X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FClass%2FMOP%2FClass.pm;h=b2cb51d9e665aca776a84672703039d0c4e5ceeb;hb=9d6dce77cd867d92c418eb4fcfd199eaca6efc10;hp=6ad65fe626121f0ea1b73bc83a304e825765bb08;hpb=6ddf42a0a45b6eaf48d311c447861489fbaf6062;p=gitmo%2FClass-MOP.git diff --git a/lib/Class/MOP/Class.pm b/lib/Class/MOP/Class.pm index 6ad65fe..b2cb51d 100644 --- a/lib/Class/MOP/Class.pm +++ b/lib/Class/MOP/Class.pm @@ -5,11 +5,28 @@ use strict; use warnings; use Carp 'confess'; -use Scalar::Util 'blessed', 'reftype'; +use Scalar::Util 'blessed', 'reftype', 'weaken'; use Sub::Name 'subname'; use B 'svref_2object'; -our $VERSION = '0.01'; +our $VERSION = '0.17'; + +use base 'Class::MOP::Module'; + +use Class::MOP::Instance; + +# Self-introspection + +sub meta { Class::MOP::Class->initialize(blessed($_[0]) || $_[0]) } + +# Class globals ... + +# NOTE: +# we need a sufficiently annoying prefix +# this should suffice for now, this is +# used in a couple of places below, so +# need to put it up here for now. +my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::'; # Creation @@ -18,15 +35,162 @@ our $VERSION = '0.01'; # there is no need to worry about destruction though # because they should die only when the program dies. # After all, do package definitions even get reaped? - my %METAS; + my %METAS; + + # means of accessing all the metaclasses that have + # been initialized thus far (for mugwumps obj browser) + sub get_all_metaclasses { %METAS } + sub get_all_metaclass_instances { values %METAS } + sub get_all_metaclass_names { keys %METAS } + sub initialize { - my ($class, $package_name) = @_; + my $class = shift; + my $package_name = shift; + (defined $package_name && $package_name && !blessed($package_name)) + || confess "You must pass a package name and it cannot be blessed"; + $class->construct_class_instance(':package' => $package_name, @_); + } + + sub reinitialize { + my $class = shift; + my $package_name = shift; + (defined $package_name && $package_name && !blessed($package_name)) + || confess "You must pass a package name and it cannot be blessed"; + $METAS{$package_name} = undef; + $class->construct_class_instance(':package' => $package_name, @_); + } + + # NOTE: (meta-circularity) + # 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 { + my $class = shift; + my %options = @_; + my $package_name = $options{':package'}; (defined $package_name && $package_name) - || confess "You must pass a package name"; - $METAS{$package_name} ||= bless [ $package_name, {} ] => blessed($class) || $class; + || confess "You must pass a package name"; + # NOTE: + # return the metaclass if we have it cached, + # and it is still defined (it has not been + # reaped by DESTROY yet, which can happen + # annoyingly enough during global destruction) + return $METAS{$package_name} + if exists $METAS{$package_name} && defined $METAS{$package_name}; + + # NOTE: + # we need to deal with the possibility + # of class immutability here, and then + # get the name of the class appropriately + $class = (blessed($class) + ? ($class->is_immutable + ? $class->get_mutable_metaclass_name() + : blessed($class)) + : $class); + + $class = blessed($class) || $class; + # now create the metaclass + my $meta; + if ($class =~ /^Class::MOP::Class$/) { + $meta = bless { + '$:package' => $package_name, + '%:attributes' => {}, + '$:attribute_metaclass' => $options{':attribute_metaclass'} || 'Class::MOP::Attribute', + '$:method_metaclass' => $options{':method_metaclass'} || 'Class::MOP::Method', + '$:instance_metaclass' => $options{':instance_metaclass'} || 'Class::MOP::Instance', + } => $class; + } + 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) + } + # and check the metaclass compatibility + $meta->check_metaclass_compatability(); + $METAS{$package_name} = $meta; + # NOTE: + # we need to weaken any anon classes + # so that they can call DESTROY properly + weaken($METAS{$package_name}) + if $package_name =~ /^$ANON_CLASS_PREFIX/; + $meta; + } + + sub check_metaclass_compatability { + my $self = shift; + + # this is always okay ... + return if blessed($self) eq 'Class::MOP::Class' && + $self->instance_metaclass eq 'Class::MOP::Instance'; + + my @class_list = $self->class_precedence_list; + shift @class_list; # shift off $self->name + + foreach my $class_name (@class_list) { + my $meta = $METAS{$class_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 + ? $meta->get_mutable_metaclass_name() + : blessed($meta)); + + ($self->isa($meta_type)) + || confess $self->name . "->meta => (" . (blessed($self)) . ")" . + " is not compatible with the " . + $class_name . "->meta => (" . ($meta_type) . ")"; + # NOTE: + # we also need to check that instance metaclasses + # are compatabile in the same the class. + ($self->instance_metaclass->isa($meta->instance_metaclass)) + || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" . + " is not compatible with the " . + $class_name . "->meta => (" . ($meta->instance_metaclass) . ")"; + } + } +} + +## ANON classes + +{ + # NOTE: + # this should be sufficient, if you have a + # use case where it is not, write a test and + # I will change it. + my $ANON_CLASS_SERIAL = 0; + + sub create_anon_class { + my ($class, %options) = @_; + my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL; + return $class->create($package_name, '0.00', %options); } +} + +# NOTE: +# this will only get called for +# anon-classes, all other calls +# are assumed to occur during +# global destruction and so don't +# really need to be handled explicitly +sub DESTROY { + my $self = shift; + return unless $self->name =~ /^$ANON_CLASS_PREFIX/; + my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/); + no strict 'refs'; + foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) { + delete ${$ANON_CLASS_PREFIX . $serial_id}{$key}; + } + delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'}; } +# creating classes with MOP ... + sub create { my ($class, $package_name, $package_version, %options) = @_; (defined $package_name && $package_name) @@ -37,36 +201,116 @@ sub create { eval $code; confess "creation of $package_name failed : $@" if $@; my $meta = $class->initialize($package_name); + + $meta->add_method('meta' => sub { + $class->initialize(blessed($_[0]) || $_[0]); + }); + $meta->superclasses(@{$options{superclasses}}) if exists $options{superclasses}; + # NOTE: + # process attributes first, so that they can + # install accessors, but locally defined methods + # can then overwrite them. It is maybe a little odd, but + # I think this should be the order of things. + if (exists $options{attributes}) { + foreach my $attr (@{$options{attributes}}) { + $meta->add_attribute($attr); + } + } if (exists $options{methods}) { foreach my $method_name (keys %{$options{methods}}) { $meta->add_method($method_name, $options{methods}->{$method_name}); } - } + } return $meta; } -# Informational +## Attribute readers -sub name { ${$_[0]}[0] } +# NOTE: +# all these attribute readers will be bootstrapped +# away in the Class::MOP bootstrap section -sub version { - my $self = shift; - no strict 'refs'; - ${$self->name . '::VERSION'}; +sub get_attribute_map { $_[0]->{'%:attributes'} } +sub attribute_metaclass { $_[0]->{'$:attribute_metaclass'} } +sub method_metaclass { $_[0]->{'$:method_metaclass'} } +sub instance_metaclass { $_[0]->{'$:instance_metaclass'} } + +# Instance Construction & Cloning + +sub new_object { + my $class = shift; + # NOTE: + # we need to protect the integrity of the + # Class::MOP::Class singletons here, so we + # delegate this to &construct_class_instance + # which will deal with the singletons + return $class->construct_class_instance(@_) + if $class->name->isa('Class::MOP::Class'); + return $class->construct_instance(@_); +} + +sub construct_instance { + my ($class, %params) = @_; + my $meta_instance = $class->get_meta_instance(); + my $instance = $meta_instance->create_instance(); + foreach my $attr ($class->compute_all_applicable_attributes()) { + $attr->initialize_instance_slot($meta_instance, $instance, \%params); + } + return $instance; +} + +sub get_meta_instance { + my $class = shift; + return $class->instance_metaclass->new( + $class, + $class->compute_all_applicable_attributes() + ); +} + +sub clone_object { + my $class = shift; + my $instance = shift; + (blessed($instance) && $instance->isa($class->name)) + || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")"; + # NOTE: + # we need to protect the integrity of the + # Class::MOP::Class singletons here, they + # should not be cloned. + return $instance if $instance->isa('Class::MOP::Class'); + $class->clone_instance($instance, @_); +} + +sub clone_instance { + my ($class, $instance, %params) = @_; + (blessed($instance)) + || confess "You can only clone instances, \$self is not a blessed instance"; + my $meta_instance = $class->get_meta_instance(); + my $clone = $meta_instance->clone_instance($instance); + foreach my $key (keys %params) { + next unless $meta_instance->is_valid_slot($key); + $meta_instance->set_slot_value($clone, $key, $params{$key}); + } + return $clone; } # Inheritance sub superclasses { my $self = shift; - no strict 'refs'; if (@_) { my @supers = @_; - @{$self->name . '::ISA'} = @supers; + @{$self->get_package_symbol('@ISA')} = @supers; + # NOTE: + # we need to check the metaclass + # compatability here so that we can + # be sure that the superclass is + # not potentially creating an issues + # we don't know about + $self->check_metaclass_compatability(); } - @{$self->name . '::ISA'}; + @{$self->get_package_symbol('@ISA')}; } sub class_precedence_list { @@ -76,8 +320,8 @@ sub class_precedence_list { # This will do nothing if all is well, and blow # up otherwise. Yes, it's an ugly hack, better # suggestions are welcome. - { $self->name->isa('This is a test for circular inheritance') } - # ... and no back to our regularly scheduled program + { ($self->name || return)->isa('This is a test for circular inheritance') } + # ... and now back to our regularly scheduled program ( $self->name, map { @@ -93,35 +337,116 @@ sub add_method { (defined $method_name && $method_name) || confess "You must define a method name"; # use reftype here to allow for blessed subs ... - (reftype($method) && reftype($method) eq 'CODE') + ('CODE' eq (reftype($method) || '')) || confess "Your code block must be a CODE reference"; my $full_method_name = ($self->name . '::' . $method_name); - - no strict 'refs'; - no warnings 'redefine'; - *{$full_method_name} = subname $full_method_name => $method; + + # FIXME: + # dont bless subs, its bad mkay + $method = $self->method_metaclass->wrap($method) unless blessed($method); + + $self->add_package_symbol("&${method_name}" => subname $full_method_name => $method); } { - - ## private utility functions for has_method - my $_find_subroutine_package_name = sub { eval { svref_2object($_[0])->GV->STASH->NAME } }; - my $_find_subroutine_name = sub { eval { svref_2object($_[0])->GV->NAME } }; - - sub has_method { + my $fetch_and_prepare_method = sub { my ($self, $method_name) = @_; + # fetch it locally + my $method = $self->get_method($method_name); + # if we dont have local ... + unless ($method) { + # try to find the next method + $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 inherience hierarchy for this class"; + # 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); + } + else { + # now make sure we wrap it properly + $method = Class::MOP::Method::Wrapped->wrap($method) + unless $method->isa('Class::MOP::Method::Wrapped'); + } + $self->add_method($method_name => $method); + return $method; + }; + + sub add_before_method_modifier { + my ($self, $method_name, $method_modifier) = @_; + (defined $method_name && $method_name) + || confess "You must pass in a method name"; + my $method = $fetch_and_prepare_method->($self, $method_name); + $method->add_before_modifier(subname ':before' => $method_modifier); + } + + sub add_after_method_modifier { + my ($self, $method_name, $method_modifier) = @_; (defined $method_name && $method_name) - || confess "You must define a method name"; + || confess "You must pass in a method name"; + my $method = $fetch_and_prepare_method->($self, $method_name); + $method->add_after_modifier(subname ':after' => $method_modifier); + } - my $sub_name = ($self->name . '::' . $method_name); + sub add_around_method_modifier { + my ($self, $method_name, $method_modifier) = @_; + (defined $method_name && $method_name) + || confess "You must pass in a method name"; + my $method = $fetch_and_prepare_method->($self, $method_name); + $method->add_around_modifier(subname ':around' => $method_modifier); + } + + # NOTE: + # the methods above used to be named like this: + # ${pkg}::${method}:(before|after|around) + # but this proved problematic when using one modifier + # to wrap multiple methods (something which is likely + # to happen pretty regularly IMO). So instead of naming + # it like this, I have chosen to just name them purely + # with their modifier names, like so: + # :(before|after|around) + # The fact is that in a stack trace, it will be fairly + # evident from the context what method they are attached + # to, and so don't need the fully qualified name. +} + +sub alias_method { + my ($self, $method_name, $method) = @_; + (defined $method_name && $method_name) + || confess "You must define a method name"; + # use reftype here to allow for blessed subs ... + ('CODE' eq (reftype($method) || '')) + || confess "Your code block must