2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
11 our $VERSION = '0.13';
12 our $AUTHORITY = 'cpan:STEVAN';
14 use Moose::Meta::Method::Accessor;
15 use Moose::Util::TypeConstraints ();
17 use base 'Class::MOP::Attribute';
19 # options which are not directly used
20 # but we store them for metadata purposes
21 __PACKAGE__->meta->add_attribute('isa' => (reader => '_isa_metadata'));
22 __PACKAGE__->meta->add_attribute('does' => (reader => '_does_metadata'));
23 __PACKAGE__->meta->add_attribute('is' => (reader => '_is_metadata'));
25 # these are actual options for the attrs
26 __PACKAGE__->meta->add_attribute('required' => (reader => 'is_required' ));
27 __PACKAGE__->meta->add_attribute('lazy' => (reader => 'is_lazy' ));
28 __PACKAGE__->meta->add_attribute('lazy_build' => (reader => 'is_lazy_build' ));
29 __PACKAGE__->meta->add_attribute('coerce' => (reader => 'should_coerce' ));
30 __PACKAGE__->meta->add_attribute('weak_ref' => (reader => 'is_weak_ref' ));
31 __PACKAGE__->meta->add_attribute('auto_deref' => (reader => 'should_auto_deref'));
32 __PACKAGE__->meta->add_attribute('type_constraint' => (
33 reader => 'type_constraint',
34 predicate => 'has_type_constraint',
36 __PACKAGE__->meta->add_attribute('trigger' => (
38 predicate => 'has_trigger',
40 __PACKAGE__->meta->add_attribute('handles' => (
42 predicate => 'has_handles',
44 __PACKAGE__->meta->add_attribute('documentation' => (
45 reader => 'documentation',
46 predicate => 'has_documentation',
50 my ($class, $name, %options) = @_;
51 $class->_process_options($name, \%options);
52 return $class->SUPER::new($name, %options);
55 sub clone_and_inherit_options {
56 my ($self, %options) = @_;
57 # you can change default, required, coerce, documentation and lazy
59 foreach my $legal_option (qw(default coerce required documentation lazy)) {
60 if (exists $options{$legal_option}) {
61 $actual_options{$legal_option} = $options{$legal_option};
62 delete $options{$legal_option};
66 # handles can only be added, not changed
67 if ($options{handles}) {
68 confess "You can only add the 'handles' option, you cannot change it"
69 if $self->has_handles;
70 $actual_options{handles} = $options{handles};
71 delete $options{handles};
74 # isa can be changed, but only if the
75 # new type is a subtype
78 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
79 $type_constraint = $options{isa};
82 $type_constraint = Moose::Util::TypeConstraints::find_type_constraint($options{isa});
83 (defined $type_constraint)
84 || confess "Could not find the type constraint '" . $options{isa} . "'";
87 # check here to see if the new type
88 # is a subtype of the old one
89 ($type_constraint->is_subtype_of($self->type_constraint->name))
90 || confess "New type constraint setting must be a subtype of inherited one"
91 # iff we have a type constraint that is ...
92 if $self->has_type_constraint;
94 $actual_options{type_constraint} = $type_constraint;
97 (scalar keys %options == 0)
98 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
99 $self->clone(%actual_options);
102 sub _process_options {
103 my ($class, $name, $options) = @_;
105 if (exists $options->{is}) {
106 if ($options->{is} eq 'ro') {
107 $options->{reader} ||= $name;
108 (!exists $options->{trigger})
109 || confess "Cannot have a trigger on a read-only attribute";
111 elsif ($options->{is} eq 'rw') {
112 $options->{accessor} = $name;
113 ((reftype($options->{trigger}) || '') eq 'CODE')
114 || confess "Trigger must be a CODE ref"
115 if exists $options->{trigger};
118 confess "I do not understand this option (is => " . $options->{is} . ")"
122 if (exists $options->{isa}) {
124 if (exists $options->{does}) {
125 if (eval { $options->{isa}->can('does') }) {
126 ($options->{isa}->does($options->{does}))
127 || confess "Cannot have an isa option and a does option if the isa does not do the does";
130 confess "Cannot have an isa option which cannot ->does()";
134 # allow for anon-subtypes here ...
135 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
136 $options->{type_constraint} = $options->{isa};
139 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
141 parent => Moose::Util::TypeConstraints::find_type_constraint('Object'),
142 constraint => sub { $_[0]->isa($options->{isa}) }
147 elsif (exists $options->{does}) {
148 # allow for anon-subtypes here ...
149 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
150 $options->{type_constraint} = $options->{isa};
153 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
154 $options->{does} => {
155 parent => Moose::Util::TypeConstraints::find_type_constraint('Role'),
156 constraint => sub { $_[0]->does($options->{does}) }
162 if (exists $options->{coerce} && $options->{coerce}) {
163 (exists $options->{type_constraint})
164 || confess "You cannot have coercion without specifying a type constraint";
165 confess "You cannot have a weak reference to a coerced value"
166 if $options->{weak_ref};
169 if (exists $options->{auto_deref} && $options->{auto_deref}) {
170 (exists $options->{type_constraint})
171 || confess "You cannot auto-dereference without specifying a type constraint";
172 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
173 $options->{type_constraint}->is_a_type_of('HashRef'))
174 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef";
177 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
178 confess("You can not use lazy_build and default for the same attribute")
179 if exists $options->{default};
180 $options->{lazy} = 1;
181 $options->{required} = 1;
183 $options->{builder} ||= "_build${name}";
184 $options->{clearer} ||= "_clear${name}";
185 $options->{predicate} ||= "_has${name}";
187 $options->{builder} ||= "build_${name}";
188 $options->{clearer} ||= "clear_${name}";
189 $options->{predicate} ||= "has_${name}";
193 if (exists $options->{lazy} && $options->{lazy}) {
194 (exists $options->{default} || exists $options->{builder} )
195 || confess "You cannot have lazy attribute without specifying a default value for it";
200 sub initialize_instance_slot {
201 my ($self, $meta_instance, $instance, $params) = @_;
202 my $init_arg = $self->init_arg();
203 # try to fetch the init arg from the %params ...
