2 package Class::MOP::Class;
8 use Scalar::Util 'blessed', 'reftype';
9 use Sub::Name 'subname';
10 use B 'svref_2object';
12 our $VERSION = '0.12';
16 sub meta { Class::MOP::Class->initialize(blessed($_[0]) || $_[0]) }
21 # Metaclasses are singletons, so we cache them here.
22 # there is no need to worry about destruction though
23 # because they should die only when the program dies.
24 # After all, do package definitions even get reaped?
27 # means of accessing all the metaclasses that have
28 # been initialized thus far (for mugwumps obj browser)
29 sub get_all_metaclasses { %METAS }
30 sub get_all_metaclass_instances { values %METAS }
31 sub get_all_metaclass_names { keys %METAS }
35 my $package_name = shift;
36 (defined $package_name && $package_name && !blessed($package_name))
37 || confess "You must pass a package name and it cannot be blessed";
38 $class->construct_class_instance(':package' => $package_name, @_);
41 # NOTE: (meta-circularity)
42 # this is a special form of &construct_instance
43 # (see below), which is used to construct class
44 # meta-object instances for any Class::MOP::*
45 # class. All other classes will use the more
46 # normal &construct_instance.
47 sub construct_class_instance {
50 my $package_name = $options{':package'};
51 (defined $package_name && $package_name)
52 || confess "You must pass a package name";
54 # return the metaclass if we have it cached,
55 # and it is still defined (it has not been
56 # reaped by DESTROY yet, which can happen
57 # annoyingly enough during global destruction)
58 return $METAS{$package_name}
59 if exists $METAS{$package_name} && defined $METAS{$package_name};
60 $class = blessed($class) || $class;
61 # now create the metaclass
63 if ($class =~ /^Class::MOP::/) {
65 '$:package' => $package_name,
67 '$:attribute_metaclass' => $options{':attribute_metaclass'} || 'Class::MOP::Attribute',
68 '$:method_metaclass' => $options{':method_metaclass'} || 'Class::MOP::Method',
73 # it is safe to use meta here because
74 # class will always be a subclass of
75 # Class::MOP::Class, which defines meta
76 $meta = bless $class->meta->construct_instance(%options) => $class
78 # and check the metaclass compatibility
79 $meta->check_metaclass_compatability();
80 $METAS{$package_name} = $meta;
83 sub check_metaclass_compatability {
86 # this is always okay ...
87 return if blessed($self) eq 'Class::MOP::Class';
89 my @class_list = $self->class_precedence_list;
90 shift @class_list; # shift off $self->name
92 foreach my $class_name (@class_list) {
93 my $meta = $METAS{$class_name} || next;
94 ($self->isa(blessed($meta)))
95 || confess $self->name . "->meta => (" . (blessed($self)) . ")" .
96 " is not compatible with the " .
97 $class_name . "->meta => (" . (blessed($meta)) . ")";
103 my ($class, $package_name, $package_version, %options) = @_;
104 (defined $package_name && $package_name)
105 || confess "You must pass a package name";
106 my $code = "package $package_name;";
107 $code .= "\$$package_name\:\:VERSION = '$package_version';"
108 if defined $package_version;
110 confess "creation of $package_name failed : $@" if $@;
111 my $meta = $class->initialize($package_name);
113 $meta->add_method('meta' => sub {
114 Class::MOP::Class->initialize(blessed($_[0]) || $_[0]);
117 $meta->superclasses(@{$options{superclasses}})
118 if exists $options{superclasses};
120 # process attributes first, so that they can
121 # install accessors, but locally defined methods
122 # can then overwrite them. It is maybe a little odd, but
123 # I think this should be the order of things.
