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 = '0.61';
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);
479 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
482 @{$self->get_package_symbol($var_spec)} = @supers;
484 # we need to check the metaclass
485 # compatibility here so that we can
486 # be sure that the superclass is
487 # not potentially creating an issues
488 # we don't know about
489 $self->check_metaclass_compatability();
491 @{$self->get_package_symbol($var_spec)};
497 my $super_class = $self->name;
500 my $find_derived_classes;
501 $find_derived_classes = sub {
502 my ($outer_class) = @_;
504 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
507 for my $symbol ( keys %$symbol_table_hashref ) {
508 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
509 my $inner_class = $1;
511 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
515 ? "${outer_class}::$inner_class"
518 if ( $class->isa($super_class) and $class ne $super_class ) {
519 push @derived_classes, $class;
522 next SYMBOL if $class eq 'main'; # skip 'main::*'
524 $find_derived_classes->($class);
528 my $root_class = q{};
529 $find_derived_classes->($root_class);
531 undef $find_derived_classes;
533 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
535 return @derived_classes;
540 return @{ mro::get_linear_isa( (shift)->name ) };
543 sub class_precedence_list {
545 my $name = $self->name;
547 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
549 # We need to check for circular inheritance here
550 # if we are are not on 5.10, cause 5.8 detects it
551 # late. This will do nothing if all is well, and
552 # blow up otherwise. Yes, it's an ugly hack, better
553 # suggestions are welcome.
555 ($name || return)->isa('This is a test for circular inheritance')
558 # if our mro is c3, we can
559 # just grab the linear_isa
560 if (mro::get_mro($name) eq 'c3') {
561 return @{ mro::get_linear_isa($name) }
565 # we can't grab the linear_isa for dfs
566 # since it has all the duplicates
571 $self->initialize($_)->class_precedence_list()
572 } $self->superclasses()
580 my ($self, $method_name, $method) = @_;
581 (defined $method_name && $method_name)
582 || confess "You must define a method name";
585 if (blessed($method)) {
586 $body = $method->body;
587 if ($method->package_name ne $self->name &&
588 $method->name ne $method_name) {
589 warn "Hello there, got somethig for you."
590 . " Method says " . $method->package_name . " " . $method->name
591 . " Class says " . $self->name . " " . $method_name;
592 $method = $method->clone(
593 package_name => $self->name,
595 ) if $method->can('clone');
600 ('CODE' eq ref($body))
601 || confess "Your code block must be a CODE reference";
602 $method = $self->method_metaclass->wrap(
604 package_name => $self->name,
609 $self->get_method_map->{$method_name} = $method;
611 my $full_method_name = ($self->name . '::' . $method_name);
612 $self->add_package_symbol(
613 { sigil => '&', type => 'CODE', name => $method_name },
614 Class::MOP::subname($full_method_name => $body)
616 $self->update_package_cache_flag;
620 my $fetch_and_prepare_method = sub {
621 my ($self, $method_name) = @_;
623 my $method = $self->get_method($method_name);
624 # if we dont have local ...
626 # try to find the next method
627 $method = $self->find_next_method_by_name($method_name);
628 # die if it does not exist
630 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
631 # and now make sure to wrap it
632 # even if it is already wrapped
633 # because we need a new sub ref
634 $method = Class::MOP::Method::Wrapped->wrap($method);
637 # now make sure we wrap it properly
638 $method = Class::MOP::Method::Wrapped->wrap($method)
639 unless $method->isa('Class::MOP::Method::Wrapped');
641 $self->add_method($method_name => $method);
645 sub add_before_method_modifier {
646 my ($self, $method_name, $method_modifier) = @_;
647 (defined $method_name && $method_name)
648 || confess "You must pass in a method name";
649 my $method = $fetch_and_prepare_method->($self, $method_name);
650 $method->add_before_modifier(
651 Class::MOP::subname(':before' => $method_modifier)
655 sub add_after_method_modifier {
656 my ($self, $method_name, $method_modifier) = @_;
657 (defined $method_name && $method_name)
658 || confess "You must pass in a method name";
659 my $method = $fetch_and_prepare_method->($self, $method_name);
660 $method->add_after_modifier(
661 Class::MOP::subname(':after' => $method_modifier)
665 sub add_around_method_modifier {
666 my ($self, $method_name, $method_modifier) = @_;
667 (defined $method_name && $method_name)
668 || confess "You must pass in a method name";
669 my $method = $fetch_and_prepare_method->($self, $method_name);
670 $method->add_around_modifier(
671 Class::MOP::subname(':around' => $method_modifier)
676 # the methods above used to be named like this:
677 # ${pkg}::${method}:(before|after|around)
678 # but this proved problematic when using one modifier
679 # to wrap multiple methods (something which is likely
680 # to happen pretty regularly IMO). So instead of naming
681 # it like this, I have chosen to just name them purely
682 # with their modifier names, like so:
683 # :(before|after|around)
684 # The fact is that in a stack trace, it will be fairly
685 # evident from the context what method they are attached
686 # to, and so don't need the fully qualified name.
