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};
69 # operations on created instances
72 my ($self, $instance, $slot_name) = @_;
73 $instance->{$slot_name};
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};
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 $self->inline_slot_access($instance, $slot_name);
144 sub inline_set_slot_value {
145 my ($self, $instance, $slot_name, $value) = @_;
146 $self->inline_slot_access($instance, $slot_name) . " = $value",
149 sub inline_initialize_slot {
150 my ($self, $instance, $slot_name) = @_;
151 $self->inline_set_slot_value($instance, $slot_name, 'undef'),
154 sub inline_deinitialize_slot {
155 my ($self, $instance, $slot_name) = @_;
156 "delete " . $self->inline_slot_access($instance, $slot_name);
158 sub inline_is_slot_initialized {
159 my ($self, $instance, $slot_name) = @_;
160 "exists " . $self->inline_slot_access($instance, $slot_name);
163 sub inline_weaken_slot_value {
164 my ($self, $instance, $slot_name) = @_;
165 sprintf "Scalar::Util::weaken( %s )", $self->inline_slot_access($instance, $slot_name);
168 sub inline_strengthen_slot_value {
169 my ($self, $instance, $slot_name) = @_;
170 $self->inline_set_slot_value($instance, $slot_name, $self->inline_slot_access($instance, $slot_name));
181 Class::MOP::Instance - Instance Meta Object
185 # for the most part, this protocol is internal
186 # and not for public usage, but this how one
194 ':instance_metaclass' => 'ArrayBasedStorage::Instance',
197 # now Foo->new produces blessed ARRAY ref based objects
201 This is a sub-protocol which governs instance creation
202 and access to the slots of the instance structure.
204 This may seem like over-abstraction, but by abstracting
205 this process into a sub-protocol we make it possible to
206 easily switch the details of how an object's instance is
207 stored with minimal impact. In most cases just subclassing
208 this class will be all you need to do (see the examples;
209 F<examples/ArrayBasedStorage.pod> and
210 F<examples/InsideOutClass.pod> for details).
216 =item B<new ($meta, @attrs)>
218 Creates a new instance meta-object and gathers all the slots from
219 the list of C<@attrs> given.
223 This will return a B<Class::MOP::Class> instance which is related
228 =head2 Creation of Instances
232 =item B<create_instance>
234 This creates the appropriate structure needed for the instance and
235 then calls C<bless_instance_structure> to bless it into the class.
237 =item B<bless_instance_structure ($instance_structure)>
239 This does just exactly what it says it does.
241 =item B<clone_instance ($instance_structure)>
245 =head2 Instrospection
247 NOTE: There might be more methods added to this part of the API,
248 we will add then when we need them basically.
252 =item B<associated_metaclass>
254 =item B<get_all_slots>
256 This will return the current list of slots based on what was
257 given to this object in C<new>.
259 =item B<is_valid_slot ($slot_name)>
263 =head2 Operations on Instance Structures
265 An important distinction of this sub-protocol is that the
266 instance meta-object is a different entity from the actual
267 instance it creates. For this reason, any actions on slots
268 require that the C<$instance_structure> is passed into them.
272 =item B<get_slot_value ($instance_structure, $slot_name)>
274 =item B<set_slot_value ($instance_structure, $slot_name, $value)>
276 =item B<initialize_slot ($instance_structure, $slot_name)>
278 =item B<deinitialize_slot ($instance_structure, $slot_name)>
280 =item B<initialize_all_slots ($instance_structure)>
282 =item B<deinitialize_all_slots ($instance_structure)>
284 =item B<is_slot_initialized ($instance_structure, $slot_name)>
286 =item B<weaken_slot_value ($instance_structure, $slot_name)>
288 =item B<strengthen_slot_value ($instance_structure, $slot_name)>
290 =item B<rebless_instance_structure ($instance_structure, $new_metaclass)>
294 =head2 Inlineable Instance Operations
296 This part of the API is currently un-used. It is there for use
297 in future experiments in class finailization mostly. Best to
302 =item B<is_inlinable>
304 Each meta-instance should override this method to tell Class::MOP if it's
305 possible to inline the slot access.
307 This is currently only used by Class::MOP::Class::Immutable when performing
310 =item B<inline_create_instance>
312 =item B<inline_slot_access ($instance_structure, $slot_name)>
314 =item B<inline_get_slot_value ($instance_structure, $slot_name)>
316 =item B<inline_set_slot_value ($instance_structure, $slot_name, $value)>
318 =item B<inline_initialize_slot ($instance_structure, $slot_name)>
320 =item B<inline_deinitialize_slot ($instance_structure, $slot_name)>
322 =item B<inline_is_slot_initialized ($instance_structure, $slot_name)>
324 =item B<inline_weaken_slot_value ($instance_structure, $slot_name)>
326 =item B<inline_strengthen_slot_value ($instance_structure, $slot_name)>
332 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
334 Stevan Little E<lt>stevan@iinteractive.comE<gt>
336 =head1 COPYRIGHT AND LICENSE
338 Copyright 2006-2008 by Infinity Interactive, Inc.
340 L<http://www.iinteractive.com>
342 This library is free software; you can redistribute it and/or modify
343 it under the same terms as Perl itself.