be a CODE reference"; + + # FIXME: + # dont bless subs, its bad mkay + $method = $self->method_metaclass->wrap($method) unless blessed($method); - no strict 'refs'; - return 0 if !defined(&{$sub_name}); - return 0 if $_find_subroutine_package_name->(\&{$sub_name}) ne $self->name && - $_find_subroutine_name->(\&{$sub_name}) ne '__ANON__'; - return 1; - } + $self->add_package_symbol("&${method_name}" => $method); +} + +sub find_method_by_name { + my ($self, $method_name) = @_; + return $self->name->can($method_name); +} +sub has_method { + my ($self, $method_name) = @_; + (defined $method_name && $method_name) + || confess "You must define a method name"; + + return 0 if !$self->has_package_symbol("&${method_name}"); + my $method = $self->get_package_symbol("&${method_name}"); + return 0 if (svref_2object($method)->GV->STASH->NAME || '') ne $self->name && + (svref_2object($method)->GV->NAME || '') ne '__ANON__'; + + # FIXME: + # dont bless subs, its bad mkay + $self->method_metaclass->wrap($method) unless blessed($method); + + return 1; } sub get_method { @@ -129,10 +454,9 @@ sub get_method { (defined $method_name && $method_name) || confess "You must define a method name"; - no strict 'refs'; - return \&{$self->name . '::' . $method_name} - if $self->has_method($method_name); - return; # <- make sure to return undef + return unless $self->has_method($method_name); + + return $self->get_package_symbol("&${method_name}"); } sub remove_method { @@ -142,8 +466,7 @@ sub remove_method { my $removed_method = $self->get_method($method_name); - no strict 'refs'; - delete ${$self->name . '::'}{$method_name} + $self->remove_package_symbol("&${method_name}") if defined $removed_method; return $removed_method; @@ -151,8 +474,7 @@ sub remove_method { sub get_method_list { my $self = shift; - no strict 'refs'; - grep { $self->has_method($_) } %{$self->name . '::'}; + grep { $self->has_method($_) } $self->list_all_package_symbols; } sub compute_all_applicable_methods { @@ -181,30 +503,6 @@ sub compute_all_applicable_methods { return @methods; } -## Recursive Version of compute_all_applicable_methods -# sub compute_all_applicable_methods { -# my ($self, $seen) = @_; -# $seen ||= {}; -# ( -# (map { -# if (exists $seen->{$_}) { -# (); -# } -# else { -# $seen->{$_}++; -# { -# name => $_, -# class => $self->name, -# code => $self->get_method($_) -# }; -# } -# } $self->get_method_list()), -# map { -# $self->initialize($_)->compute_all_applicable_methods($seen) -# } $self->superclasses() -# ); -# } - sub find_all_methods_by_name { my ($self, $method_name) = @_; (defined $method_name && $method_name) @@ -227,18 +525,126 @@ sub find_all_methods_by_name { } if $meta->has_method($method_name); } return @methods; +} +sub find_next_method_by_name { + my ($self, $method_name) = @_; + (defined $method_name && $method_name) + || confess "You must define a method name to find"; + # keep a record of what we have seen + # here, this will handle all the + # inheritence issues because we are + # using the &class_precedence_list + my %seen_class; + my @cpl = $self->class_precedence_list(); + shift @cpl; # discard ourselves + foreach my $class (@cpl) { + next if $seen_class{$class}; + $seen_class{$class}++; + # fetch the meta-class ... + my $meta = $self->initialize($class); + return $meta->get_method($method_name) + if $meta->has_method($method_name); + } + return; } ## Attributes -sub has_attribute {} -sub get_attribute {} -sub add_attribute {} -sub remove_attribute {} -sub get_attribute_list {} -sub compute_all_applicable_attributes {} -sub create_all_accessors {} +sub add_attribute { + my $self = shift; + # either we have an attribute object already + # or we need to create one from the args provided + my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_); + # make sure it is derived from the correct type though + ($attribute->isa('Class::MOP::Attribute')) + || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)"; + $attribute->attach_to_class($self); + $attribute->install_accessors(); + $self->get_attribute_map->{$attribute->name} = $attribute; +} + +sub has_attribute { + my ($self, $attribute_name) = @_; + (defined $attribute_name && $attribute_name) + || confess "You must define an attribute name"; + exists $self->get_attribute_map->{$attribute_name} ? 