2 package Class::MOP::Class;
7 use Class::MOP::Immutable;
8 use Class::MOP::Instance;
9 use Class::MOP::Method::Wrapped;
12 use Scalar::Util 'blessed', 'reftype', 'weaken';
13 use Sub::Name 'subname';
15 our $VERSION = '0.26';
16 our $AUTHORITY = 'cpan:STEVAN';
18 use base 'Class::MOP::Module';
22 sub meta { Class::MOP::Class->initialize(blessed($_[0]) || $_[0]) }
28 my $package_name = shift;
29 (defined $package_name && $package_name && !blessed($package_name))
30 || confess "You must pass a package name and it cannot be blessed";
31 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
34 $class->construct_class_instance('package' => $package_name, @_);
39 my $package_name = shift;
40 (defined $package_name && $package_name && !blessed($package_name))
41 || confess "You must pass a package name and it cannot be blessed";
42 Class::MOP::remove_metaclass_by_name($package_name);
43 $class->construct_class_instance('package' => $package_name, @_);
46 # NOTE: (meta-circularity)
47 # this is a special form of &construct_instance
48 # (see below), which is used to construct class
49 # meta-object instances for any Class::MOP::*
50 # class. All other classes will use the more
51 # normal &construct_instance.
52 sub construct_class_instance {
55 my $package_name = $options{'package'};
56 (defined $package_name && $package_name)
57 || confess "You must pass a package name";
59 # return the metaclass if we have it cached,
60 # and it is still defined (it has not been
61 # reaped by DESTROY yet, which can happen
62 # annoyingly enough during global destruction)
64 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
69 # we need to deal with the possibility
70 # of class immutability here, and then
71 # get the name of the class appropriately
72 $class = (blessed($class)
73 ? ($class->is_immutable
74 ? $class->get_mutable_metaclass_name()
78 # now create the metaclass
80 if ($class eq 'Class::MOP::Class') {
83 # inherited from Class::MOP::Package
84 '$!package' => $package_name,
87 # since the following attributes will
88 # actually be loaded from the symbol
89 # table, and actually bypass the instance
90 # entirely, we can just leave these things
91 # listed here for reference, because they
92 # should not actually have a value associated
94 '%!namespace' => \undef,
95 # inherited from Class::MOP::Module
96 '$!version' => \undef,
97 '$!authority' => \undef,
98 # defined in Class::MOP::Class
99 '@!superclasses' => \undef,
102 '%!attributes' => {},
103 '$!attribute_metaclass' => $options{'attribute_metaclass'} || 'Class::MOP::Attribute',
104 '$!method_metaclass' => $options{'method_metaclass'} || 'Class::MOP::Method',
105 '$!instance_metaclass' => $options{'instance_metaclass'} || 'Class::MOP::Instance',
107 ## uber-private variables
109 # this starts out as undef so that
110 # we can tell the first time the
111 # methods are fetched
113 '$!_package_cache_flag' => undef,
118 # it is safe to use meta here because
119 # class will always be a subclass of
120 # Class::MOP::Class, which defines meta
121 $meta = $class->meta->construct_instance(%options)
124 # and check the metaclass compatibility
125 $meta->check_metaclass_compatability();
127 Class::MOP::store_metaclass_by_name($package_name, $meta);
130 # we need to weaken any anon classes
131 # so that they can call DESTROY properly
132 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
137 sub reset_package_cache_flag { (shift)->{'$!_package_cache_flag'} = undef }
138 sub update_package_cache_flag {
141 # we can manually update the cache number
142 # since we are actually adding the method
143 # to our cache as well. This avoids us
144 # having to regenerate the method_map.
146 $self->{'$!_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
149 sub check_metaclass_compatability {
152 # this is always okay ...
153 return if blessed($self) eq 'Class::MOP::Class' &&
154 $self->instance_metaclass eq 'Class::MOP::Instance';
156 my @class_list = $self->linearized_isa;
157 shift @class_list; # shift off $self->name
159 foreach my $class_name (@class_list) {
160 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
163 # we need to deal with the possibility
164 # of class immutability here, and then
165 # get the name of the class appropriately
166 my $meta_type = ($meta->is_immutable
167 ? $meta->get_mutable_metaclass_name()
170 ($self->isa($meta_type))
171 || confess $self->name . "->meta => (" . (blessed($self)) . ")" .
172 " is not compatible with the " .
173 $class_name . "->meta => (" . ($meta_type) . ")";
175 # we also need to check that instance metaclasses
176 # are compatabile in the same the class.
177 ($self->instance_metaclass->isa($meta->instance_metaclass))
178 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
179 " is not compatible with the " .
180 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
188 # this should be sufficient, if you have a
189 # use case where it is not, write a test and
191 my $ANON_CLASS_SERIAL = 0;
194 # we need a sufficiently annoying prefix
195 # this should suffice for now, this is
196 # used in a couple of places below, so
197 # need to put it up here for now.