690 my ($self, $method_name, $method) = @_;
691 (defined $method_name && $method_name)
692 || confess "You must define a method name";
694 my $body = (blessed($method) ? $method->body : $method);
695 ('CODE' eq ref($body))
696 || confess "Your code block must be a CODE reference";
698 $self->add_package_symbol(
699 { sigil => '&', type => 'CODE', name => $method_name } => $body
701 $self->update_package_cache_flag;
705 my ($self, $method_name) = @_;
706 (defined $method_name && $method_name)
707 || confess "You must define a method name";
709 return 0 unless exists $self->get_method_map->{$method_name};
714 my ($self, $method_name) = @_;
715 (defined $method_name && $method_name)
716 || confess "You must define a method name";
719 # I don't really need this here, because
720 # if the method_map is missing a key it
721 # will just return undef for me now
722 # return unless $self->has_method($method_name);
724 return $self->get_method_map->{$method_name};
728 my ($self, $method_name) = @_;
729 (defined $method_name && $method_name)
730 || confess "You must define a method name";
732 my $removed_method = delete $self->get_method_map->{$method_name};
734 $self->remove_package_symbol(
735 { sigil => '&', type => 'CODE', name => $method_name }
738 $self->update_package_cache_flag;
740 return $removed_method;
743 sub get_method_list {
745 keys %{$self->get_method_map};
748 sub find_method_by_name {
749 my ($self, $method_name) = @_;
750 (defined $method_name && $method_name)
751 || confess "You must define a method name to find";
752 foreach my $class ($self->linearized_isa) {
753 # fetch the meta-class ...
754 my $meta = $self->initialize($class);
755 return $meta->get_method($method_name)
756 if $meta->has_method($method_name);
761 sub compute_all_applicable_methods {
763 my (@methods, %seen_method);
764 foreach my $class ($self->linearized_isa) {
765 # fetch the meta-class ...
766 my $meta = $self->initialize($class);
767 foreach my $method_name ($meta->get_method_list()) {
768 next if exists $seen_method{$method_name};
769 $seen_method{$method_name}++;
771 name => $method_name,
773 code => $meta->get_method($method_name)
780 sub find_all_methods_by_name {
781 my ($self, $method_name) = @_;
782 (defined $method_name && $method_name)
783 || confess "You must define a method name to find";
785 foreach my $class ($self->linearized_isa) {
786 # fetch the meta-class ...
787 my $meta = $self->initialize($class);
789 name => $method_name,
791 code => $meta->get_method($method_name)
792 } if $meta->has_method($method_name);
797 sub find_next_method_by_name {
798 my ($self, $method_name) = @_;
799 (defined $method_name && $method_name)
800 || confess "You must define a method name to find";
801 my @cpl = $self->linearized_isa;
802 shift @cpl; # discard ourselves
803 foreach my $class (@cpl) {
804 # fetch the meta-class ...
