use Class::MOP::Attribute;
use Class::MOP::Method;
-use Class::MOP::Class::Immutable;
+use Class::MOP::Immutable;
-our $VERSION = '0.34';
-our $AUTHORITY = 'cpan:STEVAN';
+BEGIN {
+ our $VERSION = '0.54';
+ our $AUTHORITY = 'cpan:STEVAN';
+
+ use XSLoader;
+ XSLoader::load( 'Class::MOP', $VERSION );
+
+ unless ($] < 5.009_005) {
+ require mro;
+ no warnings 'redefine', 'prototype';
+ *check_package_cache_flag = \&mro::get_pkg_gen;
+ *IS_RUNNING_ON_5_10 = sub () { 1 };
+ }
+ else {
+ *IS_RUNNING_ON_5_10 = sub () { 0 };
+ }
+}
{
# 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 }
+
# 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 load_class {
+ my $class = shift;
+ # see if this is already
+ # loaded in the symbol table
+ return 1 if is_class_loaded($class);
+ # otherwise require it ...
+ my $file = $class . '.pm';
+ $file =~ s{::}{/}g;
+ eval { CORE::require($file) };
+ confess "Could not load class ($class) because : $@" if $@;
+ unless (does_metaclass_exist($class)) {
+ eval { Class::MOP::Class->initialize($class) };
+ confess "Could not initialize class ($class) because : $@" if $@;
+ }
+ 1; # return true if it worked
+}
+
+sub is_class_loaded {
+ my $class = shift;
+ no strict 'refs';
+ return 1 if defined ${"${class}::VERSION"} || defined @{"${class}::ISA"};
+ foreach (keys %{"${class}::"}) {
+ next if substr($_, -2, 2) eq '::';
+ return 1 if defined &{"${class}::$_"};
+ }
+ return 0;
+}
+
+
## ----------------------------------------------------------------------------
## Setting up our environment ...
## ----------------------------------------------------------------------------
-## Class::MOP needs to have a few things in the global perl environment so
+## Class::MOP needs to have a few things in the global perl environment so
## that it can operate effectively. Those things are done here.
## ----------------------------------------------------------------------------
# ... nothing yet actually ;)
## ----------------------------------------------------------------------------
-## Bootstrapping
+## Bootstrapping
## ----------------------------------------------------------------------------
-## The code below here is to bootstrap our MOP with itself. This is also
+## The code below here is to bootstrap our MOP with itself. This is also
## sometimes called "tying the knot". By doing this, we make it much easier
## to extend the MOP through subclassing and such since now you can use the
-## MOP itself to extend itself.
-##
+## MOP itself to extend itself.
+##
## Yes, I know, thats weird and insane, but it's a good thing, trust me :)
-## ----------------------------------------------------------------------------
+## ----------------------------------------------------------------------------
-# We need to add in the meta-attributes here so that
-# any subclass of Class::MOP::* will be able to
+# We need to add in the meta-attributes here so that
+# any subclass of Class::MOP::* will be able to
# inherit them using &construct_instance
## --------------------------------------------------------
## Class::MOP::Package
Class::MOP::Package->meta->add_attribute(
- Class::MOP::Attribute->new('$:package' => (
+ Class::MOP::Attribute->new('$!package' => (
reader => {
- # NOTE: we need to do this in order
- # for the instance meta-object to
+ # NOTE: we need to do this in order
+ # for the instance meta-object to
# not fall into meta-circular death
- 'name' => sub { (shift)->{'$:package'} }
+ #
+ # we just alias the original method
+ # rather than re-produce it here
+ 'name' => \&Class::MOP::Package::name
},
- init_arg => ':package',
+ init_arg => 'package',
))
);
Class::MOP::Package->meta->add_attribute(
- Class::MOP::Attribute->new('%:namespace' => (
+ Class::MOP::Attribute->new('%!namespace' => (
reader => {
# NOTE:
- # because of issues with the Perl API
- # to the typeglob in some versions, we
- # need to just always grab a new