198 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
202 no warnings 'uninitialized';
203 $self->name =~ /^$ANON_CLASS_PREFIX/ ? 1 : 0;
206 sub create_anon_class {
207 my ($class, %options) = @_;
208 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
209 return $class->create($package_name, %options);
213 # this will only get called for
214 # anon-classes, all other calls
215 # are assumed to occur during
216 # global destruction and so don't
217 # really need to be handled explicitly
220 no warnings 'uninitialized';
221 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
222 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
224 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
225 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
227 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
232 # creating classes with MOP ...
236 my $package_name = shift;
238 (defined $package_name && $package_name)
239 || confess "You must pass a package name";
242 || confess "You much pass all parameters as name => value pairs " .
243 "(I found an uneven number of params in \@_)";
247 my $code = "package $package_name;";
248 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
249 if exists $options{version};
250 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
251 if exists $options{authority};
254 confess "creation of $package_name failed : $@" if $@;
256 my $meta = $class->initialize($package_name);
258 $meta->add_method('meta' => sub {
259 $class->initialize(blessed($_[0]) || $_[0]);
262 $meta->superclasses(@{$options{superclasses}})
263 if exists $options{superclasses};
265 # process attributes first, so that they can
266 # install accessors, but locally defined methods
267 # can then overwrite them. It is maybe a little odd, but
268 # I think this should be the order of things.
269 if (exists $options{attributes}) {
270 foreach my $attr (@{$options{attributes}}) {
271 $meta->add_attribute($attr);
274 if (exists $options{methods}) {
275 foreach my $method_name (keys %{$options{methods}}) {
276 $meta->add_method($method_name, $options{methods}->{$method_name});
285 # all these attribute readers will be bootstrapped
286 # away in the Class::MOP bootstrap section
288 sub get_attribute_map { $_[0]->{'%!attributes'} }
289 sub attribute_metaclass { $_[0]->{'$!attribute_metaclass'} }
290 sub method_metaclass { $_[0]->{'$!method_metaclass'} }
291 sub instance_metaclass { $_[0]->{'$!instance_metaclass'} }
294 # this is a prime canidate for conversion to XS
298 if (defined $self->{'$!_package_cache_flag'} &&
299 $self->{'$!_package_cache_flag'} == Class::MOP::check_package_cache_flag($self->name)) {
300 return $self->{'%!methods'};
303 my $map = $self->{'%!methods'};
305 my $class_name = $self->name;
306 my $method_metaclass = $self->method_metaclass;
308 foreach my $symbol ($self->list_all_package_symbols('CODE')) {
309 my $code = $self->get_package_symbol('&' . $symbol);
311 next if exists $map->{$symbol} &&
312 defined $map->{$symbol} &&
313 $map->{$symbol}->body == $code;
315 my ($pkg, $name) = Class::MOP::get_code_info($code);
316 next if ($pkg || '') ne $class_name &&
317 ($name || '') ne '__ANON__';
319 $map->{$symbol} = $method_metaclass->wrap($code);
325 # Instance Construction & Cloning
330 # we need to protect the integrity of the
331 # Class::MOP::Class singletons here, so we
332 # delegate this to &construct_class_instance
333 # which will deal with the singletons
334 return $class->construct_class_instance(@_)
335 if $class->name->isa('Class::MOP::Class');
336 return $class->construct_instance(@_);
339 sub construct_instance {
340 my ($class, %params) = @_;
341 my $meta_instance = $class->get_meta_instance();
342 my $instance = $meta_instance->create_instance();
343 foreach my $attr ($class->compute_all_applicable_attributes()) {
344 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
347 # this will only work for a HASH instance type
348 if ($class->is_anon_class) {
349 (reftype($instance) eq 'HASH')
350 || confess "Currently only HASH based instances are supported with instance of anon-classes";
352 # At some point we should make this official
353 # as a reserved slot name, but right now I am
354 # going to keep it here.
355 # my $RESERVED_MOP_SLOT = '__MOP__';
356 $instance->{'__MOP__'} = $class;
361 sub get_meta_instance {
363 return $class->instance_metaclass->new(
365 $class->compute_all_applicable_attributes()
371 my $instance = shift;
372 (blessed($instance) && $instance->isa($class->name))
373 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
375 # we need to protect the integrity of the
376 # Class::MOP::Class singletons here, they
377 # should not be cloned.
