2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
10 our $VERSION = '0.11';
11 our $AUTHORITY = 'cpan:STEVAN';
13 use Moose::Meta::Method::Accessor;
14 use Moose::Util::TypeConstraints ();
16 use base 'Class::MOP::Attribute';
18 # options which are not directly used
19 # but we store them for metadata purposes
20 __PACKAGE__->meta->add_attribute('isa' => (reader => '_isa_metadata'));
21 __PACKAGE__->meta->add_attribute('does' => (reader => '_does_metadata'));
22 __PACKAGE__->meta->add_attribute('is' => (reader => '_is_metadata'));
24 # these are actual options for the attrs
25 __PACKAGE__->meta->add_attribute('required' => (reader => 'is_required' ));
26 __PACKAGE__->meta->add_attribute('lazy' => (reader => 'is_lazy' ));
27 __PACKAGE__->meta->add_attribute('coerce' => (reader => 'should_coerce' ));
28 __PACKAGE__->meta->add_attribute('weak_ref' => (reader => 'is_weak_ref' ));
29 __PACKAGE__->meta->add_attribute('auto_deref' => (reader => 'should_auto_deref'));
30 __PACKAGE__->meta->add_attribute('type_constraint' => (
31 reader => 'type_constraint',
32 predicate => 'has_type_constraint',
34 __PACKAGE__->meta->add_attribute('trigger' => (
36 predicate => 'has_trigger',
38 __PACKAGE__->meta->add_attribute('handles' => (
40 predicate => 'has_handles',
42 __PACKAGE__->meta->add_attribute('documentation' => (
43 reader => 'documentation',
44 predicate => 'has_documentation',
48 my ($class, $name, %options) = @_;
49 $class->_process_options($name, \%options);
50 return $class->SUPER::new($name, %options);
53 sub clone_and_inherit_options {
54 my ($self, %options) = @_;
55 # you can change default, required, coerce, documentation and lazy
57 foreach my $legal_option (qw(default coerce required documentation lazy)) {
58 if (exists $options{$legal_option}) {
59 $actual_options{$legal_option} = $options{$legal_option};
60 delete $options{$legal_option};
64 # handles can only be added, not changed
65 if ($options{handles}) {
66 confess "You can only add the 'handles' option, you cannot change it"
67 if $self->has_handles;
68 $actual_options{handles} = $options{handles};
69 delete $options{handles};
72 # isa can be changed, but only if the
73 # new type is a subtype
76 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
77 $type_constraint = $options{isa};
80 $type_constraint = Moose::Util::TypeConstraints::find_type_constraint($options{isa});
81 (defined $type_constraint)
82 || confess "Could not find the type constraint '" . $options{isa} . "'";
85 # check here to see if the new type
86 # is a subtype of the old one
87 ($type_constraint->is_subtype_of($self->type_constraint->name))
88 || confess "New type constraint setting must be a subtype of inherited one"
89 # iff we have a type constraint that is ...
90 if $self->has_type_constraint;
92 $actual_options{type_constraint} = $type_constraint;
95 (scalar keys %options == 0)
96 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
97 $self->clone(%actual_options);
100 sub _process_options {
101 my ($class, $name, $options) = @_;
103 if (exists $options->{is}) {
104 if ($options->{is} eq 'ro') {
105 $options->{reader} ||= $name;
106 (!exists $options->{trigger})
107 || confess "Cannot have a trigger on a read-only attribute";
109 elsif ($options->{is} eq 'rw') {
110 $options->{accessor} = $name;
111 ((reftype($options->{trigger}) || '') eq 'CODE')
112 || confess "Trigger must be a CODE ref"
113 if exists $options->{trigger};
116 confess "I do not understand this option (is => " . $options->{is} . ")"
120 if (exists $options->{isa}) {
122 if (exists $options->{does}) {
123 if (eval { $options->{isa}->can('does') }) {
124 ($options->{isa}->does($options->{does}))
125 || confess "Cannot have an isa option and a does option if the isa does not do the does";
128 confess "Cannot have an isa option which cannot ->does()";
132 # allow for anon-subtypes here ...
133 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
134 $options->{type_constraint} = $options->{isa};
138 if ($options->{isa} =~ /\|/) {
139 my @type_constraints = split /\s*\|\s*/ => $options->{isa};
140 $options->{type_constraint} = Moose::Util::TypeConstraints::create_type_constraint_union(
145 # otherwise assume it is a constraint
146 my $constraint = Moose::Util::TypeConstraints::find_type_constraint($options->{isa});
147 # if the constraing it not found ....
148 unless (defined $constraint) {
149 # assume it is a foreign class, and make
150 # an anon constraint for it
151 $constraint = Moose::Util::TypeConstraints::subtype(
153 Moose::Util::TypeConstraints::where { $_->isa($options->{isa}) }
156 $options->{type_constraint} = $constraint;
160 elsif (exists $options->{does}) {
161 # allow for anon-subtypes here ...
162 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
163 $options->{type_constraint} = $options->{isa};
166 # otherwise assume it is a constraint
167 my $constraint = Moose::Util::TypeConstraints::find_type_constraint($options->{does});
168 # if the constraing it not found ....
