use strict;
use warnings;
-use Carp 'confess';
-use Scalar::Util 'weaken';
+use 5.008;
+
+use MRO::Compat;
+
+use Carp 'confess';
+use Devel::GlobalDestruction qw( in_global_destruction );
+use Scalar::Util 'weaken', 'reftype', 'blessed';
+use Sub::Name qw( subname );
use Class::MOP::Class;
use Class::MOP::Attribute;
use Class::MOP::Method;
-use Class::MOP::Class::Immutable;
+use Class::MOP::Immutable;
+
+BEGIN {
+ *IS_RUNNING_ON_5_10 = ($] < 5.009_005)
+ ? sub () { 0 }
+ : sub () { 1 };
+
+ sub HAVE_ISAREV () {
+ Carp::cluck("Class::MOP::HAVE_ISAREV is deprecated and will be removed in a future release. It has always returned 1 anyway.");
+ return 1;
+ }
-our $VERSION = '0.35';
+ # this is either part of core or set up appropriately by MRO::Compat
+ *check_package_cache_flag = \&mro::get_pkg_gen;
+}
+
+our $VERSION = '0.82';
+our $XS_VERSION = $VERSION;
+$VERSION = eval $VERSION;
our $AUTHORITY = 'cpan:STEVAN';
+require XSLoader;
+XSLoader::load( __PACKAGE__, $XS_VERSION );
+
+
{
# Metaclasses are singletons, so we cache them here.
# there is no need to worry about destruction though
# because they should die only when the program dies.
# After all, do package definitions even get reaped?
- my %METAS;
-
- # means of accessing all the metaclasses that have
+ my %METAS;
+
+ # means of accessing all the metaclasses that have
# been initialized thus far (for mugwumps obj browser)
- sub get_all_metaclasses { %METAS }
- sub get_all_metaclass_instances { values %METAS }
- sub get_all_metaclass_names { keys %METAS }
+ sub get_all_metaclasses { %METAS }
+ sub get_all_metaclass_instances { values %METAS }
+ sub get_all_metaclass_names { keys %METAS }
sub get_metaclass_by_name { $METAS{$_[0]} }
- sub store_metaclass_by_name { $METAS{$_[0]} = $_[1] }
- sub weaken_metaclass { weaken($METAS{$_[0]}) }
+ sub store_metaclass_by_name { $METAS{$_[0]} = $_[1] }
+ sub weaken_metaclass { weaken($METAS{$_[0]}) }
sub does_metaclass_exist { exists $METAS{$_[0]} && defined $METAS{$_[0]} }
- sub remove_metaclass_by_name { $METAS{$_[0]} = undef }
-
+ sub remove_metaclass_by_name { $METAS{$_[0]} = undef }
+
+ # This handles instances as well as class names
+ sub class_of {
+ return unless defined $_[0];
+ my $class = blessed($_[0]) || $_[0];
+ return $METAS{$class};
+ }
+
# NOTE:
- # We only cache metaclasses, meaning instances of
- # Class::MOP::Class. We do not cache instance of
+ # We only cache metaclasses, meaning instances of
+ # Class::MOP::Class. We do not cache instance of
# Class::MOP::Package or Class::MOP::Module. Mostly
- # because I don't yet see a good reason to do so.
+ # because I don't yet see a good reason to do so.
+}
+
+sub _class_to_pmfile {
+ my $class = shift;
+
+ my $file = $class . '.pm';
+ $file =~ s{::}{/}g;
+
+ return $file;
+}
+
+sub load_first_existing_class {
+ my @classes = @_
+ or return;
+
+ foreach my $class (@classes) {
+ unless ( _is_valid_class_name($class) ) {
+ my $display = defined($class) ? $class : 'undef';
+ confess "Invalid class name ($display)";
+ }
+ }
+
+ my $found;
+ my %exceptions;
+ for my $class (@classes) {
+ my $pmfile = _class_to_pmfile($class);
+ my $e = _try_load_one_class($class);
+
+ if ($e) {
+ $exceptions{$class} = $e;
+ last if $e !~ /^Can't locate \Q$pmfile\E in \@INC/;
+ }
+ else {
+ $found = $class;
+ last;
+ }
+ }
+
+ return $found if $found;
+
+ confess join(
+ "\n",
+ map {
+ sprintf(
+ "Could not load class (%s) because : %s", $_,
+ $exceptions{$_}
+ )
+ }
+ grep {
+ exists $exceptions{$_}
+ } @classes
+ );
+}
+
+sub _try_load_one_class {
+ my $class = shift;
+
+ return if is_class_loaded($class);
+
+ my $file = _class_to_pmfile($class);
+
+ return do {
+ local $@;
+ eval { require($file) };
+ $@;
+ };
+}
+
+sub load_class {
+ my $class = load_first_existing_class($_[0]);
+ return get_metaclass_by_name($class) || $class;
+}
+
+sub _is_valid_class_name {
+ my $class = shift;
+
+ return 0 if ref($class);
+ return 0 unless defined($class);
+ return 0 unless length($class);
+
+ return 1 if $class =~ /^\w+(?:::\w+)*$/;
+
+ return 0;
}
## ----------------------------------------------------------------------------
## Setting up our environment ...
## ----------------------------------------------------------------------------
-## Class::MOP needs to have a few things in the global perl environment so
+## Class::MOP needs to have a few things in the global perl environment so
## that it can operate effectively. Those things are done here.
## ----------------------------------------------------------------------------
# ... nothing yet actually ;)
## ----------------------------------------------------------------------------
-## Bootstrapping
+## Bootstrapping
## ----------------------------------------------------------------------------
-## The code below here is to bootstrap our MOP with itself. This is also
+## The code below here is to bootstrap our MOP with itself. This is also
## sometimes called "tying the knot". By doing this, we make it much easier
## to extend the MOP through subclassing and such since now you can use the
-## MOP itself to extend itself.