378 return $instance if $instance->isa('Class::MOP::Class');
379 $class->clone_instance($instance, @_);
383 my ($class, $instance, %params) = @_;
385 || confess "You can only clone instances, \$self is not a blessed instance";
386 my $meta_instance = $class->get_meta_instance();
387 my $clone = $meta_instance->clone_instance($instance);
388 foreach my $attr ($class->compute_all_applicable_attributes()) {
389 if (exists $params{$attr->init_arg}) {
390 $meta_instance->set_slot_value($clone, $attr->name, $params{$attr->init_arg});
402 @{$self->get_package_symbol('@ISA')} = @supers;
404 # we need to check the metaclass
405 # compatibility here so that we can
406 # be sure that the superclass is
407 # not potentially creating an issues
408 # we don't know about
409 $self->check_metaclass_compatability();
411 @{$self->get_package_symbol('@ISA')};
417 my $super_class = $self->name;
420 my $find_derived_classes;
421 $find_derived_classes = sub {
422 my ($outer_class) = @_;
424 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
427 for my $symbol ( keys %$symbol_table_hashref ) {
428 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
429 my $inner_class = $1;
431 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
435 ? "${outer_class}::$inner_class"
438 if ( $class->isa($super_class) and $class ne $super_class ) {
439 push @derived_classes, $class;
442 next SYMBOL if $class eq 'main'; # skip 'main::*'
444 $find_derived_classes->($class);
448 my $root_class = q{};
449 $find_derived_classes->($root_class);
451 undef $find_derived_classes;
453 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
455 return @derived_classes;
460 if (Class::MOP::IS_RUNNING_ON_5_10()) {
461 return @{ mro::get_linear_isa( (shift)->name ) };
465 return grep { !($seen{$_}++) } (shift)->class_precedence_list;
469 sub class_precedence_list {
472 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
474 # We need to check for circular inheritance here
475 # if we are are not on 5.10, cause 5.8 detects it
476 # late. This will do nothing if all is well, and
477 # blow up otherwise. Yes, it's an ugly hack, better
478 # suggestions are welcome.
480 ($self->name || return)->isa('This is a test for circular inheritance')
486 $self->initialize($_)->class_precedence_list()
487 } $self->superclasses()
494 my ($self, $method_name, $method) = @_;
495 (defined $method_name && $method_name)
496 || confess "You must define a method name";
499 if (blessed($method)) {
500 $body = $method->body;
504 ('CODE' eq (reftype($body) || ''))
505 || confess "Your code block must be a CODE reference";
506 $method = $self->method_metaclass->wrap($body);
508 $self->get_method_map->{$method_name} = $method;
510 my $full_method_name = ($self->name . '::' . $method_name);
511 $self->add_package_symbol("&${method_name}" => subname $full_method_name => $body);
512 $self->update_package_cache_flag;
516 my $fetch_and_prepare_method = sub {
517 my ($self, $method_name) = @_;
519 my $method = $self->get_method($method_name);
520 # if we dont have local ...
522 # try to find the next method
523 $method = $self->find_next_method_by_name($method_name);
524 # die if it does not exist
526 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
527 # and now make sure to wrap it
528 # even if it is already wrapped
529 # because we need a new sub ref
530 $method = Class::MOP::Method::Wrapped->wrap($method);
533 # now make sure we wrap it properly
534 $method = Class::MOP::Method::Wrapped->wrap($method)
535 unless $method->isa('Class::MOP::Method::Wrapped');
537 $self->add_method($method_name => $method);
541 sub add_before_method_modifier {
542 my ($self, $method_name, $method_modifier) = @_;
543 (defined $method_name && $method_name)
544 || confess "You must pass in a method name";
545 my $method = $fetch_and_prepare_method->($self, $method_name);
546 $method->add_before_modifier(subname ':before' => $method_modifier);
549 sub add_after_method_modifier {
550 my ($self, $method_name, $method_modifier) = @_;
551 (defined $method_name && $method_name)
552 || confess "You must pass in a method name";
553 my $method = $fetch_and_prepare_method->($self, $method_name);
554 $method->add_after_modifier(subname ':after' => $method_modifier);
557 sub add_around_method_modifier {
558 my ($self, $method_name, $method_modifier) = @_;
559 (defined $method_name && $method_name)
560 || confess "You must pass in a method name";
561 my $method = $fetch_and_prepare_method->($self, $method_name);
562 $method->add_around_modifier(subname ':around' => $method_modifier);
566 # the methods above used to be named like this:
567 # ${pkg}::${method}:(before|after|around)
568 # but this proved problematic when using one modifier
569 # to wrap multiple methods (something which is likely
570 # to happen pretty regularly IMO). So instead of naming
571 # it like this, I have chosen to just name them purely
572 # with their modifier names, like so:
573 # :(before|after|around)
574 # The fact is that in a stack trace, it will be fairly
575 # evident from the context what method they are attached
576 # to, and so don't need the fully qualified name.
580 my ($self, $method_name, $method) = @_;
581 (defined $method_name && $method_name)
582 || confess "You must define a method name";
584 my $body = (blessed($method) ? $method->body : $method);
585 ('CODE' eq (reftype($body) || ''))
586 || confess "Your code block must be a CODE reference";
588 $self->add_package_symbol("&${method_name}" => $body);
589 $self->update_package_cache_flag;
593 my ($self, $method_name) = @_;
594 (defined $method_name && $method_name)
595 || confess "You must define a method name";
597 return 0 unless exists $self->get_method_map->{$method_name};
602 my ($self, $method_name) = @_;
603 (defined $method_name && $method_name)
604 || confess "You must define a method name";
607 # I don't really need this here, because
608 # if the method_map is missing a key it
609 # will just return undef for me now
610 # return unless $self->has_method($method_name);
612 return $self->get_method_map->{$method_name};
616 my ($self, $method_name) = @_;
617 (defined $method_name && $method_name)
618 || confess "You must define a method name";
620 my $removed_method = delete $self->get_method_map->{$method_name};
622 $self->remove_package_symbol("&${method_name}");
624 $self->update_package_cache_flag;
626 return $removed_method;
629 sub get_method_list {
631 keys %{$self->get_method_map};
634 sub find_method_by_name {
635 my ($self, $method_name) = @_;
636 (defined $method_name && $method_name)
637 || confess "You must define a method name to find";
638 foreach my $class ($self->linearized_isa) {
639 # fetch the meta-class ...
