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 = '0.33';
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' => $package_name,
80 # since the following attributes will
81 # actually be loaded from the symbol
82 # table, and actually bypass the instance
83 # entirely, we can just leave these things
84 # listed here for reference, because they
85 # should not actually have a value associated
87 '%!namespace' => \undef,
88 # inherited from Class::MOP::Module
89 '$!version' => \undef,
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
352 # we need to protect the integrity of the
353 # Class::MOP::Class singletons here, so we
354 # delegate this to &construct_class_instance
355 # which will deal with the singletons
356 return $class->construct_class_instance(@_)
357 if $class->name->isa('Class::MOP::Class');
358 return $class->construct_instance(@_);
361 sub construct_instance {
362 my ($class, %params) = @_;
363 my $meta_instance = $class->get_meta_instance();
364 my $instance = $meta_instance->create_instance();
365 foreach my $attr ($class->compute_all_applicable_attributes()) {
366 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
369 # this will only work for a HASH instance type
370 if ($class->is_anon_class) {
371 (Scalar::Util::reftype($instance) eq 'HASH')
372 || confess "Currently only HASH based instances are supported with instance of anon-classes";
374 # At some point we should make this official
375 # as a reserved slot name, but right now I am
376 # going to keep it here.
377 # my $RESERVED_MOP_SLOT = '__MOP__';
378 $instance->{'__MOP__'} = $class;
384 sub get_meta_instance {
387 # just about any fiddling with @ISA or
388 # any fiddling with attributes will
389 # also fiddle with the symbol table
390 # and therefore invalidate the package
391 # cache, in which case we should blow
392 # away the meta-instance cache. Of course
393 # this will invalidate it more often then
394 # is probably needed, but better safe
397 $self->{'$!_meta_instance'} = undef
398 if defined $self->{'$!_package_cache_flag'} &&
399 $self->{'$!_package_cache_flag'} == Class::MOP::check_package_cache_flag($self->name);
400 $self->{'$!_meta_instance'} ||= $self->instance_metaclass->new(
402 $self->compute_all_applicable_attributes()
408 my $instance = shift;
409 (blessed($instance) && $instance->isa($class->name))
410 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
412 # we need to protect the integrity of the
413 # Class::MOP::Class singletons here, they
414 # should not be cloned.
415 return $instance if $instance->isa('Class::MOP::Class');
416 $class->clone_instance($instance, @_);
420 my ($class, $instance, %params) = @_;
422 || confess "You can only clone instances, \$self is not a blessed instance";
423 my $meta_instance = $class->get_meta_instance();
424 my $clone = $meta_instance->clone_instance($instance);
425 foreach my $attr ($class->compute_all_applicable_attributes()) {
426 if ( defined( my $init_arg = $attr->init_arg ) ) {
427 if (exists $params{$init_arg}) {
428 $attr->set_value($clone, $params{$init_arg});
435 sub rebless_instance {
436 my ($self, $instance, %params) = @_;
439 if ($instance->can('meta')) {
440 ($instance->meta->isa('Class::MOP::Class'))
441 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
442 $old_metaclass = $instance->meta;
445 $old_metaclass = $self->initialize(blessed($instance));
448 my $meta_instance = $self->get_meta_instance();
450 $self->name->isa($old_metaclass->name)
451 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
454 $meta_instance->rebless_instance_structure($instance, $self);
456 foreach my $attr ( $self->compute_all_applicable_attributes ) {
457 if ( $attr->has_value($instance) ) {
458 if ( defined( my $init_arg = $attr->init_arg ) ) {
459 $params{$init_arg} = $attr->get_value($instance)
460 unless exists $params{$init_arg};
463 $attr->set_value($instance, $attr->get_value($instance));
468 foreach my $attr ($self->compute_all_applicable_attributes) {
469 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
481 @{$self->get_package_symbol('@ISA')} = @supers;
483 # we need to check the metaclass
484 # compatibility here so that we can
485 # be sure that the superclass is
486 # not potentially creating an issues
487 # we don't know about
488 $self->check_metaclass_compatability();
490 @{$self->get_package_symbol('@ISA')};
496 my $super_class = $self->name;
499 my $find_derived_classes;
500 $find_derived_classes = sub {
501 my ($outer_class) = @_;
503 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
506 for my $symbol ( keys %$symbol_table_hashref ) {
507 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
508 my $inner_class = $1;
510 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
514 ? "${outer_class}::$inner_class"
517 if ( $class->isa($super_class) and $class ne $super_class ) {
518 push @derived_classes, $class;
521 next SYMBOL if $class eq 'main'; # skip 'main::*'
523 $find_derived_classes->($class);
527 my $root_class = q{};
528 $find_derived_classes->($root_class);
530 undef $find_derived_classes;
532 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
534 return @derived_classes;
539 return @{ mro::get_linear_isa( (shift)->name ) };
542 sub class_precedence_list {
544 my $name = $self->name;
546 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
548 # We need to check for circular inheritance here
549 # if we are are not on 5.10, cause 5.8 detects it
550 # late. This will do nothing if all is well, and
551 # blow up otherwise. Yes, it's an ugly hack, better
552 # suggestions are welcome.