805 my $meta = $self->initialize($class);
806 return $meta->get_method($method_name)
807 if $meta->has_method($method_name);
816 # either we have an attribute object already
817 # or we need to create one from the args provided
818 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
819 # make sure it is derived from the correct type though
820 ($attribute->isa('Class::MOP::Attribute'))
821 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
823 # first we attach our new attribute
824 # because it might need certain information
825 # about the class which it is attached to
826 $attribute->attach_to_class($self);
828 # then we remove attributes of a conflicting
829 # name here so that we can properly detach
830 # the old attr object, and remove any
831 # accessors it would have generated
832 $self->remove_attribute($attribute->name)
833 if $self->has_attribute($attribute->name);
835 # then onto installing the new accessors
836 $attribute->install_accessors();
837 $self->get_attribute_map->{$attribute->name} = $attribute;
841 my ($self, $attribute_name) = @_;
842 (defined $attribute_name && $attribute_name)
843 || confess "You must define an attribute name";
844 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
848 my ($self, $attribute_name) = @_;
849 (defined $attribute_name && $attribute_name)
850 || confess "You must define an attribute name";
851 return $self->get_attribute_map->{$attribute_name}
853 # this will return undef anyway, so no need ...
854 # if $self->has_attribute($attribute_name);
858 sub remove_attribute {
859 my ($self, $attribute_name) = @_;
860 (defined $attribute_name && $attribute_name)
861 || confess "You must define an attribute name";
862 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
863 return unless defined $removed_attribute;
864 delete $self->get_attribute_map->{$attribute_name};
865 $removed_attribute->remove_accessors();
866 $removed_attribute->detach_from_class();
867 return $removed_attribute;
870 sub get_attribute_list {
872 keys %{$self->get_attribute_map};
875 sub compute_all_applicable_attributes {
877 my (@attrs, %seen_attr);
878 foreach my $class ($self->linearized_isa) {
879 # fetch the meta-class ...
880 my $meta = $self->initialize($class);
881 foreach my $attr_name ($meta->get_attribute_list()) {
882 next if exists $seen_attr{$attr_name};
883 $seen_attr{$attr_name}++;
884 push @attrs => $meta->get_attribute($attr_name);
890 sub find_attribute_by_name {
891 my ($self, $attr_name) = @_;
892 foreach my $class ($self->linearized_isa) {
893 # fetch the meta-class ...
894 my $meta = $self->initialize($class);
895 return $meta->get_attribute($attr_name)
896 if $meta->has_attribute($attr_name);
904 sub is_immutable { 0 }
907 # Why I changed this (groditi)
908 # - One Metaclass may have many Classes through many Metaclass instances
909 # - One Metaclass should only have one Immutable Transformer instance
910 # - Each Class may have different Immutabilizing options
911 # - Therefore each Metaclass instance may have different Immutabilizing options
912 # - We need to store one Immutable Transformer instance per Metaclass
913 # - We need to store one set of Immutable Transformer options per Class
914 # - Upon make_mutable we may delete the Immutabilizing options
915 # - We could clean the immutable Transformer instance when there is no more
916 # immutable Classes of that type, but we can also keep it in case
917 # another class with this same Metaclass becomes immutable. It is a case
918 # of trading of storing an instance to avoid unnecessary instantiations of
919 # Immutable Transformers. You may view this as a memory leak, however
920 # Because we have few Metaclasses, in practice it seems acceptable
921 # - To allow Immutable Transformers instances to be cleaned up we could weaken
922 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
926 my %IMMUTABLE_TRANSFORMERS;
927 my %IMMUTABLE_OPTIONS;
929 sub get_immutable_options {
931 return if $self->is_mutable;
932 confess "unable to find immutabilizing options"
933 unless exists $IMMUTABLE_OPTIONS{$self->name};
934 my %options = %{$IMMUTABLE_OPTIONS{$self->name}};
935 delete $options{IMMUTABLE_TRANSFORMER};
939 sub get_immutable_transformer {
941 if( $self->is_mutable ){
942 my $class = blessed $self || $self;
943 return $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
945 confess "unable to find transformer for immutable class"
946 unless exists $IMMUTABLE_OPTIONS{$self->name};
947 return $IMMUTABLE_OPTIONS{$self->name}->{IMMUTABLE_TRANSFORMER};