640 my $meta = $self->initialize($class);
641 return $meta->get_method($method_name)
642 if $meta->has_method($method_name);
647 sub compute_all_applicable_methods {
649 my (@methods, %seen_method);
650 foreach my $class ($self->linearized_isa) {
651 # fetch the meta-class ...
652 my $meta = $self->initialize($class);
653 foreach my $method_name ($meta->get_method_list()) {
654 next if exists $seen_method{$method_name};
655 $seen_method{$method_name}++;
657 name => $method_name,
659 code => $meta->get_method($method_name)
666 sub find_all_methods_by_name {
667 my ($self, $method_name) = @_;
668 (defined $method_name && $method_name)
669 || confess "You must define a method name to find";
671 foreach my $class ($self->linearized_isa) {
672 # fetch the meta-class ...
673 my $meta = $self->initialize($class);
675 name => $method_name,
677 code => $meta->get_method($method_name)
678 } if $meta->has_method($method_name);
683 sub find_next_method_by_name {
684 my ($self, $method_name) = @_;
685 (defined $method_name && $method_name)
686 || confess "You must define a method name to find";
687 my @cpl = $self->linearized_isa;
688 shift @cpl; # discard ourselves
689 foreach my $class (@cpl) {
690 # fetch the meta-class ...
691 my $meta = $self->initialize($class);
692 return $meta->get_method($method_name)
693 if $meta->has_method($method_name);
702 # either we have an attribute object already
703 # or we need to create one from the args provided
704 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
705 # make sure it is derived from the correct type though
706 ($attribute->isa('Class::MOP::Attribute'))
707 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
709 # first we attach our new attribute
710 # because it might need certain information
711 # about the class which it is attached to
712 $attribute->attach_to_class($self);
714 # then we remove attributes of a conflicting
715 # name here so that we can properly detach
716 # the old attr object, and remove any
717 # accessors it would have generated
718 $self->remove_attribute($attribute->name)
719 if $self->has_attribute($attribute->name);
721 # then onto installing the new accessors
722 $attribute->install_accessors();
723 $self->get_attribute_map->{$attribute->name} = $attribute;
727 my ($self, $attribute_name) = @_;
728 (defined $attribute_name && $attribute_name)
729 || confess "You must define an attribute name";
730 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
734 my ($self, $attribute_name) = @_;
735 (defined $attribute_name && $attribute_name)
736 || confess "You must define an attribute name";
737 return $self->get_attribute_map->{$attribute_name}
739 # this will return undef anyway, so no need ...
740 # if $self->has_attribute($attribute_name);
744 sub remove_attribute {
745 my ($self, $attribute_name) = @_;
746 (defined $attribute_name && $attribute_name)
747 || confess "You must define an attribute name";
748 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
749 return unless defined $removed_attribute;
750 delete $self->get_attribute_map->{$attribute_name};
751 $removed_attribute->remove_accessors();
752 $removed_attribute->detach_from_class();
753 return $removed_attribute;
756 sub get_attribute_list {
758 keys %{$self->get_attribute_map};
761 sub compute_all_applicable_attributes {
763 my (@attrs, %seen_attr);
764 foreach my $class ($self->linearized_isa) {
765 # fetch the meta-class ...
766 my $meta = $self->initialize($class);
767 foreach my $attr_name ($meta->get_attribute_list()) {
768 next if exists $seen_attr{$attr_name};
769 $seen_attr{$attr_name}++;
770 push @attrs => $meta->get_attribute($attr_name);
776 sub find_attribute_by_name {
777 my ($self, $attr_name) = @_;
778 foreach my $class ($self->linearized_isa) {
779 # fetch the meta-class ...