554 ($name || return)->isa('This is a test for circular inheritance')
557 # if our mro is c3, we can
558 # just grab the linear_isa
559 if (mro::get_mro($name) eq 'c3') {
560 return @{ mro::get_linear_isa($name) }
564 # we can't grab the linear_isa for dfs
565 # since it has all the duplicates
570 $self->initialize($_)->class_precedence_list()
571 } $self->superclasses()
579 my ($self, $method_name, $method) = @_;
580 (defined $method_name && $method_name)
581 || confess "You must define a method name";
584 if (blessed($method)) {
585 $body = $method->body;
586 if ($method->package_name ne $self->name &&
587 $method->name ne $method_name) {
588 warn "Hello there, got somethig for you."
589 . " Method says " . $method->package_name . " " . $method->name
590 . " Class says " . $self->name . " " . $method_name;
591 $method = $method->clone(
592 package_name => $self->name,
594 ) if $method->can('clone');
599 ('CODE' eq ref($body))
600 || confess "Your code block must be a CODE reference";
601 $method = $self->method_metaclass->wrap(
603 package_name => $self->name,
608 $self->get_method_map->{$method_name} = $method;
610 my $full_method_name = ($self->name . '::' . $method_name);
611 $self->add_package_symbol("&${method_name}" =>
612 Class::MOP::subname($full_method_name => $body)
614 $self->update_package_cache_flag;
618 my $fetch_and_prepare_method = sub {
619 my ($self, $method_name) = @_;
621 my $method = $self->get_method($method_name);
622 # if we dont have local ...
624 # try to find the next method
625 $method = $self->find_next_method_by_name($method_name);
626 # die if it does not exist
628 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
629 # and now make sure to wrap it
630 # even if it is already wrapped
631 # because we need a new sub ref
632 $method = Class::MOP::Method::Wrapped->wrap($method);
635 # now make sure we wrap it properly
636 $method = Class::MOP::Method::Wrapped->wrap($method)
637 unless $method->isa('Class::MOP::Method::Wrapped');
639 $self->add_method($method_name => $method);
643 sub add_before_method_modifier {
644 my ($self, $method_name, $method_modifier) = @_;
645 (defined $method_name && $method_name)
646 || confess "You must pass in a method name";
647 my $method = $fetch_and_prepare_method->($self, $method_name);
648 $method->add_before_modifier(
649 Class::MOP::subname(':before' => $method_modifier)
653 sub add_after_method_modifier {
654 my ($self, $method_name, $method_modifier) = @_;
655 (defined $method_name && $method_name)
656 || confess "You must pass in a method name";
657 my $method = $fetch_and_prepare_method->($self, $method_name);
658 $method->add_after_modifier(
659 Class::MOP::subname(':after' => $method_modifier)
663 sub add_around_method_modifier {
664 my ($self, $method_name, $method_modifier) = @_;
665 (defined $method_name && $method_name)
666 || confess "You must pass in a method name";
667 my $method = $fetch_and_prepare_method->($self, $method_name);
668 $method->add_around_modifier(
669 Class::MOP::subname(':around' => $method_modifier)
674 # the methods above used to be named like this:
675 # ${pkg}::${method}:(before|after|around)
676 # but this proved problematic when using one modifier
677 # to wrap multiple methods (something which is likely
678 # to happen pretty regularly IMO). So instead of naming
679 # it like this, I have chosen to just name them purely
680 # with their modifier names, like so:
681 # :(before|after|around)
682 # The fact is that in a stack trace, it will be fairly
683 # evident from the context what method they are attached
684 # to, and so don't need the fully qualified name.