954 my $transformer = $self->get_immutable_transformer;
955 $transformer->make_metaclass_immutable($self, \%options);
956 $IMMUTABLE_OPTIONS{$self->name} =
957 { %options, IMMUTABLE_TRANSFORMER => $transformer };
959 if( exists $options{debug} && $options{debug} ){
960 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
961 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
969 return if $self->is_mutable;
970 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
971 confess "unable to find immutabilizing options" unless ref $options;
972 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
973 $transformer->make_metaclass_mutable($self, $options);
978 sub create_immutable_transformer {
980 my $class = Class::MOP::Immutable->new($self, {
981 read_only => [qw/superclasses/],
988 remove_package_symbol
991 class_precedence_list => 'ARRAY',
992 linearized_isa => 'ARRAY',
993 compute_all_applicable_attributes => 'ARRAY',
994 get_meta_instance => 'SCALAR',
995 get_method_map => 'SCALAR',
998 # this is ugly, but so are typeglobs,
999 # so whattayahgonnadoboutit
1002 add_package_symbol => sub {
1003 my $original = shift;
1004 confess "Cannot add package symbols to an immutable metaclass"
1005 unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
1006 goto $original->body;
1021 Class::MOP::Class - Class Meta Object
1025 # assuming that class Foo
1026 # has been defined, you can
1028 # use this for introspection ...
1030 # add a method to Foo ...
1031 Foo->meta->add_method('bar' => sub { ... })
1033 # get a list of all the classes searched
1034 # the method dispatcher in the correct order
1035 Foo->meta->class_precedence_list()
1037 # remove a method from Foo
1038 Foo->meta->remove_method('bar');
1040 # or use this to actually create classes ...
1042 Class::MOP::Class->create('Bar' => (
1044 superclasses => [ 'Foo' ],
1046 Class::MOP:::Attribute->new('$bar'),
1047 Class::MOP:::Attribute->new('$baz'),
1050 calculate_bar => sub { ... },
1051 construct_baz => sub { ... }
1057 This is the largest and currently most complex part of the Perl 5
1058 meta-object protocol. It controls the introspection and
1059 manipulation of Perl 5 classes (and it can create them too). The
1060 best way to understand what this module can do, is to read the
1061 documentation for each of it's methods.
1065 =head2 Self Introspection
1071 This will return a B<Class::MOP::Class> instance which is related
1072 to this class. Thereby allowing B<Class::MOP::Class> to actually
1075 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
1076 bootstrap this module by installing a number of attribute meta-objects
1077 into it's metaclass. This will allow this class to reap all the benifits
1078 of the MOP when subclassing it.
1082 =head2 Class construction
1084 These methods will handle creating B<Class::MOP::Class> objects,
1085 which can be used to both create new classes, and analyze
1086 pre-existing classes.
1088 This module will internally store references to all the instances
1089 you create with these methods, so that they do not need to be
1090 created any more than nessecary. Basically, they are singletons.
1094 =item B<create ($package_name,
1095 version =E<gt> ?$version,
1096 authority =E<gt> ?$authority,
1097 superclasses =E<gt> ?@superclasses,
1098 methods =E<gt> ?%methods,
1099 attributes =E<gt> ?%attributes)>
1101 This returns a B<Class::MOP::Class> object, bringing the specified
1102 C<$package_name> into existence and adding any of the C<$version>,
1103 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1106 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1107 methods =E<gt> ?%methods,
1108 attributes =E<gt> ?%attributes)>
1110 This will create an anonymous class, it works much like C<create> but
1111 it does not need a C<$package_name>. Instead it will create a suitably
1112 unique package name for you to stash things into.
1114 On very important distinction is that anon classes are destroyed once
1115 the metaclass they are attached to goes out of scope. In the DESTROY
1116 method, the created package will be removed from the symbol table.
1118 It is also worth noting that any instances created with an anon-class
1119 will keep a special reference to the anon-meta which will prevent the
1120 anon-class from going out of scope until all instances of it have also
1121 been destroyed. This however only works for HASH based instance types,
1122 as we use a special reserved slot (C<__MOP__>) to store this.