169 unless (defined $constraint) {
170 # assume it is a foreign class, and make
171 # an anon constraint for it
172 $constraint = Moose::Util::TypeConstraints::subtype(
174 Moose::Util::TypeConstraints::where { $_->does($options->{does}) }
177 $options->{type_constraint} = $constraint;
181 if (exists $options->{coerce} && $options->{coerce}) {
182 (exists $options->{type_constraint})
183 || confess "You cannot have coercion without specifying a type constraint";
184 confess "You cannot have a weak reference to a coerced value"
185 if $options->{weak_ref};
188 if (exists $options->{auto_deref} && $options->{auto_deref}) {
189 (exists $options->{type_constraint})
190 || confess "You cannot auto-dereference without specifying a type constraint";
191 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
192 $options->{type_constraint}->is_a_type_of('HashRef'))
193 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef";
196 if (exists $options->{lazy} && $options->{lazy}) {
197 (exists $options->{default})
198 || confess "You cannot have lazy attribute without specifying a default value for it";
202 sub initialize_instance_slot {
203 my ($self, $meta_instance, $instance, $params) = @_;
204 my $init_arg = $self->init_arg();
205 # try to fetch the init arg from the %params ...
208 if (exists $params->{$init_arg}) {
209 $val = $params->{$init_arg};
211 if (!defined $val && $self->is_required) {
212 confess "Attribute (" . $self->name . ") is required and cannot be undef";
216 # skip it if it's lazy
217 return if $self->is_lazy;
218 # and die if it's required and doesn't have a default value
219 confess "Attribute (" . $self->name . ") is required"
220 if $self->is_required && !$self->has_default;
223 # if nothing was in the %params, we can use the
224 # attribute's default value (if it has one)
225 if (!defined $val && $self->has_default) {
226 $val = $self->default($instance);
230 if ($self->has_type_constraint) {
231 my $type_constraint = $self->type_constraint;
232 if ($self->should_coerce && $type_constraint->has_coercion) {
233 $val = $type_constraint->coerce($val);
235 (defined($type_constraint->check($val)))
236 || confess "Attribute (" .
238 ") does not pass the type constraint (" .
239 $type_constraint->name .
244 $meta_instance->set_slot_value($instance, $self->name, $val);
245 $meta_instance->weaken_slot_value($instance, $self->name)
246 if ref $val && $self->is_weak_ref;
252 my ($self, $instance, $value) = @_;
254 my $attr_name = $self->name;
256 if ($self->is_required) {
258 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
261 if ($self->has_type_constraint) {
263 my $type_constraint = $self->type_constraint;
265 if ($self->should_coerce) {
266 $value = $type_constraint->coerce($value);
268 defined($type_constraint->_compiled_type_constraint->($value))
269 || confess "Attribute ($attr_name) does not pass the type constraint ("
270 . $type_constraint->name . ") with " . (defined($value) ? ("'" . $value . "'") : "undef")
274 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
277 $meta_instance->set_slot_value($instance, $attr_name, $value);
279 if (ref $value && $self->is_weak_ref) {
280 $meta_instance->weaken_slot_value($instance, $attr_name);
283 if ($self->has_trigger) {
284 $self->trigger->($instance, $value, $self);
289 my ($self, $instance) = @_;
291 if ($self->is_lazy) {
292 unless ($self->has_value($instance)) {
293 if ($self->has_default) {
294 my $default = $self->default($instance);
295 $self->set_value($instance, $default);
298 $self->set_value($instance, undef);
303 if ($self->should_auto_deref) {
305 my $type_constraint = $self->type_constraint;
307 if ($type_constraint->is_a_type_of('ArrayRef')) {
308 my $rv = $self->SUPER::get_value($instance);
309 return unless defined $rv;
310 return wantarray ? @{ $rv } : $rv;
312 elsif ($type_constraint->is_a_type_of('HashRef')) {
313 my $rv = $self->SUPER::get_value($instance);
314 return unless defined $rv;
315 return wantarray ? %{ $rv } : $rv;
318 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
324 return $self->SUPER::get_value($instance);
328 ## installing accessors
330 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
332 sub install_accessors {
334 $self->SUPER::install_accessors(@_);
336 if ($self->has_handles) {
339 # Here we canonicalize the 'handles' option
340 # this will sort out any details and always
341 # return an hash of methods which we want
342 # to delagate to, see that method for details
343 my %handles = $self->_canonicalize_handles();
345 # find the name of the accessor for this attribute
346 my $accessor_name = $self->reader || $self->accessor;
347 (defined $accessor_name)
348 || confess "You cannot install delegation without a reader or accessor for the attribute";
350 # make sure we handle HASH accessors correctly
351 ($accessor_name) = keys %{$accessor_name}
352 if ref($accessor_name) eq 'HASH';
354 # install the delegation ...
355 my $associated_class = $self->associated_class;
356 foreach my $handle (keys %handles) {
357 my $method_to_call = $handles{$handle};
359 (!$associated_class->has_method($handle))
360 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
363 # handles is not allowed to delegate
364 # any of these methods, as they will
365 # override the ones in your class, which
366 # is almost certainly not what you want.
