2 package # hide the package from PAUSE
3 InsideOutClass::Attribute;
11 use Scalar::Util 'refaddr';
13 use base 'Class::MOP::Attribute';
15 sub initialize_instance_slot {
16 my ($self, $meta_instance, $instance, $params) = @_;
17 my $init_arg = $self->init_arg;
18 # try to fetch the init arg from the %params ...
20 $val = $params->{$init_arg} if exists $params->{$init_arg};
21 # if nothing was in the %params, we can use the
22 # attribute's default value (if it has one)
23 if (!defined $val && defined $self->default) {
24 $val = $self->default($instance);
26 my $_meta_instance = $self->associated_class->get_meta_instance;
27 $_meta_instance->initialize_slot($instance, $self->name);
28 $_meta_instance->set_slot_value($instance, $self->name, $val);
31 sub accessor_metaclass { 'InsideOutClass::Method::Accessor' }
33 package # hide the package from PAUSE
34 InsideOutClass::Method::Accessor;
39 our $VERSION = '0.01';
42 use Scalar::Util 'refaddr';
44 use base 'Class::MOP::Method::Accessor';
46 ## Method generation helpers
48 sub _generate_accessor_method {
49 my $attr = (shift)->associated_attribute;
50 my $meta_class = $attr->associated_class;
51 my $attr_name = $attr->name;
53 my $meta_instance = $meta_class->get_meta_instance;
54 $meta_instance->set_slot_value($_[0], $attr_name, $_[1]) if scalar(@_) == 2;
55 $meta_instance->get_slot_value($_[0], $attr_name);
59 sub _generate_reader_method {
60 my $attr = (shift)->associated_attribute;
61 my $meta_class = $attr->associated_class;
62 my $attr_name = $attr->name;
64 confess "Cannot assign a value to a read-only accessor" if @_ > 1;
65 $meta_class->get_meta_instance
66 ->get_slot_value($_[0], $attr_name);
70 sub _generate_writer_method {
71 my $attr = (shift)->associated_attribute;
72 my $meta_class = $attr->associated_class;
73 my $attr_name = $attr->name;
75 $meta_class->get_meta_instance
76 ->set_slot_value($_[0], $attr_name, $_[1]);
80 sub _generate_predicate_method {
81 my $attr = (shift)->associated_attribute;
82 my $meta_class = $attr->associated_class;
83 my $attr_name = $attr->name;
85 defined $meta_class->get_meta_instance
86 ->get_slot_value($_[0], $attr_name) ? 1 : 0;
90 package # hide the package from PAUSE
91 InsideOutClass::Instance;
96 our $VERSION = '0.01';
99 use Scalar::Util 'refaddr';
101 use base 'Class::MOP::Instance';
103 sub create_instance {
104 my ($self, $class) = @_;
105 bless \(my $instance), $self->_class_name;
109 my ($self, $instance, $slot_name) = @_;
110 $self->associated_metaclass->get_package_symbol('%' . $slot_name)->{refaddr $instance};
114 my ($self, $instance, $slot_name, $value) = @_;
115 $self->associated_metaclass->get_package_symbol('%' . $slot_name)->{refaddr $instance} = $value;
118 sub initialize_slot {
119 my ($self, $instance, $slot_name) = @_;
120 $self->associated_metaclass->add_package_symbol(('%' . $slot_name) => {})
121 unless $self->associated_metaclass->has_package_symbol('%' . $slot_name);
122 $self->associated_metaclass->get_package_symbol('%' . $slot_name)->{refaddr $instance} = undef;
125 sub is_slot_initialized {
126 my ($self, $instance, $slot_name) = @_;
127 return 0 unless $self->associated_metaclass->has_package_symbol('%' . $slot_name);
128 return exists $self->associated_metaclass->get_package_symbol('%' . $slot_name)->{refaddr $instance} ? 1 : 0;
139 InsideOutClass - A set of example metaclasses which implement the Inside-Out technique
146 ':attribute_metaclass' => 'InsideOutClass::Attribute',
147 ':instance_metaclass' => 'InsideOutClass::Instance'
150 __PACKAGE__->meta->add_attribute('foo' => (
157 $class->meta->new_object(@_);
160 # now you can just use the class as normal
164 This is a set of example metaclasses which implement the Inside-Out
165 class technique. What follows is a brief explaination of the code
166 found in this module.
168 We must create a subclass of B<Class::MOP::Instance> and override
169 the slot operations. This requires
170 overloading C<get_slot_value>, C<set_slot_value>, C<slot_initialized>, and
171 C<initialize_slot>, as well as their inline counterparts. Additionally we
172 overload C<add_slot> in order to initialize the global hash containing the
175 And that is pretty much all. Of course I am ignoring need for
176 inside-out objects to be C<DESTROY>-ed, and some other details as
177 well (threading, etc), but this is an example. A real implementation is left as
178 an exercise to the reader.
182 Stevan Little E<lt>stevan@iinteractive.comE<gt>
184 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
186 =head1 COPYRIGHT AND LICENSE
188 Copyright 2006-2008 by Infinity Interactive, Inc.
190 L<http://www.iinteractive.com>
192 This library is free software; you can redistribute it and/or modify
193 it under the same terms as Perl itself.