2 package Class::MOP::Instance;
7 use Scalar::Util 'weaken', 'blessed';
10 our $AUTHORITY = 'cpan:STEVAN';
13 require Class::MOP::Class;
14 Class::MOP::Class->initialize(blessed($_[0]) || $_[0]);
18 my ($class, $meta, @attrs) = @_;
19 my @slots = map { $_->slots } @attrs;
20 my $instance = bless {
22 # I am not sure that it makes
23 # sense to pass in the meta
24 # The ideal would be to just
25 # pass in the class name, but
26 # that is placing too much of
27 # an assumption on bless(),
28 # which is *probably* a safe
29 # assumption,.. but you can
32 '@!slots' => { map { $_ => undef } @slots },
35 weaken($instance->{'$!meta'});
40 sub associated_metaclass { (shift)->{'$!meta'} }
44 $self->bless_instance_structure({});
47 sub bless_instance_structure {
48 my ($self, $instance_structure) = @_;
49 bless $instance_structure, $self->associated_metaclass->name;
53 my ($self, $instance) = @_;
54 $self->bless_instance_structure({ %$instance });
57 # operations on meta instance
61 return keys %{$self->{'@!slots'}};
65 my ($self, $slot_name) = @_;
66 exists $self->{'@!slots'}->{$slot_name} ? 1 : 0;
69 # operations on created instances
72 my ($self, $instance, $slot_name) = @_;
73 $self->is_slot_initialized($instance, $slot_name) ? $instance->{$slot_name} : undef;
77 my ($self, $instance, $slot_name, $value) = @_;
78 $instance->{$slot_name} = $value;
82 my ($self, $instance, $slot_name) = @_;
83 #$self->set_slot_value($instance, $slot_name, undef);
86 sub deinitialize_slot {
87 my ( $self, $instance, $slot_name ) = @_;
88 delete $instance->{$slot_name};
91 sub initialize_all_slots {
92 my ($self, $instance) = @_;
93 foreach my $slot_name ($self->get_all_slots) {
94 $self->initialize_slot($instance, $slot_name);
98 sub deinitialize_all_slots {
99 my ($self, $instance) = @_;
100 foreach my $slot_name ($self->get_all_slots) {
101 $self->deinitialize_slot($instance, $slot_name);
105 sub is_slot_initialized {
106 my ($self, $instance, $slot_name, $value) = @_;
107 exists $instance->{$slot_name} ? 1 : 0;
110 sub weaken_slot_value {
111 my ($self, $instance, $slot_name) = @_;
112 weaken $instance->{$slot_name};
115 sub strengthen_slot_value {
116 my ($self, $instance, $slot_name) = @_;
117 $self->set_slot_value($instance, $slot_name, $self->get_slot_value($instance, $slot_name));
120 sub rebless_instance_structure {
121 my ($self, $instance, $metaclass) = @_;
122 bless $instance, $metaclass->name;
125 # inlinable operation snippets
127 sub is_inlinable { 1 }
129 sub inline_create_instance {
130 my ($self, $class_variable) = @_;
131 'bless {} => ' . $class_variable;
134 sub inline_slot_access {
135 my ($self, $instance, $slot_name) = @_;
136 sprintf "%s->{%s}", $instance, $slot_name;
139 sub inline_get_slot_value {
140 my ($self, $instance, $slot_name) = @_;
141 'exists ' . $self->inline_slot_access($instance, $slot_name) .
142 ' ? ' . $self->inline_slot_access($instance, $slot_name) . ' : undef'
145 sub inline_set_slot_value {
146 my ($self, $instance, $slot_name, $value) = @_;
147 $self->inline_slot_access($instance, $slot_name) . " = $value",
150 sub inline_initialize_slot {
151 my ($self, $instance, $slot_name) = @_;
152 $self->inline_set_slot_value($instance, $slot_name, 'undef'),
155 sub inline_deinitialize_slot {
156 my ($self, $instance, $slot_name) = @_;
157 "delete " . $self->inline_slot_access($instance, $slot_name);
159 sub inline_is_slot_initialized {
160 my ($self, $instance, $slot_name) = @_;
161 "exists " . $self->inline_slot_access($instance, $slot_name) . " ? 1 : 0";
164 sub inline_weaken_slot_value {
165 my ($self, $instance, $slot_name) = @_;
166 sprintf "Scalar::Util::weaken( %s )", $self->inline_slot_access($instance, $slot_name);
169 sub inline_strengthen_slot_value {
170 my ($self, $instance, $slot_name) = @_;
171 $self->inline_set_slot_value($instance, $slot_name, $self->inline_slot_access($instance, $slot_name));
182 Class::MOP::Instance - Instance Meta Object
186 # for the most part, this protocol is internal
187 # and not for public usage, but this how one
195 ':instance_metaclass' => 'ArrayBasedStorage::Instance',
198 # now Foo->new produces blessed ARRAY ref based objects
202 This is a sub-protocol which governs instance creation
203 and access to the slots of the instance structure.