1124 =item B<initialize ($package_name, %options)>
1126 This initializes and returns returns a B<Class::MOP::Class> object
1127 for a given a C<$package_name>.
1129 =item B<reinitialize ($package_name, %options)>
1131 This removes the old metaclass, and creates a new one in it's place.
1132 Do B<not> use this unless you really know what you are doing, it could
1133 very easily make a very large mess of your program.
1135 =item B<construct_class_instance (%options)>
1137 This will construct an instance of B<Class::MOP::Class>, it is
1138 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1139 to use C<construct_instance> once all the bootstrapping is done. This
1140 method is used internally by C<initialize> and should never be called
1141 from outside of that method really.
1143 =item B<check_metaclass_compatability>
1145 This method is called as the very last thing in the
1146 C<construct_class_instance> method. This will check that the
1147 metaclass you are creating is compatible with the metaclasses of all
1148 your ancestors. For more inforamtion about metaclass compatibility
1149 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1151 =item B<update_package_cache_flag>
1153 This will reset the package cache flag for this particular metaclass
1154 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1155 function. This is very rarely needed from outside of C<Class::MOP::Class>
1156 but in some cases you might want to use it, so it is here.
1158 =item B<reset_package_cache_flag>
1160 Clears the package cache flag to announce to the internals that we need
1161 to rebuild the method map.
1165 =head2 Object instance construction and cloning
1167 These methods are B<entirely optional>, it is up to you whether you want
1172 =item B<instance_metaclass>
1174 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1175 for more information on the instance metaclasses.
1177 =item B<get_meta_instance>
1179 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1180 of a new instance of the class.
1182 =item B<new_object (%params)>
1184 This is a convience method for creating a new object of the class, and
1185 blessing it into the appropriate package as well. Ideally your class
1186 would call a C<new> this method like so:
1189 my ($class, %param) = @_;
1190 $class->meta->new_object(%params);
1193 =item B<construct_instance (%params)>
1195 This method is used to construct an instance structure suitable for
1196 C<bless>-ing into your package of choice. It works in conjunction
1197 with the Attribute protocol to collect all applicable attributes.
1199 This will construct and instance using a HASH ref as storage
1200 (currently only HASH references are supported). This will collect all
1201 the applicable attributes and layout out the fields in the HASH ref,
1202 it will then initialize them using either use the corresponding key
1203 in C<%params> or any default value or initializer found in the
1204 attribute meta-object.
1206 =item B<clone_object ($instance, %params)>
1208 This is a convience method for cloning an object instance, then
1209 blessing it into the appropriate package. This method will call
1210 C<clone_instance>, which performs a shallow copy of the object,
1211 see that methods documentation for more details. Ideally your
1212 class would call a C<clone> this method like so:
1214 sub MyClass::clone {
1215 my ($self, %param) = @_;
1216 $self->meta->clone_object($self, %params);
1219 =item B<clone_instance($instance, %params)>
1221 This method is a compliment of C<construct_instance> (which means if
1222 you override C<construct_instance>, you need to override this one too),
1223 and clones the instance shallowly.
1225 The cloned structure returned is (like with C<construct_instance>) an
1226 unC<bless>ed HASH reference, it is your responsibility to then bless
1227 this cloned structure into the right class (which C<clone_object> will
1230 As of 0.11, this method will clone the C<$instance> structure shallowly,
1231 as opposed to the deep cloning implemented in prior versions. After much
1232 thought, research and discussion, I have decided that anything but basic
1233 shallow cloning is outside the scope of the meta-object protocol. I
1234 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1235 is too I<context-specific> to be part of the MOP.
1237 =item B<rebless_instance($instance, ?%params)>
1239 This will change the class of C<$instance> to the class of the invoking
1240 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1241 itself. You may pass in optional C<%params> which are like constructor
1242 params and will override anything already defined in the instance.