124 if (exists $options{attributes}) {
125 foreach my $attr (@{$options{attributes}}) {
126 $meta->add_attribute($attr);
129 if (exists $options{methods}) {
130 foreach my $method_name (keys %{$options{methods}}) {
131 $meta->add_method($method_name, $options{methods}->{$method_name});
139 # this should be sufficient, if you have a
140 # use case where it is not, write a test and
142 my $ANON_CLASS_SERIAL = 0;
144 sub create_anon_class {
145 my ($class, %options) = @_;
146 my $package_name = 'Class::MOP::Class::__ANON__::SERIAL::' . ++$ANON_CLASS_SERIAL;
147 return $class->create($package_name, '0.00', %options);
154 # all these attribute readers will be bootstrapped
155 # away in the Class::MOP bootstrap section
157 sub name { $_[0]->{'$:package'} }
158 sub get_attribute_map { $_[0]->{'%:attributes'} }
159 sub attribute_metaclass { $_[0]->{'$:attribute_metaclass'} }
160 sub method_metaclass { $_[0]->{'$:method_metaclass'} }
162 # Instance Construction & Cloning
167 # we need to protect the integrity of the
168 # Class::MOP::Class singletons here, so we
169 # delegate this to &construct_class_instance
170 # which will deal with the singletons
171 return $class->construct_class_instance(@_)
172 if $class->name->isa('Class::MOP::Class');
173 bless $class->construct_instance(@_) => $class->name;
176 sub construct_instance {
177 my ($class, %params) = @_;
179 foreach my $attr ($class->compute_all_applicable_attributes()) {
180 $attr->initialize_instance_slot($instance, \%params);
187 my $instance = shift;
188 (blessed($instance) && $instance->isa($class->name))
189 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
191 # we need to protect the integrity of the
192 # Class::MOP::Class singletons here, they
193 # should not be cloned.
194 return $instance if $instance->isa('Class::MOP::Class');
195 bless $class->clone_instance($instance, @_) => blessed($instance);
199 my ($class, $instance, %params) = @_;
201 || confess "You can only clone instances, \$self is not a blessed instance";
202 my $clone = { %$instance, %params };
208 # &name should be here too, but it is above
209 # because it gets bootstrapped away
213 ${$self->get_package_variable('$VERSION')};
222 @{$self->get_package_variable('@ISA')} = @supers;
224 @{$self->get_package_variable('@ISA')};
227 sub class_precedence_list {
230 # We need to check for ciruclar inheirtance here.
231 # This will do nothing if all is well, and blow
232 # up otherwise. Yes, it's an ugly hack, better
233 # suggestions are welcome.
234 { $self->name->isa('This is a test for circular inheritance') }
235 # ... and now back to our regularly scheduled program
239 $self->initialize($_)->class_precedence_list()
240 } $self->superclasses()
247 my ($self, $method_name, $method) = @_;
248 (defined $method_name && $method_name)
249 || confess "You must define a method name";
250 # use reftype here to allow for blessed subs ...
251 ('CODE' eq (reftype($method) || ''))
252 || confess "Your code block must be a CODE reference";
253 my $full_method_name = ($self->name . '::' . $method_name);
255 $method = $self->method_metaclass->wrap($method) unless blessed($method);
258 no warnings 'redefine';
259 *{$full_method_name} = subname $full_method_name => $method;
263 my $fetch_and_prepare_method = sub {
264 my ($self, $method_name) = @_;
266 my $method = $self->get_method($method_name);
267 # if we dont have local ...
269 # make sure this method even exists ...
270 ($self->find_next_method_by_name($method_name))
271 || confess "The method '$method_name' is not found in the inherience hierarchy for this class";
272 # if so, then create a local which just
273 # calls the next applicable method ...
274 $self->add_method($method_name => sub {
275 $self->find_next_method_by_name($method_name)->(@_);
277 $method = $self->get_method($method_name);
280 # now make sure we wrap it properly
281 # (if it isnt already)
282 unless ($method->isa('Class::MOP::Method::Wrapped')) {
283 $method = Class::MOP::Method::Wrapped->wrap($method);
284 $self->add_method($method_name => $method);
289 sub add_before_method_modifier {
290 my ($self, $method_name, $method_modifier) = @_;
291 (defined $method_name && $method_name)
292 || confess "You must pass in a method name";
293 my $method = $fetch_and_prepare_method->($self, $method_name);
294 $method->add_before_modifier(subname ':before' => $method_modifier);
297 sub add_after_method_modifier {
298 my ($self, $method_name, $method_modifier) = @_;
299 (defined $method_name && $method_name)
300 || confess "You must pass in a method name";
301 my $method = $fetch_and_prepare_method->($self, $method_name);
302 $method->add_after_modifier(subname ':after' => $method_modifier);
305 sub add_around_method_modifier {
306 my ($self, $method_name, $method_modifier) = @_;
307 (defined $method_name && $method_name)
308 || confess "You must pass in a method name";
309 my $method = $fetch_and_prepare_method->($self, $method_name);
310 $method->add_around_modifier(subname ':around' => $method_modifier);
314 # the methods above used to be named like this:
315 # ${pkg}::${method}:(before|after|around)
316 # but this proved problematic when using one modifier
317 # to wrap multiple methods (something which is likely
318 # to happen pretty regularly IMO). So instead of naming
319 # it like this, I have chosen to just name them purely
320 # with their modifier names, like so:
321 # :(before|after|around)
322 # The fact is that in a stack trace, it will be fairly
323 # evident from the context what method they are attached
324 # to, and so don't need the fully qualified name.