1 : 0; +} + +sub get_attribute { + my ($self, $attribute_name) = @_; + (defined $attribute_name && $attribute_name) + || confess "You must define an attribute name"; + return $self->get_attribute_map->{$attribute_name} + if $self->has_attribute($attribute_name); + return; +} + +sub remove_attribute { + my ($self, $attribute_name) = @_; + (defined $attribute_name && $attribute_name) + || confess "You must define an attribute name"; + my $removed_attribute = $self->get_attribute_map->{$attribute_name}; + return unless defined $removed_attribute; + delete $self->get_attribute_map->{$attribute_name}; + $removed_attribute->remove_accessors(); + $removed_attribute->detach_from_class(); + return $removed_attribute; +} + +sub get_attribute_list { + my $self = shift; + keys %{$self->get_attribute_map}; +} + +sub compute_all_applicable_attributes { + my $self = shift; + my @attrs; + # keep a record of what we have seen + # here, this will handle all the + # inheritence issues because we are + # using the &class_precedence_list + my (%seen_class, %seen_attr); + foreach my $class ($self->class_precedence_list()) { + next if $seen_class{$class}; + $seen_class{$class}++; + # fetch the meta-class ... + my $meta = $self->initialize($class); + foreach my $attr_name ($meta->get_attribute_list()) { + next if exists $seen_attr{$attr_name}; + $seen_attr{$attr_name}++; + push @attrs => $meta->get_attribute($attr_name); + } + } + return @attrs; +} + +sub find_attribute_by_name { + my ($self, $attr_name) = @_; + # keep a record of what we have seen + # here, this will handle all the + # inheritence issues because we are + # using the &class_precedence_list + my %seen_class; + foreach my $class ($self->class_precedence_list()) { + next if $seen_class{$class}; + $seen_class{$class}++; + # fetch the meta-class ... + my $meta = $self->initialize($class); + return $meta->get_attribute($attr_name) + if $meta->has_attribute($attr_name); + } + return; +} + +## Class closing + +sub is_mutable { 1 } +sub is_immutable { 0 } + +sub make_immutable { + return Class::MOP::Class::Immutable->make_metaclass_immutable(@_); +} 1; @@ -252,14 +658,82 @@ Class::MOP::Class - Class Meta Object =head1 SYNOPSIS + # assuming that class Foo + # has been defined, you can + + # use this for introspection ... + + # add a method to Foo ... + 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() + + # remove a method from Foo + Foo->meta->remove_method('bar'); + + # or use this to actually create classes ... + + Class::MOP::Class->create('Bar' => '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 +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 + +=item B + +This will return a B instance which is related +to this class. Thereby allowing B to actually +introspect itself. + +As with B, B 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. + +=item B + +This will return an hash of all the metaclass instances that have +been cached by B keyed by the package name. + +=item B + +This will return an array of all the metaclass instances that have +been cached by B. + +=item B + +This will return an array of all the metaclass names that have +been cached by B. + +=back + =head2 Class construction -These methods handle creating Class objects, which can be used to -both create new classes, and analyze pre-existing ones. +These methods will handle creating B objects, +which can be used to both create new classes, and analyze +pre-existing classes. This module will internally store references to all the instances you create with these methods, so that they do not need to be @@ -268,33 +742,123 @@ created any more than nessecary. Basically, they are singletons. =over 4 =item B ?@superclasses, - methods => ?%methods, - attributes => ?%attributes)> + superclasses =E ?@superclasses, + methods =E ?%methods, + attributes =E ?%attributes)> -This returns the basic Class object, bringing the specified +This returns a B object, bringing the specified C<$package_name> into existence and adding any of the C<$package_version>, C<@superclasses>, C<%methods> and C<%attributes> to it. -=item B +=item B ?@superclasses, + methods =E ?%methods, + attributes =E ?