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';
14 use B 'svref_2object';
16 our $VERSION = '0.23';
17 our $AUTHORITY = 'cpan:STEVAN';
19 use base 'Class::MOP::Module';
23 sub meta { Class::MOP::Class->initialize(blessed($_[0]) || $_[0]) }
29 my $package_name = shift;
30 (defined $package_name && $package_name && !blessed($package_name))
31 || confess "You must pass a package name and it cannot be blessed";
32 $class->construct_class_instance('package' => $package_name, @_);
37 my $package_name = shift;
38 (defined $package_name && $package_name && !blessed($package_name))
39 || confess "You must pass a package name and it cannot be blessed";
40 Class::MOP::remove_metaclass_by_name($package_name);
41 $class->construct_class_instance('package' => $package_name, @_);
44 # NOTE: (meta-circularity)
45 # this is a special form of &construct_instance
46 # (see below), which is used to construct class
47 # meta-object instances for any Class::MOP::*
48 # class. All other classes will use the more
49 # normal &construct_instance.
50 sub construct_class_instance {
53 my $package_name = $options{'package'};
54 (defined $package_name && $package_name)
55 || confess "You must pass a package name";
57 # return the metaclass if we have it cached,
58 # and it is still defined (it has not been
59 # reaped by DESTROY yet, which can happen
60 # annoyingly enough during global destruction)
61 return Class::MOP::get_metaclass_by_name($package_name)
62 if Class::MOP::does_metaclass_exist($package_name);
65 # we need to deal with the possibility
66 # of class immutability here, and then
67 # get the name of the class appropriately
68 $class = (blessed($class)
69 ? ($class->is_immutable
70 ? $class->get_mutable_metaclass_name()
74 # now create the metaclass
76 if ($class =~ /^Class::MOP::Class$/) {
79 # inherited from Class::MOP::Package
80 '$!package' => $package_name,
83 # since the following attributes will
84 # actually be loaded from the symbol
85 # table, and actually bypass the instance
86 # entirely, we can just leave these things
87 # listed here for reference, because they
88 # should not actually have a value associated
90 '%!namespace' => \undef,
91 # inherited from Class::MOP::Module
92 '$!version' => \undef,
93 '$!authority' => \undef,
94 # defined in Class::MOP::Class
95 '@!superclasses' => \undef,
99 '$!attribute_metaclass' => $options{'attribute_metaclass'} || 'Class::MOP::Attribute',
100 '$!method_metaclass' => $options{'method_metaclass'} || 'Class::MOP::Method',
101 '$!instance_metaclass' => $options{'instance_metaclass'} || 'Class::MOP::Instance',
106 # it is safe to use meta here because
107 # class will always be a subclass of
108 # Class::MOP::Class, which defines meta
109 $meta = $class->meta->construct_instance(%options)
112 # and check the metaclass compatibility
113 $meta->check_metaclass_compatability();
115 Class::MOP::store_metaclass_by_name($package_name, $meta);
118 # we need to weaken any anon classes
119 # so that they can call DESTROY properly
120 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
125 sub check_metaclass_compatability {
128 # this is always okay ...
129 return if blessed($self) eq 'Class::MOP::Class' &&
130 $self->instance_metaclass eq 'Class::MOP::Instance';
132 my @class_list = $self->class_precedence_list;
133 shift @class_list; # shift off $self->name
135 foreach my $class_name (@class_list) {
136 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
139 # we need to deal with the possibility
140 # of class immutability here, and then
141 # get the name of the class appropriately
142 my $meta_type = ($meta->is_immutable
143 ? $meta->get_mutable_metaclass_name()
146 ($self->isa($meta_type))
147 || confess $self->name . "->meta => (" . (blessed($self)) . ")" .
148 " is not compatible with the " .
149 $class_name . "->meta => (" . ($meta_type) . ")";
151 # we also need to check that instance metaclasses
152 # are compatabile in the same the class.
153 ($self->instance_metaclass->isa($meta->instance_metaclass))
154 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
155 " is not compatible with the " .
156 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
164 # this should be sufficient, if you have a
165 # use case where it is not, write a test and
167 my $ANON_CLASS_SERIAL = 0;
170 # we need a sufficiently annoying prefix
171 # this should suffice for now, this is
172 # used in a couple of places below, so
173 # need to put it up here for now.
174 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
178 no warnings 'uninitialized';
179 $self->name =~ /^$ANON_CLASS_PREFIX/ ? 1 : 0;
182 sub create_anon_class {
183 my ($class, %options) = @_;
184 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
185 return $class->create($package_name, %options);
189 # this will only get called for
190 # anon-classes, all other calls
191 # are assumed to occur during
192 # global destruction and so don't
193 # really need to be handled explicitly
196 no warnings 'uninitialized';
197 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
198 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
200 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
201 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
203 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
208 # creating classes with MOP ...