328 my ($self, $method_name, $method) = @_;
329 (defined $method_name && $method_name)
330 || confess "You must define a method name";
331 # use reftype here to allow for blessed subs ...
332 ('CODE' eq (reftype($method) || ''))
333 || confess "Your code block must be a CODE reference";
334 my $full_method_name = ($self->name . '::' . $method_name);
336 $method = $self->method_metaclass->wrap($method) unless blessed($method);
339 no warnings 'redefine';
340 *{$full_method_name} = $method;
344 my ($self, $method_name) = @_;
345 (defined $method_name && $method_name)
346 || confess "You must define a method name";
348 my $sub_name = ($self->name . '::' . $method_name);
351 return 0 if !defined(&{$sub_name});
352 my $method = \&{$sub_name};
353 return 0 if (svref_2object($method)->GV->STASH->NAME || '') ne $self->name &&
354 (svref_2object($method)->GV->NAME || '') ne '__ANON__';
356 # at this point we are relatively sure
357 # it is our method, so we bless/wrap it
358 $self->method_metaclass->wrap($method) unless blessed($method);
363 my ($self, $method_name) = @_;
364 (defined $method_name && $method_name)
365 || confess "You must define a method name";
367 return unless $self->has_method($method_name);
370 return \&{$self->name . '::' . $method_name};
374 my ($self, $method_name) = @_;
375 (defined $method_name && $method_name)
376 || confess "You must define a method name";
378 my $removed_method = $self->get_method($method_name);
381 delete ${$self->name . '::'}{$method_name}
382 if defined $removed_method;
384 return $removed_method;
387 sub get_method_list {
390 grep { $self->has_method($_) } %{$self->name . '::'};
393 sub compute_all_applicable_methods {
396 # keep a record of what we have seen
397 # here, this will handle all the
398 # inheritence issues because we are
399 # using the &class_precedence_list
400 my (%seen_class, %seen_method);
401 foreach my $class ($self->class_precedence_list()) {
402 next if $seen_class{$class};
403 $seen_class{$class}++;
404 # fetch the meta-class ...
405 my $meta = $self->initialize($class);
406 foreach my $method_name ($meta->get_method_list()) {
407 next if exists $seen_method{$method_name};
408 $seen_method{$method_name}++;
410 name => $method_name,
412 code => $meta->get_method($method_name)
419 sub find_all_methods_by_name {
420 my ($self, $method_name) = @_;
421 (defined $method_name && $method_name)
422 || confess "You must define a method name to find";
424 # keep a record of what we have seen
425 # here, this will handle all the
426 # inheritence issues because we are
427 # using the &class_precedence_list
429 foreach my $class ($self->class_precedence_list()) {
430 next if $seen_class{$class};
431 $seen_class{$class}++;
432 # fetch the meta-class ...
433 my $meta = $self->initialize($class);
435 name => $method_name,
437 code => $meta->get_method($method_name)
438 } if $meta->has_method($method_name);
443 sub find_next_method_by_name {
444 my ($self, $method_name) = @_;
445 (defined $method_name && $method_name)
446 || confess "You must define a method name to find";
447 # keep a record of what we have seen
448 # here, this will handle all the
449 # inheritence issues because we are
450 # using the &class_precedence_list
452 my @cpl = $self->class_precedence_list();
453 shift @cpl; # discard ourselves
454 foreach my $class (@cpl) {
455 next if $seen_class{$class};
456 $seen_class{$class}++;
457 # fetch the meta-class ...