688 my ($self, $method_name, $method) = @_;
689 (defined $method_name && $method_name)
690 || confess "You must define a method name";
692 my $body = (blessed($method) ? $method->body : $method);
693 ('CODE' eq ref($body))
694 || confess "Your code block must be a CODE reference";
696 $self->add_package_symbol("&${method_name}" => $body);
697 $self->update_package_cache_flag;
701 my ($self, $method_name) = @_;
702 (defined $method_name && $method_name)
703 || confess "You must define a method name";
705 return 0 unless exists $self->get_method_map->{$method_name};
710 my ($self, $method_name) = @_;
711 (defined $method_name && $method_name)
712 || confess "You must define a method name";
715 # I don't really need this here, because
716 # if the method_map is missing a key it
717 # will just return undef for me now
718 # return unless $self->has_method($method_name);
720 return $self->get_method_map->{$method_name};
724 my ($self, $method_name) = @_;
725 (defined $method_name && $method_name)
726 || confess "You must define a method name";
728 my $removed_method = delete $self->get_method_map->{$method_name};
730 $self->remove_package_symbol("&${method_name}");
732 $self->update_package_cache_flag;
734 return $removed_method;
737 sub get_method_list {
739 keys %{$self->get_method_map};
742 sub find_method_by_name {
743 my ($self, $method_name) = @_;
744 (defined $method_name && $method_name)
745 || confess "You must define a method name to find";
746 foreach my $class ($self->linearized_isa) {
747 # fetch the meta-class ...
748 my $meta = $self->initialize($class);
749 return $meta->get_method($method_name)
750 if $meta->has_method($method_name);
755 sub compute_all_applicable_methods {
757 my (@methods, %seen_method);
758 foreach my $class ($self->linearized_isa) {
759 # fetch the meta-class ...
760 my $meta = $self->initialize($class);
761 foreach my $method_name ($meta->get_method_list()) {
762 next if exists $seen_method{$method_name};
763 $seen_method{$method_name}++;
765 name => $method_name,
767 code => $meta->get_method($method_name)
774 sub find_all_methods_by_name {
775 my ($self, $method_name) = @_;
776 (defined $method_name && $method_name)
777 || confess "You must define a method name to find";
779 foreach my $class ($self->linearized_isa) {
780 # fetch the meta-class ...
781 my $meta = $self->initialize($class);
783 name => $method_name,
785 code => $meta->get_method($method_name)
786 } if $meta->has_method($method_name);
791 sub find_next_method_by_name {
792 my ($self, $method_name) = @_;
793 (defined $method_name && $method_name)
794 || confess "You must define a method name to find";
795 my @cpl = $self->linearized_isa;
796 shift @cpl; # discard ourselves
797 foreach my $class (@cpl) {
798 # fetch the meta-class ...
799 my $meta = $self->initialize($class);
800 return $meta->get_method($method_name)
801 if $meta->has_method($method_name);
810 # either we have an attribute object already
811 # or we need to create one from the args provided
812 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
813 # make sure it is derived from the correct type though
814 ($attribute->isa('Class::MOP::Attribute'))
815 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
817 # first we attach our new attribute
818 # because it might need certain information
819 # about the class which it is attached to
820 $attribute->attach_to_class($self);
822 # then we remove attributes of a conflicting
823 # name here so that we can properly detach
824 # the old attr object, and remove any
825 # accessors it would have generated
826 $self->remove_attribute($attribute->name)
827 if $self->has_attribute($attribute->name);
829 # then onto installing the new accessors
830 $attribute->install_accessors();
831 $self->get_attribute_map->{$attribute->name} = $attribute;
835 my ($self, $attribute_name) = @_;
836 (defined $attribute_name && $attribute_name)
837 || confess "You must define an attribute name";
838 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
842 my ($self, $attribute_name) = @_;
843 (defined $attribute_name && $attribute_name)
844 || confess "You must define an attribute name";
845 return $self->get_attribute_map->{$attribute_name}
847 # this will return undef anyway, so no need ...
848 # if $self->has_attribute($attribute_name);
852 sub remove_attribute {
853 my ($self, $attribute_name) = @_;
854 (defined $attribute_name && $attribute_name)
855 || confess "You must define an attribute name";
856 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
857 return unless defined $removed_attribute;
858 delete $self->get_attribute_map->{$attribute_name};
859 $removed_attribute->remove_accessors();
860 $removed_attribute->detach_from_class();
861 return $removed_attribute;
864 sub get_attribute_list {
866 keys %{$self->get_attribute_map};
869 sub compute_all_applicable_attributes {
871 my (@attrs, %seen_attr);
872 foreach my $class ($self->linearized_isa) {
873 # fetch the meta-class ...