212 my $package_name = shift;
214 (defined $package_name && $package_name)
215 || confess "You must pass a package name";
218 || confess "You much pass all parameters as name => value pairs " .
219 "(I found an uneven number of params in \@_)";
223 my $code = "package $package_name;";
224 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
225 if exists $options{version};
226 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
227 if exists $options{authority};
230 confess "creation of $package_name failed : $@" if $@;
232 my $meta = $class->initialize($package_name);
234 $meta->add_method('meta' => sub {
235 $class->initialize(blessed($_[0]) || $_[0]);
238 $meta->superclasses(@{$options{superclasses}})
239 if exists $options{superclasses};
241 # process attributes first, so that they can
242 # install accessors, but locally defined methods
243 # can then overwrite them. It is maybe a little odd, but
244 # I think this should be the order of things.
245 if (exists $options{attributes}) {
246 foreach my $attr (@{$options{attributes}}) {
247 $meta->add_attribute($attr);
250 if (exists $options{methods}) {
251 foreach my $method_name (keys %{$options{methods}}) {
252 $meta->add_method($method_name, $options{methods}->{$method_name});
261 # all these attribute readers will be bootstrapped
262 # away in the Class::MOP bootstrap section
264 sub get_attribute_map { $_[0]->{'%!attributes'} }
265 sub attribute_metaclass { $_[0]->{'$!attribute_metaclass'} }
266 sub method_metaclass { $_[0]->{'$!method_metaclass'} }
267 sub instance_metaclass { $_[0]->{'$!instance_metaclass'} }
270 # this is a prime canidate for conversion to XS
273 my $map = $self->{'%!methods'};
275 my $class_name = $self->name;
276 my $method_metaclass = $self->method_metaclass;
278 foreach my $symbol ($self->list_all_package_symbols('CODE')) {
279 my $code = $self->get_package_symbol('&' . $symbol);
281 next if exists $map->{$symbol} &&
282 defined $map->{$symbol} &&
283 $map->{$symbol}->body == $code;
285 my $gv = svref_2object($code)->GV;
286 next if ($gv->STASH->NAME || '') ne $class_name &&
287 ($gv->NAME || '') ne '__ANON__';
289 $map->{$symbol} = $method_metaclass->wrap($code);
295 # Instance Construction & Cloning
300 # we need to protect the integrity of the
301 # Class::MOP::Class singletons here, so we
302 # delegate this to &construct_class_instance
303 # which will deal with the singletons
304 return $class->construct_class_instance(@_)
305 if $class->name->isa('Class::MOP::Class');
306 return $class->construct_instance(@_);
309 sub construct_instance {
310 my ($class, %params) = @_;
311 my $meta_instance = $class->get_meta_instance();
312 my $instance = $meta_instance->create_instance();
313 foreach my $attr ($class->compute_all_applicable_attributes()) {
314 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
319 sub get_meta_instance {
321 return $class->instance_metaclass->new(
323 $class->compute_all_applicable_attributes()
329 my $instance = shift;
330 (blessed($instance) && $instance->isa($class->name))
331 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
333 # we need to protect the integrity of the
334 # Class::MOP::Class singletons here, they
335 # should not be cloned.
336 return $instance if $instance->isa('Class::MOP::Class');
337 $class->clone_instance($instance, @_);
341 my ($class, $instance, %params) = @_;
343 || confess "You can only clone instances, \$self is not a blessed instance";
344 my $meta_instance = $class->get_meta_instance();
345 my $clone = $meta_instance->clone_instance($instance);
346 foreach my $attr ($class->compute_all_applicable_attributes()) {
347 if (exists $params{$attr->init_arg}) {
348 $meta_instance->set_slot_value($clone, $attr->name, $params{$attr->init_arg});
360 @{$self->get_package_symbol('@ISA')} = @supers;
362 # we need to check the metaclass
363 # compatability here so that we can
364 # be sure that the superclass is
365 # not potentially creating an issues
366 # we don't know about
367 $self->check_metaclass_compatability();
369 @{$self->get_package_symbol('@ISA')};
372 sub class_precedence_list {
375 # We need to check for ciruclar inheirtance here.
376 # This will do nothing if all is well, and blow
377 # up otherwise. Yes, it's an ugly hack, better
378 # suggestions are welcome.