-##
+## MOP itself to extend itself.
+##
## Yes, I know, thats weird and insane, but it's a good thing, trust me :)
-## ----------------------------------------------------------------------------
+## ----------------------------------------------------------------------------
-# We need to add in the meta-attributes here so that
-# any subclass of Class::MOP::* will be able to
-# inherit them using &construct_instance
+# We need to add in the meta-attributes here so that
+# any subclass of Class::MOP::* will be able to
+# inherit them using _construct_instance
## --------------------------------------------------------
## Class::MOP::Package
Class::MOP::Package->meta->add_attribute(
- Class::MOP::Attribute->new('$:package' => (
+ Class::MOP::Attribute->new('package' => (
reader => {
- # NOTE: we need to do this in order
- # for the instance meta-object to
+ # NOTE: we need to do this in order
+ # for the instance meta-object to
# not fall into meta-circular death
- #
+ #
# we just alias the original method
- # rather than re-produce it here
+ # rather than re-produce it here
'name' => \&Class::MOP::Package::name
},
- init_arg => ':package',
))
);
Class::MOP::Package->meta->add_attribute(
- Class::MOP::Attribute->new('%:namespace' => (
+ Class::MOP::Attribute->new('namespace' => (
reader => {
# NOTE:
# we just alias the original method
# rather than re-produce it here
'namespace' => \&Class::MOP::Package::namespace
},
- # NOTE:
- # protect this from silliness
- init_arg => '!............( DO NOT DO THIS )............!',
+ init_arg => undef,
default => sub { \undef }
))
);
-# NOTE:
-# use the metaclass to construct the meta-package
-# which is a superclass of the metaclass itself :P
-Class::MOP::Package->meta->add_method('initialize' => sub {
- my $class = shift;
- my $package_name = shift;
- $class->meta->new_object(':package' => $package_name, @_);
-});
-
## --------------------------------------------------------
## Class::MOP::Module
# NOTE:
-# yeah this is kind of stretching things a bit,
+# yeah this is kind of stretching things a bit,
# but truthfully the version should be an attribute
-# of the Module, the weirdness comes from having to
-# stick to Perl 5 convention and store it in the
-# $VERSION package variable. Basically if you just
-# squint at it, it will look how you want it to look.
+# of the Module, the weirdness comes from having to
+# stick to Perl 5 convention and store it in the
+# $VERSION package variable. Basically if you just
+# squint at it, it will look how you want it to look.
# Either as a package variable, or as a attribute of
# the metaclass, isn't abstraction great :)
Class::MOP::Module->meta->add_attribute(
- Class::MOP::Attribute->new('$:version' => (
+ Class::MOP::Attribute->new('version' => (
reader => {
# NOTE:
# we just alias the original method
- # rather than re-produce it here
+ # rather than re-produce it here
'version' => \&Class::MOP::Module::version
},
- # NOTE:
- # protect this from silliness
- init_arg => '!............( DO NOT DO THIS )............!',
+ init_arg => undef,
default => sub { \undef }
))
);
# NOTE:
-# By following the same conventions as version here,
-# we are opening up the possibility that people can
-# use the $AUTHORITY in non-Class::MOP modules as
-# well.
+# By following the same conventions as version here,
+# we are opening up the possibility that people can
+# use the $AUTHORITY in non-Class::MOP modules as
+# well.
Class::MOP::Module->meta->add_attribute(
- Class::MOP::Attribute->new('$:authority' => (
+ Class::MOP::Attribute->new('authority' => (
reader => {
# NOTE:
# we just alias the original method
- # rather than re-produce it here
+ # rather than re-produce it here
'authority' => \&Class::MOP::Module::authority
- },
- # NOTE:
- # protect this from silliness
- init_arg => '!............( DO NOT DO THIS )............!',
+ },
+ init_arg => undef,
default => sub { \undef }
))
);
## Class::MOP::Class
Class::MOP::Class->meta->add_attribute(
- Class::MOP::Attribute->new('%:attributes' => (
+ Class::MOP::Attribute->new('attributes' => (
reader => {
- # NOTE: we need to do this in order
- # for the instance meta-object to
- # not fall into meta-circular death
- #
+ # NOTE: we need to do this in order
+ # for the instance meta-object to
+ # not fall into meta-circular death
+ #
# we just alias the original method
- # rather than re-produce it here
+ # rather than re-produce it here
'get_attribute_map' => \&Class::MOP::Class::get_attribute_map
},
- init_arg => ':attributes',
default => sub { {} }
))
);
Class::MOP::Class->meta->add_attribute(
- Class::MOP::Attribute->new('%:methods' => (
- reader => {
+ Class::MOP::Attribute->new('methods' => (
+ reader => {
# NOTE:
# we just alias the original method
- # rather than re-produce it here
+ # rather than re-produce it here
'get_method_map' => \&Class::MOP::Class::get_method_map
},
default => sub { {} }
);
Class::MOP::Class->meta->add_attribute(
- Class::MOP::Attribute->new('$:attribute_metaclass' => (
- reader => {
+ Class::MOP::Attribute->new('superclasses' => (
+ accessor => {
+ # NOTE:
+ # we just alias the original method
+ # rather than re-produce it here
+ 'superclasses' => \&Class::MOP::Class::superclasses
+ },
+ init_arg => undef,
+ default => sub { \undef }
+ ))
+);
+
+Class::MOP::Class->meta->add_attribute(
+ Class::MOP::Attribute->new('attribute_metaclass' => (
+ reader => {