458 my $meta = $self->initialize($class);
459 return $meta->get_method($method_name)
460 if $meta->has_method($method_name);
469 # either we have an attribute object already
470 # or we need to create one from the args provided
471 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
472 # make sure it is derived from the correct type though
473 ($attribute->isa('Class::MOP::Attribute'))
474 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
475 $attribute->attach_to_class($self);
476 $attribute->install_accessors();
477 $self->get_attribute_map->{$attribute->name} = $attribute;
481 my ($self, $attribute_name) = @_;
482 (defined $attribute_name && $attribute_name)
483 || confess "You must define an attribute name";
484 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
488 my ($self, $attribute_name) = @_;
489 (defined $attribute_name && $attribute_name)
490 || confess "You must define an attribute name";
491 return $self->get_attribute_map->{$attribute_name}
492 if $self->has_attribute($attribute_name);
496 sub remove_attribute {
497 my ($self, $attribute_name) = @_;
498 (defined $attribute_name && $attribute_name)
499 || confess "You must define an attribute name";
500 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
501 return unless defined $removed_attribute;
502 delete $self->get_attribute_map->{$attribute_name};
503 $removed_attribute->remove_accessors();
504 $removed_attribute->detach_from_class();
505 return $removed_attribute;
508 sub get_attribute_list {
510 keys %{$self->get_attribute_map};
513 sub compute_all_applicable_attributes {
516 # keep a record of what we have seen
517 # here, this will handle all the
518 # inheritence issues because we are
519 # using the &class_precedence_list
520 my (%seen_class, %seen_attr);
521 foreach my $class ($self->class_precedence_list()) {
522 next if $seen_class{$class};
523 $seen_class{$class}++;
524 # fetch the meta-class ...
525 my $meta = $self->initialize($class);
526 foreach my $attr_name ($meta->get_attribute_list()) {
527 next if exists $seen_attr{$attr_name};
528 $seen_attr{$attr_name}++;
529 push @attrs => $meta->get_attribute($attr_name);
537 sub add_package_variable {
538 my ($self, $variable, $initial_value) = @_;
539 (defined $variable && $variable =~ /^[\$\@\%]/)
540 || confess "variable name does not have a sigil";
542 my ($sigil, $name) = ($variable =~ /^(.)(.*)$/);
543 if (defined $initial_value) {
545 *{$self->name . '::' . $name} = $initial_value;
551 # We HAVE to localize $@ or all
552 # hell breaks loose. It is not
553 # good, believe me, not good.
555 eval $sigil . $self->name . '::' . $name;
558 confess "Could not create package variable ($variable) because : $e" if $e;
562 sub has_package_variable {
563 my ($self, $variable) = @_;
564 (defined $variable && $variable =~ /^[\$\@\%]/)
565 || confess "variable name does not have a sigil";
566 my ($sigil, $name) = ($variable =~ /^(.)(.*)$/);
568 defined ${$self->name . '::'}{$name} ? 1 : 0;
571 sub get_package_variable {
572 my ($self, $variable) = @_;
573 (defined $variable && $variable =~ /^[\$\@\%]/)
574 || confess "variable name does not have a sigil";
575 my ($sigil, $name) = ($variable =~ /^(.)(.*)$/);
579 # We HAVE to localize $@ or all
580 # hell breaks loose. It is not
581 # good, believe me, not good.
583 $ref = eval '\\' . $sigil . $self->name . '::' . $name;
586 confess "Could not get the package variable ($variable) because : $e" if $e;
587 # if we didn't die, then we can return it
591 sub remove_package_variable {
592 my ($self, $variable) = @_;
593 (defined $variable && $variable =~ /^[\$\@\%]/)
594 || confess "variable name does not have a sigil";
595 my ($sigil, $name) = ($variable =~ /^(.)(.*)$/);
597 delete ${$self->name . '::'}{$name};
608 Class::MOP::Class - Class Meta Object
612 # assuming that class Foo
613 # has been defined, you can
615 # use this for introspection ...
617 # add a method to Foo ...
618 Foo->meta->add_method('bar' => sub { ... })
620 # get a list of all the classes searched
621 # the method dispatcher in the correct order
622 Foo->meta->class_precedence_list()
624 # remove a method from Foo
625 Foo->meta->remove_method('bar');
627 # or use this to actually create classes ...