379 { ($self->name || return)->isa('This is a test for circular inheritance') }
380 # ... and now back to our regularly scheduled program
384 $self->initialize($_)->class_precedence_list()
385 } $self->superclasses()
392 my ($self, $method_name, $method) = @_;
393 (defined $method_name && $method_name)
394 || confess "You must define a method name";
397 if (blessed($method)) {
398 $body = $method->body;
402 ('CODE' eq (reftype($body) || ''))
403 || confess "Your code block must be a CODE reference";
404 $method = $self->method_metaclass->wrap($body);
406 $self->get_method_map->{$method_name} = $method;
408 my $full_method_name = ($self->name . '::' . $method_name);
409 $self->add_package_symbol("&${method_name}" => subname $full_method_name => $body);
413 my $fetch_and_prepare_method = sub {
414 my ($self, $method_name) = @_;
416 my $method = $self->get_method($method_name);
417 # if we dont have local ...
419 # try to find the next method
420 $method = $self->find_next_method_by_name($method_name);
421 # die if it does not exist
423 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
424 # and now make sure to wrap it
425 # even if it is already wrapped
426 # because we need a new sub ref
427 $method = Class::MOP::Method::Wrapped->wrap($method);
430 # now make sure we wrap it properly
431 $method = Class::MOP::Method::Wrapped->wrap($method)
432 unless $method->isa('Class::MOP::Method::Wrapped');
434 $self->add_method($method_name => $method);
438 sub add_before_method_modifier {
439 my ($self, $method_name, $method_modifier) = @_;
440 (defined $method_name && $method_name)
441 || confess "You must pass in a method name";
442 my $method = $fetch_and_prepare_method->($self, $method_name);
443 $method->add_before_modifier(subname ':before' => $method_modifier);
446 sub add_after_method_modifier {
447 my ($self, $method_name, $method_modifier) = @_;
448 (defined $method_name && $method_name)
449 || confess "You must pass in a method name";
450 my $method = $fetch_and_prepare_method->($self, $method_name);
451 $method->add_after_modifier(subname ':after' => $method_modifier);
454 sub add_around_method_modifier {
455 my ($self, $method_name, $method_modifier) = @_;
456 (defined $method_name && $method_name)
457 || confess "You must pass in a method name";
458 my $method = $fetch_and_prepare_method->($self, $method_name);
459 $method->add_around_modifier(subname ':around' => $method_modifier);
463 # the methods above used to be named like this:
464 # ${pkg}::${method}:(before|after|around)
465 # but this proved problematic when using one modifier
466 # to wrap multiple methods (something which is likely
467 # to happen pretty regularly IMO). So instead of naming
468 # it like this, I have chosen to just name them purely
469 # with their modifier names, like so:
470 # :(before|after|around)
471 # The fact is that in a stack trace, it will be fairly
472 # evident from the context what method they are attached
473 # to, and so don't need the fully qualified name.
477 my ($self, $method_name, $method) = @_;
478 (defined $method_name && $method_name)
479 || confess "You must define a method name";
481 my $body = (blessed($method) ? $method->body : $method);
482 ('CODE' eq (reftype($body) || ''))
483 || confess "Your code block must be a CODE reference";
485 $self->add_package_symbol("&${method_name}" => $body);
489 my ($self, $method_name) = @_;
490 (defined $method_name && $method_name)
491 || confess "You must define a method name";
493 return 0 unless exists $self->get_method_map->{$method_name};
498 my ($self, $method_name) = @_;
499 (defined $method_name && $method_name)
500 || confess "You must define a method name";
503 # I don't really need this here, because
504 # if the method_map is missing a key it
505 # will just return undef for me now
506 # return unless $self->has_method($method_name);
508 return $self->get_method_map->{$method_name};
512 my ($self, $method_name) = @_;
513 (defined $method_name && $method_name)
514 || confess "You must define a method name";
516 my $removed_method = $self->get_method($method_name);
519 $self->remove_package_symbol("&${method_name}");
520 delete $self->get_method_map->{$method_name};
521 } if defined $removed_method;
523 return $removed_method;
526 sub get_method_list {
528 keys %{$self->get_method_map};
531 sub find_method_by_name {
532 my ($self, $method_name) = @_;
533 (defined $method_name && $method_name)
534 || confess "You must define a method name to find";
535 # keep a record of what we have seen
536 # here, this will handle all the
537 # inheritence issues because we are
538 # using the &class_precedence_list
540 my @cpl = $self->class_precedence_list();
541 foreach my $class (@cpl) {
542 next if $seen_class{$class};
543 $seen_class{$class}++;
544 # fetch the meta-class ...