# NOTE:
# we just alias the original method
- # rather than re-produce it here
+ # rather than re-produce it here
'attribute_metaclass' => \&Class::MOP::Class::attribute_metaclass
- },
- init_arg => ':attribute_metaclass',
+ },
default => 'Class::MOP::Attribute',
))
);
Class::MOP::Class->meta->add_attribute(
- Class::MOP::Attribute->new('$:method_metaclass' => (
- reader => {
+ Class::MOP::Attribute->new('method_metaclass' => (
+ reader => {
# NOTE:
# we just alias the original method
- # rather than re-produce it here
+ # rather than re-produce it here
'method_metaclass' => \&Class::MOP::Class::method_metaclass
},
- init_arg => ':method_metaclass',
- default => 'Class::MOP::Method',
+ default => 'Class::MOP::Method',
))
);
Class::MOP::Class->meta->add_attribute(
- Class::MOP::Attribute->new('$:instance_metaclass' => (
+ Class::MOP::Attribute->new('wrapped_method_metaclass' => (
reader => {
- # NOTE: we need to do this in order
- # for the instance meta-object to
- # not fall into meta-circular death
- #
+ # NOTE:
# we just alias the original method
- # rather than re-produce it here
+ # rather than re-produce it here
+ 'wrapped_method_metaclass' => \&Class::MOP::Class::wrapped_method_metaclass
+ },
+ default => 'Class::MOP::Method::Wrapped',
+ ))
+);
+
+Class::MOP::Class->meta->add_attribute(
+ Class::MOP::Attribute->new('instance_metaclass' => (
+ reader => {
+ # NOTE: we need to do this in order
+ # for the instance meta-object to
+ # not fall into meta-circular death
+ #
+ # we just alias the original method
+ # rather than re-produce it here
'instance_metaclass' => \&Class::MOP::Class::instance_metaclass
},
- init_arg => ':instance_metaclass',
- default => 'Class::MOP::Instance',
+ default => 'Class::MOP::Instance',
+ ))
+);
+
+Class::MOP::Class->meta->add_attribute(
+ Class::MOP::Attribute->new('immutable_transformer' => (
+ reader => {
+ 'immutable_transformer' => \&Class::MOP::Class::immutable_transformer
+ },
+ writer => {
+ '_set_immutable_transformer' => \&Class::MOP::Class::_set_immutable_transformer
+ },
))
);
# NOTE:
-# we don't actually need to tie the knot with
-# Class::MOP::Class here, it is actually handled
-# within Class::MOP::Class itself in the
-# construct_class_instance method.
+# we don't actually need to tie the knot with
+# Class::MOP::Class here, it is actually handled
+# within Class::MOP::Class itself in the
+# _construct_class_instance method.
## --------------------------------------------------------
## Class::MOP::Attribute
Class::MOP::Attribute->meta->add_attribute(
Class::MOP::Attribute->new('name' => (
- reader => {
- # NOTE: we need to do this in order
- # for the instance meta-object to
- # not fall into meta-circular death
- #
+ reader => {
+ # NOTE: we need to do this in order
+ # for the instance meta-object to
+ # not fall into meta-circular death
+ #
# we just alias the original method
- # rather than re-produce it here
+ # rather than re-produce it here
'name' => \&Class::MOP::Attribute::name
}
))
Class::MOP::Attribute->meta->add_attribute(
Class::MOP::Attribute->new('associated_class' => (
- reader => {
- # NOTE: we need to do this in order
- # for the instance meta-object to
- # not fall into meta-circular death
- #
+ reader => {
+ # NOTE: we need to do this in order
+ # for the instance meta-object to
+ # not fall into meta-circular death
+ #
# we just alias the original method
- # rather than re-produce it here
+ # rather than re-produce it here
'associated_class' => \&Class::MOP::Attribute::associated_class
}
))
);
Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('initializer' => (
+ reader => { 'initializer' => \&Class::MOP::Attribute::initializer },
+ predicate => { 'has_initializer' => \&Class::MOP::Attribute::has_initializer },
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('definition_context' => (
+ reader => { 'definition_context' => \&Class::MOP::Attribute::definition_context },
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
Class::MOP::Attribute->new('writer' => (
reader => { 'writer' => \&Class::MOP::Attribute::writer },
predicate => { 'has_writer' => \&Class::MOP::Attribute::has_writer },
);
Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('builder' => (
+ reader => { 'builder' => \&Class::MOP::Attribute::builder },
+ predicate => { 'has_builder' => \&Class::MOP::Attribute::has_builder },
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
Class::MOP::Attribute->new('init_arg' => (
reader => { 'init_arg' => \&Class::MOP::Attribute::init_arg },
predicate => { 'has_init_arg' => \&Class::MOP::Attribute::has_init_arg },
Class::MOP::Attribute->meta->add_attribute(
Class::MOP::Attribute->new('default' => (
# default has a custom 'reader' method ...
- predicate => { 'has_default' => \&Class::MOP::Attribute::has_default },
- ))
-);
-
-
-# NOTE: (meta-circularity)
-# This should be one of the last things done
-# it will "tie the knot" with Class::MOP::Attribute
-# so that it uses the attributes meta-objects
-# to construct itself.
-Class::MOP::Attribute->meta->add_method('new' => sub {
- my $class = shift;
- my $name = shift;
- my %options = @_;
-
- (defined $name && $name)
- || confess "You must provide a name for the attribute";
- $options{init_arg} = $name
- if not exists $options{init_arg};
-
- (Class::MOP::Attribute::is_default_a_coderef(\%options))
- || confess("References are not allowed as default values, you must ".
