use Carp 'confess';
use Scalar::Util 'blessed', 'weaken';
-our $VERSION = '0.71';
+our $VERSION = '0.82';
$VERSION = eval $VERSION;
our $AUTHORITY = 'cpan:STEVAN';
|| confess "You must pass a package name and it cannot be blessed";
return Class::MOP::get_metaclass_by_name($package_name)
- || $class->construct_class_instance(package => $package_name, @_);
+ || $class->_construct_class_instance(package => $package_name, @_);
+}
+
+sub construct_class_instance {
+ Carp::cluck('The construct_class_instance method has been made private.'
+ . " The public version is deprecated and will be removed in a future release.\n");
+ shift->_construct_class_instance(@_);
}
# NOTE: (meta-circularity)
-# this is a special form of &construct_instance
+# this is a special form of _construct_instance
# (see below), which is used to construct class
# meta-object instances for any Class::MOP::*
# class. All other classes will use the more
# normal &construct_instance.
-sub construct_class_instance {
+sub _construct_class_instance {
my $class = shift;
my $options = @_ == 1 ? $_[0] : {@_};
my $package_name = $options->{package};
# now create the metaclass
my $meta;
if ($class eq 'Class::MOP::Class') {
- no strict 'refs';
- $meta = $class->_new($options)
+ $meta = $class->_new($options);
}
else {
# NOTE:
# it is safe to use meta here because
# class will always be a subclass of
# Class::MOP::Class, which defines meta
- $meta = $class->meta->construct_instance($options)
+ $meta = $class->meta->_construct_instance($options)
}
# and check the metaclass compatibility
- $meta->check_metaclass_compatibility();
+ $meta->_check_metaclass_compatibility();
Class::MOP::store_metaclass_by_name($package_name, $meta);
bless {
# inherited from Class::MOP::Package
- 'package' => $options->{package},
+ 'package' => $options->{package},
# NOTE:
# since the following attributes will
# listed here for reference, because they
# should not actually have a value associated
# with the slot.
- 'namespace' => \undef,
+ 'namespace' => \undef,
+
# inherited from Class::MOP::Module
- 'version' => \undef,
- 'authority' => \undef,
+ 'version' => \undef,
+ 'authority' => \undef,
+
# defined in Class::MOP::Class
- 'superclasses' => \undef,
+ 'superclasses' => \undef,
'methods' => {},
'attributes' => {},
- 'attribute_metaclass' => $options->{'attribute_metaclass'} || 'Class::MOP::Attribute',
- 'method_metaclass' => $options->{'method_metaclass'} || 'Class::MOP::Method',
- 'instance_metaclass' => $options->{'instance_metaclass'} || 'Class::MOP::Instance',
+ 'attribute_metaclass' => $options->{'attribute_metaclass'}
+ || 'Class::MOP::Attribute',
+ 'method_metaclass' => $options->{'method_metaclass'}
+ || 'Class::MOP::Method',
+ 'wrapped_method_metaclass' => $options->{'wrapped_method_metaclass'}
+ || 'Class::MOP::Method::Wrapped',
+ 'instance_metaclass' => $options->{'instance_metaclass'}
+ || 'Class::MOP::Instance',
}, $class;
}
$self->{'_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
}
+
sub check_metaclass_compatibility {
+ Carp::cluck('The check_metaclass_compatibility method has been made private.'
+ . " The public version is deprecated and will be removed in a future release.\n");
+ shift->_check_metaclass_compatibility(@_);
+}
+
+sub _check_metaclass_compatibility {
my $self = shift;
# this is always okay ...
my @class_list = $self->linearized_isa;
shift @class_list; # shift off $self->name
- foreach my $class_name (@class_list) {
- my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
+ foreach my $superclass_name (@class_list) {
+ my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name) || next;
# NOTE:
# we need to deal with the possibility
# of class immutability here, and then
# get the name of the class appropriately
- my $meta_type = ($meta->is_immutable
- ? $meta->get_mutable_metaclass_name()
- : ref($meta));
-
- ($self->isa($meta_type))
- || confess $self->name . "->meta => (" . (ref($self)) . ")" .
- " is not compatible with the " .
- $class_name . "->meta => (" . ($meta_type) . ")";
+ my $super_meta_type
+ = $super_meta->is_immutable
+ ? $super_meta->get_mutable_metaclass_name()
+ : ref($super_meta);
+
+ ($self->isa($super_meta_type))
+ || confess "Class::MOP::class_of(" . $self->name . ") => ("
+ . (ref($self)) . ")" . " is not compatible with the " .
+ "Class::MOP::class_of(".$superclass_name . ") => ("
+ . ($super_meta_type) . ")";
# NOTE:
# we also need to check that instance metaclasses
# are compatibile in the same the class.
- ($self->instance_metaclass->isa($meta->instance_metaclass))
- || confess $self->name . "->meta->instance_metaclass => (" . ($self->instance_metaclass) . ")" .
+ ($self->instance_metaclass->isa($super_meta->instance_metaclass))
+ || confess "Class::MOP::class_of(" . $self->name . ")->instance_metaclass => (" . ($self->instance_metaclass) . ")" .
" is not compatible with the " .
- $class_name . "->meta->instance_metaclass => (" . ($meta->instance_metaclass) . ")";
+ "Class::MOP::class_of(" . $superclass_name . ")->instance_metaclass => (" . ($super_meta->instance_metaclass) . ")";
}
}
-# backwards compat for stevan's inability to spell ;)
-sub check_metaclass_compatability {
- my $self = shift;
- $self->check_metaclass_compatibility(@_);
-}
-
## ANON classes
{
|| confess "You must pass a HASH ref of methods"
if exists $options{methods};
- $class->SUPER::create(%options);
-
my (%initialize_options) = @args;
delete @initialize_options{qw(
package
)};
my $meta = $class->initialize( $package_name => %initialize_options );
+ $meta->_instantiate_module( $options{version}, $options{authority} );
+
# FIXME totally lame
$meta->add_method('meta' => sub {
$class->initialize(ref($_[0]) || $_[0]);
# all these attribute readers will be bootstrapped
# away in the Class::MOP bootstrap section
-sub get_attribute_map { $_[0]->{'attributes'} }
-sub attribute_metaclass { $_[0]->{'attribute_metaclass'} }
-sub method_metaclass { $_[0]->{'method_metaclass'} }
-sub instance_metaclass { $_[0]->{'instance_metaclass'} }
-
-# FIXME:
-# this is a prime canidate for conversion to XS
-sub get_method_map {
- my $self = shift;
-
- my $class_name = $self->name;
-
- my $current = Class::MOP::check_package_cache_flag($class_name);
-
- if (defined $self->{'_package_cache_flag'} && $self->{'_package_cache_flag'} == $current) {
- return $self->{'methods'} ||= {};
- }
-
- $self->{_package_cache_flag} = $current;
-
- my $map = $self->{'methods'} ||= {};
-
- my $method_metaclass = $self->method_metaclass;
-
- my %all_code = $self->get_all_package_symbols('CODE');
-
- foreach my $symbol (keys %all_code) {
- my $code = $all_code{$symbol};
-
- next if exists $map->{$symbol} &&
- defined $map->{$symbol} &&
- $map->{$symbol}->body == $code;
-
- my ($pkg, $name) = Class::MOP::get_code_info($code);
-
- # NOTE:
- # in 5.10 constant.pm the constants show up
- # as being in the right package, but in pre-5.10
- # they show up as constant::__ANON__ so we
- # make an exception here to be sure that things
- # work as expected in both.