%attributes)> + +This will create an anonymous class, it works much like C but +it does not need a C<$package_name>. Instead it will create a suitably +unique package name for you to stash things into. + +=item B + +This initializes and returns returns a B object +for a given a C<$package_name>. -This initializes a Class object for a given a C<$package_name>. +=item B + +This removes the old metaclass, and creates a new one in it's place. +Do B use this unless you really know what you are doing, it could +very easily make a very large mess of your program. + +=item B + +This will construct an instance of B, it is +here so that we can actually "tie the knot" for B +to use C once all the bootstrapping is done. This +method is used internally by C and should never be called +from outside of that method really. + +=item B + +This method is called as the very last thing in the +C method. This will check that the +metaclass you are creating is compatible with the metaclasses of all +your ancestors. For more inforamtion about metaclass compatibility +see the C section in L. =back -=head2 Instance construction +=head2 Object instance construction and cloning + +These methods are B, it is up to you whether you want +to use them or not. =over 4 -=item B +=item B -This will construct and instance using the C<$canidate> as storage +=item B + +=item B + +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 this method like so: + + sub MyClass::new { + my ($class, %param) = @_; + $class->meta->new_object(%params); + } + +Of course the ideal place for this would actually be in C +but that is considered bad style, so we do not do that. + +=item B + +This method is used to construct an instace structure suitable for +C-ing into your package of choice. It works in conjunction +with the Attribute protocol to collect all applicable attributes. + +This will construct and instance using a HASH ref as storage (currently only HASH references are supported). This will collect all -the applicable attribute meta-objects and layout out the fields in the -C<$canidate>, 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. +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. + +=item B + +This is a convience method for cloning an object instance, then +blessing it into the appropriate package. This method will call +C, which performs a shallow copy of the object, +see that methods documentation for more details. Ideally your +class would call a C this method like so: + + sub MyClass::clone { + my ($self, %param) = @_; + $self->meta->clone_object($self, %params); + } + +Of course the ideal place for this would actually be in C +but that is considered bad style, so we do not do that. + +=item B + +This method is a compliment of C (which means if +you override C, you need to override this one too), +and clones the instance shallowly. + +The cloned structure returned is (like with C) an +unCed HASH reference, it is your responsibility to then bless +this cloned structure into the right class (which C will +do for you). + +As of 0.11, this method will clone the C<$instance> structure shallowly, +as opposed to the deep cloning implemented in prior versions. After much +thought, research and discussion, I have decided that anything but basic +shallow cloning is outside the scope of the meta-object protocol. I +think Yuval "nothingmuch" Kogman put it best when he said that cloning +is too I to be part of the MOP. =back @@ -304,13 +868,13 @@ found in the attribute meta-object. =item B -This is a read-only attribute which returns the package name that -the Class is stored in. +This is a read-only attribute which returns the package name for the +given B instance. =item B This is a read-only attribute which returns the C<$VERSION> of the -package the Class is stored in. +package for the given B instance. =back @@ -321,13 +885,21 @@ package the Class is stored in. =item B This is a read-write attribute which represents the superclass -relationships of this Class. Basically, it can get and set the -C<@ISA> for you. +relationships of the class the B instance is +associated with. Basically, it can get and set the C<@ISA> for you. + +B +Perl will occasionally perform some C<@ISA> and method caching, if +you decide to change your superclass relationship at runtime (which +is quite insane and very much not recommened), then you should be +aware of this and the fact that this module does not make any +attempt to address this issue. =item B -This computes the a list of the Class's ancestors in the same order -in which method dispatch will be done. +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 does, but we don't remove duplicate names. =back @@ -335,21 +907,34 @@ in which method dispatch will be done. =over 4 +=item B + =item B This will take a C<$method_name> and CODE reference to that -C<$method> and install it into the Class. +C<$method> and install it into the class's package. -B : This does absolutely nothing special to C<$method> +B: +This does absolutely nothing