- # reference to the hash here. Ideally
- # we could just store a ref and it would
- # Just Work, but oh well :\
- 'namespace' => sub {
- no strict 'refs';
- \%{$_[0]->name . '::'}
- }
+ # 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 }
))
);
Class::MOP::Package->meta->add_method('initialize' => sub {
my $class = shift;
my $package_name = shift;
- $class->meta->new_object(':package' => $package_name, @_);
+ $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 => {
- 'version' => sub {
- my $self = shift;
- ${$self->get_package_symbol('$VERSION')};
- }
+ # NOTE:
+ # we just alias the original method
+ # 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 => {
- 'authority' => sub {
- my $self = shift;
- ${$self->get_package_symbol('$AUTHORITY')};
- }
- },
- # NOTE:
- # protect this from silliness
- init_arg => '!............( DO NOT DO THIS )............!',
+ # NOTE:
+ # we just alias the original method
+ # rather than re-produce it here
+ 'authority' => \&Class::MOP::Module::authority
+ },
+ 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
- 'get_attribute_map' => sub { (shift)->{'%:attributes'} }
+ # 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
+ 'get_attribute_map' => \&Class::MOP::Class::get_attribute_map
},
- init_arg => ':attributes',
+ init_arg => 'attributes',
default => sub { {} }
))
);
Class::MOP::Class->meta->add_attribute(
- Class::MOP::Attribute->new('%:methods' => (
- reader => {
- 'get_method_map' => sub {
- my $self = shift;
- my $map = $self->{'%:methods'};
- foreach my $symbol ($self->list_all_package_symbols('CODE')) {
- my $code = $self->get_package_symbol('&' . $symbol);
- next if exists $map->{$symbol} && $map->{$symbol}->body == $code;
- $map->{$symbol} = $self->method_metaclass->wrap($code);
- }
- return $map;
- }
+ Class::MOP::Attribute->new('%!methods' => (
+ init_arg => 'methods',
+ reader => {
+ # NOTE:
+ # we just alias the original method
+ # rather than re-produce it here
+ 'get_method_map' => \&Class::MOP::Class::get_method_map
},
default => sub { {} }
))
);
Class::MOP::Class->meta->add_attribute(
- Class::MOP::Attribute->new('$:attribute_metaclass' => (
- reader => 'attribute_metaclass',
- init_arg => ':attribute_metaclass',
+ 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('$!attribute_metaclass' => (
+ reader => {
+ # NOTE:
+ # we just alias the original method
+ # rather than re-produce it here
+ 'attribute_metaclass' => \&Class::MOP::Class::attribute_metaclass
+ },
+ init_arg => 'attribute_metaclass',
default => 'Class::MOP::Attribute',
))
);
Class::MOP::Class->meta->add_attribute(
- Class::MOP::Attribute->new('$:method_metaclass' => (
- reader => 'method_metaclass',
- init_arg => ':method_metaclass',
- default => 'Class::MOP::Method',
+ Class::MOP::Attribute->new('$!method_metaclass' => (
+ reader => {
+ # NOTE:
+ # we just alias the original method
+ # rather than re-produce it here
+ 'method_metaclass' => \&Class::MOP::Class::method_metaclass
+ },
+ init_arg => 'method_metaclass',
+ default => 'Class::MOP::Method',
))
);
Class::MOP::Class->meta->add_attribute(
- Class::MOP::Attribute->new('$:instance_metaclass' => (
+ Class::MOP::Attribute->new('$!instance_metaclass' => (
reader => {
- # NOTE: we need to do this in order
- # for the instance meta-object to
- # not fall into meta-circular death
- 'instance_metaclass' => sub { (shift)->{'$:instance_metaclass'} }
+ # 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',
+ init_arg => 'instance_metaclass',
+ default => 'Class::MOP::Instance',
))
);
# 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
- 'name' => sub { (shift)->{name} }
+ Class::MOP::Attribute->new('$!name' => (
+ init_arg => 'name',
+ reader => {
+ # NOTE: we need to do this in order
+ # for the instance meta-object to
+ # not fall into meta-circular death
+ #
+ # we just alias the original method
+ # rather than re-produce it here
+ 'name' => \&Class::MOP::Attribute::name