874 my $meta = $self->initialize($class);
875 foreach my $attr_name ($meta->get_attribute_list()) {
876 next if exists $seen_attr{$attr_name};
877 $seen_attr{$attr_name}++;
878 push @attrs => $meta->get_attribute($attr_name);
884 sub find_attribute_by_name {
885 my ($self, $attr_name) = @_;
886 foreach my $class ($self->linearized_isa) {
887 # fetch the meta-class ...
888 my $meta = $self->initialize($class);
889 return $meta->get_attribute($attr_name)
890 if $meta->has_attribute($attr_name);
898 sub is_immutable { 0 }
901 # Why I changed this (groditi)
902 # - One Metaclass may have many Classes through many Metaclass instances
903 # - One Metaclass should only have one Immutable Transformer instance
904 # - Each Class may have different Immutabilizing options
905 # - Therefore each Metaclass instance may have different Immutabilizing options
906 # - We need to store one Immutable Transformer instance per Metaclass
907 # - We need to store one set of Immutable Transformer options per Class
908 # - Upon make_mutable we may delete the Immutabilizing options
909 # - We could clean the immutable Transformer instance when there is no more
910 # immutable Classes of that type, but we can also keep it in case
911 # another class with this same Metaclass becomes immutable. It is a case
912 # of trading of storing an instance to avoid unnecessary instantiations of
913 # Immutable Transformers. You may view this as a memory leak, however
914 # Because we have few Metaclasses, in practice it seems acceptable
915 # - To allow Immutable Transformers instances to be cleaned up we could weaken
916 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
919 my %IMMUTABLE_TRANSFORMERS;
920 my %IMMUTABLE_OPTIONS;
924 my $class = blessed $self || $self;
926 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
927 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
929 $transformer->make_metaclass_immutable($self, \%options);
930 $IMMUTABLE_OPTIONS{$self->name} =
931 { %options, IMMUTABLE_TRANSFORMER => $transformer };
933 if( exists $options{debug} && $options{debug} ){
934 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
935 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
943 return if $self->is_mutable;
944 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
945 confess "unable to find immutabilizing options" unless ref $options;
946 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
947 $transformer->make_metaclass_mutable($self, $options);
952 sub create_immutable_transformer {
954 my $class = Class::MOP::Immutable->new($self, {
955 read_only => [qw/superclasses/],
962 remove_package_symbol
965 class_precedence_list => 'ARRAY',
966 linearized_isa => 'ARRAY',
967 compute_all_applicable_attributes => 'ARRAY',
968 get_meta_instance => 'SCALAR',
969 get_method_map => 'SCALAR',
972 # this is ugly, but so are typeglobs,
973 # so whattayahgonnadoboutit
976 add_package_symbol => sub {
977 my $original = shift;
978 confess "Cannot add package symbols to an immutable metaclass"
979 unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
980 goto $original->body;
995 Class::MOP::Class - Class Meta Object
999 # assuming that class Foo
1000 # has been defined, you can
1002 # use this for introspection ...
1004 # add a method to Foo ...
1005 Foo->meta->add_method('bar' => sub { ... })
1007 # get a list of all the classes searched
1008 # the method dispatcher in the correct order
1009 Foo->meta->class_precedence_list()
1011 # remove a method from Foo
1012 Foo->meta->remove_method('bar');
1014 # or use this to actually create classes ...
1016 Class::MOP::Class->create('Bar' => (
1018 superclasses => [ 'Foo' ],
1020 Class::MOP:::Attribute->new('$bar'),
1021 Class::MOP:::Attribute->new('$baz'),
1024 calculate_bar => sub { ... },
1025 construct_baz => sub { ... }
1031 This is the largest and currently most complex part of the Perl 5
1032 meta-object protocol. It controls the introspection and
1033 manipulation of Perl 5 classes (and it can create them too). The
1034 best way to understand what this module can do, is to read the
1035 documentation for each of it's methods.