- "wrap then in a CODE reference (ex: sub { [] } and not [])")
- if exists $options{default} && ref $options{default};
-
- # return the new object
- $class->meta->new_object(name => $name, %options);
-});
+ predicate => { 'has_default' => \&Class::MOP::Attribute::has_default },
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('associated_methods' => (
+ reader => { 'associated_methods' => \&Class::MOP::Attribute::associated_methods },
+ default => sub { [] }
+ ))
+);
Class::MOP::Attribute->meta->add_method('clone' => sub {
my $self = shift;
- $self->meta->clone_object($self, @_);
+ $self->meta->clone_object($self, @_);
});
## --------------------------------------------------------
## Class::MOP::Method
-
Class::MOP::Method->meta->add_attribute(
Class::MOP::Attribute->new('body' => (
- reader => { 'body' => \&Class::MOP::Method::body },
+ reader => { 'body' => \&Class::MOP::Method::body },
+ ))
+);
+
+Class::MOP::Method->meta->add_attribute(
+ Class::MOP::Attribute->new('associated_metaclass' => (
+ reader => { 'associated_metaclass' => \&Class::MOP::Method::associated_metaclass },
+ ))
+);
+
+Class::MOP::Method->meta->add_attribute(
+ Class::MOP::Attribute->new('package_name' => (
+ reader => { 'package_name' => \&Class::MOP::Method::package_name },
))
);
+Class::MOP::Method->meta->add_attribute(
+ Class::MOP::Attribute->new('name' => (
+ reader => { 'name' => \&Class::MOP::Method::name },
+ ))
+);
+
+Class::MOP::Method->meta->add_attribute(
+ Class::MOP::Attribute->new('original_method' => (
+ reader => { 'original_method' => \&Class::MOP::Method::original_method },
+ writer => { '_set_original_method' => \&Class::MOP::Method::_set_original_method },
+ ))
+);
+
+Class::MOP::Method->meta->add_method('clone' => sub {
+ my $self = shift;
+ my $clone = $self->meta->clone_object($self, @_);
+ $clone->_set_original_method($self);
+ return $clone;
+});
+
## --------------------------------------------------------
## Class::MOP::Method::Wrapped
# NOTE:
-# the way this item is initialized, this
-# really does not follow the standard
-# practices of attributes, but we put
+# the way this item is initialized, this
+# really does not follow the standard
+# practices of attributes, but we put
# it here for completeness
Class::MOP::Method::Wrapped->meta->add_attribute(
Class::MOP::Attribute->new('modifier_table')
);
## --------------------------------------------------------
+## Class::MOP::Method::Generated
+
+Class::MOP::Method::Generated->meta->add_attribute(
+ Class::MOP::Attribute->new('is_inline' => (
+ reader => { 'is_inline' => \&Class::MOP::Method::Generated::is_inline },
+ default => 0,
+ ))
+);
+
+Class::MOP::Method::Generated->meta->add_attribute(
+ Class::MOP::Attribute->new('definition_context' => (
+ reader => { 'definition_context' => \&Class::MOP::Method::Generated::definition_context },
+ ))
+);
+
+## --------------------------------------------------------
+## Class::MOP::Method::Accessor
+
+Class::MOP::Method::Accessor->meta->add_attribute(
+ Class::MOP::Attribute->new('attribute' => (
+ reader => {
+ 'associated_attribute' => \&Class::MOP::Method::Accessor::associated_attribute
+ },
+ ))
+);
+
+Class::MOP::Method::Accessor->meta->add_attribute(
+ Class::MOP::Attribute->new('accessor_type' => (
+ reader => { 'accessor_type' => \&Class::MOP::Method::Accessor::accessor_type },
+ ))
+);
+
+## --------------------------------------------------------
+## Class::MOP::Method::Constructor
+
+Class::MOP::Method::Constructor->meta->add_attribute(
+ Class::MOP::Attribute->new('options' => (
+ reader => {
+ 'options' => \&Class::MOP::Method::Constructor::options
+ },
+ default => sub { +{} }
+ ))
+);
+
+Class::MOP::Method::Constructor->meta->add_attribute(
+ Class::MOP::Attribute->new('associated_metaclass' => (
+ init_arg => "metaclass", # FIXME alias and rename
+ reader => {
+ 'associated_metaclass' => \&Class::MOP::Method::Constructor::associated_metaclass
+ },
+ ))
+);
+
+## --------------------------------------------------------
## Class::MOP::Instance
# NOTE:
-# these don't yet do much of anything, but are just
+# these don't yet do much of anything, but are just
# included for completeness
Class::MOP::Instance->meta->add_attribute(
- Class::MOP::Attribute->new('meta')
+ Class::MOP::Attribute->new('associated_metaclass',
+ reader => { associated_metaclass => \&Class::MOP::Instance::associated_metaclass },
+ ),
+);
+
+Class::MOP::Instance->meta->add_attribute(
+ Class::MOP::Attribute->new('_class_name',
+ init_arg => undef,
+ reader => { _class_name => \&Class::MOP::Instance::_class_name },
+ #lazy => 1, # not yet supported by Class::MOP but out our version does it anyway
+ #default => sub { $_[0]->associated_metaclass->name },
+ ),
+);
+
+Class::MOP::Instance->meta->add_attribute(
+ Class::MOP::Attribute->new('attributes',
+ reader => { attributes => \&Class::MOP::Instance::get_all_attributes },
+ ),
+);
+
+Class::MOP::Instance->meta->add_attribute(
+ Class::MOP::Attribute->new('slots',
+ reader => { slots => \&Class::MOP::Instance::slots },
+ ),
);
Class::MOP::Instance->meta->add_attribute(
- Class::MOP::Attribute->new('slots')
+ Class::MOP::Attribute->new('slot_hash',
+ reader => { slot_hash => \&Class::MOP::Instance::slot_hash },
+ ),
);
+
+# we need the meta instance of the meta instance to be created now, in order
+# for the constructor to be able to use it
+Class::MOP::Instance->meta->get_meta_instance;
+
+# pretend the add_method never happenned. it hasn't yet affected anything
+undef Class::MOP::Instance->meta->{_package_cache_flag};
+
## --------------------------------------------------------
## Now close all the Class::MOP::* classes
-# NOTE:
-# we don't need to inline the
-# constructors or the accessors
-# this only lengthens the compile
-# time of the MOP, and gives us
-# no actual benefits.