780 my $meta = $self->initialize($class);
781 return $meta->get_attribute($attr_name)
782 if $meta->has_attribute($attr_name);
790 sub is_immutable { 0 }
793 # Why I changed this (groditi)
794 # - One Metaclass may have many Classes through many Metaclass instances
795 # - One Metaclass should only have one Immutable Transformer instance
796 # - Each Class may have different Immutabilizing options
797 # - Therefore each Metaclass instance may have different Immutabilizing options
798 # - We need to store one Immutable Transformer instance per Metaclass
799 # - We need to store one set of Immutable Transformer options per Class
800 # - Upon make_mutable we may delete the Immutabilizing options
801 # - We could clean the immutable Transformer instance when there is no more
802 # immutable Classes of that type, but we can also keep it in case
803 # another class with this same Metaclass becomes immutable. It is a case
804 # of trading of storing an instance to avoid unnecessary instantiations of
805 # Immutable Transformers. You may view this as a memory leak, however
806 # Because we have few Metaclasses, in practice it seems acceptable
807 # - To allow Immutable Transformers instances to be cleaned up we could weaken
808 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
811 my %IMMUTABLE_TRANSFORMERS;
812 my %IMMUTABLE_OPTIONS;
816 my $class = blessed $self || $self;
818 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
819 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
821 $transformer->make_metaclass_immutable($self, \%options);
822 $IMMUTABLE_OPTIONS{$self->name} =
823 { %options, IMMUTABLE_TRANSFORMER => $transformer };
825 if( exists $options{debug} && $options{debug} ){
826 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
827 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
833 return if $self->is_mutable;
834 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
835 confess "unable to find immutabilizing options" unless ref $options;
836 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
837 $transformer->make_metaclass_mutable($self, $options);
841 sub create_immutable_transformer {
843 my $class = Class::MOP::Immutable->new($self, {
844 read_only => [qw/superclasses/],
852 remove_package_symbol
855 class_precedence_list => 'ARRAY',
856 linearized_isa => 'ARRAY',
857 compute_all_applicable_attributes => 'ARRAY',
858 get_meta_instance => 'SCALAR',
859 get_method_map => 'SCALAR',
873 Class::MOP::Class - Class Meta Object
877 # assuming that class Foo
878 # has been defined, you can
880 # use this for introspection ...
882 # add a method to Foo ...
883 Foo->meta->add_method('bar' => sub { ... })
885 # get a list of all the classes searched
886 # the method dispatcher in the correct order
887 Foo->meta->class_precedence_list()
889 # remove a method from Foo
890 Foo->meta->remove_method('bar');
892 # or use this to actually create classes ...
894 Class::MOP::Class->create('Bar' => (
896 superclasses => [ 'Foo' ],
898 Class::MOP:::Attribute->new('$bar'),
899 Class::MOP:::Attribute->new('$baz'),
902 calculate_bar => sub { ... },
903 construct_baz => sub { ... }
909 This is the largest and currently most complex part of the Perl 5
910 meta-object protocol. It controls the introspection and
911 manipulation of Perl 5 classes (and it can create them too). The
912 best way to understand what this module can do, is to read the
913 documentation for each of it's methods.
917 =head2 Self Introspection
923 This will return a B<Class::MOP::Class> instance which is related
924 to this class. Thereby allowing B<Class::MOP::Class> to actually
927 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
928 bootstrap this module by installing a number of attribute meta-objects
929 into it's metaclass. This will allow this class to reap all the benifits
930 of the MOP when subclassing it.
934 =head2 Class construction
936 These methods will handle creating B<Class::MOP::Class> objects,
937 which can be used to both create new classes, and analyze
938 pre-existing classes.
940 This module will internally store references to all the instances
941 you create with these methods, so that they do not need to be
942 created any more than nessecary. Basically, they are singletons.
946 =item B<create ($package_name,
947 version =E<gt> ?$version,
948 authority =E<gt> ?$authority,
949 superclasses =E<gt> ?@superclasses,
950 methods =E<gt> ?%methods,
951 attributes =E<gt> ?%attributes)>
953 This returns a B<Class::MOP::Class> object, bringing the specified
954 C<$package_name> into existence and adding any of the C<$version>,
955 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
958 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
959 methods =E<gt> ?%methods,
960 attributes =E<gt> ?%attributes)>
962 This will create an anonymous class, it works much like C<create> but
963 it does not need a C<$package_name>. Instead it will create a suitably
964 unique package name for you to stash things into.
966 On very important distinction is that anon classes are destroyed once
967 the metaclass they are attached to goes out of scope. In the DESTROY
968 method, the created package will be removed from the symbol table.
970 It is also worth noting that any instances created with an anon-class
971 will keep a special reference to the anon-meta which will prevent the
972 anon-class from going out of scope until all instances of it have also
973 been destroyed. This however only works for HASH based instance types,
974 as we use a special reserved slot (C<__MOP__>) to store this.
976 =item B<initialize ($package_name, %options)>
978 This initializes and returns returns a B<Class::MOP::Class> object
979 for a given a C<$package_name>.
981 =item B<reinitialize ($package_name, %options)>
983 This removes the old metaclass, and creates a new one in it's place.
984 Do B<not> use this unless you really know what you are doing, it could
985 very easily make a very large mess of your program.
987 =item B<construct_class_instance (%options)>
989 This will construct an instance of B<Class::MOP::Class>, it is
990 here so that we can actually "tie the knot" for B<Class::MOP::Class>
991 to use C<construct_instance> once all the bootstrapping is done. This
992 method is used internally by C<initialize> and should never be called
993 from outside of that method really.