}
))
);
Class::MOP::Attribute->meta->add_attribute(
- Class::MOP::Attribute->new('associated_class' => (
- reader => {
- # NOTE: we need to do this in order
- # for the instance meta-object to
- # not fall into meta-circular death
- 'associated_class' => sub { (shift)->{associated_class} }
+ Class::MOP::Attribute->new('$!associated_class' => (
+ init_arg => 'associated_class',
+ 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
+ 'associated_class' => \&Class::MOP::Attribute::associated_class
}
))
);
Class::MOP::Attribute->meta->add_attribute(
- Class::MOP::Attribute->new('accessor' => (
- reader => 'accessor',
- predicate => 'has_accessor',
+ Class::MOP::Attribute->new('$!accessor' => (
+ init_arg => 'accessor',
+ reader => { 'accessor' => \&Class::MOP::Attribute::accessor },
+ predicate => { 'has_accessor' => \&Class::MOP::Attribute::has_accessor },
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('$!reader' => (
+ init_arg => 'reader',
+ reader => { 'reader' => \&Class::MOP::Attribute::reader },
+ predicate => { 'has_reader' => \&Class::MOP::Attribute::has_reader },
))
);
Class::MOP::Attribute->meta->add_attribute(
- Class::MOP::Attribute->new('reader' => (
- reader => 'reader',
- predicate => 'has_reader',
+ Class::MOP::Attribute->new('$!initializer' => (
+ init_arg => 'initializer',
+ reader => { 'initializer' => \&Class::MOP::Attribute::initializer },
+ predicate => { 'has_initializer' => \&Class::MOP::Attribute::has_initializer },
))
);
Class::MOP::Attribute->meta->add_attribute(
- Class::MOP::Attribute->new('writer' => (
- reader => 'writer',
- predicate => 'has_writer',
+ Class::MOP::Attribute->new('$!writer' => (
+ init_arg => '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('predicate' => (
- reader => 'predicate',
- predicate => 'has_predicate',
+ Class::MOP::Attribute->new('$!predicate' => (
+ init_arg => 'predicate',
+ reader => { 'predicate' => \&Class::MOP::Attribute::predicate },
+ predicate => { 'has_predicate' => \&Class::MOP::Attribute::has_predicate },
))
);
Class::MOP::Attribute->meta->add_attribute(
- Class::MOP::Attribute->new('clearer' => (
- reader => 'clearer',
- predicate => 'has_clearer',
+ Class::MOP::Attribute->new('$!clearer' => (
+ init_arg => 'clearer',
+ reader => { 'clearer' => \&Class::MOP::Attribute::clearer },
+ predicate => { 'has_clearer' => \&Class::MOP::Attribute::has_clearer },
))
);
Class::MOP::Attribute->meta->add_attribute(
- Class::MOP::Attribute->new('init_arg' => (
- reader => 'init_arg',
- predicate => 'has_init_arg',
+ Class::MOP::Attribute->new('$!builder' => (
+ init_arg => 'builder',
+ reader => { 'builder' => \&Class::MOP::Attribute::builder },
+ predicate => { 'has_builder' => \&Class::MOP::Attribute::has_builder },
))
);
Class::MOP::Attribute->meta->add_attribute(
- Class::MOP::Attribute->new('default' => (
+ Class::MOP::Attribute->new('$!init_arg' => (
+ init_arg => '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' => (
+ init_arg => 'default',
# default has a custom 'reader' method ...
- predicate => 'has_default',
+ predicate => { 'has_default' => \&Class::MOP::Attribute::has_default },
))
);
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('@!associated_methods' => (
+ init_arg => 'associated_methods',
+ reader => { 'associated_methods' => \&Class::MOP::Attribute::associated_methods },
+ default => sub { [] }
+ ))
+);
# 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.
+# 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 = @_;
-
+ my %options = @_;
+
(defined $name && $name)
|| confess "You must provide a name for the attribute";
- $options{init_arg} = $name
+ $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};
+ if(exists $options{builder}){
+ confess("builder must be a defined scalar value which is a method name")
+ if ref $options{builder} || !(defined $options{builder});
+ confess("Setting both default and builder is not allowed.")