- # - SL
- unless ($pkg eq 'constant' && $name eq '__ANON__') {
- next if ($pkg || '') ne $class_name ||
- (($name || '') ne '__ANON__' && ($pkg || '') ne $class_name);
- }
-
- $map->{$symbol} = $method_metaclass->wrap(
- $code,
- associated_metaclass => $self,
- package_name => $class_name,
- name => $symbol,
- );
- }
-
- return $map;
-}
+sub get_attribute_map { $_[0]->{'attributes'} }
+sub attribute_metaclass { $_[0]->{'attribute_metaclass'} }
+sub method_metaclass { $_[0]->{'method_metaclass'} }
+sub wrapped_method_metaclass { $_[0]->{'wrapped_method_metaclass'} }
+sub instance_metaclass { $_[0]->{'instance_metaclass'} }
# Instance Construction & Cloning
# Class::MOP::Class singletons here, so we
# delegate this to &construct_class_instance
# which will deal with the singletons
- return $class->construct_class_instance(@_)
+ return $class->_construct_class_instance(@_)
if $class->name->isa('Class::MOP::Class');
- return $class->construct_instance(@_);
+ return $class->_construct_instance(@_);
}
sub construct_instance {
+ Carp::cluck('The construct_instance method has been made private.'
+ . " The public version is deprecated and will be removed in a future release.\n");
+ shift->_construct_instance(@_);
+}
+
+sub _construct_instance {
my $class = shift;
my $params = @_ == 1 ? $_[0] : {@_};
my $meta_instance = $class->get_meta_instance();
my $instance = $meta_instance->create_instance();
- foreach my $attr ($class->compute_all_applicable_attributes()) {
+ foreach my $attr ($class->get_all_attributes()) {
$attr->initialize_instance_slot($meta_instance, $instance, $params);
}
# NOTE:
sub get_meta_instance {
my $self = shift;
- $self->{'_meta_instance'} ||= $self->create_meta_instance();
+ $self->{'_meta_instance'} ||= $self->_create_meta_instance();
}
sub create_meta_instance {
+ Carp::cluck('The create_meta_instance method has been made private.'
+ . " The public version is deprecated and will be removed in a future release.\n");
+ shift->_create_meta_instance(@_);
+}
+
+sub _create_meta_instance {
my $self = shift;
my $instance = $self->instance_metaclass->new(
associated_metaclass => $self,
- attributes => [ $self->compute_all_applicable_attributes() ],
+ attributes => [ $self->get_all_attributes() ],
);
$self->add_meta_instance_dependencies()
# Class::MOP::Class singletons here, they
# should not be cloned.
return $instance if $instance->isa('Class::MOP::Class');
- $class->clone_instance($instance, @_);
+ $class->_clone_instance($instance, @_);
}
sub clone_instance {
+ Carp::cluck('The clone_instance method has been made private.'
+ . " The public version is deprecated and will be removed in a future release.\n");
+ shift->_clone_instance(@_);
+}
+
+sub _clone_instance {
my ($class, $instance, %params) = @_;
(blessed($instance))
|| confess "You can only clone instances, ($instance) is not a blessed instance";
my $meta_instance = $class->get_meta_instance();
my $clone = $meta_instance->clone_instance($instance);
- foreach my $attr ($class->compute_all_applicable_attributes()) {
+ foreach my $attr ($class->get_all_attributes()) {
if ( defined( my $init_arg = $attr->init_arg ) ) {
if (exists $params{$init_arg}) {
$attr->set_value($clone, $params{$init_arg});
sub rebless_instance {
my ($self, $instance, %params) = @_;
- my $old_metaclass;
- if ($instance->can('meta')) {
- ($instance->meta->isa('Class::MOP::Class'))
- || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
- $old_metaclass = $instance->meta;
- }
- else {
- $old_metaclass = $self->initialize(ref($instance));
- }
+ my $old_metaclass = Class::MOP::class_of($instance);
- my $meta_instance = $self->get_meta_instance();
+ my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
+ $self->name->isa($old_class)
+ || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
+
+ $old_metaclass->rebless_instance_away($instance, $self, %params)
+ if $old_metaclass;
- $self->name->isa($old_metaclass->name)
- || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
+ my $meta_instance = $self->get_meta_instance();
# rebless!
- $meta_instance->rebless_instance_structure($instance, $self);
+ # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
+ $meta_instance->rebless_instance_structure($_[1], $self);
- foreach my $attr ( $self->compute_all_applicable_attributes ) {
+ foreach my $attr ( $self->get_all_attributes ) {
if ( $attr->has_value($instance) ) {
if ( defined( my $init_arg = $attr->init_arg ) ) {
$params{$init_arg} = $attr->get_value($instance)
}
}
- foreach my $attr ($self->compute_all_applicable_attributes) {
+ foreach my $attr ($self->get_all_attributes) {
$attr->initialize_instance_slot($meta_instance, $instance, \%params);
}
$instance;
}
+sub rebless_instance_away {
+ # this intentionally does nothing, it is just a hook
+}
+
# Inheritance
sub superclasses {
# not potentially creating an issues
# we don't know about
- $self->check_metaclass_compatibility();
+ $self->_check_metaclass_compatibility();
$self->update_meta_instance_dependencies();
}
@{$self->get_package_symbol($var_spec)};
sub subclasses {
my $self = shift;
-
my $super_class = $self->name;
- if ( Class::MOP::HAVE_ISAREV() ) {
- return @{ $super_class->mro::get_isarev() };
- } else {
- my @derived_classes;
-
- my $find_derived_classes;
- $find_derived_classes = sub {
- my ($outer_class) = @_;
-
- my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
-
- SYMBOL:
- for my $symbol ( keys %$symbol_table_hashref ) {
- next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
- my $inner_class = $1;
-
- next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
-
- my $class =
- $outer_class
- ? "${outer_class}::$inner_class"
- : $inner_class;
-
- if ( $class->isa($super_class) and $class ne $super_class ) {
- push @derived_classes, $class;
- }
-
- next SYMBOL if $class eq 'main'; # skip 'main::*'
-
- $find_derived_classes->($class);
- }
- };
-
- my $root_class = q{};
- $find_derived_classes->($root_class);
-
- undef $find_derived_classes;
-
- @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
-
- return @derived_classes;
- }
+ return @{ $super_class->mro::get_isarev() };
}
{
my $fetch_and_prepare_method = sub {
my ($self, $method_name) = @_;
+ my $wrapped_metaclass = $self->wrapped_method_metaclass;
# fetch it locally
my $method = $self->get_method($method_name);
# if we dont have local ...
$method = $self->find_next_method_by_name($method_name);
# die if it does not exist
(defined $method)
- || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
+ || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
# and now make sure to wrap it
# even if it is already wrapped
# because we need a new sub ref
- $method = Class::MOP::Method::Wrapped->wrap($method);
+ $method = $wrapped_metaclass->wrap($method);
}
else {
# now make sure we wrap it properly
- $method = Class::MOP::Method::Wrapped->wrap($method)
- unless $method->isa('Class::MOP::Method::Wrapped');
+ $method = $wrapped_metaclass->wrap($method)
+ unless $method->isa($wrapped_metaclass);
}
$self->add_method($method_name => $method);
return $method;
}
sub alias_method {
- my $self = shift;
+ Carp::cluck("The alias_method method is deprecated. Use add_method instead.\n");
- $self->add_method(@_);
+ shift->add_method(@_);
}
sub has_method {
(defined $method_name && $method_name)
|| confess "You must define a method name";
- # NOTE:
- # I don't really need this here, because
- # if the method_map is missing a key it
- # will just return undef for me now
- # return unless $self->has_method($method_name);
-
return $self->{methods}{$method_name} || $self->get_method_map->{$method_name};
}
return values %methods;
}
-# compatibility
sub compute_all_applicable_methods {
+ Carp::cluck('The compute_all_applicable_methods method is deprecated.'