1039 =head2 Self Introspection
1045 This will return a B<Class::MOP::Class> instance which is related
1046 to this class. Thereby allowing B<Class::MOP::Class> to actually
1049 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
1050 bootstrap this module by installing a number of attribute meta-objects
1051 into it's metaclass. This will allow this class to reap all the benifits
1052 of the MOP when subclassing it.
1056 =head2 Class construction
1058 These methods will handle creating B<Class::MOP::Class> objects,
1059 which can be used to both create new classes, and analyze
1060 pre-existing classes.
1062 This module will internally store references to all the instances
1063 you create with these methods, so that they do not need to be
1064 created any more than nessecary. Basically, they are singletons.
1068 =item B<create ($package_name,
1069 version =E<gt> ?$version,
1070 authority =E<gt> ?$authority,
1071 superclasses =E<gt> ?@superclasses,
1072 methods =E<gt> ?%methods,
1073 attributes =E<gt> ?%attributes)>
1075 This returns a B<Class::MOP::Class> object, bringing the specified
1076 C<$package_name> into existence and adding any of the C<$version>,
1077 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1080 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1081 methods =E<gt> ?%methods,
1082 attributes =E<gt> ?%attributes)>
1084 This will create an anonymous class, it works much like C<create> but
1085 it does not need a C<$package_name>. Instead it will create a suitably
1086 unique package name for you to stash things into.
1088 On very important distinction is that anon classes are destroyed once
1089 the metaclass they are attached to goes out of scope. In the DESTROY
1090 method, the created package will be removed from the symbol table.
1092 It is also worth noting that any instances created with an anon-class
1093 will keep a special reference to the anon-meta which will prevent the
1094 anon-class from going out of scope until all instances of it have also
1095 been destroyed. This however only works for HASH based instance types,
1096 as we use a special reserved slot (C<__MOP__>) to store this.
1098 =item B<initialize ($package_name, %options)>
1100 This initializes and returns returns a B<Class::MOP::Class> object
1101 for a given a C<$package_name>.
1103 =item B<reinitialize ($package_name, %options)>
1105 This removes the old metaclass, and creates a new one in it's place.
1106 Do B<not> use this unless you really know what you are doing, it could
1107 very easily make a very large mess of your program.
1109 =item B<construct_class_instance (%options)>
1111 This will construct an instance of B<Class::MOP::Class>, it is
1112 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1113 to use C<construct_instance> once all the bootstrapping is done. This
1114 method is used internally by C<initialize> and should never be called
1115 from outside of that method really.
1117 =item B<check_metaclass_compatability>
1119 This method is called as the very last thing in the
1120 C<construct_class_instance> method. This will check that the
1121 metaclass you are creating is compatible with the metaclasses of all
1122 your ancestors. For more inforamtion about metaclass compatibility
1123 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1125 =item B<update_package_cache_flag>
1127 This will reset the package cache flag for this particular metaclass
1128 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1129 function. This is very rarely needed from outside of C<Class::MOP::Class>
1130 but in some cases you might want to use it, so it is here.
1132 =item B<reset_package_cache_flag>
1134 Clears the package cache flag to announce to the internals that we need
1135 to rebuild the method map.
1139 =head2 Object instance construction and cloning
1141 These methods are B<entirely optional>, it is up to you whether you want
1146 =item B<instance_metaclass>
1148 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1149 for more information on the instance metaclasses.
1151 =item B<get_meta_instance>
1153 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1154 of a new instance of the class.
1156 =item B<new_object (%params)>
1158 This is a convience method for creating a new object of the class, and
1159 blessing it into the appropriate package as well. Ideally your class
1160 would call a C<new> this method like so:
1163 my ($class, %param) = @_;
1164 $class->meta->new_object(%params);
1167 =item B<construct_instance (%params)>
1169 This method is used to construct an instance structure suitable for
1170 C<bless>-ing into your package of choice. It works in conjunction
1171 with the Attribute protocol to collect all applicable attributes.
1173 This will construct and instance using a HASH ref as storage
1174 (currently only HASH references are supported). This will collect all
1175 the applicable attributes and layout out the fields in the HASH ref,
1176 it will then initialize them using either use the corresponding key
1177 in C<%params> or any default value or initializer found in the
1178 attribute meta-object.