1246 =head2 Informational
1248 These are a few predicate methods for asking information about the class.
1252 =item B<is_anon_class>
1254 This returns true if the class is a C<Class::MOP::Class> created anon class.
1258 This returns true if the class is still mutable.
1260 =item B<is_immutable>
1262 This returns true if the class has been made immutable.
1266 =head2 Inheritance Relationships
1270 =item B<superclasses (?@superclasses)>
1272 This is a read-write attribute which represents the superclass
1273 relationships of the class the B<Class::MOP::Class> instance is
1274 associated with. Basically, it can get and set the C<@ISA> for you.
1276 =item B<class_precedence_list>
1278 This computes the a list of all the class's ancestors in the same order
1279 in which method dispatch will be done. This is similair to what
1280 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1282 =item B<linearized_isa>
1284 This returns a list based on C<class_precedence_list> but with all
1289 This returns a list of subclasses for this class.
1297 =item B<get_method_map>
1299 Returns a HASH ref of name to CODE reference mapping for this class.
1301 =item B<method_metaclass>
1303 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1304 for more information on the method metaclasses.
1306 =item B<add_method ($method_name, $method)>
1308 This will take a C<$method_name> and CODE reference to that
1309 C<$method> and install it into the class's package.
1312 This does absolutely nothing special to C<$method>
1313 other than use B<Sub::Name> to make sure it is tagged with the
1314 correct name, and therefore show up correctly in stack traces and
1317 =item B<alias_method ($method_name, $method)>
1319 This will take a C<$method_name> and CODE reference to that
1320 C<$method> and alias the method into the class's package.
1323 Unlike C<add_method>, this will B<not> try to name the
1324 C<$method> using B<Sub::Name>, it only aliases the method in
1325 the class's package.
1327 =item B<has_method ($method_name)>
1329 This just provides a simple way to check if the class implements
1330 a specific C<$method_name>. It will I<not> however, attempt to check
1331 if the class inherits the method (use C<UNIVERSAL::can> for that).
1333 This will correctly handle functions defined outside of the package
1334 that use a fully qualified name (C<sub Package::name { ... }>).
1336 This will correctly handle functions renamed with B<Sub::Name> and
1337 installed using the symbol tables. However, if you are naming the
1338 subroutine outside of the package scope, you must use the fully
1339 qualified name, including the package name, for C<has_method> to
1340 correctly identify it.
1342 This will attempt to correctly ignore functions imported from other
1343 packages using B<Exporter>. It breaks down if the function imported
1344 is an C<__ANON__> sub (such as with C<use constant>), which very well
1345 may be a valid method being applied to the class.
1347 In short, this method cannot always be trusted to determine if the
1348 C<$method_name> is actually a method. However, it will DWIM about
1349 90% of the time, so it's a small trade off I think.
1351 =item B<get_method ($method_name)>
1353 This will return a Class::MOP::Method instance related to the specified
1354 C<$method_name>, or return undef if that method does not exist.
1356 The Class::MOP::Method is codifiable, so you can use it like a normal
1357 CODE reference, see L<Class::MOP::Method> for more information.
1359 =item B<find_method_by_name ($method_name)>
1361 This will return a CODE reference of the specified C<$method_name>,
1362 or return undef if that method does not exist.
1364 Unlike C<get_method> this will also look in the superclasses.
1366 =item B<remove_method ($method_name)>
1368 This will attempt to remove a given C<$method_name> from the class.
1369 It will return the CODE reference that it has removed, and will
1370 attempt to use B<Sub::Name> to clear the methods associated name.
1372 =item B<get_method_list>
1374 This will return a list of method names for all I<locally> defined
1375 methods. It does B<not> provide a list of all applicable methods,
1376 including any inherited ones. If you want a list of all applicable
1377 methods, use the C<compute_all_applicable_methods> method.
1379 =item B<compute_all_applicable_methods>
1381 This will return a list of all the methods names this class will
1382 respond to, taking into account inheritance. The list will be a list of
1383 HASH references, each one containing the following information; method
1384 name, the name of the class in which the method lives and a CODE
1385 reference for the actual method.