545 my $meta = $self->initialize($class);
546 return $meta->get_method($method_name)
547 if $meta->has_method($method_name);
552 sub compute_all_applicable_methods {
555 # keep a record of what we have seen
556 # here, this will handle all the
557 # inheritence issues because we are
558 # using the &class_precedence_list
559 my (%seen_class, %seen_method);
560 foreach my $class ($self->class_precedence_list()) {
561 next if $seen_class{$class};
562 $seen_class{$class}++;
563 # fetch the meta-class ...
564 my $meta = $self->initialize($class);
565 foreach my $method_name ($meta->get_method_list()) {
566 next if exists $seen_method{$method_name};
567 $seen_method{$method_name}++;
569 name => $method_name,
571 code => $meta->get_method($method_name)
578 sub find_all_methods_by_name {
579 my ($self, $method_name) = @_;
580 (defined $method_name && $method_name)
581 || confess "You must define a method name to find";
583 # keep a record of what we have seen
584 # here, this will handle all the
585 # inheritence issues because we are
586 # using the &class_precedence_list
588 foreach my $class ($self->class_precedence_list()) {
589 next if $seen_class{$class};
590 $seen_class{$class}++;
591 # fetch the meta-class ...
592 my $meta = $self->initialize($class);
594 name => $method_name,
596 code => $meta->get_method($method_name)
597 } if $meta->has_method($method_name);
602 sub find_next_method_by_name {
603 my ($self, $method_name) = @_;
604 (defined $method_name && $method_name)
605 || confess "You must define a method name to find";
606 # keep a record of what we have seen
607 # here, this will handle all the
608 # inheritence issues because we are
609 # using the &class_precedence_list
611 my @cpl = $self->class_precedence_list();
612 shift @cpl; # discard ourselves
613 foreach my $class (@cpl) {
614 next if $seen_class{$class};
615 $seen_class{$class}++;
616 # fetch the meta-class ...
617 my $meta = $self->initialize($class);
618 return $meta->get_method($method_name)
619 if $meta->has_method($method_name);
628 # either we have an attribute object already
629 # or we need to create one from the args provided
630 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
631 # make sure it is derived from the correct type though
632 ($attribute->isa('Class::MOP::Attribute'))
633 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
635 # first we attach our new attribute
636 # because it might need certain information
637 # about the class which it is attached to
638 $attribute->attach_to_class($self);
640 # then we remove attributes of a conflicting
641 # name here so that we can properly detach
642 # the old attr object, and remove any
643 # accessors it would have generated
644 $self->remove_attribute($attribute->name)
645 if $self->has_attribute($attribute->name);
647 # then onto installing the new accessors
648 $attribute->install_accessors();
649 $self->get_attribute_map->{$attribute->name} = $attribute;
653 my ($self, $attribute_name) = @_;
654 (defined $attribute_name && $attribute_name)
655 || confess "You must define an attribute name";
656 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
660 my ($self, $attribute_name) = @_;
661 (defined $attribute_name && $attribute_name)
662 || confess "You must define an attribute name";
663 return $self->get_attribute_map->{$attribute_name}
665 # this will return undef anyway, so no need ...
666 # if $self->has_attribute($attribute_name);
670 sub remove_attribute {
671 my ($self, $attribute_name) = @_;
672 (defined $attribute_name && $attribute_name)
673 || confess "You must define an attribute name";
674 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
675 return unless defined $removed_attribute;
676 delete $self->get_attribute_map->{$attribute_name};
677 $removed_attribute->remove_accessors();
678 $removed_attribute->detach_from_class();
679 return $removed_attribute;
682 sub get_attribute_list {
684 keys %{$self->get_attribute_map};
687 sub compute_all_applicable_attributes {
690 # keep a record of what we have seen
691 # here, this will handle all the
692 # inheritence issues because we are
693 # using the &class_precedence_list
694 my (%seen_class, %seen_attr);
695 foreach my $class ($self->class_precedence_list()) {
696 next if $seen_class{$class};
697 $seen_class{$class}++;
698 # fetch the meta-class ...
699 my $meta = $self->initialize($class);
700 foreach my $attr_name ($meta->get_attribute_list()) {
701 next if exists $seen_attr{$attr_name};
702 $seen_attr{$attr_name}++;
703 push @attrs => $meta->get_attribute($attr_name);
709 sub find_attribute_by_name {
710 my ($self, $attr_name) = @_;
711 # keep a record of what we have seen
712 # here, this will handle all the
713 # inheritence issues because we are
714 # using the &class_precedence_list
716 foreach my $class ($self->class_precedence_list()) {
717 next if $seen_class{$class};
718 $seen_class{$class}++;
719 # fetch the meta-class ...