+ . " Use get_all_methods instead.\n");
+
return map {
{
name => $_->name,
} shift->get_all_methods(@_);
}
+sub get_all_method_names {
+ my $self = shift;
+ my %uniq;
+ grep { $uniq{$_}++ == 0 } map { $_->name } $self->get_all_methods;
+}
+
sub find_all_methods_by_name {
my ($self, $method_name) = @_;
(defined $method_name && $method_name)
sub add_meta_instance_dependencies {
my $self = shift;
- $self->remove_meta_instance_depdendencies;
+ $self->remove_meta_instance_dependencies;
- my @attrs = $self->compute_all_applicable_attributes();
+ my @attrs = $self->get_all_attributes();
my %seen;
my @classes = grep { not $seen{$_->name}++ } map { $_->associated_class } @attrs;
$self->{meta_instance_dependencies} = \@classes;
}
-sub remove_meta_instance_depdendencies {
+sub remove_meta_instance_dependencies {
my $self = shift;
if ( my $classes = delete $self->{meta_instance_dependencies} ) {
}
sub get_all_attributes {
- shift->compute_all_applicable_attributes(@_);
-}
-
-sub compute_all_applicable_attributes {
my $self = shift;
my %attrs = map { %{ $self->initialize($_)->get_attribute_map } } reverse $self->linearized_isa;
return values %attrs;
}
+sub compute_all_applicable_attributes {
+ Carp::cluck('The compute_all_applicable_attributes method has been deprecated.'
+ . " Use get_all_attributes instead.\n");
+
+ shift->get_all_attributes(@_);
+}
+
sub find_attribute_by_name {
my ($self, $attr_name) = @_;
foreach my $class ($self->linearized_isa) {
sub is_mutable { 1 }
sub is_immutable { 0 }
-# NOTE:
-# Why I changed this (groditi)
-# - One Metaclass may have many Classes through many Metaclass instances
-# - One Metaclass should only have one Immutable Transformer instance
-# - Each Class may have different Immutabilizing options
-# - Therefore each Metaclass instance may have different Immutabilizing options
-# - We need to store one Immutable Transformer instance per Metaclass
-# - We need to store one set of Immutable Transformer options per Class
-# - Upon make_mutable we may delete the Immutabilizing options
-# - We could clean the immutable Transformer instance when there is no more
-# immutable Classes of that type, but we can also keep it in case
-# another class with this same Metaclass becomes immutable. It is a case
-# of trading of storing an instance to avoid unnecessary instantiations of
-# Immutable Transformers. You may view this as a memory leak, however
-# Because we have few Metaclasses, in practice it seems acceptable
-# - To allow Immutable Transformers instances to be cleaned up we could weaken
-# the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
-
-{
-
- my %IMMUTABLE_TRANSFORMERS;
- my %IMMUTABLE_OPTIONS;
-
- sub get_immutable_options {
- my $self = shift;
- return if $self->is_mutable;
- confess "unable to find immutabilizing options"
- unless exists $IMMUTABLE_OPTIONS{$self->name};
- my %options = %{$IMMUTABLE_OPTIONS{$self->name}};
- delete $options{IMMUTABLE_TRANSFORMER};
- return \%options;
- }
-
- sub get_immutable_transformer {
- my $self = shift;
- if( $self->is_mutable ){
- my $class = ref $self || $self;
- return $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
- }
- confess "unable to find transformer for immutable class"
- unless exists $IMMUTABLE_OPTIONS{$self->name};
- return $IMMUTABLE_OPTIONS{$self->name}->{IMMUTABLE_TRANSFORMER};
- }
+sub immutable_transformer { $_[0]->{immutable_transformer} }
+sub _set_immutable_transformer { $_[0]->{immutable_transformer} = $_[1] }
- sub make_immutable {
- my $self = shift;
- my %options = @_;
+sub make_immutable {
+ my $self = shift;
- my $transformer = $self->get_immutable_transformer;
- $transformer->make_metaclass_immutable($self, \%options);
- $IMMUTABLE_OPTIONS{$self->name} =
- { %options, IMMUTABLE_TRANSFORMER => $transformer };
+ return if $self->is_immutable;
- if( exists $options{debug} && $options{debug} ){
- print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
- print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
- }
+ my $transformer = $self->immutable_transformer
+ || $self->_make_immutable_transformer(@_);
- 1;
- }
+ $self->_set_immutable_transformer($transformer);
- sub make_mutable{
- my $self = shift;
- return if $self->is_mutable;
- my $options = delete $IMMUTABLE_OPTIONS{$self->name};
- confess "unable to find immutabilizing options" unless ref $options;
- my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
- $transformer->make_metaclass_mutable($self, $options);
- 1;
- }
+ $transformer->make_metaclass_immutable;
}
-sub create_immutable_transformer {
- my $self = shift;
- my $class = Class::MOP::Immutable->new($self, {
+{
+ my %Default_Immutable_Options = (
read_only => [qw/superclasses/],
- cannot_call => [qw/
- add_method
- alias_method
- remove_method
- add_attribute
- remove_attribute
- remove_package_symbol
- /],
- memoize => {
- class_precedence_list => 'ARRAY',
- linearized_isa => 'ARRAY', # FIXME perl 5.10 memoizes this on its own, no need?
- get_all_methods => 'ARRAY',
- #get_all_attributes => 'ARRAY', # it's an alias, no need, but maybe in the future
- compute_all_applicable_attributes => 'ARRAY',
- get_meta_instance => 'SCALAR',
- get_method_map => 'SCALAR',
+ cannot_call => [
+ qw(
+ add_method
+ alias_method
+ remove_method
+ add_attribute
+ remove_attribute
+ remove_package_symbol
+ )
+ ],
+ memoize => {
+ class_precedence_list => 'ARRAY',
+ # FIXME perl 5.10 memoizes this on its own, no need?