629 Class::MOP::Class->create('Bar' => '0.01' => (
630 superclasses => [ 'Foo' ],
632 Class::MOP:::Attribute->new('$bar'),
633 Class::MOP:::Attribute->new('$baz'),
636 calculate_bar => sub { ... },
637 construct_baz => sub { ... }
643 This is the largest and currently most complex part of the Perl 5
644 meta-object protocol. It controls the introspection and
645 manipulation of Perl 5 classes (and it can create them too). The
646 best way to understand what this module can do, is to read the
647 documentation for each of it's methods.
651 =head2 Self Introspection
657 This will return a B<Class::MOP::Class> instance which is related
658 to this class. Thereby allowing B<Class::MOP::Class> to actually
661 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
662 bootstrap this module by installing a number of attribute meta-objects
663 into it's metaclass. This will allow this class to reap all the benifits
664 of the MOP when subclassing it.
666 =item B<get_all_metaclasses>
668 This will return an hash of all the metaclass instances that have
669 been cached by B<Class::MOP::Class> keyed by the package name.
671 =item B<get_all_metaclass_instances>
673 This will return an array of all the metaclass instances that have
674 been cached by B<Class::MOP::Class>.
676 =item B<get_all_metaclass_names>
678 This will return an array of all the metaclass names that have
679 been cached by B<Class::MOP::Class>.
683 =head2 Class construction
685 These methods will handle creating B<Class::MOP::Class> objects,
686 which can be used to both create new classes, and analyze
687 pre-existing classes.
689 This module will internally store references to all the instances
690 you create with these methods, so that they do not need to be
691 created any more than nessecary. Basically, they are singletons.
695 =item B<create ($package_name, ?$package_version,
696 superclasses =E<gt> ?@superclasses,
697 methods =E<gt> ?%methods,
698 attributes =E<gt> ?%attributes)>
700 This returns a B<Class::MOP::Class> object, bringing the specified
701 C<$package_name> into existence and adding any of the
702 C<$package_version>, C<@superclasses>, C<%methods> and C<%attributes>
705 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
706 methods =E<gt> ?%methods,
707 attributes =E<gt> ?%attributes)>
709 This will create an anonymous class, it works much like C<create> but
710 it does not need a C<$package_name>. Instead it will create a suitably
711 unique package name for you to stash things into.
713 =item B<initialize ($package_name)>
715 This initializes and returns returns a B<Class::MOP::Class> object
716 for a given a C<$package_name>.
718 =item B<construct_class_instance (%options)>
720 This will construct an instance of B<Class::MOP::Class>, it is
721 here so that we can actually "tie the knot" for B<Class::MOP::Class>
722 to use C<construct_instance> once all the bootstrapping is done. This
723 method is used internally by C<initialize> and should never be called
724 from outside of that method really.
726 =item B<check_metaclass_compatability>
728 This method is called as the very last thing in the
729 C<construct_class_instance> method. This will check that the
730 metaclass you are creating is compatible with the metaclasses of all
731 your ancestors. For more inforamtion about metaclass compatibility
732 see the C<About Metaclass compatibility> section in L<Class::MOP>.
736 =head2 Object instance construction and cloning
738 These methods are B<entirely optional>, it is up to you whether you want
743 =item B<new_object (%params)>
745 This is a convience method for creating a new object of the class, and
746 blessing it into the appropriate package as well. Ideally your class
747 would call a C<new> this method like so:
750 my ($class, %param) = @_;
751 $class->meta->new_object(%params);
754 Of course the ideal place for this would actually be in C<UNIVERSAL::>
755 but that is considered bad style, so we do not do that.
757 =item B<construct_instance (%params)>
759 This method is used to construct an instace structure suitable for
760 C<bless>-ing into your package of choice. It works in conjunction
761 with the Attribute protocol to collect all applicable attributes.
763 This will construct and instance using a HASH ref as storage
764 (currently only HASH references are supported). This will collect all
765 the applicable attributes and layout out the fields in the HASH ref,
766 it will then initialize them using either use the corresponding key
767 in C<%params> or any default value or initializer found in the
768 attribute meta-object.