+# NOTE: we don't need to inline the the accessors this only lengthens
+# the compile time of the MOP, and gives us no actual benefits.
$_->meta->make_immutable(
- inline_constructor => 0,
- inline_accessors => 0,
+ inline_constructor => 1,
+ replace_constructor => 1,
+ constructor_name => "_new",
+ inline_accessors => 0,
) for qw/
- Class::MOP::Package
- Class::MOP::Module
- Class::MOP::Class
-
+ Class::MOP::Package
+ Class::MOP::Module
+ Class::MOP::Class
+
Class::MOP::Attribute
- Class::MOP::Method
- Class::MOP::Instance
-
- Class::MOP::Object
+ Class::MOP::Method
+ Class::MOP::Instance
+
+ Class::MOP::Object
- Class::MOP::Attribute::Accessor
- Class::MOP::Method::Wrapped
+ Class::MOP::Method::Generated
+
+ Class::MOP::Method::Accessor
+ Class::MOP::Method::Constructor
+ Class::MOP::Method::Wrapped
/;
1;
=pod
-=head1 NAME
+=head1 NAME
Class::MOP - A Meta Object Protocol for Perl 5
-=head1 SYNOPSIS
-
- # ... This will come later, for now see
- # the other SYNOPSIS for more information
+=head1 DESCRIPTION
-=head1 DESCRIPTON
-
-This module is an attempt to create a meta object protocol for the
-Perl 5 object system. It makes no attempt to change the behavior or
-characteristics of the Perl 5 object system, only to create a
+This module is a fully functioning meta object protocol for the
+Perl 5 object system. It makes no attempt to change the behavior or
+characteristics of the Perl 5 object system, only to create a
protocol for its manipulation and introspection.
-That said, it does attempt to create the tools for building a rich
-set of extensions to the Perl 5 object system. Every attempt has been
-made for these tools to keep to the spirit of the Perl 5 object
-system that we all know and love.
+That said, it does attempt to create the tools for building a rich set
+of extensions to the Perl 5 object system. Every attempt has been made
+to abide by the spirit of the Perl 5 object system that we all know
+and love.
-This documentation is admittedly sparse on details, as time permits
-I will try to improve them. For now, I suggest looking at the items
-listed in the L<SEE ALSO> section for more information. In particular
-the book "The Art of the Meta Object Protocol" was very influential
-in the development of this system.
+This documentation is sparse on conceptual details. We suggest looking
+at the items listed in the L<SEE ALSO> section for more
+information. In particular the book "The Art of the Meta Object
+Protocol" was very influential in the development of this system.
=head2 What is a Meta Object Protocol?
-A meta object protocol is an API to an object system.
+A meta object protocol is an API to an object system.
+
+To be more specific, it abstracts the components of an object system
+(classes, object, methods, object attributes, etc.). These
+abstractions can then be used to inspect and manipulate the object
+system which they describe.
-To be more specific, it is a set of abstractions of the components of
-an object system (typically things like; classes, object, methods,
-object attributes, etc.). These abstractions can then be used to both
-inspect and manipulate the object system which they describe.
+It can be said that there are two MOPs for any object system; the
+implicit MOP and the explicit MOP. The implicit MOP handles things
+like method dispatch or inheritance, which happen automatically as
+part of how the object system works. The explicit MOP typically
+handles the introspection/reflection features of the object system.
-It can be said that there are two MOPs for any object system; the
-implicit MOP, and the explicit MOP. The implicit MOP handles things
-like method dispatch or inheritance, which happen automatically as
-part of how the object system works. The explicit MOP typically
-handles the introspection/reflection features of the object system.
-All object systems have implicit MOPs, without one, they would not
-work. Explict MOPs however as less common, and depending on the
-language can vary from restrictive (Reflection in Java or C#) to
-wide open (CLOS is a perfect example).
+All object systems have implicit MOPs. Without one, they would not
+work. Explicit MOPs are much less common, and depending on the
+language can vary from restrictive (Reflection in Java or C#) to wide
+open (CLOS is a perfect example).
-=head2 Yet Another Class Builder!! Why?
+=head2 Yet Another Class Builder! Why?
-This is B<not> a class builder so much as it is a I<class builder
-B<builder>>. My intent is that an end user does not use this module
-directly, but instead this module is used by module authors to
-build extensions and features onto the Perl 5 object system.
+This is B<not> a class builder so much as a I<class builder
+B<builder>>. The intent is that an end user will not use this module
+directly, but instead this module is used by module authors to build
+extensions and features onto the Perl 5 object system.
+
+This system is used by L<Moose>, which supplies a powerful class
+builder system built entirely on top of C<Class::MOP>.
=head2 Who is this module for?
-This module is specifically for anyone who has ever created or
-wanted to create a module for the Class:: namespace. The tools which
-this module will provide will hopefully make it easier to do more
-complex things with Perl 5 classes by removing such barriers as
-the need to hack the symbol tables, or understand the fine details
-of method dispatch.
+This module is for anyone who has ever created or wanted to create a
+module for the Class:: namespace. The tools which this module provides
+make doing complex Perl 5 wizardry simpler, by removing such barriers
+as the need to hack symbol tables, or understand the fine details of
+method dispatch.
=head2 What changes do I have to make to use this module?
-This module was designed to be as unintrusive as possible. Many of
-its features are accessible without B<any> change to your existsing
-code at all. It is meant to be a compliment to your existing code and
-not an intrusion on your code base. Unlike many other B<Class::>
-modules, this module B<does not> require you subclass it, or even that
-you C<use> it in within your module's package.
+This module was designed to be as unintrusive as possible. Many of its
+features are accessible without B<any> change to your existing
+code. It is meant to be a compliment to your existing code and not an
+intrusion on your code base. Unlike many other B<Class::> modules,
+this module B<does not> require you subclass it, or even that you
+C<use> it in within your module's package.