367 next if $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
369 if ((reftype($method_to_call) || '') eq 'CODE') {
370 $associated_class->add_method($handle => $method_to_call);
373 $associated_class->add_method($handle => sub {
375 # we should check for lack of
376 # a callable return value from
378 my $proxy = (shift)->$accessor_name();
380 goto &{ $proxy->can($method_to_call)};
389 # private methods to help delegation ...
391 sub _canonicalize_handles {
393 my $handles = $self->handles;
394 if (my $handle_type = ref($handles)) {
395 if ($handle_type eq 'HASH') {
398 elsif ($handle_type eq 'ARRAY') {
399 return map { $_ => $_ } @{$handles};
401 elsif ($handle_type eq 'Regexp') {
402 ($self->has_type_constraint)
403 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
404 return map { ($_ => $_) }
405 grep { /$handles/ } $self->_get_delegate_method_list;
407 elsif ($handle_type eq 'CODE') {
408 return $handles->($self, $self->_find_delegate_metaclass);
411 confess "Unable to canonicalize the 'handles' option with $handles";
415 my $role_meta = eval { $handles->meta };
417 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
420 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
421 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
423 return map { $_ => $_ } (
424 $role_meta->get_method_list,
425 $role_meta->get_required_method_list
430 sub _find_delegate_metaclass {
432 if (my $class = $self->_isa_metadata) {
433 # if the class does have
434 # a meta method, use it
435 return $class->meta if $class->can('meta');
436 # otherwise we might be
437 # dealing with a non-Moose
438 # class, and need to make
440 return Moose::Meta::Class->initialize($class);
442 elsif (my $role = $self->_does_metadata) {
443 # our role will always have
448 confess "Cannot find delegate metaclass for attribute " . $self->name;
452 sub _get_delegate_method_list {
454 my $meta = $self->_find_delegate_metaclass;
455 if ($meta->isa('Class::MOP::Class')) {
456 return map { $_->{name} } # NOTE: !never! delegate &meta
457 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
458 $meta->compute_all_applicable_methods;
460 elsif ($meta->isa('Moose::Meta::Role')) {
461 return $meta->get_method_list;
464 confess "Unable to recognize the delegate metaclass '$meta'";
476 Moose::Meta::Attribute - The Moose attribute metaclass
480 This is a subclass of L<Class::MOP::Attribute> with Moose specific
483 For the most part, the only time you will ever encounter an
484 instance of this class is if you are doing some serious deep
485 introspection. To really understand this class, you need to refer
486 to the L<Class::MOP::Attribute> documentation.
490 =head2 Overridden methods
492 These methods override methods in L<Class::MOP::Attribute> and add
493 Moose specific features. You can safely assume though that they
494 will behave just as L<Class::MOP::Attribute> does.
500 =item B<initialize_instance_slot>
502 =item B<install_accessors>
504 =item B<accessor_metaclass>
512 =head2 Additional Moose features
514 Moose attributes support type-constraint checking, weak reference
515 creation and type coercion.
519 =item B<clone_and_inherit_options>
521 This is to support the C<has '+foo'> feature, it clones an attribute
522 from a superclass and allows a very specific set of changes to be made
525 =item B<has_type_constraint>
527 Returns true if this meta-attribute has a type constraint.
529 =item B<type_constraint>
531 A read-only accessor for this meta-attribute's type constraint. For
532 more information on what you can do with this, see the documentation
533 for L<Moose::Meta::TypeConstraint>.
537 Returns true if this meta-attribute performs delegation.
541 This returns the value which was passed into the handles option.
545 Returns true if this meta-attribute produces a weak reference.
549 Returns true if this meta-attribute is required to have a value.
553 Returns true if this meta-attribute should be initialized lazily.
555 NOTE: lazy attributes, B<must> have a C<default> field set.
557 =item B<should_coerce>
559 Returns true if this meta-attribute should perform type coercion.
561 =item B<should_auto_deref>
563 Returns true if this meta-attribute should perform automatic
566 NOTE: This can only be done for attributes whose type constraint is
567 either I<ArrayRef> or I<HashRef>.
571 Returns true if this meta-attribute has a trigger set.
575 This is a CODE reference which will be executed every time the
576 value of an attribute is assigned. The CODE ref will get two values,
577 the invocant and the new value. This can be used to handle I<basic>
578 bi-directional relations.
580 =item B<documentation>
582 This is a string which contains the documentation for this attribute.
583 It serves no direct purpose right now, but it might in the future
584 in some kind of automated documentation system perhaps.
586 =item B<has_documentation>
588 Returns true if this meta-attribute has any documentation.
594 All complex software has bugs lurking in it, and this module is no
595 exception. If you find a bug please either email me, or add the bug
600 Stevan Little E<lt>stevan@iinteractive.comE<gt>
602 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
604 =head1 COPYRIGHT AND LICENSE
606 Copyright 2006, 2007 by Infinity Interactive, Inc.
608 L<http://www.iinteractive.com>
610 This library is free software; you can redistribute it and/or modify
611 it under the same terms as Perl itself.