995 =item B<check_metaclass_compatability>
997 This method is called as the very last thing in the
998 C<construct_class_instance> method. This will check that the
999 metaclass you are creating is compatible with the metaclasses of all
1000 your ancestors. For more inforamtion about metaclass compatibility
1001 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1003 =item B<update_package_cache_flag>
1005 This will reset the package cache flag for this particular metaclass
1006 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1007 function. This is very rarely needed from outside of C<Class::MOP::Class>
1008 but in some cases you might want to use it, so it is here.
1010 =item B<reset_package_cache_flag>
1012 Clear this flag, used in Moose.
1016 =head2 Object instance construction and cloning
1018 These methods are B<entirely optional>, it is up to you whether you want
1023 =item B<instance_metaclass>
1025 =item B<get_meta_instance>
1027 =item B<new_object (%params)>
1029 This is a convience method for creating a new object of the class, and
1030 blessing it into the appropriate package as well. Ideally your class
1031 would call a C<new> this method like so:
1034 my ($class, %param) = @_;
1035 $class->meta->new_object(%params);
1038 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1039 but that is considered bad style, so we do not do that.
1041 =item B<construct_instance (%params)>
1043 This method is used to construct an instace structure suitable for
1044 C<bless>-ing into your package of choice. It works in conjunction
1045 with the Attribute protocol to collect all applicable attributes.
1047 This will construct and instance using a HASH ref as storage
1048 (currently only HASH references are supported). This will collect all
1049 the applicable attributes and layout out the fields in the HASH ref,
1050 it will then initialize them using either use the corresponding key
1051 in C<%params> or any default value or initializer found in the
1052 attribute meta-object.
1054 =item B<clone_object ($instance, %params)>
1056 This is a convience method for cloning an object instance, then
1057 blessing it into the appropriate package. This method will call
1058 C<clone_instance>, which performs a shallow copy of the object,
1059 see that methods documentation for more details. Ideally your
1060 class would call a C<clone> this method like so:
1062 sub MyClass::clone {
1063 my ($self, %param) = @_;
1064 $self->meta->clone_object($self, %params);
1067 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1068 but that is considered bad style, so we do not do that.
1070 =item B<clone_instance($instance, %params)>
1072 This method is a compliment of C<construct_instance> (which means if
1073 you override C<construct_instance>, you need to override this one too),
1074 and clones the instance shallowly.
1076 The cloned structure returned is (like with C<construct_instance>) an
1077 unC<bless>ed HASH reference, it is your responsibility to then bless
1078 this cloned structure into the right class (which C<clone_object> will
1081 As of 0.11, this method will clone the C<$instance> structure shallowly,
1082 as opposed to the deep cloning implemented in prior versions. After much
1083 thought, research and discussion, I have decided that anything but basic
1084 shallow cloning is outside the scope of the meta-object protocol. I
1085 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1086 is too I<context-specific> to be part of the MOP.
1090 =head2 Informational
1092 These are a few predicate methods for asking information about the class.
1096 =item B<is_anon_class>
1098 This returns true if the class is a C<Class::MOP::Class> created anon class.
1102 This returns true if the class is still mutable.
1104 =item B<is_immutable>
1106 This returns true if the class has been made immutable.
1110 =head2 Inheritance Relationships
1114 =item B<superclasses (?@superclasses)>
1116 This is a read-write attribute which represents the superclass
1117 relationships of the class the B<Class::MOP::Class> instance is
1118 associated with. Basically, it can get and set the C<@ISA> for you.
1121 Perl will occasionally perform some C<@ISA> and method caching, if
1122 you decide to change your superclass relationship at runtime (which
1123 is quite insane and very much not recommened), then you should be
1124 aware of this and the fact that this module does not make any
1125 attempt to address this issue.
1127 =item B<class_precedence_list>
1129 This computes the a list of all the class's ancestors in the same order
1130 in which method dispatch will be done. This is similair to
1131 what B<Class::ISA::super_path> does, but we don't remove duplicate names.
1133 =item B<linearized_isa>
1135 This returns a list based on C<class_precedence_list> but with all
1140 This returns a list of subclasses for this class.
1148 =item B<get_method_map>
1150 =item B<method_metaclass>
1152 =item B<add_method ($method_name, $method)>
1154 This will take a C<$method_name> and CODE reference to that
1155 C<$method> and install it into the class's package.
1158 This does absolutely nothing special to C<$method>
1159 other than use B<Sub::Name> to make sure it is tagged with the
1160 correct name, and therefore show up correctly in stack traces and
1163 =item B<alias_method ($method_name, $method)>
1165 This will take a C<$method_name> and CODE reference to that
1166 C<$method> and alias the method into the class's package.
1169 Unlike C<add_method>, this will B<not> try to name the
1170 C<$method> using B<Sub::Name>, it only aliases the method in
1171 the class's package.
1173 =item B<has_method ($method_name)>
1175 This just provides a simple way to check if the class implements
1176 a specific C<$method_name>. It will I<not> however, attempt to check
1177 if the class inherits the method (use C<UNIVERSAL::can> for that).