1387 =item B<find_all_methods_by_name ($method_name)>
1389 This will traverse the inheritence hierarchy and locate all methods
1390 with a given C<$method_name>. Similar to
1391 C<compute_all_applicable_methods> it returns a list of HASH references
1392 with the following information; method name (which will always be the
1393 same as C<$method_name>), the name of the class in which the method
1394 lives and a CODE reference for the actual method.
1396 The list of methods produced is a distinct list, meaning there are no
1397 duplicates in it. This is especially useful for things like object
1398 initialization and destruction where you only want the method called
1399 once, and in the correct order.
1401 =item B<find_next_method_by_name ($method_name)>
1403 This will return the first method to match a given C<$method_name> in
1404 the superclasses, this is basically equivalent to calling
1405 C<SUPER::$method_name>, but it can be dispatched at runtime.
1409 =head2 Method Modifiers
1411 Method modifiers are a concept borrowed from CLOS, in which a method
1412 can be wrapped with I<before>, I<after> and I<around> method modifiers
1413 that will be called everytime the method is called.
1415 =head3 How method modifiers work?
1417 Method modifiers work by wrapping the original method and then replacing
1418 it in the classes symbol table. The wrappers will handle calling all the
1419 modifiers in the appropariate orders and preserving the calling context
1420 for the original method.
1422 Each method modifier serves a particular purpose, which may not be
1423 obvious to users of other method wrapping modules. To start with, the
1424 return values of I<before> and I<after> modifiers are ignored. This is
1425 because thier purpose is B<not> to filter the input and output of the
1426 primary method (this is done with an I<around> modifier). This may seem
1427 like an odd restriction to some, but doing this allows for simple code
1428 to be added at the begining or end of a method call without jeapordizing
1429 the normal functioning of the primary method or placing any extra
1430 responsibility on the code of the modifier. Of course if you have more
1431 complex needs, then use the I<around> modifier, which uses a variation
1432 of continutation passing style to allow for a high degree of flexibility.
1434 Before and around modifiers are called in last-defined-first-called order,
1435 while after modifiers are called in first-defined-first-called order. So
1436 the call tree might looks something like this:
1446 To see examples of using method modifiers, see the following examples
1447 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1448 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1449 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1451 =head3 What is the performance impact?
1453 Of course there is a performance cost associated with method modifiers,
1454 but we have made every effort to make that cost be directly proportional
1455 to the amount of modifier features you utilize.
1457 The wrapping method does it's best to B<only> do as much work as it
1458 absolutely needs to. In order to do this we have moved some of the
1459 performance costs to set-up time, where they are easier to amortize.
1461 All this said, my benchmarks have indicated the following:
1463 simple wrapper with no modifiers 100% slower
1464 simple wrapper with simple before modifier 400% slower
1465 simple wrapper with simple after modifier 450% slower
1466 simple wrapper with simple around modifier 500-550% slower
1467 simple wrapper with all 3 modifiers 1100% slower
1469 These numbers may seem daunting, but you must remember, every feature
1470 comes with some cost. To put things in perspective, just doing a simple
1471 C<AUTOLOAD> which does nothing but extract the name of the method called
1472 and return it costs about 400% over a normal method call.
1476 =item B<add_before_method_modifier ($method_name, $code)>
1478 This will wrap the method at C<$method_name> and the supplied C<$code>
1479 will be passed the C<@_> arguments, and called before the original
1480 method is called. As specified above, the return value of the I<before>
1481 method modifiers is ignored, and it's ability to modify C<@_> is
1482 fairly limited. If you need to do either of these things, use an
1483 C<around> method modifier.
1485 =item B<add_after_method_modifier ($method_name, $code)>
1487 This will wrap the method at C<$method_name> so that the original
1488 method will be called, it's return values stashed, and then the
1489 supplied C<$code> will be passed the C<@_> arguments, and called.