1180 =item B<clone_object ($instance, %params)>
1182 This is a convience method for cloning an object instance, then
1183 blessing it into the appropriate package. This method will call
1184 C<clone_instance>, which performs a shallow copy of the object,
1185 see that methods documentation for more details. Ideally your
1186 class would call a C<clone> this method like so:
1188 sub MyClass::clone {
1189 my ($self, %param) = @_;
1190 $self->meta->clone_object($self, %params);
1193 =item B<clone_instance($instance, %params)>
1195 This method is a compliment of C<construct_instance> (which means if
1196 you override C<construct_instance>, you need to override this one too),
1197 and clones the instance shallowly.
1199 The cloned structure returned is (like with C<construct_instance>) an
1200 unC<bless>ed HASH reference, it is your responsibility to then bless
1201 this cloned structure into the right class (which C<clone_object> will
1204 As of 0.11, this method will clone the C<$instance> structure shallowly,
1205 as opposed to the deep cloning implemented in prior versions. After much
1206 thought, research and discussion, I have decided that anything but basic
1207 shallow cloning is outside the scope of the meta-object protocol. I
1208 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1209 is too I<context-specific> to be part of the MOP.
1211 =item B<rebless_instance($instance, ?%params)>
1213 This will change the class of C<$instance> to the class of the invoking
1214 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1215 itself. You may pass in optional C<%params> which are like constructor
1216 params and will override anything already defined in the instance.
1220 =head2 Informational
1222 These are a few predicate methods for asking information about the class.
1226 =item B<is_anon_class>
1228 This returns true if the class is a C<Class::MOP::Class> created anon class.
1232 This returns true if the class is still mutable.
1234 =item B<is_immutable>
1236 This returns true if the class has been made immutable.
1240 =head2 Inheritance Relationships
1244 =item B<superclasses (?@superclasses)>
1246 This is a read-write attribute which represents the superclass
1247 relationships of the class the B<Class::MOP::Class> instance is
1248 associated with. Basically, it can get and set the C<@ISA> for you.
1250 =item B<class_precedence_list>
1252 This computes the a list of all the class's ancestors in the same order
1253 in which method dispatch will be done. This is similair to what
1254 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1256 =item B<linearized_isa>
1258 This returns a list based on C<class_precedence_list> but with all
1263 This returns a list of subclasses for this class.
1271 =item B<get_method_map>
1273 Returns a HASH ref of name to CODE reference mapping for this class.
1275 =item B<method_metaclass>
1277 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1278 for more information on the method metaclasses.
1280 =item B<add_method ($method_name, $method)>
1282 This will take a C<$method_name> and CODE reference to that
1283 C<$method> and install it into the class's package.
1286 This does absolutely nothing special to C<$method>
1287 other than use B<Sub::Name> to make sure it is tagged with the
1288 correct name, and therefore show up correctly in stack traces and
1291 =item B<alias_method ($method_name, $method)>
1293 This will take a C<$method_name> and CODE reference to that
1294 C<$method> and alias the method into the class's package.
1297 Unlike C<add_method>, this will B<not> try to name the
1298 C<$method> using B<Sub::Name>, it only aliases the method in
1299 the class's package.
1301 =item B<has_method ($method_name)>
1303 This just provides a simple way to check if the class implements
1304 a specific C<$method_name>. It will I<not> however, attempt to check
1305 if the class inherits the method (use C<UNIVERSAL::can> for that).
1307 This will correctly handle functions defined outside of the package
1308 that use a fully qualified name (C<sub Package::name { ... }>).
1310 This will correctly handle functions renamed with B<Sub::Name> and
1311 installed using the symbol tables. However, if you are naming the
1312 subroutine outside of the package scope, you must use the fully
1313 qualified name, including the package name, for C<has_method> to
1314 correctly identify it.
1316 This will attempt to correctly ignore functions imported from other
1317 packages using B<Exporter>. It breaks down if the function imported
1318 is an C<__ANON__> sub (such as with C<use constant>), which very well
1319 may be a valid method being applied to the class.
1321 In short, this method cannot always be trusted to determine if the
1322 C<$method_name> is actually a method. However, it will DWIM about
1323 90% of the time, so it's a small trade off I think.
1325 =item B<get_method ($method_name)>
1327 This will return a Class::MOP::Method instance related to the specified
1328 C<$method_name>, or return undef if that method does not exist.
1330 The Class::MOP::Method is codifiable, so you can use it like a normal
1331 CODE reference, see L<Class::MOP::Method> for more information.
1333 =item B<find_method_by_name ($method_name)>
1335 This will return a CODE reference of the specified C<$method_name>,
1336 or return undef if that method does not exist.
