use the I<around> modifier, which uses a variation
1434 of continutation passing style to allow for a high degree of flexibility.
1436 Before and around modifiers are called in last-defined-first-called order,
1437 while after modifiers are called in first-defined-first-called order. So
1438 the call tree might looks something like this:
1448 To see examples of using method modifiers, see the following examples
1449 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1450 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1451 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1453 =head3 What is the performance impact?
1455 Of course there is a performance cost associated with method modifiers,
1456 but we have made every effort to make that cost be directly proportional
1457 to the amount of modifier features you utilize.
1459 The wrapping method does it's best to B<only> do as much work as it
1460 absolutely needs to. In order to do this we have moved some of the
1461 performance costs to set-up time, where they are easier to amortize.
1463 All this said, my benchmarks have indicated the following:
1465 simple wrapper with no modifiers 100% slower
1466 simple wrapper with simple before modifier 400% slower
1467 simple wrapper with simple after modifier 450% slower
1468 simple wrapper with simple around modifier 500-550% slower
1469 simple wrapper with all 3 modifiers 1100% slower
1471 These numbers may seem daunting, but you must remember, every feature
1472 comes with some cost. To put things in perspective, just doing a simple
1473 C<AUTOLOAD> which does nothing but extract the name of the method called
1474 and return it costs about 400% over a normal method call.
1478 =item B<add_before_method_modifier ($method_name, $code)>
1480 This will wrap the method at C<$method_name> and the supplied C<$code>
1481 will be passed the C<@_> arguments, and called before the original
1482 method is called. As specified above, the return value of the I<before>
1483 method modifiers is ignored, and it's ability to modify C<@_> is
1484 fairly limited. If you need to do either of these things, use an
1485 C<around> method modifier.
1487 =item B<add_after_method_modifier ($method_name, $code)>
1489 This will wrap the method at C<$method_name> so that the original
1490 method will be called, it's return values stashed, and then the
1491 supplied C<$code> will be passed the C<@_> arguments, and called.
1492 As specified above, the return value of the I<after> method
1493 modifiers is ignored, and it cannot modify the return values of
1494 the original method. If you need to do either of these things, use an
1495 C<around> method modifier.
1497 =item B<add_around_method_modifier ($method_name, $code)>
1499 This will wrap the method at C<$method_name> so that C<$code>
1500 will be called and passed the original method as an extra argument
1501 at the begining of the C<@_> argument list. This is a variation of
1502 continuation passing style, where the function prepended to C<@_>
1503 can be considered a continuation. It is up to C<$code> if it calls
1504 the original method or not, there is no restriction on what the
1505 C<$code> can or cannot do.
1511 It should be noted that since there is no one consistent way to define
1512 the attributes of a class in Perl 5. These methods can only work with
1513 the information given, and can not easily discover information on
1514 their own. See L<Class::MOP::Attribute> for more details.
1518 =item B<attribute_metaclass>
1520 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1521 for more information on the attribute metaclasses.
1523 =item B<get_attribute_map>
1525 This returns a HASH ref of name to attribute meta-object mapping.
1527 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1529 This stores the C<$attribute_meta_object> (or creates one from the
1530 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1531 instance associated with the given class. Unlike methods, attributes
1532 within the MOP are stored as meta-information only. They will be used
1533 later to construct instances from (see C<construct_instance> above).
1534 More details about the attribute meta-objects can be found in the
1535 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1538 It should be noted that any accessor, reader/writer or predicate
1539 methods which the C<$attribute_meta_object> has will be installed
1540 into the class at this time.
1543 If an attribute already exists for C<$attribute_name>, the old one
1544 will be removed (as well as removing all it's accessors), and then
1547 =item B<has_attribute ($attribute_name)>
1549 Checks to see if this class has an attribute by the name of
1550 C<$attribute_name> and returns a boolean.
1552 =item B<get_attribute ($attribute_name)>
1554 Returns the attribute meta-object associated with C<$attribute_name>,
1555 if none is found, it will return undef.
1557 =item B<remove_attribute ($attribute_name)>
1559 This will remove the attribute meta-object stored at
1560 C<$attribute_name>, then return the removed attribute meta-object.
1563 Removing an attribute will only affect future instances of
1564 the class, it will not make any attempt to remove the attribute from
1565 any existing instances of the class.
1567 It should be noted that any accessor, reader/writer or predicate
1568 methods which the attribute meta-object stored at C<$attribute_name>
1569 has will be removed from the class at this time. This B<will> make
1570 these attributes somewhat inaccessable in previously created
1571 instances. But if you are crazy enough to do this at runtime, then
1572 you are crazy enough to deal with something like this :).
1574 =item B<get_attribute_list>
1576 This returns a list of attribute names which are defined in the local
1577 class. If you want a list of all applicable attributes for a class,
1578 use the C<compute_all_applicable_attributes> method.
1580 =item B<compute_all_applicable_attributes>
1582 This will traverse the inheritance heirachy and return a list of all
1583 the applicable attributes for this class. It does not construct a
1584 HASH reference like C<compute_all_applicable_methods> because all
1585 that same information is discoverable through the attribute
1588 =item B<find_attribute_by_name ($attr_name)>
1590 This method will traverse the inheritance heirachy and find the
1591 first attribute whose name matches C<$attr_name>, then return it.
1592 It will return undef if nothing is found.
1596 =head2 Class Immutability
1600 =item B<make_immutable (%options)>
1602 This method will invoke a tranforamtion upon the class which will
1603 make it immutable. Details of this transformation can be found in
1604 the L<Class::MOP::Immutable> documentation.
1606 =item B<make_mutable>
1608 This method will reverse tranforamtion upon the class which
1611 =item B<get_immutable_transformer>
1613 Return a transformer suitable for making this class immutable or, if this
1614 class is immutable, the transformer used to make it immutable.
1616 =item B<get_immutable_options>
1618 If the class is immutable, return the options used to make it immutable.
1620 =item B<create_immutable_transformer>
1622 Create a transformer suitable for making this class immutable
1628 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1630 =head1 COPYRIGHT AND LICENSE
1632 Copyright 2006-2008 by Infinity Interactive, Inc.
1634 L<http://www.iinteractive.com>
1636 This library is free software; you can redistribute it and/or modify
1637 it under the same terms as Perl itself.