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';
48 ## Method generation helpers
50 sub _generate_accessor_method {
51 my $attr = (shift)->associated_attribute;
52 my $meta_class = $attr->associated_class;
53 my $attr_name = $attr->name;
55 my $meta_instance = $meta_class->get_meta_instance;
56 $meta_instance->set_slot_value($_[0], $attr_name, $_[1]) if scalar(@_) == 2;
57 $meta_instance->get_slot_value($_[0], $attr_name);
61 sub _generate_reader_method {
62 my $attr = (shift)->associated_attribute;
63 my $meta_class = $attr->associated_class;
64 my $attr_name = $attr->name;
66 confess "Cannot assign a value to a read-only accessor" if @_ > 1;
67 $meta_class->get_meta_instance
68 ->get_slot_value($_[0], $attr_name);
72 sub _generate_writer_method {
73 my $attr = (shift)->associated_attribute;
74 my $meta_class = $attr->associated_class;
75 my $attr_name = $attr->name;
77 $meta_class->get_meta_instance
78 ->set_slot_value($_[0], $attr_name, $_[1]);
82 sub _generate_predicate_method {
83 my $attr = (shift)->associated_attribute;
84 my $meta_class = $attr->associated_class;
85 my $attr_name = $attr->name;
87 defined $meta_class->get_meta_instance
88 ->get_slot_value($_[0], $attr_name) ? 1 : 0;
92 package # hide the package from PAUSE
93 InsideOutClass::Instance;
98 our $VERSION = '0.01';
101 use Scalar::Util 'refaddr';
103 use base 'Class::MOP::Instance';
105 sub create_instance {
106 my ($self, $class) = @_;
107 bless \(my $instance), $self->_class_name;
111 my ($self, $instance, $slot_name) = @_;
112 $self->associated_metaclass->get_package_symbol('%' . $slot_name)->{refaddr $instance};
116 my ($self, $instance, $slot_name, $value) = @_;
117 $self->associated_metaclass->get_package_symbol('%' . $slot_name)->{refaddr $instance} = $value;
120 sub initialize_slot {
121 my ($self, $instance, $slot_name) = @_;
122 $self->associated_metaclass->add_package_symbol(('%' . $slot_name) => {})
123 unless $self->associated_metaclass->has_package_symbol('%' . $slot_name);
124 $self->associated_metaclass->get_package_symbol('%' . $slot_name)->{refaddr $instance} = undef;
127 sub is_slot_initialized {
128 my ($self, $instance, $slot_name) = @_;
129 return 0 unless $self->associated_metaclass->has_package_symbol('%' . $slot_name);
130 return exists $self->associated_metaclass->get_package_symbol('%' . $slot_name)->{refaddr $instance} ? 1 : 0;
141 InsideOutClass - A set of example metaclasses which implement the Inside-Out technique
148 ':attribute_metaclass' => 'InsideOutClass::Attribute',
149 ':instance_metaclass' => 'InsideOutClass::Instance'
152 __PACKAGE__->meta->add_attribute('foo' => (
159 $class->meta->new_object(@_);
162 # now you can just use the class as normal
166 This is a set of example metaclasses which implement the Inside-Out
167 class technique. What follows is a brief explaination of the code
168 found in this module.
170 We must create a subclass of B<Class::MOP::Instance> and override
171 the slot operations. This requires
172 overloading C<get_slot_value>, C<set_slot_value>, C<slot_initialized>, and
173 C<initialize_slot>, as well as their inline counterparts. Additionally we
174 overload C<add_slot> in order to initialize the global hash containing the
177 And that is pretty much all. Of course I am ignoring need for
178 inside-out objects to be C<DESTROY>-ed, and some other details as
179 well (threading, etc), but this is an example. A real implementation is left as
180 an exercise to the reader.
184 Stevan Little E<lt>stevan@iinteractive.comE<gt>
186 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
188 =head1 COPYRIGHT AND LICENSE
190 Copyright 2006-2008 by Infinity Interactive, Inc.
192 L<http://www.iinteractive.com>
194 This library is free software; you can redistribute it and/or modify
195 it under the same terms as Perl itself.