+ linearized_isa => 'ARRAY',
+ get_all_methods => 'ARRAY',
+ get_all_method_names => 'ARRAY',
+ get_all_attributes => 'ARRAY',
+ get_meta_instance => 'SCALAR',
+ get_method_map => 'SCALAR',
},
+
# NOTE:
- # this is ugly, but so are typeglobs,
+ # this is ugly, but so are typeglobs,
# so whattayahgonnadoboutit
# - SL
- wrapped => {
+ wrapped => {
add_package_symbol => sub {
my $original = shift;
- confess "Cannot add package symbols to an immutable metaclass"
- unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
+ confess "Cannot add package symbols to an immutable metaclass"
+ unless ( caller(2) )[3] eq
+ 'Class::MOP::Package::get_package_symbol';
# This is a workaround for a bug in 5.8.1 which thinks that
# goto $original->body
goto $body;
},
},
- });
- return $class;
+ );
+
+ sub _default_immutable_transformer_options {
+ return %Default_Immutable_Options;
+ }
+}
+
+sub _make_immutable_transformer {
+ my $self = shift;
+
+ Class::MOP::Immutable->new(
+ $self,
+ $self->_default_immutable_transformer_options,
+ @_
+ );
+}
+
+sub make_mutable {
+ my $self = shift;
+
+ return if $self->is_mutable;
+
+ $self->immutable_transformer->make_metaclass_mutable;
}
1;
# use this for introspection ...
# add a method to Foo ...
- Foo->meta->add_method('bar' => sub { ... })
+ Foo->meta->add_method( 'bar' => sub {...} )
- # get a list of all the classes searched
- # the method dispatcher in the correct order
- Foo->meta->class_precedence_list()
+ # get a list of all the classes searched
+ # the method dispatcher in the correct order
+ Foo->meta->class_precedence_list()
- # remove a method from Foo
- Foo->meta->remove_method('bar');
+ # remove a method from Foo
+ Foo->meta->remove_method('bar');
# or use this to actually create classes ...
- Class::MOP::Class->create('Bar' => (
- version => '0.01',
- superclasses => [ 'Foo' ],
- attributes => [
- Class::MOP:::Attribute->new('$bar'),
- Class::MOP:::Attribute->new('$baz'),
- ],
- methods => {
- calculate_bar => sub { ... },
- construct_baz => sub { ... }
- }
- ));
+ Class::MOP::Class->create(
+ 'Bar' => (
+ version => '0.01',
+ superclasses => ['Foo'],
+ attributes => [
+ Class::MOP:: : Attribute->new('$bar'),
+ Class::MOP:: : Attribute->new('$baz'),
+ ],
+ methods => {
+ calculate_bar => sub {...},
+ construct_baz => sub {...}
+ }
+ )
+ );
=head1 DESCRIPTION
-This is the largest and currently most complex part of the Perl 5
-meta-object protocol. It controls the introspection and
-manipulation of Perl 5 classes (and it can create them too). The
+The Class Protocol is the largest and most complex part of the
+Class::MOP meta-object protocol. It controls the introspection and
+manipulation of Perl 5 classes, and it can create them as well. The
best way to understand what this module can do, is to read the
-documentation for each of it's methods.
-
-=head1 METHODS
-
-=head2 Self Introspection
-
-=over 4
+documentation for each of its methods.
-=item B<meta>
+=head1 INHERITANCE
-This will return a B<Class::MOP::Class> instance which is related
-to this class. Thereby allowing B<Class::MOP::Class> to actually
-introspect itself.
+C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
-As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
-bootstrap this module by installing a number of attribute meta-objects
-into it's metaclass. This will allow this class to reap all the benifits
-of the MOP when subclassing it.
-
-=back
+=head1 METHODS
=head2 Class construction
-These methods will handle creating B<Class::MOP::Class> objects,
-which can be used to both create new classes, and analyze
-pre-existing classes.
+These methods all create new C<Class::MOP::Class> objects. These
+objects can represent existing classes, or they can be used to create
+new classes from scratch.
-This module will internally store references to all the instances
-you create with these methods, so that they do not need to be
-created any more than nessecary. Basically, they are singletons.
+The metaclass object for a given class is a singleton. If you attempt
+to create a metaclass for the same class twice, you will just get the
+existing object.
=over 4
-=item B<create ($package_name,
- version =E<gt> ?$version,
- authority =E<gt> ?$authority,
- superclasses =E<gt> ?@superclasses,
- methods =E<gt> ?%methods,
- attributes =E<gt> ?%attributes)>
+=item B<< Class::MOP::Class->create($package_name, %options) >>
-This returns a B<Class::MOP::Class> object, bringing the specified
-C<$package_name> into existence and adding any of the C<$version>,
-C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
-it.
+This method creates a new C<Class::MOP::Class> object with the given
+package name. It accepts a number of options.
-=item B<create_anon_class (superclasses =E<gt> ?@superclasses,
- methods =E<gt> ?%methods,
- attributes =E<gt> ?%attributes)>
+=over 8
-This will create an anonymous class, it works much like C<create> but
-it does not need a C<$package_name>. Instead it will create a suitably
-unique package name for you to stash things into.
+=item * version
-On very important distinction is that anon classes are destroyed once
-the metaclass they are attached to goes out of scope. In the DESTROY
-method, the created package will be removed from the symbol table.
+An optional version number for the newly created package.
-It is also worth noting that any instances created with an anon-class
-will keep a special reference to the anon-meta which will prevent the
-anon-class from going out of scope until all instances of it have also
-been destroyed. This however only works for HASH based instance types,
-as we use a special reserved slot (C<__MOP__>) to store this.
+=item * authority
-=item B<initialize ($package_name, %options)>
+An optional authority for the newly created package.
-This initializes and returns returns a B<Class::MOP::Class> object
-for a given a C<$package_name>.
+=item * superclasses
-=item B<construct_class_instance (%options)>
+An optional array reference of superclass names.
-This will construct an instance of B<Class::MOP::Class>, it is
-here so that we can actually "tie the knot" for B<Class::MOP::Class>
-to use C<construct_instance> once all the bootstrapping is done. This
-method is used internally by C<initialize> and should never be called
-from outside of that method really.
+=item * methods
-=item B<check_metaclass_compatibility>
+An optional hash reference of methods for the class. The keys of the
+hash reference are method names, and values are subroutine references.
-This method is called as the very last thing in the
-C<construct_class_instance> method. This will check that the
-metaclass you are creating is compatible with the metaclasses of all
-your ancestors. For more inforamtion about metaclass compatibility
-see the C<About Metaclass compatibility> section in L<Class::MOP>.
+=item * attributes
-=item B<update_package_cache_flag>
+An optional array reference of attributes.
-This will reset the package cache flag for this particular metaclass
-it is basically the value of the C<Class::MOP::get_package_cache_flag>
-function. This is very rarely needed from outside of C<Class::MOP::Class>
-but in some cases you might want to use it, so it is here.
+An attribute can be passed as an existing L<Class::MOP::Attribute>
+object, I<or> or as a hash reference of options which will be passed
+to the attribute metaclass's constructor.
-=item B<reset_package_cache_flag>
-
-Clears the package cache flag to announce to the internals that we need
-to rebuild the method map.
-
-=item B<add_meta_instance_dependencies>
-
-Registers this class as dependent on its superclasses.
-
-Only superclasses from which this class inherits attributes will be added.
-
-=item B<remove_meta_instance_depdendencies>
+=back
-Unregisters this class from its superclasses.
+=item B<< Class::MOP::Class->create_anon_class(%options) >>
-=item B<update_meta_instance_dependencies>
+This method works just like C<< Class::MOP::Class->create >> but it
+creates an "anonymous" class. In fact, the class does have a name, but
+that name is a unique name generated internally by this module.
-Reregisters if necessary.