-The only features which requires additions to your code are the
+The only features which requires additions to your code are the
attribute handling and instance construction features, and these are
-both completely optional features. The only reason for this is because
-Perl 5's object system does not actually have these features built
+both completely optional features. The only reason for this is because
+Perl 5's object system does not actually have these features built
in. More information about this feature can be found below.
-=head2 A Note about Performance?
+=head2 About Performance
+
+It is a common misconception that explicit MOPs are a performance hit.
+This is not a universal truth, it is a side-effect of some specific
+implementations. For instance, using Java reflection is slow because
+the JVM cannot take advantage of any compiler optimizations, and the
+JVM has to deal with much more runtime type information as well.
-It is a common misconception that explict MOPs are performance drains.
-But this is not a universal truth at all, it is an side-effect of
-specific implementations. For instance, using Java reflection is much
-slower because the JVM cannot take advantage of any compiler
-optimizations, and the JVM has to deal with much more runtime type
-information as well. Reflection in C# is marginally better as it was
-designed into the language and runtime (the CLR). In contrast, CLOS
-(the Common Lisp Object System) was built to support an explicit MOP,
-and so performance is tuned for it.
+Reflection in C# is marginally better as it was designed into the
+language and runtime (the CLR). In contrast, CLOS (the Common Lisp
+Object System) was built to support an explicit MOP, and so
+performance is tuned for it.
-This library in particular does it's absolute best to avoid putting
-B<any> drain at all upon your code's performance. In fact, by itself
-it does nothing to affect your existing code. So you only pay for
-what you actually use.
+This library in particular does its absolute best to avoid putting
+B<any> drain at all upon your code's performance. In fact, by itself
+it does nothing to affect your existing code. So you only pay for what
+you actually use.
=head2 About Metaclass compatibility
-This module makes sure that all metaclasses created are both upwards
-and downwards compatible. The topic of metaclass compatibility is
-highly esoteric and is something only encountered when doing deep and
-involved metaclass hacking. There are two basic kinds of metaclass
-incompatibility; upwards and downwards.
+This module makes sure that all metaclasses created are both upwards
+and downwards compatible. The topic of metaclass compatibility is
+highly esoteric and is something only encountered when doing deep and
+involved metaclass hacking. There are two basic kinds of metaclass
+incompatibility; upwards and downwards.
-Upwards metaclass compatibility means that the metaclass of a
-given class is either the same as (or a subclass of) all of the
+Upwards metaclass compatibility means that the metaclass of a
+given class is either the same as (or a subclass of) all of the
class's ancestors.
-Downward metaclass compatibility means that the metaclasses of a
-given class's anscestors are all either the same as (or a subclass
+Downward metaclass compatibility means that the metaclasses of a
+given class's ancestors are all either the same as (or a subclass
of) that metaclass.
-Here is a diagram showing a set of two classes (C<A> and C<B>) and
-two metaclasses (C<Meta::A> and C<Meta::B>) which have correct
+Here is a diagram showing a set of two classes (C<A> and C<B>) and
+two metaclasses (C<Meta::A> and C<Meta::B>) which have correct
metaclass compatibility both upwards and downwards.
+---------+ +---------+
| Meta::A |<----| Meta::B | <....... (instance of )
- +---------+ +---------+ <------- (inherits from)
+ +---------+ +---------+ <------- (inherits from)
^ ^
: :
+---------+ +---------+
| A |<----| B |
+---------+ +---------+
-As I said this is a highly esoteric topic and one you will only run
-into if you do a lot of subclassing of B<Class::MOP::Class>. If you
-are interested in why this is an issue see the paper
-I<Uniform and safe metaclass composition> linked to in the
-L<SEE ALSO> section of this document.
+As I said this is a highly esoteric topic and one you will only run
+into if you do a lot of subclassing of L<Class::MOP::Class>. If you
+are interested in why this is an issue see the paper I<Uniform and
+safe metaclass composition> linked to in the L<SEE ALSO> section of
+this document.
=head2 Using custom metaclasses
-Always use the metaclass pragma when using a custom metaclass, this
-will ensure the proper initialization order and not accidentely
-create an incorrect type of metaclass for you. This is a very rare
-problem, and one which can only occur if you are doing deep metaclass
+Always use the L<metaclass> pragma when using a custom metaclass, this
+will ensure the proper initialization order and not accidentally
+create an incorrect type of metaclass for you. This is a very rare
+problem, and one which can only occur if you are doing deep metaclass
programming. So in other words, don't worry about it.
+Note that if you're using L<Moose> we encourage you to I<not> use
+L<metaclass> pragma, and instead use L<Moose::Util::MetaRole> to apply
+roles to a class's metaclasses. This topic is covered at length in
+various L<Moose::Cookbook> recipes.
+
=head1 PROTOCOLS
-The protocol is divided into 3 main sub-protocols:
+The meta-object protocol is divided into 4 main sub-protocols:
-=over 4
+=head2 The Class protocol
-=item The Class protocol
-
-This provides a means of manipulating and introspecting a Perl 5
-class. It handles all of symbol table hacking for you, and provides
-a rich set of methods that go beyond simple package introspection.
+This provides a means of manipulating and introspecting a Perl 5
+class. It handles symbol table hacking for you, and provides a rich
+set of methods that go beyond simple package introspection.
See L<Class::MOP::Class> for more details.
-=item The Attribute protocol
+=head2 The Attribute protocol
-This provides a consistent represenation for an attribute of a
-Perl 5 class. Since there are so many ways to create and handle
-atttributes in Perl 5 OO, this attempts to provide as much of a
-unified approach as possible, while giving the freedom and
-flexibility to subclass for specialization.