720 my $meta = $self->initialize($class);
721 return $meta->get_attribute($attr_name)
722 if $meta->has_attribute($attr_name);
730 sub is_immutable { 0 }
734 # the immutable version of a
735 # particular metaclass is
736 # really class-level data so
737 # we don't want to regenerate
738 # it any more than we need to
739 my $IMMUTABLE_METACLASS;
743 $IMMUTABLE_METACLASS ||= Class::MOP::Immutable->new($self, {
744 read_only => [qw/superclasses/],
752 remove_package_symbol
755 class_precedence_list => 'ARRAY',
756 compute_all_applicable_attributes => 'ARRAY',
757 get_meta_instance => 'SCALAR',
758 get_method_map => 'SCALAR',
762 $IMMUTABLE_METACLASS->make_metaclass_immutable(@_)
774 Class::MOP::Class - Class Meta Object
778 # assuming that class Foo
779 # has been defined, you can
781 # use this for introspection ...
783 # add a method to Foo ...
784 Foo->meta->add_method('bar' => sub { ... })
786 # get a list of all the classes searched
787 # the method dispatcher in the correct order
788 Foo->meta->class_precedence_list()
790 # remove a method from Foo
791 Foo->meta->remove_method('bar');
793 # or use this to actually create classes ...
795 Class::MOP::Class->create('Bar' => (
797 superclasses => [ 'Foo' ],
799 Class::MOP:::Attribute->new('$bar'),
800 Class::MOP:::Attribute->new('$baz'),
803 calculate_bar => sub { ... },
804 construct_baz => sub { ... }
810 This is the largest and currently most complex part of the Perl 5
811 meta-object protocol. It controls the introspection and
812 manipulation of Perl 5 classes (and it can create them too). The
813 best way to understand what this module can do, is to read the
814 documentation for each of it's methods.
818 =head2 Self Introspection
824 This will return a B<Class::MOP::Class> instance which is related
825 to this class. Thereby allowing B<Class::MOP::Class> to actually
828 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
829 bootstrap this module by installing a number of attribute meta-objects
830 into it's metaclass. This will allow this class to reap all the benifits
831 of the MOP when subclassing it.
835 =head2 Class construction
837 These methods will handle creating B<Class::MOP::Class> objects,
838 which can be used to both create new classes, and analyze
839 pre-existing classes.
841 This module will internally store references to all the instances
842 you create with these methods, so that they do not need to be
843 created any more than nessecary. Basically, they are singletons.
847 =item B<create ($package_name,
848 version =E<gt> ?$version,
849 authority =E<gt> ?$authority,
850 superclasses =E<gt> ?@superclasses,
851 methods =E<gt> ?%methods,
852 attributes =E<gt> ?%attributes)>
854 This returns a B<Class::MOP::Class> object, bringing the specified
855 C<$package_name> into existence and adding any of the C<$version>,
856 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
859 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
860 methods =E<gt> ?%methods,
861 attributes =E<gt> ?%attributes)>
863 This will create an anonymous class, it works much like C<create> but
864 it does not need a C<$package_name>. Instead it will create a suitably
865 unique package name for you to stash things into.
867 On very important distinction is that anon classes are destroyed once
868 the metaclass they are attached to goes out of scope. In the DESTROY
869 method, the created package will be removed from the symbol table.
871 =item B<initialize ($package_name, %options)>
873 This initializes and returns returns a B<Class::MOP::Class> object
874 for a given a C<$package_name>.
876 =item B<reinitialize ($package_name, %options)>
878 This removes the old metaclass, and creates a new one in it's place.
879 Do B<not> use this unless you really know what you are doing, it could
880 very easily make a very large mess of your program.
882 =item B<construct_class_instance (%options)>
884 This will construct an instance of B<Class::MOP::Class>, it is
885 here so that we can actually "tie the knot" for B<Class::MOP::Class>
886 to use C<construct_instance> once all the bootstrapping is done. This
887 method is used internally by C<initialize> and should never be called
888 from outside of that method really.
890 =item B<check_metaclass_compatability>
892 This method is called as the very last thing in the
893 C<construct_class_instance> method. This will check that the
894 metaclass you are creating is compatible with the metaclasses of all
895 your ancestors. For more inforamtion about metaclass compatibility
896 see the C<About Metaclass compatibility> section in L<Class::MOP>.
900 =head2 Object instance construction and cloning
902 These methods are B<entirely optional>, it is up to you whether you want
907 =item B<instance_metaclass>
909 =item B<get_meta_instance>
911 =item B<new_object (%params)>
913 This is a convience method for creating a new object of the class, and
914 blessing it into the appropriate package as well. Ideally your class
915 would call a C<new> this method like so:
918 my ($class, %param) = @_;
919 $class->meta->new_object(%params);
922 Of course the ideal place for this would actually be in C<UNIVERSAL::>
923 but that is considered bad style, so we do not do that.