+ if exists $options{default};
+ } else {
+ (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);
});
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' => (
+ init_arg => 'body',
+ reader => { 'body' => \&Class::MOP::Method::body },
+ ))
+);
+
+## --------------------------------------------------------
+## Class::MOP::Method::Wrapped
+
+# NOTE:
+# 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('$!is_inline' => (
+ init_arg => 'is_inline',
+ reader => { 'is_inline' => \&Class::MOP::Method::Generated::is_inline },
+ ))
+);
+
+## --------------------------------------------------------
+## Class::MOP::Method::Accessor
+
+Class::MOP::Method::Accessor->meta->add_attribute(
+ Class::MOP::Attribute->new('$!attribute' => (
+ init_arg => 'attribute',
+ reader => {
+ 'associated_attribute' => \&Class::MOP::Method::Accessor::associated_attribute
+ },
+ ))
+);
+
+Class::MOP::Method::Accessor->meta->add_attribute(
+ Class::MOP::Attribute->new('$!accessor_type' => (
+ init_arg => 'accessor_type',
+ reader => { 'accessor_type' => \&Class::MOP::Method::Accessor::accessor_type },
+ ))
+);
+
+
+## --------------------------------------------------------
+## Class::MOP::Method::Constructor
+
+Class::MOP::Method::Constructor->meta->add_attribute(
+ Class::MOP::Attribute->new('%!options' => (
+ init_arg => 'options',
+ reader => {
+ 'options' => \&Class::MOP::Method::Constructor::options
+ },
+ ))
+);
+
+Class::MOP::Method::Constructor->meta->add_attribute(
+ Class::MOP::Attribute->new('$!associated_metaclass' => (
+ init_arg => 'metaclass',
+ reader => {
+ 'associated_metaclass' => \&Class::MOP::Method::Constructor::associated_metaclass
+ },
+ ))
+);
+
+## --------------------------------------------------------
+## Class::MOP::Instance
+
+# NOTE:
+# these don't yet do much of anything, but are just
+# included for completeness
+
+Class::MOP::Instance->meta->add_attribute(
+ Class::MOP::Attribute->new('$!meta')
+);
+
+Class::MOP::Instance->meta->add_attribute(
+ Class::MOP::Attribute->new('@!slots')
+);
+
+## --------------------------------------------------------
## Now close all the Class::MOP::* classes
-Class::MOP::Package ->meta->make_immutable(inline_constructor => 0);
-Class::MOP::Module ->meta->make_immutable(inline_constructor => 0);
-Class::MOP::Class ->meta->make_immutable(inline_constructor => 0);
-Class::MOP::Attribute->meta->make_immutable(inline_constructor => 0);
-Class::MOP::Method ->meta->make_immutable(inline_constructor => 0);
-Class::MOP::Instance ->meta->make_immutable(inline_constructor => 0);
-Class::MOP::Object ->meta->make_immutable(inline_constructor => 0);
+# NOTE:
+# we don't need to inline the
+# constructors or the accessors
+# this only lengthens the compile
+# time of the MOP, and gives us
+# no actual benefits.
+
+$_->meta->make_immutable(
+ inline_constructor => 0,
+ inline_accessors => 0,
+) for qw/
+ Class::MOP::Package
+ Class::MOP::Module
+ Class::MOP::Class
+
+ Class::MOP::Attribute
+ Class::MOP::Method
+ Class::MOP::Instance
+
+ Class::MOP::Object
+
+ 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 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
+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.