+This provides a consistent representation for an attribute of a Perl 5
+class. Since there are so many ways to create and handle attributes in
+Perl 5 OO, the Attribute protocol provide as much of a unified
+approach as possible. Of course, you are always free to extend this
+protocol by subclassing the appropriate classes.
See L<Class::MOP::Attribute> for more details.
-=item The Method protocol
+=head2 The Method protocol
-This provides a means of manipulating and introspecting methods in
-the Perl 5 object system. As with attributes, there are many ways to
-approach this topic, so we try to keep it pretty basic, while still
+This provides a means of manipulating and introspecting methods in the
+Perl 5 object system. As with attributes, there are many ways to
+approach this topic, so we try to keep it pretty basic, while still
making it possible to extend the system in many ways.
See L<Class::MOP::Method> for more details.
-=back
+=head2 The Instance protocol
+
+This provides a layer of abstraction for creating object instances.
+Since the other layers use this protocol, it is relatively easy to
+change the type of your instances from the default hash reference to
+some other type of reference. Several examples are provided in the
+F<examples/> directory included in this distribution.
+
+See L<Class::MOP::Instance> for more details.
=head1 FUNCTIONS
-Class::MOP holds a cache of metaclasses, the following are functions
-(B<not methods>) which can be used to access that cache. It is not
-recommended that you mess with this, bad things could happen. But if
-you are brave and willing to risk it, go for it.
+Note that this module does not export any constants or functions.
+
+=head2 Constants
=over 4
-=item B<get_all_metaclasses>
+=item I<Class::MOP::IS_RUNNING_ON_5_10>
-This will return an hash of all the metaclass instances that have
-been cached by B<Class::MOP::Class> keyed by the package name.
+We set this constant depending on what version perl we are on, this
+allows us to take advantage of new 5.10 features and stay backwards
+compatible.
-=item B<get_all_metaclass_instances>
+=back
-This will return an array of all the metaclass instances that have
-been cached by B<Class::MOP::Class>.
+=head2 Utility functions
-=item B<get_all_metaclass_names>
+Note that these are all called as B<functions, not methods>.
-This will return an array of all the metaclass names that have
-been cached by B<Class::MOP::Class>.
+=over 4
-=item B<get_metaclass_by_name ($name)>
+=item B<Class::MOP::load_class($class_name)>
-=item B<store_metaclass_by_name ($name, $meta)>
+This will load the specified C<$class_name>. This function can be used
+in place of tricks like C<eval "use $module"> or using C<require>
+unconditionally. This will return the metaclass of C<$class_name>.
-=item B<weaken_metaclass ($name)>
+=item B<Class::MOP::is_class_loaded($class_name)>
-=item B<does_metaclass_exist ($name)>
+Returns a boolean indicating whether or not C<$class_name> has been
+loaded.
-=item B<remove_metaclass_by_name ($name)>
+This does a basic check of the symbol table to try and determine as
+best it can if the C<$class_name> is loaded, it is probably correct
+about 99% of the time, but it can be fooled into reporting false
+positives.
+
+=item B<Class::MOP::get_code_info($code)>
+
+This function returns two values, the name of the package the C<$code>
+is from and the name of the C<$code> itself. This is used by several
+elements of the MOP to determine where a given C<$code> reference is
+from.
+
+=item B<Class::MOP::class_of($instance_or_class_name)>
+
+This will return the metaclass of the given instance or class name.
+Even if the class lacks a metaclass, no metaclass will be initialized
+and C<undef> will be returned.
+
+=item B<Class::MOP::check_package_cache_flag($pkg)>
+
+B<NOTE: DO NOT USE THIS FUNCTION, IT IS FOR INTERNAL USE ONLY!>
+
+This will return an integer that is managed by L<Class::MOP::Class> to
+determine if a module's symbol table has been altered.
+
+In Perl 5.10 or greater, this flag is package specific. However in
+versions prior to 5.10, this will use the C<PL_sub_generation>
+variable which is not package specific.
+
+=item B<Class::MOP::load_first_existing_class(@class_names)>
+
+B<NOTE: DO NOT USE THIS FUNCTION, IT IS FOR INTERNAL USE ONLY!>
+
+Given a list of class names, this function will attempt to load each
+one in turn.
+
+If it finds a class it can load, it will return that class' name. If
+none of the classes can be loaded, it will throw an exception.
+
+=back
+
+=head2 Metaclass cache functions
+
+Class::MOP holds a cache of metaclasses. The following are functions
+(B<not methods>) which can be used to access that cache. It is not
+recommended that you mess with these. Bad things could happen, but if
+you are brave and willing to risk it: go for it!
+
+=over 4
+
+=item B<Class::MOP::get_all_metaclasses>
+
+This will return a hash of all the metaclass instances that have
+been cached by L<Class::MOP::Class>, keyed by the package name.
+
+=item B<Class::MOP::get_all_metaclass_instances>
+
+This will return a list of all the metaclass instances that have
+been cached by L<Class::MOP::Class>.
+
+=item B<Class::MOP::get_all_metaclass_names>
+
+This will return a list of all the metaclass names that have
+been cached by L<Class::MOP::Class>.
+
+=item B<Class::MOP::get_metaclass_by_name($name)>
+
+This will return a cached L<Class::MOP::Class> instance, or nothing
+if no metaclass exists with that C<$name>.
+
+=item B<Class::MOP::store_metaclass_by_name($name, $meta)>
+
+This will store a metaclass in the cache at the supplied C<$key>.
+
+=item B<Class::MOP::weaken_metaclass($name)>
+
+In rare cases (e.g. anonymous metaclasses) it is desirable to
+store a weakened reference in the metaclass cache. This
+function will weaken the reference to the metaclass stored
+in C<$name>.
+
+=item B<Class::MOP::does_metaclass_exist($name)>
+
+This will return true of there exists a metaclass stored in the
+C<$name> key, and return false otherwise.