+It accepts the same C<superclasses>, C<methods>, and C<attributes>
+parameters that C<create> accepts.
-=item B<add_dependent_meta_instance> $metaclass
+Anonymous classes are destroyed once the metaclass they are attached
+to goes out of scope, and will be removed from Perl's internal symbol
+table.
-Registers the class as having a meta instance dependent on this class.
+All instances of an anonymous class keep a special reference to the
+metaclass object, which prevents the metaclass from going out of scope
+while any instances exist.
-=item B<remove_dependent_meta_instance> $metaclass
+This only works if the instance if based on a hash reference, however.
-Remove the class from the list of dependent classes.
+=item B<< Class::MOP::Class->initialize($package_name, %options) >>
-=item B<invalidate_meta_instances>
+This method will initialize a C<Class::MOP::Class> object for the
+named package. Unlike C<create>, this method I<will not> create a new
+class.
-Clears the cached meta instance for this metaclass and all of the registered
-classes with dependent meta instances.
+The purpose of this method is to retrieve a C<Class::MOP::Class>
+object for introspecting an existing class.
-Called by C<add_attribute> and C<remove_attribute> to recalculate the attribute
-slots.
+If an existing C<Class::MOP::Class> object exists for the named
+package, it will be returned, and any options provided will be
+ignored!
-=item B<invalidate_meta_instance>
+If the object does not yet exist, it will be created.
-Used by C<invalidate_meta_instances>.
+The valid options that can be passed to this method are
+C<attribute_metaclass>, C<method_metaclass>,
+C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
+optional, and default to the appropriate class in the C<Class::MOP>
+distribution.
=back
=head2 Object instance construction and cloning
-These methods are B<entirely optional>, it is up to you whether you want
-to use them or not.
+These methods are all related to creating and/or cloning object
+instances.
=over 4
-=item B<instance_metaclass>
-
-Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
-for more information on the instance metaclasses.
-
-=item B<get_meta_instance>
-
-Returns an instance of L<Class::MOP::Instance> to be used in the construction
-of a new instance of the class.
+=item B<< $metaclass->clone_object($instance, %params) >>
-=item B<create_meta_instance>
+This method clones an existing object instance. Any parameters you
+provide are will override existing attribute values in the object.
-Called by C<get_meta_instance> if necessary.
+This is a convenience method for cloning an object instance, then
+blessing it into the appropriate package.
-=item B<new_object (%params)>
+You could implement a clone method in your class, using this method:
-This is a convience method for creating a new object of the class, and
-blessing it into the appropriate package as well. Ideally your class
-would call a C<new> this method like so:
-
- sub MyClass::new {
- my ($class, %param) = @_;
- $class->meta->new_object(%params);
+ sub clone {
+ my ($self, %params) = @_;
+ $self->meta->clone_object($self, %params);
}
-=item B<construct_instance (%params)>
+=item B<< $metaclass->rebless_instance($instance, %params) >>
-This method is used to construct an instance structure suitable for
-C<bless>-ing into your package of choice. It works in conjunction
-with the Attribute protocol to collect all applicable attributes.
+This method changes the class of C<$instance> to the metaclass's class.
-This will construct and instance using a HASH ref as storage
-(currently only HASH references are supported). This will collect all
-the applicable attributes and layout out the fields in the HASH ref,
-it will then initialize them using either use the corresponding key
-in C<%params> or any default value or initializer found in the
-attribute meta-object.
+You can only rebless an instance into a subclass of its current
+class. If you pass any additional parameters, these will be treated
+like constructor parameters and used to initialize the object's
+attributes. Any existing attributes that are already set will be
+overwritten.
-=item B<clone_object ($instance, %params)>
+Before reblessing the instance, this method will call
+C<rebless_instance_away> on the instance's current metaclass. This method
+will be passed the instance, the new metaclass, and any parameters
+specified to C<rebless_instance>. By default, C<rebless_instance_away>
+does nothing; it is merely a hook.
-This is a convience method for cloning an object instance, then
-blessing it into the appropriate package. This method will call
-C<clone_instance>, which performs a shallow copy of the object,
-see that methods documentation for more details. Ideally your
-class would call a C<clone> this method like so:
+=item B<< $metaclass->new_object(%params) >>
- sub MyClass::clone {
- my ($self, %param) = @_;
- $self->meta->clone_object($self, %params);
- }
-
-=item B<clone_instance($instance, %params)>
-
-This method is a compliment of C<construct_instance> (which means if
-you override C<construct_instance>, you need to override this one too),
-and clones the instance shallowly.
+This method is used to create a new object of the metaclass's
+class. Any parameters you provide are used to initialize the
+instance's attributes.
-The cloned structure returned is (like with C<construct_instance>) an
-unC<bless>ed HASH reference, it is your responsibility to then bless
-this cloned structure into the right class (which C<clone_object> will
-do for you).
+=item B<< $metaclass->instance_metaclass >>
-As of 0.11, this method will clone the C<$instance> structure shallowly,
-as opposed to the deep cloning implemented in prior versions. After much
-thought, research and discussion, I have decided that anything but basic
-shallow cloning is outside the scope of the meta-object protocol. I
-think Yuval "nothingmuch" Kogman put it best when he said that cloning
-is too I<context-specific> to be part of the MOP.
+Returns the class name of the instance metaclass, see
+L<Class::MOP::Instance> for more information on the instance
+metaclass.
-=item B<rebless_instance($instance, ?%params)>
+=item B<< $metaclass->get_meta_instance >>
-This will change the class of C<$instance> to the class of the invoking
-C<Class::MOP::Class>. You may only rebless the instance to a subclass of
-itself. You may pass in optional C<%params> which are like constructor
-params and will override anything already defined in the instance.
+Returns an instance of the C<instance_metaclass> to be used in the
+construction of a new instance of the class.
=back
-=head2 Informational
+=head2 Informational predicates
-These are a few predicate methods for asking information about the class.
+These are a few predicate methods for asking information about the
+class itself.
=over 4
-=item B<is_anon_class>
+=item B<< $metaclass->is_anon_class >>
-This returns true if the class is a C<Class::MOP::Class> created anon class.
+This returns true if the class was created by calling C<<
+Class::MOP::Class->create_anon_class >>.
-=item B<is_mutable>
+=item B<< $metaclass->is_mutable >>
This returns true if the class is still mutable.
-=item B<is_immutable>
+=item B<< $metaclass->is_immutable >>
This returns true if the class has been made immutable.
-=item B<is_pristine>
+=item B<< $metaclass->is_pristine >>
-Checks whether the class has any data that will be lost if C<reinitialize> is
-called.
+A class is I<not> pristine if it has non-inherited attributes or if it
+has any generated methods.
=back
=over 4
-=item B<superclasses (?@superclasses)>
+=item B<< $metaclass->superclasses(@superclasses) >>
-This is a read-write attribute which represents the superclass
-relationships of the class the B<Class::MOP::Class> instance is
-associated with. Basically, it can get and set the C<@ISA> for you.
+This is a read-write accessor which represents the superclass
+relationships of the metaclass's class.
-=item B<class_precedence_list>
+This is basically sugar around getting and setting C<@ISA>.
-This computes the a list of all the class's ancestors in the same order
-in which method dispatch will be done. This is similair to what
-B<Class::ISA::super_path> does, but we don't remove duplicate names.