-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
+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.
=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 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
+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.
-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).
+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).
=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 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.
=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 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.
=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 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.
-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?
-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.
-
-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
+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.
+
+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.
=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 anscestors 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
+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.
=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 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
programming. So in other words, don't worry about it.
=head1 PROTOCOLS
-The protocol is divided into 3 main sub-protocols:
+The protocol is divided into 4 main sub-protocols:
=over 4
=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
+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.
See L<Class::MOP::Class> for more details.
=item 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
+This provides a consistent represenation for an attribute of a
+Perl 5 class. Since there are so many ways to create and handle
+attributes 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.
See L<Class::MOP::Attribute> for more details.
=item 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.
+=item 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 ref to other
+types of references. Several examples are provided in the F<examples/>
+directory included in this distribution.
+
+See L<Class::MOP::Instance> for more details.
+
=back
=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
+=head2 Constants
+
+=over 4
+
+=item I<IS_RUNNING_ON_5_10>
+
+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
+compat.
+
+=back
+
+=head2 Utility functions
+
+=over 4
+
+=item B<load_class ($class_name)>
+
+This will load a given C<$class_name> and if it does not have an
+already initialized metaclass, then it will intialize one for it.
+This function can be used in place of tricks like
+C<eval "use $module"> or using C<require>.
+
+=item B<is_class_loaded ($class_name)>
+
+This will return a boolean depending on if the C<$class_name> has
+been loaded.
+
+NOTE: This does a basic check of the symbol table to try and
+determine as best it can if the C<$class_name> is loaded, it
+is probably correct about 99% of the time.
+
+=item B<check_package_cache_flag ($pkg)>
+
+This will return an integer that is managed by C<Class::MOP::Class>
+to determine if a module's symbol table has been altered.
+
+In Perl 5.10 or greater, this flag is package specific. However in
+versions prior to 5.10, this will use the C<PL_sub_generation> variable
+which is not package specific.
+
+=item B<get_code_info ($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 detemine where a given C<$code> reference is from.
+
+=back
+
+=head2 Metaclass cache functions
+
+Class::MOP holds a cache of metaclasses, the following are functions
+(B<not methods>) which can be used to access that cache. It is not
+recommended that you mess with this, bad things could happen. But if
you are brave and willing to risk it, go for it.
=over 4
=item B<get_all_metaclasses>
-This will return an hash of all the metaclass instances that have
-been cached by B<Class::MOP::Class> keyed by the package name.
+This will return an hash of all the metaclass instances that have
+been cached by B<Class::MOP::Class> keyed by the package name.
=item B<get_all_metaclass_instances>
-This will return an array of all the metaclass instances that have
+This will return an array of all the metaclass instances that have
been cached by B<Class::MOP::Class>.
=item B<get_all_metaclass_names>
-This will return an array of all the metaclass names that have
+This will return an array of all the metaclass names that have
been cached by B<Class::MOP::Class>.
=item B<get_metaclass_by_name ($name)>
+This will return a cached B<Class::MOP::Class> instance of nothing
+if no metaclass exist by that C<$name>.
+
=item B<store_metaclass_by_name ($name, $meta)>
+This will store a metaclass in the cache at the supplied C<$key>.
+
=item B<weaken_metaclass ($name)>
+In rare cases it is desireable to store a weakened reference in
+the metaclass cache. This function will weaken the reference to
+the metaclass stored in C<$name>.
+
=item B<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<remove_metaclass_by_name ($name)>
+This will remove a the metaclass stored in the C<$name> key.
+
=back
=head1 SEE ALSO
=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 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
-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 Articles
+
+=over 4
+
+=item CPAN Module Review of Class::MOP
+
+L<http://www.oreillynet.com/onlamp/blog/2006/06/cpan_module_review_classmop.html>
+
+=back
+
=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
+
+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 2006-2008 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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