+
+=item B<Class::MOP::remove_metaclass_by_name($name)>
+
+This will remove the metaclass stored in the C<$name> key.
=back
=head2 Books
-There are very few books out on Meta Object Protocols and Metaclasses
-because it is such an esoteric topic. The following books are really
-the only ones I have found. If you know of any more, B<I<please>>
+There are very few books out on Meta Object Protocols and Metaclasses
+because it is such an esoteric topic. The following books are really
+the only ones I have found. If you know of any more, B<I<please>>
email me and let me know, I would love to hear about them.
=over 4
-=item "The Art of the Meta Object Protocol"
+=item I<The Art of the Meta Object Protocol>
-=item "Advances in Object-Oriented Metalevel Architecture and Reflection"
+=item I<Advances in Object-Oriented Metalevel Architecture and Reflection>
-=item "Putting MetaClasses to Work"
+=item I<Putting MetaClasses to Work>
-=item "Smalltalk: The Language"
+=item I<Smalltalk: The Language>
=back
=over 4
-=item Uniform and safe metaclass composition
+=item "Uniform and safe metaclass composition"
-An excellent paper by the people who brought us the original Traits paper.
-This paper is on how Traits can be used to do safe metaclass composition,
-and offers an excellent introduction section which delves into the topic of
+An excellent paper by the people who brought us the original Traits paper.
+This paper is on how Traits can be used to do safe metaclass composition,
+and offers an excellent introduction section which delves into the topic of
metaclass compatibility.
L<http://www.iam.unibe.ch/~scg/Archive/Papers/Duca05ySafeMetaclassTrait.pdf>
-=item Safe Metaclass Programming
+=item "Safe Metaclass Programming"
-This paper seems to precede the above paper, and propose a mix-in based
-approach as opposed to the Traits based approach. Both papers have similar
-information on the metaclass compatibility problem space.
+This paper seems to precede the above paper, and propose a mix-in based
+approach as opposed to the Traits based approach. Both papers have similar
+information on the metaclass compatibility problem space.
L<http://citeseer.ist.psu.edu/37617.html>
=back
-=head2 Article
+=head2 Articles
=over 4
-=item CPAN Module Review of Class::MOP
+=item CPAN Module Review of Class::MOP
L<http://www.oreillynet.com/onlamp/blog/2006/06/cpan_module_review_classmop.html>
=head1 SIMILAR MODULES
-As I have said above, this module is a class-builder-builder, so it is
-not the same thing as modules like L<Class::Accessor> and
-L<Class::MethodMaker>. That being said there are very few modules on CPAN
-with similar goals to this module. The one I have found which is most
-like this module is L<Class::Meta>, although it's philosophy and the MOP it
-creates are very different from this modules.
+As I have said above, this module is a class-builder-builder, so it is
+not the same thing as modules like L<Class::Accessor> and
+L<Class::MethodMaker>. That being said there are very few modules on CPAN
+with similar goals to this module. The one I have found which is most
+like this module is L<Class::Meta>, although it's philosophy and the MOP it
+creates are very different from this modules.
=head1 BUGS
-All complex software has bugs lurking in it, and this module is no
+All complex software has bugs lurking in it, and this module is no
exception. If you find a bug please either email me, or add the bug
to cpan-RT.
-=head1 CODE COVERAGE
-
-I use L<Devel::Cover> to test the code coverage of my tests, below is the
-L<Devel::Cover> report on this module's test suite.
-
- ---------------------------- ------ ------ ------ ------ ------ ------ ------
- File stmt bran cond sub pod time total
- ---------------------------- ------ ------ ------ ------ ------ ------ ------
- Class/MOP.pm 78.0 87.5 55.6 71.4 100.0 12.4 76.8
- Class/MOP/Attribute.pm 83.4 75.6 86.7 94.4 100.0 8.9 85.2
- Class/MOP/Class.pm 96.9 75.8 43.2 98.0 100.0 55.3 83.6
- Class/MOP/Class/Immutable.pm 88.5 53.8 n/a 95.8 100.0 1.1 84.7
- Class/MOP/Instance.pm 87.9 75.0 33.3 89.7 100.0 10.1 89.1
- Class/MOP/Method.pm 97.6 60.0 57.9 76.9 100.0 1.5 82.8
- Class/MOP/Module.pm 87.5 n/a 11.1 83.3 100.0 0.3 66.7
- Class/MOP/Object.pm 100.0 n/a 33.3 100.0 100.0 0.1 89.5
- Class/MOP/Package.pm 95.1 69.0 33.3 100.0 100.0 9.9 85.5
- metaclass.pm 100.0 100.0 83.3 100.0 n/a 0.5 97.7
- ---------------------------- ------ ------ ------ ------ ------ ------ ------
- Total 91.5 72.1 48.8 90.7 100.0 100.0 84.2
- ---------------------------- ------ ------ ------ ------ ------ ------ ------
-
=head1 ACKNOWLEDGEMENTS
=over 4
=item Rob Kinyon
-Thanks to Rob for actually getting the development of this module kick-started.
+Thanks to Rob for actually getting the development of this module kick-started.
=back
Stevan Little E<lt>stevan@iinteractive.comE<gt>
-Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
+B<with contributions from:>
+
+Brandon (blblack) Black
+
+Florian (rafl) Ragwitz
+
+Guillermo (groditi) Roditi
+
+Matt (mst) Trout
+
+Rob (robkinyon) Kinyon
+
+Yuval (nothingmuch) Kogman
+
+Scott (konobi) McWhirter
=head1 COPYRIGHT AND LICENSE
-Copyright 2006 by Infinity Interactive, Inc.
+Copyright 2006-2009 by Infinity Interactive, Inc.
L<http://www.iinteractive.com>
This library is free software; you can redistribute it and/or modify
-it under the same terms as Perl itself.
+it under the same terms as Perl itself.
=cut
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