special to C<$method> other than use B to make sure it is tagged with the correct name, and therefore show up correctly in stack traces and such. +=item B + +This will take a C<$method_name> and CODE reference to that +C<$method> and alias the method into the class's package. + +B: +Unlike C, this will B try to name the +C<$method> using B, it only aliases the method in +the class's package. + =item B -This just provides a simple way to check if the Class implements +This just provides a simple way to check if the class implements a specific C<$method_name>. It will I however, attempt to check -if the class inherits the method. +if the class inherits the method (use C for that). This will correctly handle functions defined outside of the package that use a fully qualified name (C). @@ -367,16 +952,23 @@ may be a valid method being applied to the class. In short, this method cannot always be trusted to determine if the C<$method_name> is actually a method. However, it will DWIM about -90% of the time, so it's a small trade off IMO. +90% of the time, so it's a small trade off I think. =item B This will return a CODE reference of the specified C<$method_name>, or return undef if that method does not exist. +=item B + +This will return a CODE reference of the specified C<$method_name>, +or return undef if that method does not exist. + +Unlike C this will also look in the superclasses. + =item B -This will attempt to remove a given C<$method_name> from the Class. +This will attempt to remove a given C<$method_name> from the class. It will return the CODE reference that it has removed, and will attempt to use B to clear the methods associated name. @@ -389,8 +981,8 @@ methods, use the C method. =item B -This will return a list of all the methods names this Class will -support, taking into account inheritance. The list will be a list of +This will return a list of all the methods names this class will +respond to, taking into account inheritance. The list will be a list of HASH references, each one containing the following information; method name, the name of the class in which the method lives and a CODE reference for the actual method. @@ -409,6 +1001,110 @@ 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. +=item B + +This will return the first method to match a given C<$method_name> in +the superclasses, this is basically equivalent to calling +C, but it can be dispatched at runtime. + +=back + +=head2 Method Modifiers + +Method modifiers are a concept borrowed from CLOS, in which a method +can be wrapped with I, I and I method modifiers +that will be called everytime the method is called. + +=head3 How method modifiers work? + +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 and I modifiers are ignored. This is +because thier purpose is B to filter the input and output of the +primary method (this is done with an I 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 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: + + before 2 + before 1 + around 2 + around 1 + primary + after 1 + after 2 + +To see examples of using method modifiers, see the following examples +included in the distribution; F, F, +F and F. There is also a +classic CLOS usage example in the test F<017_add_method_modifier.t>. + +=head3 What is the performance impact? + +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. + +The wrapping method does it's best to B 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. + +All this said, my benchmarks have indicated the following: + + 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 + +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 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 + +This will wrap the method at C<$method_name> and the supplied C<$code> +will be passed the C<@_> arguments, and called before the original +method is called. As specified above, the return value of the I +method modifiers is ignored, and it's ability to modify C<@_> is +fairly limited. If you need to do either of these things, use an +C method modifier. + +=item B + +This will wrap the method at C<$method_name> so that the original +method will be called, it's return values stashed, and then the +supplied C<$code> will be passed the C<@_> arguments, and called. +As specified above, the return value of the I method +modifiers is ignored, and it cannot modify the return values of +the original method. If you need to do either of these things, use an +C method modifier. + +=item B + +This