+=item B<< $metaclass->class_precedence_list >>
-=item B<linearized_isa>
+This returns a list of all of the class's ancestor classes. The
+classes are returned in method dispatch order.
-This returns a list based on C<class_precedence_list> but with all
+=item B<< $metaclass->linearized_isa >>
+
+This returns a list based on C<class_precedence_list> but with all
duplicates removed.
-=item B<subclasses>
+=item B<< $metaclass->subclasses >>
-This returns a list of subclasses for this class.
+This returns a list of subclasses for this class.
=back
-=head2 Methods
+=head2 Method introspection and creation
-=over 4
+These methods allow you to introspect a class's methods, as well as
+add, remove, or change methods.
-=item B<get_method_map>
+Determining what is truly a method in a Perl 5 class requires some
+heuristics (aka guessing).
-Returns a HASH ref of name to CODE reference mapping for this class.
+Methods defined outside the package with a fully qualified name (C<sub
+Package::name { ... }>) will be included. Similarly, methods named
+with a fully qualified name using L<Sub::Name> are also included.
-=item B<method_metaclass>
+However, we attempt to ignore imported functions.
-Returns the class name of the method metaclass, see L<Class::MOP::Method>
-for more information on the method metaclasses.
+Ultimately, we are using heuristics to determine what truly is a
+method in a class, and these heuristics may get the wrong answer in
+some edge cases. However, for most "normal" cases the heuristics work
+correctly.
-=item B<wrap_method_body(%attrs)>
+=over 4
-Wrap a code ref (C<$attrs{body>) with C<method_metaclass>.
+=item B<< $metaclass->get_method($method_name) >>
-=item B<add_method ($method_name, $method)>
+This will return a L<Class::MOP::Method> for the specified
+C<$method_name>. If the class does not have the specified method, it
+returns C<undef>
-This will take a C<$method_name> and CODE reference or meta method
-objectand install it into the class's package.
+=item B<< $metaclass->has_method($method_name) >>
-You are strongly encouraged to pass a meta method object instead of a
-code reference. If you do so, that object gets stored as part of the
-class's method map, providing more useful information about the method
-for introspection.
+Returns a boolean indicating whether or not the class defines the
+named method. It does not include methods inherited from parent
+classes.
-When you provide a method object, this method will clone that object
-if the object's package name does not match the class name. This lets
-us track the original source of any methods added from other classes
-(notably Moose roles).
+=item B<< $metaclass->get_method_map >>
-B<NOTE>:
-This does absolutely nothing special to C<$method>
-other than use B<Sub::Name> to make sure it is tagged with the
-correct name, and therefore show up correctly in stack traces and
-such.
+Returns a hash reference representing the methods defined in this
+class. The keys are method names and the values are
+L<Class::MOP::Method> objects.
-=item B<has_method ($method_name)>
+=item B<< $metaclass->get_method_list >>
-This just provides a simple way to check if the class implements
-a specific C<$method_name>. It will I<not> however, attempt to check
-if the class inherits the method (use C<UNIVERSAL::can> for that).
+This will return a list of method I<names> for all methods defined in
+this class.
-This will correctly handle functions defined outside of the package
-that use a fully qualified name (C<sub Package::name { ... }>).
+=item B<< $metaclass->get_all_methods >>
-This will correctly handle functions renamed with B<Sub::Name> and
-installed using the symbol tables. However, if you are naming the
-subroutine outside of the package scope, you must use the fully
-qualified name, including the package name, for C<has_method> to
-correctly identify it.
+This will traverse the inheritance hierarchy and return a list of all
+the L<Class::MOP::Method> objects for this class and its parents.
-This will attempt to correctly ignore functions imported from other
-packages using B<Exporter>. It breaks down if the function imported
-is an C<__ANON__> sub (such as with C<use constant>), which very well
-may be a valid method being applied to the class.
+=item B<< $metaclass->find_method_by_name($method_name) >>
-In short, this method cannot always be trusted to determine if the
-C<$method_name> is actually a method. However, it will DWIM about
-90% of the time, so it's a small trade off I think.
+This will return a L<Class::MOP::Method> for the specified
+C<$method_name>. If the class does not have the specified method, it
+returns C<undef>
-=item B<get_method ($method_name)>
+Unlike C<get_method>, this method I<will> look for the named method in
+superclasses.
-This will return a Class::MOP::Method instance related to the specified
-C<$method_name>, or return undef if that method does not exist.
+=item B<< $metaclass->get_all_method_names >>
-The Class::MOP::Method is codifiable, so you can use it like a normal
-CODE reference, see L<Class::MOP::Method> for more information.
+This will return a list of method I<names> for all of this class's
+methods, including inherited methods.
-=item B<find_method_by_name ($method_name)>
+=item B<< $metaclass->find_all_methods_by_name($method_name) >>
-This will return a CODE reference of the specified C<$method_name>,
-or return undef if that method does not exist.
+This method looks for the named method in the class and all of its
+parents. It returns every matching method it finds in the inheritance
+tree, so it returns a list of methods.
-Unlike C<get_method> this will also look in the superclasses.
+Each method is returned as a hash reference with three keys. The keys
+are C<name>, C<class>, and C<code>. The C<code> key has a
+L<Class::MOP::Method> object as its value.
-=item B<remove_method ($method_name)>
+The list of methods is distinct.
-This will attempt to remove a given C<$method_name> from the class.
-It will return the CODE reference that it has removed, and will
-attempt to use B<Sub::Name> to clear the methods associated name.
+=item B<< $metaclass->find_next_method_by_name($method_name) >>
-=item B<get_method_list>
+This method returns the first method in any superclass matching the
+given name. It is effectively the method that C<SUPER::$method_name>
+would dispatch to.
-This will return a list of method names for all I<locally> defined
-methods. It does B<not> provide a list of all applicable methods,
-including any inherited ones. If you want a list of all applicable
-methods, use the C<compute_all_applicable_methods> method.
+=item B<< $metaclass->add_method($method_name, $method) >>
-=item B<get_all_methods>
+This method takes a method name and a subroutine reference, and adds
+the method to the class.
-This will traverse the inheritance heirachy and return a list of all
-the applicable L<Class::MOP::Method> objects for this class.
+The subroutine reference can be a L<Class::MOP::Method>, and you are
+strongly encouraged to pass a meta method object instead of a code
+reference. If you do so, that object gets stored as part of the
+class's method map directly. If not, the meta information will have to
+be recreated later, and may be incorrect.
-=item B<compute_all_applicable_methods>
+If you provide a method object, this method will clone that object if
+the object's package name does not match the class name. This lets us
+track the original source of any methods added from other classes
+(notably Moose roles).
-Deprecated.
+=item B<< $metaclass->remove_method($method_name) >>
-This method returns a list of hashes describing the all the methods of the
-class.
+Remove the named method from the class. This method returns the
+L<Class::MOP::Method> object for the method.
-Use L<get_all_methods>, which is easier/better/faster. This method predates
-L<Class::MOP::Method>.
+=item B<< $metaclass->method_metaclass >>
-=item B<find_all_methods_by_name ($method_name)>
+Returns the class name of the method metaclass, see
+L<Class::MOP::Method> for more information on the method metaclass.