1179 This will correctly handle functions defined outside of the package
1180 that use a fully qualified name (C<sub Package::name { ... }>).
1182 This will correctly handle functions renamed with B<Sub::Name> and
1183 installed using the symbol tables. However, if you are naming the
1184 subroutine outside of the package scope, you must use the fully
1185 qualified name, including the package name, for C<has_method> to
1186 correctly identify it.
1188 This will attempt to correctly ignore functions imported from other
1189 packages using B<Exporter>. It breaks down if the function imported
1190 is an C<__ANON__> sub (such as with C<use constant>), which very well
1191 may be a valid method being applied to the class.
1193 In short, this method cannot always be trusted to determine if the
1194 C<$method_name> is actually a method. However, it will DWIM about
1195 90% of the time, so it's a small trade off I think.
1197 =item B<get_method ($method_name)>
1199 This will return a Class::MOP::Method instance related to the specified
1200 C<$method_name>, or return undef if that method does not exist.
1202 The Class::MOP::Method is codifiable, so you can use it like a normal
1203 CODE reference, see L<Class::MOP::Method> for more information.
1205 =item B<find_method_by_name ($method_name>
1207 This will return a CODE reference of the specified C<$method_name>,
1208 or return undef if that method does not exist.
1210 Unlike C<get_method> this will also look in the superclasses.
1212 =item B<remove_method ($method_name)>
1214 This will attempt to remove a given C<$method_name> from the class.
1215 It will return the CODE reference that it has removed, and will
1216 attempt to use B<Sub::Name> to clear the methods associated name.
1218 =item B<get_method_list>
1220 This will return a list of method names for all I<locally> defined
1221 methods. It does B<not> provide a list of all applicable methods,
1222 including any inherited ones. If you want a list of all applicable
1223 methods, use the C<compute_all_applicable_methods> method.
1225 =item B<compute_all_applicable_methods>
1227 This will return a list of all the methods names this class will
1228 respond to, taking into account inheritance. The list will be a list of
1229 HASH references, each one containing the following information; method
1230 name, the name of the class in which the method lives and a CODE
1231 reference for the actual method.
1233 =item B<find_all_methods_by_name ($method_name)>
1235 This will traverse the inheritence hierarchy and locate all methods
1236 with a given C<$method_name>. Similar to
1237 C<compute_all_applicable_methods> it returns a list of HASH references
1238 with the following information; method name (which will always be the
1239 same as C<$method_name>), the name of the class in which the method
1240 lives and a CODE reference for the actual method.
1242 The list of methods produced is a distinct list, meaning there are no
1243 duplicates in it. This is especially useful for things like object
1244 initialization and destruction where you only want the method called
1245 once, and in the correct order.
1247 =item B<find_next_method_by_name ($method_name)>
1249 This will return the first method to match a given C<$method_name> in
1250 the superclasses, this is basically equivalent to calling
1251 C<SUPER::$method_name>, but it can be dispatched at runtime.
1255 =head2 Method Modifiers
1257 Method modifiers are a concept borrowed from CLOS, in which a method
1258 can be wrapped with I<before>, I<after> and I<around> method modifiers
1259 that will be called everytime the method is called.
1261 =head3 How method modifiers work?
1263 Method modifiers work by wrapping the original method and then replacing
1264 it in the classes symbol table. The wrappers will handle calling all the
1265 modifiers in the appropariate orders and preserving the calling context
1266 for the original method.
1268 Each method modifier serves a particular purpose, which may not be
1269 obvious to users of other method wrapping modules. To start with, the
1270 return values of I<before> and I<after> modifiers are ignored. This is
1271 because thier purpose is B<not> to filter the input and output of the
1272 primary method (this is done with an I<around> modifier). This may seem
1273 like an odd restriction to some, but doing this allows for simple code
1274 to be added at the begining or end of a method call without jeapordizing
1275 the normal functioning of the primary method or placing any extra
1276 responsibility on the code of the modifier. Of course if you have more
1277 complex needs, then use the I<around> modifier, which uses a variation
1278 of continutation passing style to allow for a high degree of flexibility.
1280 Before and around modifiers are called in last-defined-first-called order,
1281 while after modifiers are called in first-defined-first-called order. So
1282 the call tree might looks something like this:
1292 To see examples of using method modifiers, see the following examples
1293 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1294 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1295 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1297 =head3 What is the performance impact?
1299 Of course there is a performance cost associated with method modifiers,
1300 but we have made every effort to make that cost be directly proportional
1301 to the amount of modifier features you utilize.
1303 The wrapping method does it's best to B<only> do as much work as it
1304 absolutely needs to. In order to do this we have moved some of the
1305 performance costs to set-up time, where they are easier to amortize.