770 =item B<clone_object ($instance, %params)>
772 This is a convience method for cloning an object instance, then
773 blessing it into the appropriate package. This method will call
774 C<clone_instance>, which performs a shallow copy of the object,
775 see that methods documentation for more details. Ideally your
776 class would call a C<clone> this method like so:
779 my ($self, %param) = @_;
780 $self->meta->clone_object($self, %params);
783 Of course the ideal place for this would actually be in C<UNIVERSAL::>
784 but that is considered bad style, so we do not do that.
786 =item B<clone_instance($instance, %params)>
788 This method is a compliment of C<construct_instance> (which means if
789 you override C<construct_instance>, you need to override this one too),
790 and clones the instance shallowly.
792 The cloned structure returned is (like with C<construct_instance>) an
793 unC<bless>ed HASH reference, it is your responsibility to then bless
794 this cloned structure into the right class (which C<clone_object> will
797 As of 0.11, this method will clone the C<$instance> structure shallowly,
798 as opposed to the deep cloning implemented in prior versions. After much
799 thought, research and discussion, I have decided that anything but basic
800 shallow cloning is outside the scope of the meta-object protocol. I
801 think Yuval "nothingmuch" Kogman put it best when he said that cloning
802 is too I<context-specific> to be part of the MOP.
812 This is a read-only attribute which returns the package name for the
813 given B<Class::MOP::Class> instance.
817 This is a read-only attribute which returns the C<$VERSION> of the
818 package for the given B<Class::MOP::Class> instance.
822 =head2 Inheritance Relationships
826 =item B<superclasses (?@superclasses)>
828 This is a read-write attribute which represents the superclass
829 relationships of the class the B<Class::MOP::Class> instance is
830 associated with. Basically, it can get and set the C<@ISA> for you.
833 Perl will occasionally perform some C<@ISA> and method caching, if
834 you decide to change your superclass relationship at runtime (which
835 is quite insane and very much not recommened), then you should be
836 aware of this and the fact that this module does not make any
837 attempt to address this issue.
839 =item B<class_precedence_list>
841 This computes the a list of all the class's ancestors in the same order
842 in which method dispatch will be done. This is similair to
843 what B<Class::ISA::super_path> does, but we don't remove duplicate names.
851 =item B<method_metaclass>
853 =item B<add_method ($method_name, $method)>
855 This will take a C<$method_name> and CODE reference to that
856 C<$method> and install it into the class's package.
859 This does absolutely nothing special to C<$method>
860 other than use B<Sub::Name> to make sure it is tagged with the
861 correct name, and therefore show up correctly in stack traces and
864 =item B<alias_method ($method_name, $method)>
866 This will take a C<$method_name> and CODE reference to that
867 C<$method> and alias the method into the class's package.
870 Unlike C<add_method>, this will B<not> try to name the
871 C<$method> using B<Sub::Name>, it only aliases the method in
874 =item B<has_method ($method_name)>
876 This just provides a simple way to check if the class implements
877 a specific C<$method_name>. It will I<not> however, attempt to check
878 if the class inherits the method (use C<UNIVERSAL::can> for that).
880 This will correctly handle functions defined outside of the package
881 that use a fully qualified name (C<sub Package::name { ... }>).
883 This will correctly handle functions renamed with B<Sub::Name> and
884 installed using the symbol tables. However, if you are naming the
885 subroutine outside of the package scope, you must use the fully
886 qualified name, including the package name, for C<has_method> to
887 correctly identify it.
889 This will attempt to correctly ignore functions imported from other
890 packages using B<Exporter>. It breaks down if the function imported
891 is an C<__ANON__> sub (such as with C<use constant>), which very well
892 may be a valid method being applied to the class.
894 In short, this method cannot always be trusted to determine if the
895 C<$method_name> is actually a method. However, it will DWIM about
896 90% of the time, so it's a small trade off I think.
898 =item B<get_method ($method_name)>
900 This will return a CODE reference of the specified C<$method_name>,
901 or return undef if that method does not exist.
903 =item B<remove_method ($method_name)>
905 This will attempt to remove a given C<$method_name> from the class.
906 It will return the CODE reference that it has removed, and will
907 attempt to use B<Sub::Name> to clear the methods associated name.