1338 Unlike C<get_method> this will also look in the superclasses.
1340 =item B<remove_method ($method_name)>
1342 This will attempt to remove a given C<$method_name> from the class.
1343 It will return the CODE reference that it has removed, and will
1344 attempt to use B<Sub::Name> to clear the methods associated name.
1346 =item B<get_method_list>
1348 This will return a list of method names for all I<locally> defined
1349 methods. It does B<not> provide a list of all applicable methods,
1350 including any inherited ones. If you want a list of all applicable
1351 methods, use the C<compute_all_applicable_methods> method.
1353 =item B<compute_all_applicable_methods>
1355 This will return a list of all the methods names this class will
1356 respond to, taking into account inheritance. The list will be a list of
1357 HASH references, each one containing the following information; method
1358 name, the name of the class in which the method lives and a CODE
1359 reference for the actual method.
1361 =item B<find_all_methods_by_name ($method_name)>
1363 This will traverse the inheritence hierarchy and locate all methods
1364 with a given C<$method_name>. Similar to
1365 C<compute_all_applicable_methods> it returns a list of HASH references
1366 with the following information; method name (which will always be the
1367 same as C<$method_name>), the name of the class in which the method
1368 lives and a CODE reference for the actual method.
1370 The list of methods produced is a distinct list, meaning there are no
1371 duplicates in it. This is especially useful for things like object
1372 initialization and destruction where you only want the method called
1373 once, and in the correct order.
1375 =item B<find_next_method_by_name ($method_name)>
1377 This will return the first method to match a given C<$method_name> in
1378 the superclasses, this is basically equivalent to calling
1379 C<SUPER::$method_name>, but it can be dispatched at runtime.
1383 =head2 Method Modifiers
1385 Method modifiers are a concept borrowed from CLOS, in which a method
1386 can be wrapped with I<before>, I<after> and I<around> method modifiers
1387 that will be called everytime the method is called.
1389 =head3 How method modifiers work?
1391 Method modifiers work by wrapping the original method and then replacing
1392 it in the classes symbol table. The wrappers will handle calling all the
1393 modifiers in the appropariate orders and preserving the calling context
1394 for the original method.
1396 Each method modifier serves a particular purpose, which may not be
1397 obvious to users of other method wrapping modules. To start with, the
1398 return values of I<before> and I<after> modifiers are ignored. This is
1399 because thier purpose is B<not> to filter the input and output of the
1400 primary method (this is done with an I<around> modifier). This may seem
1401 like an odd restriction to some, but doing this allows for simple code
1402 to be added at the begining or end of a method call without jeapordizing
1403 the normal functioning of the primary method or placing any extra
1404 responsibility on the code of the modifier. Of course if you have more
1405 complex needs, then use the I<around> modifier, which uses a variation
1406 of continutation passing style to allow for a high degree of flexibility.
1408 Before and around modifiers are called in last-defined-first-called order,
1409 while after modifiers are called in first-defined-first-called order. So
1410 the call tree might looks something like this:
1420 To see examples of using method modifiers, see the following examples
1421 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1422 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1423 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1425 =head3 What is the performance impact?
1427 Of course there is a performance cost associated with method modifiers,
1428 but we have made every effort to make that cost be directly proportional
1429 to the amount of modifier features you utilize.
1431 The wrapping method does it's best to B<only> do as much work as it
1432 absolutely needs to. In order to do this we have moved some of the
1433 performance costs to set-up time, where they are easier to amortize.
1435 All this said, my benchmarks have indicated the following:
1437 simple wrapper with no modifiers 100% slower
1438 simple wrapper with simple before modifier 400% slower
1439 simple wrapper with simple after modifier 450% slower
1440 simple wrapper with simple around modifier 500-550% slower
1441 simple wrapper with all 3 modifiers 1100% slower
1443 These numbers may seem daunting, but you must remember, every feature
1444 comes with some cost. To put things in perspective, just doing a simple
1445 C<AUTOLOAD> which does nothing but extract the name of the method called
1446 and return it costs about 400% over a normal method call.
1450 =item B<add_before_method_modifier ($method_name, $code)>
1452 This will wrap the method at C<$method_name> and the supplied C<$code>
1453 will be passed the C<@_> arguments, and called before the original
1454 method is called. As specified above, the return value of the I<before>
1455 method modifiers is ignored, and it's ability to modify C<@_> is
1456 fairly limited. If you need to do either of these things, use an
1457 C<around> method modifier.
1459 =item B<add_after_method_modifier ($method_name, $code)>
1461 This will wrap the method at C<$method_name> so that the original
1462 method will be called, it's return values stashed, and then the
1463 supplied C<$code> will be passed the C<@_> arguments, and called.