925 =item B<construct_instance (%params)>
927 This method is used to construct an instace structure suitable for
928 C<bless>-ing into your package of choice. It works in conjunction
929 with the Attribute protocol to collect all applicable attributes.
931 This will construct and instance using a HASH ref as storage
932 (currently only HASH references are supported). This will collect all
933 the applicable attributes and layout out the fields in the HASH ref,
934 it will then initialize them using either use the corresponding key
935 in C<%params> or any default value or initializer found in the
936 attribute meta-object.
938 =item B<clone_object ($instance, %params)>
940 This is a convience method for cloning an object instance, then
941 blessing it into the appropriate package. This method will call
942 C<clone_instance>, which performs a shallow copy of the object,
943 see that methods documentation for more details. Ideally your
944 class would call a C<clone> this method like so:
947 my ($self, %param) = @_;
948 $self->meta->clone_object($self, %params);
951 Of course the ideal place for this would actually be in C<UNIVERSAL::>
952 but that is considered bad style, so we do not do that.
954 =item B<clone_instance($instance, %params)>
956 This method is a compliment of C<construct_instance> (which means if
957 you override C<construct_instance>, you need to override this one too),
958 and clones the instance shallowly.
960 The cloned structure returned is (like with C<construct_instance>) an
961 unC<bless>ed HASH reference, it is your responsibility to then bless
962 this cloned structure into the right class (which C<clone_object> will
965 As of 0.11, this method will clone the C<$instance> structure shallowly,
966 as opposed to the deep cloning implemented in prior versions. After much
967 thought, research and discussion, I have decided that anything but basic
968 shallow cloning is outside the scope of the meta-object protocol. I
969 think Yuval "nothingmuch" Kogman put it best when he said that cloning
970 is too I<context-specific> to be part of the MOP.
976 These are a few predicate methods for asking information about the class.
980 =item B<is_anon_class>
982 This returns true if the class is a C<Class::MOP::Class> created anon class.
986 This returns true if the class is still mutable.
988 =item B<is_immutable>
990 This returns true if the class has been made immutable.
994 =head2 Inheritance Relationships
998 =item B<superclasses (?@superclasses)>
1000 This is a read-write attribute which represents the superclass
1001 relationships of the class the B<Class::MOP::Class> instance is
1002 associated with. Basically, it can get and set the C<@ISA> for you.
1005 Perl will occasionally perform some C<@ISA> and method caching, if
1006 you decide to change your superclass relationship at runtime (which
1007 is quite insane and very much not recommened), then you should be
1008 aware of this and the fact that this module does not make any
1009 attempt to address this issue.
1011 =item B<class_precedence_list>
1013 This computes the a list of all the class's ancestors in the same order
1014 in which method dispatch will be done. This is similair to
1015 what B<Class::ISA::super_path> does, but we don't remove duplicate names.
1023 =item B<get_method_map>
1025 =item B<method_metaclass>
1027 =item B<add_method ($method_name, $method)>
1029 This will take a C<$method_name> and CODE reference to that
1030 C<$method> and install it into the class's package.
1033 This does absolutely nothing special to C<$method>
1034 other than use B<Sub::Name> to make sure it is tagged with the
1035 correct name, and therefore show up correctly in stack traces and
1038 =item B<alias_method ($method_name, $method)>
1040 This will take a C<$method_name> and CODE reference to that
1041 C<$method> and alias the method into the class's package.
1044 Unlike C<add_method>, this will B<not> try to name the
1045 C<$method> using B<Sub::Name>, it only aliases the method in
1046 the class's package.
1048 =item B<has_method ($method_name)>
1050 This just provides a simple way to check if the class implements
1051 a specific C<$method_name>. It will I<not> however, attempt to check
1052 if the class inherits the method (use C<UNIVERSAL::can> for that).
1054 This will correctly handle functions defined outside of the package
1055 that use a fully qualified name (C<sub Package::name { ... }>).
1057 This will correctly handle functions renamed with B<Sub::Name> and
1058 installed using the symbol tables. However, if you are naming the
1059 subroutine outside of the package scope, you must use the fully
1060 qualified name, including the package name, for C<has_method> to
1061 correctly identify it.
1063 This will attempt to correctly ignore functions imported from other
1064 packages using B<Exporter>. It breaks down if the function imported
1065 is an C<__ANON__> sub (such as with C<use constant>), which very well
1066 may be a valid method being applied to the class.