909 =item B<get_method_list>
911 This will return a list of method names for all I<locally> defined
912 methods. It does B<not> provide a list of all applicable methods,
913 including any inherited ones. If you want a list of all applicable
914 methods, use the C<compute_all_applicable_methods> method.
916 =item B<compute_all_applicable_methods>
918 This will return a list of all the methods names this class will
919 respond to, taking into account inheritance. The list will be a list of
920 HASH references, each one containing the following information; method
921 name, the name of the class in which the method lives and a CODE
922 reference for the actual method.
924 =item B<find_all_methods_by_name ($method_name)>
926 This will traverse the inheritence hierarchy and locate all methods
927 with a given C<$method_name>. Similar to
928 C<compute_all_applicable_methods> it returns a list of HASH references
929 with the following information; method name (which will always be the
930 same as C<$method_name>), the name of the class in which the method
931 lives and a CODE reference for the actual method.
933 The list of methods produced is a distinct list, meaning there are no
934 duplicates in it. This is especially useful for things like object
935 initialization and destruction where you only want the method called
936 once, and in the correct order.
938 =item B<find_next_method_by_name ($method_name)>
940 This will return the first method to match a given C<$method_name> in
941 the superclasses, this is basically equivalent to calling
942 C<SUPER::$method_name>, but it can be dispatched at runtime.
946 =head2 Method Modifiers
948 Method modifiers are a concept borrowed from CLOS, in which a method
949 can be wrapped with I<before>, I<after> and I<around> method modifiers
950 that will be called everytime the method is called.
952 =head3 How method modifiers work?
954 Method modifiers work by wrapping the original method and then replacing
955 it in the classes symbol table. The wrappers will handle calling all the
956 modifiers in the appropariate orders and preserving the calling context
957 for the original method.
959 Each method modifier serves a particular purpose, which may not be
960 obvious to users of other method wrapping modules. To start with, the
961 return values of I<before> and I<after> modifiers are ignored. This is
962 because thier purpose is B<not> to filter the input and output of the
963 primary method (this is done with an I<around> modifier). This may seem
964 like an odd restriction to some, but doing this allows for simple code
965 to be added at the begining or end of a method call without jeapordizing
966 the normal functioning of the primary method or placing any extra
967 responsibility on the code of the modifier. Of course if you have more
968 complex needs, then use the I<around> modifier, which uses a variation
969 of continutation passing style to allow for a high degree of flexibility.
971 Before and around modifiers are called in last-defined-first-called order,
972 while after modifiers are called in first-defined-first-called order. So
973 the call tree might looks something like this:
983 To see examples of using method modifiers, see the following examples
984 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
985 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
986 classic CLOS usage example in the test F<017_add_method_modifier.t>.
988 =head3 What is the performance impact?
990 Of course there is a performance cost associated with method modifiers,
991 but we have made every effort to make that cost be directly proportional
992 to the amount of modifier features you utilize.
994 The wrapping method does it's best to B<only> do as much work as it
995 absolutely needs to. In order to do this we have moved some of the
996 performance costs to set-up time, where they are easier to amortize.
998 All this said, my benchmarks have indicated the following:
1000 simple wrapper with no modifiers 100% slower
1001 simple wrapper with simple before modifier 400% slower
1002 simple wrapper with simple after modifier 450% slower
1003 simple wrapper with simple around modifier 500-550% slower
1004 simple wrapper with all 3 modifiers 1100% slower
1006 These numbers may seem daunting, but you must remember, every feature
1007 comes with some cost. To put things in perspective, just doing a simple
1008 C<AUTOLOAD> which does nothing but extract the name of the method called
1009 and return it costs about 400% over a normal method call.
1013 =item B<add_before_method_modifier ($method_name, $code)>
1015 This will wrap the method at C<$method_name> and the supplied C<$code>
1016 will be passed the C<@_> arguments, and called before the original
1017 method is called. As specified above, the return value of the I<before>
1018 method modifiers is ignored, and it's ability to modify C<@_> is
1019 fairly limited. If you need to do either of these things, use an
1020 C<around> method modifier.
1022 =item B<add_after_method_modifier ($method_name, $code)>
1024 This will wrap the method at C<$method_name> so that the original
1025 method will be called, it's return values stashed, and then the
1026 supplied C<$code> will be passed the C<@_> arguments, and called.