1490 As specified above, the return value of the I<after> method
1491 modifiers is ignored, and it cannot modify the return values of
1492 the original method. If you need to do either of these things, use an
1493 C<around> method modifier.
1495 =item B<add_around_method_modifier ($method_name, $code)>
1497 This will wrap the method at C<$method_name> so that C<$code>
1498 will be called and passed the original method as an extra argument
1499 at the begining of the C<@_> argument list. This is a variation of
1500 continuation passing style, where the function prepended to C<@_>
1501 can be considered a continuation. It is up to C<$code> if it calls
1502 the original method or not, there is no restriction on what the
1503 C<$code> can or cannot do.
1509 It should be noted that since there is no one consistent way to define
1510 the attributes of a class in Perl 5. These methods can only work with
1511 the information given, and can not easily discover information on
1512 their own. See L<Class::MOP::Attribute> for more details.
1516 =item B<attribute_metaclass>
1518 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1519 for more information on the attribute metaclasses.
1521 =item B<get_attribute_map>
1523 This returns a HASH ref of name to attribute meta-object mapping.
1525 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1527 This stores the C<$attribute_meta_object> (or creates one from the
1528 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1529 instance associated with the given class. Unlike methods, attributes
1530 within the MOP are stored as meta-information only. They will be used
1531 later to construct instances from (see C<construct_instance> above).
1532 More details about the attribute meta-objects can be found in the
1533 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1536 It should be noted that any accessor, reader/writer or predicate
1537 methods which the C<$attribute_meta_object> has will be installed
1538 into the class at this time.
1541 If an attribute already exists for C<$attribute_name>, the old one
1542 will be removed (as well as removing all it's accessors), and then
1545 =item B<has_attribute ($attribute_name)>
1547 Checks to see if this class has an attribute by the name of
1548 C<$attribute_name> and returns a boolean.
1550 =item B<get_attribute ($attribute_name)>
1552 Returns the attribute meta-object associated with C<$attribute_name>,
1553 if none is found, it will return undef.
1555 =item B<remove_attribute ($attribute_name)>
1557 This will remove the attribute meta-object stored at
1558 C<$attribute_name>, then return the removed attribute meta-object.
1561 Removing an attribute will only affect future instances of
1562 the class, it will not make any attempt to remove the attribute from
1563 any existing instances of the class.
1565 It should be noted that any accessor, reader/writer or predicate
1566 methods which the attribute meta-object stored at C<$attribute_name>
1567 has will be removed from the class at this time. This B<will> make
1568 these attributes somewhat inaccessable in previously created
1569 instances. But if you are crazy enough to do this at runtime, then
1570 you are crazy enough to deal with something like this :).
1572 =item B<get_attribute_list>
1574 This returns a list of attribute names which are defined in the local
1575 class. If you want a list of all applicable attributes for a class,
1576 use the C<compute_all_applicable_attributes> method.
1578 =item B<compute_all_applicable_attributes>
1580 This will traverse the inheritance heirachy and return a list of all
1581 the applicable attributes for this class. It does not construct a
1582 HASH reference like C<compute_all_applicable_methods> because all
1583 that same information is discoverable through the attribute
1586 =item B<find_attribute_by_name ($attr_name)>
1588 This method will traverse the inheritance heirachy and find the
1589 first attribute whose name matches C<$attr_name>, then return it.
1590 It will return undef if nothing is found.
1594 =head2 Class Immutability
1598 =item B<make_immutable (%options)>
1600 This method will invoke a tranforamtion upon the class which will
1601 make it immutable. Details of this transformation can be found in
1602 the L<Class::MOP::Immutable> documentation.
1604 =item B<make_mutable>
1606 This method will reverse tranforamtion upon the class which
1609 =item B<get_immutable_transformer>
1611 Return a transformer suitable for making this class immutable or, if this
1612 class is immutable, the transformer used to make it immutable.
1614 =item B<get_immutable_options>
1616 If the class is immutable, return the options used to make it immutable.
1618 =item B<create_immutable_transformer>
1620 Create a transformer suitable for making this class immutable
1626 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1628 =head1 COPYRIGHT AND LICENSE
1630 Copyright 2006-2008 by Infinity Interactive, Inc.
1632 L<http://www.iinteractive.com>
1634 This library is free software; you can redistribute it and/or modify
1635 it under the same terms as Perl itself.