1068 In short, this method cannot always be trusted to determine if the
1069 C<$method_name> is actually a method. However, it will DWIM about
1070 90% of the time, so it's a small trade off I think.
1072 =item B<get_method ($method_name)>
1074 This will return a Class::MOP::Method instance related to the specified
1075 C<$method_name>, or return undef if that method does not exist.
1077 The Class::MOP::Method is codifiable, so you can use it like a normal
1078 CODE reference, see L<Class::MOP::Method> for more information.
1080 =item B<find_method_by_name ($method_name>
1082 This will return a CODE reference of the specified C<$method_name>,
1083 or return undef if that method does not exist.
1085 Unlike C<get_method> this will also look in the superclasses.
1087 =item B<remove_method ($method_name)>
1089 This will attempt to remove a given C<$method_name> from the class.
1090 It will return the CODE reference that it has removed, and will
1091 attempt to use B<Sub::Name> to clear the methods associated name.
1093 =item B<get_method_list>
1095 This will return a list of method names for all I<locally> defined
1096 methods. It does B<not> provide a list of all applicable methods,
1097 including any inherited ones. If you want a list of all applicable
1098 methods, use the C<compute_all_applicable_methods> method.
1100 =item B<compute_all_applicable_methods>
1102 This will return a list of all the methods names this class will
1103 respond to, taking into account inheritance. The list will be a list of
1104 HASH references, each one containing the following information; method
1105 name, the name of the class in which the method lives and a CODE
1106 reference for the actual method.
1108 =item B<find_all_methods_by_name ($method_name)>
1110 This will traverse the inheritence hierarchy and locate all methods
1111 with a given C<$method_name>. Similar to
1112 C<compute_all_applicable_methods> it returns a list of HASH references
1113 with the following information; method name (which will always be the
1114 same as C<$method_name>), the name of the class in which the method
1115 lives and a CODE reference for the actual method.
1117 The list of methods produced is a distinct list, meaning there are no
1118 duplicates in it. This is especially useful for things like object
1119 initialization and destruction where you only want the method called
1120 once, and in the correct order.
1122 =item B<find_next_method_by_name ($method_name)>
1124 This will return the first method to match a given C<$method_name> in
1125 the superclasses, this is basically equivalent to calling
1126 C<SUPER::$method_name>, but it can be dispatched at runtime.
1130 =head2 Method Modifiers
1132 Method modifiers are a concept borrowed from CLOS, in which a method
1133 can be wrapped with I<before>, I<after> and I<around> method modifiers
1134 that will be called everytime the method is called.
1136 =head3 How method modifiers work?
1138 Method modifiers work by wrapping the original method and then replacing
1139 it in the classes symbol table. The wrappers will handle calling all the
1140 modifiers in the appropariate orders and preserving the calling context
1141 for the original method.
1143 Each method modifier serves a particular purpose, which may not be
1144 obvious to users of other method wrapping modules. To start with, the
1145 return values of I<before> and I<after> modifiers are ignored. This is
1146 because thier purpose is B<not> to filter the input and output of the
1147 primary method (this is done with an I<around> modifier). This may seem
1148 like an odd restriction to some, but doing this allows for simple code
1149 to be added at the begining or end of a method call without jeapordizing
1150 the normal functioning of the primary method or placing any extra
1151 responsibility on the code of the modifier. Of course if you have more
1152 complex needs, then use the I<around> modifier, which uses a variation
1153 of continutation passing style to allow for a high degree of flexibility.
1155 Before and around modifiers are called in last-defined-first-called order,
1156 while after modifiers are called in first-defined-first-called order. So
1157 the call tree might looks something like this:
1167 To see examples of using method modifiers, see the following examples
1168 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1169 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1170 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1172 =head3 What is the performance impact?
1174 Of course there is a performance cost associated with method modifiers,
1175 but we have made every effort to make that cost be directly proportional
1176 to the amount of modifier features you utilize.
1178 The wrapping method does it's best to B<only> do as much work as it
1179 absolutely needs to. In order to do this we have moved some of the
1180 performance costs to set-up time, where they are easier to amortize.
1182 All this said, my benchmarks have indicated the following:
1184 simple wrapper with no modifiers 100% slower
1185 simple wrapper with simple before modifier 400% slower
1186 simple wrapper with simple after modifier 450% slower
1187 simple wrapper with simple around modifier 500-550% slower
1188 simple wrapper with all 3 modifiers 1100% slower
1190 These numbers may seem daunting, but you must remember, every feature
1191 comes with some cost. To put things in perspective, just doing a simple
1192 C<AUTOLOAD> which does nothing but extract the name of the method called
1193 and return it costs about 400% over a normal method call.