205 This may seem like over-abstraction, but by abstracting
206 this process into a sub-protocol we make it possible to
207 easily switch the details of how an object's instance is
208 stored with minimal impact. In most cases just subclassing
209 this class will be all you need to do (see the examples;
210 F<examples/ArrayBasedStorage.pod> and
211 F<examples/InsideOutClass.pod> for details).
217 =item B<new ($meta, @attrs)>
219 Creates a new instance meta-object and gathers all the slots from
220 the list of C<@attrs> given.
224 This will return a B<Class::MOP::Class> instance which is related
229 =head2 Creation of Instances
233 =item B<create_instance>
235 This creates the appropriate structure needed for the instance and
236 then calls C<bless_instance_structure> to bless it into the class.
238 =item B<bless_instance_structure ($instance_structure)>
240 This does just exactly what it says it does.
242 =item B<clone_instance ($instance_structure)>
246 =head2 Instrospection
248 NOTE: There might be more methods added to this part of the API,
249 we will add then when we need them basically.
253 =item B<associated_metaclass>
255 =item B<get_all_slots>
257 This will return the current list of slots based on what was
258 given to this object in C<new>.
260 =item B<is_valid_slot ($slot_name)>
264 =head2 Operations on Instance Structures
266 An important distinction of this sub-protocol is that the
267 instance meta-object is a different entity from the actual
268 instance it creates. For this reason, any actions on slots
269 require that the C<$instance_structure> is passed into them.
273 =item B<get_slot_value ($instance_structure, $slot_name)>
275 =item B<set_slot_value ($instance_structure, $slot_name, $value)>
277 =item B<initialize_slot ($instance_structure, $slot_name)>
279 =item B<deinitialize_slot ($instance_structure, $slot_name)>
281 =item B<initialize_all_slots ($instance_structure)>
283 =item B<deinitialize_all_slots ($instance_structure)>
285 =item B<is_slot_initialized ($instance_structure, $slot_name)>
287 =item B<weaken_slot_value ($instance_structure, $slot_name)>
289 =item B<strengthen_slot_value ($instance_structure, $slot_name)>
291 =item B<rebless_instance_structure ($instance_structure, $new_metaclass)>
295 =head2 Inlineable Instance Operations
297 This part of the API is currently un-used. It is there for use
298 in future experiments in class finailization mostly. Best to
303 =item B<is_inlinable>
305 Each meta-instance should override this method to tell Class::MOP if it's
306 possible to inline the slot access.
308 This is currently only used by Class::MOP::Class::Immutable when performing
311 =item B<inline_create_instance>
313 =item B<inline_slot_access ($instance_structure, $slot_name)>
315 =item B<inline_get_slot_value ($instance_structure, $slot_name)>
317 =item B<inline_set_slot_value ($instance_structure, $slot_name, $value)>
319 =item B<inline_initialize_slot ($instance_structure, $slot_name)>
321 =item B<inline_deinitialize_slot ($instance_structure, $slot_name)>
323 =item B<inline_is_slot_initialized ($instance_structure, $slot_name)>
325 =item B<inline_weaken_slot_value ($instance_structure, $slot_name)>
327 =item B<inline_strengthen_slot_value ($instance_structure, $slot_name)>
333 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
335 Stevan Little E<lt>stevan@iinteractive.comE<gt>
337 =head1 COPYRIGHT AND LICENSE
339 Copyright 2006-2008 by Infinity Interactive, Inc.
341 L<http://www.iinteractive.com>
343 This library is free software; you can redistribute it and/or modify
344 it under the same terms as Perl itself.