-This will traverse the inheritence hierarchy and locate all methods
-with a given C<$method_name>. Similar to
-C<compute_all_applicable_methods> it returns a list of HASH references
-with the following information; method name (which will always be the
-same as C<$method_name>), the name of the class in which the method
-lives and a CODE reference for the actual method.
+=item B<< $metaclass->wrapped_method_metaclass >>
-The list of methods produced is a distinct list, meaning there are no
-duplicates in it. This is especially useful for things like object
-initialization and destruction where you only want the method called
-once, and in the correct order.
+Returns the class name of the wrapped method metaclass, see
+L<Class::MOP::Method::Wrapped> for more information on the wrapped
+method metaclass.
-=item B<find_next_method_by_name ($method_name)>
+=back
-This will return the first method to match a given C<$method_name> in
-the superclasses, this is basically equivalent to calling
-C<SUPER::$method_name>, but it can be dispatched at runtime.
+=head2 Attribute introspection and creation
-=item B<alias_method ($method_name, $method)>
+Because Perl 5 does not have a core concept of attributes in classes,
+we can only return information about attributes which have been added
+via this class's methods. We cannot discover information about
+attributes which are defined in terms of "regular" Perl 5 methods.
-B<NOTE>: This method is now deprecated. Just use C<add_method>
-instead.
+=over 4
-=back
+=item B<< $metaclass->get_attribute($attribute_name) >>
-=head2 Method Modifiers
+This will return a L<Class::MOP::Attribute> for the specified
+C<$attribute_name>. If the class does not have the specified
+attribute, it returns C<undef>
-Method modifiers are a concept borrowed from CLOS, in which a method
-can be wrapped with I<before>, I<after> and I<around> method modifiers
-that will be called everytime the method is called.
+=item B<< $metaclass->has_attribute($attribute_name) >>
-=head3 How method modifiers work?
+Returns a boolean indicating whether or not the class defines the
+named attribute. It does not include attributes inherited from parent
+classes.
-Method modifiers work by wrapping the original method and then replacing
-it in the classes symbol table. The wrappers will handle calling all the
-modifiers in the appropariate orders and preserving the calling context
-for the original method.
-
-Each method modifier serves a particular purpose, which may not be
-obvious to users of other method wrapping modules. To start with, the
-return values of I<before> and I<after> modifiers are ignored. This is
-because thier purpose is B<not> to filter the input and output of the
-primary method (this is done with an I<around> modifier). This may seem
-like an odd restriction to some, but doing this allows for simple code
-to be added at the begining or end of a method call without jeapordizing
-the normal functioning of the primary method or placing any extra
-responsibility on the code of the modifier. Of course if you have more
-complex needs, then use the I<around> modifier, which uses a variation
-of continutation passing style to allow for a high degree of flexibility.
-
-Before and around modifiers are called in last-defined-first-called order,
-while after modifiers are called in first-defined-first-called order. So
-the call tree might looks something like this:
+=item B<< $metaclass->get_attribute_map >>
- before 2
- before 1
- around 2
- around 1
- primary
- after 1
- after 2
+Returns a hash reference representing the attributes defined in this
+class. The keys are attribute names and the values are
+L<Class::MOP::Attribute> objects.
-To see examples of using method modifiers, see the following examples
-included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
-F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
-classic CLOS usage example in the test F<017_add_method_modifier.t>.
+=item B<< $metaclass->get_attribute_list >>
-=head3 What is the performance impact?
+This will return a list of attributes I<names> for all attributes
+defined in this class.
-Of course there is a performance cost associated with method modifiers,
-but we have made every effort to make that cost be directly proportional
-to the amount of modifier features you utilize.
+=item B<< $metaclass->get_all_attributes >>
-The wrapping method does it's best to B<only> do as much work as it
-absolutely needs to. In order to do this we have moved some of the
-performance costs to set-up time, where they are easier to amortize.
+This will traverse the inheritance hierarchy and return a list of all
+the L<Class::MOP::Attribute> objects for this class and its parents.
-All this said, my benchmarks have indicated the following:
+=item B<< $metaclass->find_attribute_by_name($attribute_name) >>
- simple wrapper with no modifiers 100% slower
- simple wrapper with simple before modifier 400% slower
- simple wrapper with simple after modifier 450% slower
- simple wrapper with simple around modifier 500-550% slower
- simple wrapper with all 3 modifiers 1100% slower
+This will return a L<Class::MOP::Attribute> for the specified
+C<$attribute_name>. If the class does not have the specified
+attribute, it returns C<undef>
-These numbers may seem daunting, but you must remember, every feature
-comes with some cost. To put things in perspective, just doing a simple
-C<AUTOLOAD> which does nothing but extract the name of the method called
-and return it costs about 400% over a normal method call.
+Unlike C<get_attribute>, this attribute I<will> look for the named
+attribute in superclasses.
-=over 4
+=item B<< $metaclass->add_attribute(...) >>
+
+This method accepts either an existing L<Class::MOP::Attribute>
+object, or parameters suitable for passing to that class's C<new>
+method.
+
+The attribute provided will be added to the class.
-=item B<add_before_method_modifier ($method_name, $code)>
+Any accessor methods defined by the attribute will be added to the
+class when the attribute is added.
-This will wrap the method at C<$method_name> and the supplied C<$code>
-will be passed the C<@_> arguments, and called before the original
-method is called. As specified above, the return value of the I<before>
-method modifiers is ignored, and it's ability to modify C<@_> is
-fairly limited. If you need to do either of these things, use an
-C<around> method modifier.
+If an attribute of the same name already exists, the old attribute
+will be removed first.
-=item B<add_after_method_modifier ($method_name, $code)>
+=item B<< $metaclass->remove_attribute($attribute_name) >>
-This will wrap the method at C<$method_name> so that the original
-method will be called, it's return values stashed, and then the
-supplied C<$code> will be passed the C<@_> arguments, and called.
-As specified above, the return value of the I<after> method
-modifiers is ignored, and it cannot modify the return values of
-the original method. If you need to do either of these things, use an
-C<around> method modifier.
+This will remove the named attribute from the class, and
+L<Class::MOP::Attribute> object.
-=item B<add_around_method_modifier ($method_name, $code)>
+Removing an attribute also removes any accessor methods defined by the
+attribute.
-This will wrap the method at C<$method_name> so that C<$code>
-will be called and passed the original method as an extra argument
-at the begining of the C<@_> argument list. This is a variation of
-continuation passing style, where the function prepended to C<@_>
-can be considered a continuation. It is up to C<$code> if it calls
-the original method or not, there is no restriction on what the
-C<$code> can or cannot do.
+However, note that removing an attribute will only affect I<future>
+object instances created for this class, not existing instances.
+
+=item B<< $metaclass->attribute_metaclass >>
+
+Returns the class name of the attribute metaclass for this class. By
+default, this is L<Class::MOP::Attribute>. for more information on
=back
-=head2 Attributes
+=head2 Class Immutability
-It should be noted that since there is no one consistent way to define
-the attributes of a class in Perl 5. These methods can only work with
-the information given, and can not easily discover information on
-their own. See L<Class::MOP::Attribute> for more details.
+Making a class immutable "freezes" the class definition. You can no
+longer call methods which alter the class, such as adding or removing
+methods or attributes.
-=over 4
+Making a class immutable lets us optimize the class by inlining some
+methods, and also allows us to optimize some methods on the metaclass
+object itself.