will wrap the method at C<$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<$code> can or cannot do. + =back =head2 Attributes @@ -416,22 +1112,32 @@ once, and in the correct order. It should be noted that since there is no one consistent way to define the attributes of a class in Perl 5. These methods can only work with the information given, and can not easily discover information on -their own. +their own. See L for more details. =over 4 +=item B + +=item B + =item B -This stores a C<$attribute_meta_object> in the Class object and -associates it with the C<$attribute_name>. Unlike methods, attributes -within the MOP are stored as meta-information only. They will be used -later to construct instances from (see C above). +This stores a C<$attribute_meta_object> in the B +instance associated with the given class, and associates it with +the C<$attribute_name>. Unlike methods, attributes within the MOP +are stored as meta-information only. They will be used later to +construct instances from (see C above). More details about the attribute meta-objects can be found in the -L section of this document. +L or the L +section. + +It should be noted that any accessor, reader/writer or predicate +methods which the C<$attribute_meta_object> has will be installed +into the class at this time. =item B -Checks to see if this Class has an attribute by the name of +Checks to see if this class has an attribute by the name of C<$attribute_name> and returns a boolean. =item B @@ -444,10 +1150,18 @@ if none is found, it will return undef. This will remove the attribute meta-object stored at C<$attribute_name>, then return the removed attribute meta-object. -B Removing an attribute will only affect future instances of +B +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. +It should be noted that any accessor, reader/writer or predicate +methods which the attribute meta-object stored at C<$attribute_name> +has will be removed from the class at this time. This B make +these attributes somewhat inaccessable in previously created +instances. But if you are crazy enough to do this at runtime, then +you are crazy enough to deal with something like this :). + =item B This returns a list of attribute names which are defined in the local @@ -456,23 +1170,70 @@ use the C method. =item B -This will traverse the inheritance heirachy and return a list of HASH -references for all the applicable attributes for this class. The HASH -references will contain the following information; the attribute name, -the class which the attribute is associated with and the actual -attribute meta-object +This will traverse the inheritance heirachy and return a list of all +the applicable attributes for this class. It does not construct a +HASH reference like C because all +that same information is discoverable through the attribute +meta-object itself. + +=item B + +This method will traverse the inheritance heirachy and find the +first attribute whose name matches C<$attr_name>, then return it. +It will return undef if nothing is found. + +=back + +=head2 Package Variables + +Since Perl's classes are built atop the Perl package system, it is +fairly common to use package scoped variables for things like static +class variables. The following methods are convience methods for +the creation and inspection of package scoped variables. + +=over 4 + +=item B + +Given a C<$variable_name>, which must contain a leading sigil, this +method will create that variable within the package which houses the +class. It also takes an optional C<$initial_value>, which must be a +reference of the same type as the sigil of the C<$variable_name> +implies. -=item B +=item B -This will communicate with all of the classes attributes to create -and install the appropriate accessors. (see L -below for more details). +This will return a reference to the package variable in +C<$variable_name>. + +=item B + +Returns true (C<1>) if there is a package variable defined for +C<$variable_name>, and false (C<0>) otherwise. + +=item B + +This will attempt to remove the package variable at C<$variable_name>. =back -=head1 AUTHOR +=head2 Class closing + +=over 4 + +=item B + +=item B + +=item B + +=back + +=head1 AUTHORS + +Stevan Little Estevan@iinteractive.comE -Stevan Little Estevan@iinteractive.comE +Yuval Kogman Enothingmuch@woobling.comE =head1 COPYRIGHT AND LICENSE @@ -483,4 +1244,4 @@ L This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself. -=cut \ No newline at end of file +=cut