1464 As specified above, the return value of the I<after> method
1465 modifiers is ignored, and it cannot modify the return values of
1466 the original method. If you need to do either of these things, use an
1467 C<around> method modifier.
1469 =item B<add_around_method_modifier ($method_name, $code)>
1471 This will wrap the method at C<$method_name> so that C<$code>
1472 will be called and passed the original method as an extra argument
1473 at the begining of the C<@_> argument list. This is a variation of
1474 continuation passing style, where the function prepended to C<@_>
1475 can be considered a continuation. It is up to C<$code> if it calls
1476 the original method or not, there is no restriction on what the
1477 C<$code> can or cannot do.
1483 It should be noted that since there is no one consistent way to define
1484 the attributes of a class in Perl 5. These methods can only work with
1485 the information given, and can not easily discover information on
1486 their own. See L<Class::MOP::Attribute> for more details.
1490 =item B<attribute_metaclass>
1492 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1493 for more information on the attribute metaclasses.
1495 =item B<get_attribute_map>
1497 This returns a HASH ref of name to attribute meta-object mapping.
1499 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1501 This stores the C<$attribute_meta_object> (or creates one from the
1502 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1503 instance associated with the given class. Unlike methods, attributes
1504 within the MOP are stored as meta-information only. They will be used
1505 later to construct instances from (see C<construct_instance> above).
1506 More details about the attribute meta-objects can be found in the
1507 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1510 It should be noted that any accessor, reader/writer or predicate
1511 methods which the C<$attribute_meta_object> has will be installed
1512 into the class at this time.
1515 If an attribute already exists for C<$attribute_name>, the old one
1516 will be removed (as well as removing all it's accessors), and then
1519 =item B<has_attribute ($attribute_name)>
1521 Checks to see if this class has an attribute by the name of
1522 C<$attribute_name> and returns a boolean.
1524 =item B<get_attribute ($attribute_name)>
1526 Returns the attribute meta-object associated with C<$attribute_name>,
1527 if none is found, it will return undef.
1529 =item B<remove_attribute ($attribute_name)>
1531 This will remove the attribute meta-object stored at
1532 C<$attribute_name>, then return the removed attribute meta-object.
1535 Removing an attribute will only affect future instances of
1536 the class, it will not make any attempt to remove the attribute from
1537 any existing instances of the class.
1539 It should be noted that any accessor, reader/writer or predicate
1540 methods which the attribute meta-object stored at C<$attribute_name>
1541 has will be removed from the class at this time. This B<will> make
1542 these attributes somewhat inaccessable in previously created
1543 instances. But if you are crazy enough to do this at runtime, then
1544 you are crazy enough to deal with something like this :).
1546 =item B<get_attribute_list>
1548 This returns a list of attribute names which are defined in the local
1549 class. If you want a list of all applicable attributes for a class,
1550 use the C<compute_all_applicable_attributes> method.
1552 =item B<compute_all_applicable_attributes>
1554 This will traverse the inheritance heirachy and return a list of all
1555 the applicable attributes for this class. It does not construct a
1556 HASH reference like C<compute_all_applicable_methods> because all
1557 that same information is discoverable through the attribute
1560 =item B<find_attribute_by_name ($attr_name)>
1562 This method will traverse the inheritance heirachy and find the
1563 first attribute whose name matches C<$attr_name>, then return it.
1564 It will return undef if nothing is found.
1568 =head2 Class Immutability
1572 =item B<make_immutable (%options)>
1574 This method will invoke a tranforamtion upon the class which will
1575 make it immutable. Details of this transformation can be found in
1576 the L<Class::MOP::Immutable> documentation.
1578 =item B<make_mutable>
1580 This method will reverse tranforamtion upon the class which
1583 =item B<create_immutable_transformer>
1585 Create a transformer suitable for making this class immutable
1591 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1593 =head1 COPYRIGHT AND LICENSE
1595 Copyright 2006-2008 by Infinity Interactive, Inc.
1597 L<http://www.iinteractive.com>
1599 This library is free software; you can redistribute it and/or modify
1600 it under the same terms as Perl itself.