1027 As specified above, the return value of the I<after> method
1028 modifiers is ignored, and it cannot modify the return values of
1029 the original method. If you need to do either of these things, use an
1030 C<around> method modifier.
1032 =item B<add_around_method_modifier ($method_name, $code)>
1034 This will wrap the method at C<$method_name> so that C<$code>
1035 will be called and passed the original method as an extra argument
1036 at the begining of the C<@_> argument list. This is a variation of
1037 continuation passing style, where the function prepended to C<@_>
1038 can be considered a continuation. It is up to C<$code> if it calls
1039 the original method or not, there is no restriction on what the
1040 C<$code> can or cannot do.
1046 It should be noted that since there is no one consistent way to define
1047 the attributes of a class in Perl 5. These methods can only work with
1048 the information given, and can not easily discover information on
1049 their own. See L<Class::MOP::Attribute> for more details.
1053 =item B<attribute_metaclass>
1055 =item B<get_attribute_map>
1057 =item B<add_attribute ($attribute_name, $attribute_meta_object)>
1059 This stores a C<$attribute_meta_object> in the B<Class::MOP::Class>
1060 instance associated with the given class, and associates it with
1061 the C<$attribute_name>. Unlike methods, attributes within the MOP
1062 are stored as meta-information only. They will be used later to
1063 construct instances from (see C<construct_instance> above).
1064 More details about the attribute meta-objects can be found in the
1065 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1068 It should be noted that any accessor, reader/writer or predicate
1069 methods which the C<$attribute_meta_object> has will be installed
1070 into the class at this time.
1072 =item B<has_attribute ($attribute_name)>
1074 Checks to see if this class has an attribute by the name of
1075 C<$attribute_name> and returns a boolean.
1077 =item B<get_attribute ($attribute_name)>
1079 Returns the attribute meta-object associated with C<$attribute_name>,
1080 if none is found, it will return undef.
1082 =item B<remove_attribute ($attribute_name)>
1084 This will remove the attribute meta-object stored at
1085 C<$attribute_name>, then return the removed attribute meta-object.
1088 Removing an attribute will only affect future instances of
1089 the class, it will not make any attempt to remove the attribute from
1090 any existing instances of the class.
1092 It should be noted that any accessor, reader/writer or predicate
1093 methods which the attribute meta-object stored at C<$attribute_name>
1094 has will be removed from the class at this time. This B<will> make
1095 these attributes somewhat inaccessable in previously created
1096 instances. But if you are crazy enough to do this at runtime, then
1097 you are crazy enough to deal with something like this :).
1099 =item B<get_attribute_list>
1101 This returns a list of attribute names which are defined in the local
1102 class. If you want a list of all applicable attributes for a class,
1103 use the C<compute_all_applicable_attributes> method.
1105 =item B<compute_all_applicable_attributes>
1107 This will traverse the inheritance heirachy and return a list of all
1108 the applicable attributes for this class. It does not construct a
1109 HASH reference like C<compute_all_applicable_methods> because all
1110 that same information is discoverable through the attribute
1115 =head2 Package Variables
1117 Since Perl's classes are built atop the Perl package system, it is
1118 fairly common to use package scoped variables for things like static
1119 class variables. The following methods are convience methods for
1120 the creation and inspection of package scoped variables.
1124 =item B<add_package_variable ($variable_name, ?$initial_value)>
1126 Given a C<$variable_name>, which must contain a leading sigil, this
1127 method will create that variable within the package which houses the
1128 class. It also takes an optional C<$initial_value>, which must be a
1129 reference of the same type as the sigil of the C<$variable_name>
1132 =item B<get_package_variable ($variable_name)>
1134 This will return a reference to the package variable in
1137 =item B<has_package_variable ($variable_name)>
1139 Returns true (C<1>) if there is a package variable defined for
1140 C<$variable_name>, and false (C<0>) otherwise.
1142 =item B<remove_package_variable ($variable_name)>
1144 This will attempt to remove the package variable at C<$variable_name>.
1150 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1152 =head1 COPYRIGHT AND LICENSE
1154 Copyright 2006 by Infinity Interactive, Inc.
1156 L<http://www.iinteractive.com>
1158 This library is free software; you can redistribute it and/or modify
1159 it under the same terms as Perl itself.