-=item B<attribute_metaclass>
+The immutabilization system in L<Moose> takes much greater advantage
+of the inlining features than Class::MOP itself does.
-Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
-for more information on the attribute metaclasses.
+=over 4
-=item B<get_attribute_map>
+=item B<< $metaclass->make_immutable(%options) >>
-This returns a HASH ref of name to attribute meta-object mapping.
+This method will create an immutable transformer and uses it to make
+the class and its metaclass object immutable.
-=item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
+Details of how immutabilization works are in L<Class::MOP::Immutable>
+documentation.
-This stores the C<$attribute_meta_object> (or creates one from the
-C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
-instance associated with the given class. Unlike methods, attributes
-within the MOP are stored as meta-information only. They will be used
-later to construct instances from (see C<construct_instance> above).
-More details about the attribute meta-objects can be found in the
-L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
-section.
+=item B<< $metaclass->make_mutable >>
-It should be noted that any accessor, reader/writer or predicate
-methods which the C<$attribute_meta_object> has will be installed
-into the class at this time.
+Calling this method reverse the immutabilization transformation.
-B<NOTE>
-If an attribute already exists for C<$attribute_name>, the old one
-will be removed (as well as removing all it's accessors), and then
-the new one added.
+=item B<< $metaclass->immutable_transformer >>
-=item B<has_attribute ($attribute_name)>
+If the class has been made immutable previously, this returns the
+L<Class::MOP::Immutable> object that was created to do the
+transformation.
-Checks to see if this class has an attribute by the name of
-C<$attribute_name> and returns a boolean.
+If the class was never made immutable, this method will die.
-=item B<get_attribute ($attribute_name)>
+=back
-Returns the attribute meta-object associated with C<$attribute_name>,
-if none is found, it will return undef.
+=head2 Method Modifiers
-=item B<remove_attribute ($attribute_name)>
+Method modifiers are hooks which allow a method to be wrapped with
+I<before>, I<after> and I<around> method modifiers. Every time a
+method is called, it's modifiers are also called.
-This will remove the attribute meta-object stored at
-C<$attribute_name>, then return the removed attribute meta-object.
+A class can modify its own methods, as well as methods defined in
+parent classes.
-B<NOTE:>
-Removing an attribute will only affect future instances of
-the class, it will not make any attempt to remove the attribute from
-any existing instances of the class.
+=head3 How method modifiers work?
+
+Method modifiers work by wrapping the original method and then
+replacing it in the class's symbol table. The wrappers will handle
+calling all the modifiers in the appropriate order and preserving the
+calling context for the original method.
-It should be noted that any accessor, reader/writer or predicate
-methods which the attribute meta-object stored at C<$attribute_name>
-has will be removed from the class at this time. This B<will> make
-these attributes somewhat inaccessable in previously created
-instances. But if you are crazy enough to do this at runtime, then
-you are crazy enough to deal with something like this :).
+The return values of C<before> and C<after> modifiers are
+ignored. This is because their purpose is B<not> to filter the input
+and output of the primary method (this is done with an I<around>
+modifier).
-=item B<get_attribute_list>
+This may seem like an odd restriction to some, but doing this allows
+for simple code to be added at the beginning or end of a method call
+without altering the function of the wrapped method or placing any
+extra responsibility on the code of the modifier.
-This returns a list of attribute names which are defined in the local
-class. If you want a list of all applicable attributes for a class,
-use the C<compute_all_applicable_attributes> method.
+Of course if you have more complex needs, you can use the C<around>
+modifier which allows you to change both the parameters passed to the
+wrapped method, as well as its return value.
-=item B<compute_all_applicable_attributes>
+Before and around modifiers are called in last-defined-first-called
+order, while after modifiers are called in first-defined-first-called
+order. So the call tree might looks something like this:
-=item B<get_all_attributes>
+ before 2
+ before 1
+ around 2
+ around 1
+ primary
+ around 1
+ around 2
+ after 1
+ after 2
-This will traverse the inheritance heirachy and return a list of all
-the applicable L<Class::MOP::Attribute> objects for this class.
+=head3 What is the performance impact?
-C<get_all_attributes> is an alias for consistency with C<get_all_methods>.
+Of course there is a performance cost associated with method
+modifiers, but we have made every effort to make that cost directly
+proportional to the number of modifier features you utilize.
-=item B<find_attribute_by_name ($attr_name)>
+The wrapping method does it's best to B<only> do as much work as it
+absolutely needs to. In order to do this we have moved some of the
+performance costs to set-up time, where they are easier to amortize.
-This method will traverse the inheritance heirachy and find the
-first attribute whose name matches C<$attr_name>, then return it.
-It will return undef if nothing is found.
+All this said, our benchmarks have indicated the following:
-=back
+ simple wrapper with no modifiers 100% slower
+ simple wrapper with simple before modifier 400% slower
+ simple wrapper with simple after modifier 450% slower
+ simple wrapper with simple around modifier 500-550% slower
+ simple wrapper with all 3 modifiers 1100% slower
-=head2 Class Immutability
+These numbers may seem daunting, but you must remember, every feature
+comes with some cost. To put things in perspective, just doing a
+simple C<AUTOLOAD> which does nothing but extract the name of the
+method called and return it costs about 400% over a normal method
+call.
=over 4
-=item B<make_immutable (%options)>
+=item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
+
+This wraps the specified method with the supplied subroutine
+reference. The modifier will be called as a method itself, and will
+receive the same arguments as are passed to the method.
+
+When the modifier exits, the wrapped method will be called.
+
+The return value of the modifier will be ignored.
+
+=item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
+
+This wraps the specified method with the supplied subroutine
+reference. The modifier will be called as a method itself, and will
+receive the same arguments as are passed to the method.
-This method will invoke a tranforamtion upon the class which will
-make it immutable. Details of this transformation can be found in
-the L<Class::MOP::Immutable> documentation.
+When the wrapped methods exits, the modifier will be called.
-=item B<make_mutable>
+The return value of the modifier will be ignored.
-This method will reverse tranforamtion upon the class which
-made it immutable.
+=item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
-=item B<get_immutable_transformer>
+This wraps the specified method with the supplied subroutine
+reference.
-Return a transformer suitable for making this class immutable or, if this
-class is immutable, the transformer used to make it immutable.
+The first argument passed to the modifier will be a subroutine
+reference to the wrapped method. The second argument is the object,
+and after that come any arguments passed when the method is called.
-=item B<get_immutable_options>
+The around modifier can choose to call the original method, as well as
+what arguments to pass if it does so.
+
+The return value of the modifier is what will be seen by the caller.
+
+=back
+
+=head2 Introspection
+
+=over 4
-If the class is immutable, return the options used to make it immutable.
+=item B<< Class::MOP::Class->meta >>
-=item B<create_immutable_transformer>
+This will return a L<Class::MOP::Class> instance for this class.
-Create a transformer suitable for making this class immutable
+It should also be noted that L<Class::MOP> will actually bootstrap
+this module by installing a number of attribute meta-objects into its
+metaclass.
=back
=head1 COPYRIGHT AND LICENSE
-Copyright 2006-2008 by Infinity Interactive, Inc.
+Copyright 2006-2009 by Infinity Interactive, Inc.
L<http://www.iinteractive.com>
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