1307 All this said, my benchmarks have indicated the following:
1309 simple wrapper with no modifiers 100% slower
1310 simple wrapper with simple before modifier 400% slower
1311 simple wrapper with simple after modifier 450% slower
1312 simple wrapper with simple around modifier 500-550% slower
1313 simple wrapper with all 3 modifiers 1100% slower
1315 These numbers may seem daunting, but you must remember, every feature
1316 comes with some cost. To put things in perspective, just doing a simple
1317 C<AUTOLOAD> which does nothing but extract the name of the method called
1318 and return it costs about 400% over a normal method call.
1322 =item B<add_before_method_modifier ($method_name, $code)>
1324 This will wrap the method at C<$method_name> and the supplied C<$code>
1325 will be passed the C<@_> arguments, and called before the original
1326 method is called. As specified above, the return value of the I<before>
1327 method modifiers is ignored, and it's ability to modify C<@_> is
1328 fairly limited. If you need to do either of these things, use an
1329 C<around> method modifier.
1331 =item B<add_after_method_modifier ($method_name, $code)>
1333 This will wrap the method at C<$method_name> so that the original
1334 method will be called, it's return values stashed, and then the
1335 supplied C<$code> will be passed the C<@_> arguments, and called.
1336 As specified above, the return value of the I<after> method
1337 modifiers is ignored, and it cannot modify the return values of
1338 the original method. If you need to do either of these things, use an
1339 C<around> method modifier.
1341 =item B<add_around_method_modifier ($method_name, $code)>
1343 This will wrap the method at C<$method_name> so that C<$code>
1344 will be called and passed the original method as an extra argument
1345 at the begining of the C<@_> argument list. This is a variation of
1346 continuation passing style, where the function prepended to C<@_>
1347 can be considered a continuation. It is up to C<$code> if it calls
1348 the original method or not, there is no restriction on what the
1349 C<$code> can or cannot do.
1355 It should be noted that since there is no one consistent way to define
1356 the attributes of a class in Perl 5. These methods can only work with
1357 the information given, and can not easily discover information on
1358 their own. See L<Class::MOP::Attribute> for more details.
1362 =item B<attribute_metaclass>
1364 =item B<get_attribute_map>
1366 =item B<add_attribute ($attribute_meta_object | $attribute_name, %attribute_spec)>
1368 This stores the C<$attribute_meta_object> (or creates one from the
1369 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1370 instance associated with the given class. Unlike methods, attributes
1371 within the MOP are stored as meta-information only. They will be used
1372 later to construct instances from (see C<construct_instance> above).
1373 More details about the attribute meta-objects can be found in the
1374 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1377 It should be noted that any accessor, reader/writer or predicate
1378 methods which the C<$attribute_meta_object> has will be installed
1379 into the class at this time.
1382 If an attribute already exists for C<$attribute_name>, the old one
1383 will be removed (as well as removing all it's accessors), and then
1386 =item B<has_attribute ($attribute_name)>
1388 Checks to see if this class has an attribute by the name of
1389 C<$attribute_name> and returns a boolean.
1391 =item B<get_attribute ($attribute_name)>
1393 Returns the attribute meta-object associated with C<$attribute_name>,
1394 if none is found, it will return undef.
1396 =item B<remove_attribute ($attribute_name)>
1398 This will remove the attribute meta-object stored at
1399 C<$attribute_name>, then return the removed attribute meta-object.
1402 Removing an attribute will only affect future instances of
1403 the class, it will not make any attempt to remove the attribute from
1404 any existing instances of the class.
1406 It should be noted that any accessor, reader/writer or predicate
1407 methods which the attribute meta-object stored at C<$attribute_name>
1408 has will be removed from the class at this time. This B<will> make
1409 these attributes somewhat inaccessable in previously created
1410 instances. But if you are crazy enough to do this at runtime, then
1411 you are crazy enough to deal with something like this :).
1413 =item B<get_attribute_list>
1415 This returns a list of attribute names which are defined in the local
1416 class. If you want a list of all applicable attributes for a class,
1417 use the C<compute_all_applicable_attributes> method.
1419 =item B<compute_all_applicable_attributes>
1421 This will traverse the inheritance heirachy and return a list of all
1422 the applicable attributes for this class. It does not construct a
1423 HASH reference like C<compute_all_applicable_methods> because all
1424 that same information is discoverable through the attribute
1427 =item B<find_attribute_by_name ($attr_name)>
1429 This method will traverse the inheritance heirachy and find the
1430 first attribute whose name matches C<$attr_name>, then return it.
1431 It will return undef if nothing is found.
1435 =head2 Class Immutability
1439 =item B<make_immutable (%options)>
1441 This method will invoke a tranforamtion upon the class which will
1442 make it immutable. Details of this transformation can be found in
1443 the L<Class::MOP::Immutable> documentation.
1445 =item B<make_mutable>
1447 This method will reverse tranforamtion upon the class which
1450 =item B<create_immutable_transformer>
1452 Create a transformer suitable for making this class immutable
1458 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1460 =head1 COPYRIGHT AND LICENSE
1462 Copyright 2006-2008 by Infinity Interactive, Inc.
1464 L<http://www.iinteractive.com>
1466 This library is free software; you can redistribute it and/or modify
1467 it under the same terms as Perl itself.