1197 =item B<add_before_method_modifier ($method_name, $code)>
1199 This will wrap the method at C<$method_name> and the supplied C<$code>
1200 will be passed the C<@_> arguments, and called before the original
1201 method is called. As specified above, the return value of the I<before>
1202 method modifiers is ignored, and it's ability to modify C<@_> is
1203 fairly limited. If you need to do either of these things, use an
1204 C<around> method modifier.
1206 =item B<add_after_method_modifier ($method_name, $code)>
1208 This will wrap the method at C<$method_name> so that the original
1209 method will be called, it's return values stashed, and then the
1210 supplied C<$code> will be passed the C<@_> arguments, and called.
1211 As specified above, the return value of the I<after> method
1212 modifiers is ignored, and it cannot modify the return values of
1213 the original method. If you need to do either of these things, use an
1214 C<around> method modifier.
1216 =item B<add_around_method_modifier ($method_name, $code)>
1218 This will wrap the method at C<$method_name> so that C<$code>
1219 will be called and passed the original method as an extra argument
1220 at the begining of the C<@_> argument list. This is a variation of
1221 continuation passing style, where the function prepended to C<@_>
1222 can be considered a continuation. It is up to C<$code> if it calls
1223 the original method or not, there is no restriction on what the
1224 C<$code> can or cannot do.
1230 It should be noted that since there is no one consistent way to define
1231 the attributes of a class in Perl 5. These methods can only work with
1232 the information given, and can not easily discover information on
1233 their own. See L<Class::MOP::Attribute> for more details.
1237 =item B<attribute_metaclass>
1239 =item B<get_attribute_map>
1241 =item B<add_attribute ($attribute_meta_object | $attribute_name, %attribute_spec)>
1243 This stores the C<$attribute_meta_object> (or creates one from the
1244 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1245 instance associated with the given class. Unlike methods, attributes
1246 within the MOP are stored as meta-information only. They will be used
1247 later to construct instances from (see C<construct_instance> above).
1248 More details about the attribute meta-objects can be found in the
1249 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1252 It should be noted that any accessor, reader/writer or predicate
1253 methods which the C<$attribute_meta_object> has will be installed
1254 into the class at this time.
1257 If an attribute already exists for C<$attribute_name>, the old one
1258 will be removed (as well as removing all it's accessors), and then
1261 =item B<has_attribute ($attribute_name)>
1263 Checks to see if this class has an attribute by the name of
1264 C<$attribute_name> and returns a boolean.
1266 =item B<get_attribute ($attribute_name)>
1268 Returns the attribute meta-object associated with C<$attribute_name>,
1269 if none is found, it will return undef.
1271 =item B<remove_attribute ($attribute_name)>
1273 This will remove the attribute meta-object stored at
1274 C<$attribute_name>, then return the removed attribute meta-object.
1277 Removing an attribute will only affect future instances of
1278 the class, it will not make any attempt to remove the attribute from
1279 any existing instances of the class.
1281 It should be noted that any accessor, reader/writer or predicate
1282 methods which the attribute meta-object stored at C<$attribute_name>
1283 has will be removed from the class at this time. This B<will> make
1284 these attributes somewhat inaccessable in previously created
1285 instances. But if you are crazy enough to do this at runtime, then
1286 you are crazy enough to deal with something like this :).
1288 =item B<get_attribute_list>
1290 This returns a list of attribute names which are defined in the local
1291 class. If you want a list of all applicable attributes for a class,
1292 use the C<compute_all_applicable_attributes> method.
1294 =item B<compute_all_applicable_attributes>
1296 This will traverse the inheritance heirachy and return a list of all
1297 the applicable attributes for this class. It does not construct a
1298 HASH reference like C<compute_all_applicable_methods> because all
1299 that same information is discoverable through the attribute
1302 =item B<find_attribute_by_name ($attr_name)>
1304 This method will traverse the inheritance heirachy and find the
1305 first attribute whose name matches C<$attr_name>, then return it.
1306 It will return undef if nothing is found.
1310 =head2 Class Immutability
1314 =item B<make_immutable (%options)>
1316 This method will invoke a tranforamtion upon the class which will
1317 make it immutable. Details of this transformation can be found in
1318 the L<Class::MOP::Immutable> documentation.
1324 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1326 =head1 COPYRIGHT AND LICENSE
1328 Copyright 2006, 2007 by Infinity Interactive, Inc.
1330 L<http://www.iinteractive.com>
1332 This library is free software; you can redistribute it and/or modify
1333 it under the same terms as Perl itself.