206 if (exists $params->{$init_arg}) {
207 $val = $params->{$init_arg};
209 if (!defined $val && $self->is_required) {
210 confess "Attribute (" . $self->name . ") is required and cannot be undef";
214 # skip it if it's lazy
215 return if $self->is_lazy;
216 # and die if it's required and doesn't have a default value
217 confess "Attribute (" . $self->name . ") is required"
218 if $self->is_required && !$self->has_default && !$self->has_builder;
221 # if nothing was in the %params, we can use the
222 # attribute's default value (if it has one)
223 if (!defined $val && $self->has_default) {
224 $val = $self->default($instance);
225 } elsif (!defined $val && $self->has_builder) {
226 my $builder = $self->builder;
227 confess(blessed($instance)." does not support builder method '$builder' for attribute '" . $self->name . "'")
228 unless $instance->can($builder);
229 $val = $instance->$builder;
232 if (defined $val || $self->has_default) {
233 if ($self->has_type_constraint) {
234 my $type_constraint = $self->type_constraint;
235 if ($self->should_coerce && $type_constraint->has_coercion) {
236 $val = $type_constraint->coerce($val);
238 (defined($type_constraint->check($val)))
239 || confess "Attribute (" .
241 ") does not pass the type constraint (" .
242 $type_constraint->name .
245 ? (blessed($val) && overload::Overloaded($val)
246 ? overload::StrVal($val)
253 $meta_instance->set_slot_value($instance, $self->name, $val);
254 $meta_instance->weaken_slot_value($instance, $self->name)
255 if ref $val && $self->is_weak_ref;
261 my ($self, $instance, $value) = @_;
263 my $attr_name = $self->name;
265 if ($self->is_required) {
267 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
270 if ($self->has_type_constraint) {
272 my $type_constraint = $self->type_constraint;
274 if ($self->should_coerce) {
275 $value = $type_constraint->coerce($value);
277 defined($type_constraint->_compiled_type_constraint->($value))
278 || confess "Attribute ($attr_name) does not pass the type constraint ("
279 . $type_constraint->name
283 (blessed($value) && overload::Overloaded($value)
284 ? overload::StrVal($value)
291 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
294 $meta_instance->set_slot_value($instance, $attr_name, $value);
296 if (ref $value && $self->is_weak_ref) {
297 $meta_instance->weaken_slot_value($instance, $attr_name);
300 if ($self->has_trigger) {
301 $self->trigger->($instance, $value, $self);
306 my ($self, $instance) = @_;
308 if ($self->is_lazy) {
309 unless ($self->has_value($instance)) {
310 if ($self->has_default) {
311 my $default = $self->default($instance);
312 $self->set_value($instance, $default);
314 if ( $self->has_builder ){
315 my $builder = $self->builder;
316 confess(blessed($instance)." does not support builder method '$builder' for attribute '" . $self->name . "'")
317 unless $instance->can($builder);
318 $self->set_value($instance, $instance->$builder);
320 $self->set_value($instance, undef);
325 if ($self->should_auto_deref) {
327 my $type_constraint = $self->type_constraint;
329 if ($type_constraint->is_a_type_of('ArrayRef')) {
330 my $rv = $self->SUPER::get_value($instance);
331 return unless defined $rv;
332 return wantarray ? @{ $rv } : $rv;
334 elsif ($type_constraint->is_a_type_of('HashRef')) {
335 my $rv = $self->SUPER::get_value($instance);
336 return unless defined $rv;
337 return wantarray ? %{ $rv } : $rv;
340 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
346 return $self->SUPER::get_value($instance);
350 ## installing accessors
352 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
354 sub install_accessors {
356 $self->SUPER::install_accessors(@_);
358 if ($self->has_handles) {
361 # Here we canonicalize the 'handles' option
362 # this will sort out any details and always
363 # return an hash of methods which we want
364 # to delagate to, see that method for details
365 my %handles = $self->_canonicalize_handles();
367 # find the name of the accessor for this attribute
368 my $accessor_name = $self->reader || $self->accessor;
369 (defined $accessor_name)
370 || confess "You cannot install delegation without a reader or accessor for the attribute";
372 # make sure we handle HASH accessors correctly
373 ($accessor_name) = keys %{$accessor_name}
374 if ref($accessor_name) eq 'HASH';
376 # install the delegation ...
377 my $associated_class = $self->associated_class;
378 foreach my $handle (keys %handles) {
379 my $method_to_call = $handles{$handle};
381 (!$associated_class->has_method($handle))
382 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
385 # handles is not allowed to delegate
386 # any of these methods, as they will
387 # override the ones in your class, which
388 # is almost certainly not what you want.
389 next if $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
391 if ((reftype($method_to_call) || '') eq 'CODE') {
392 $associated_class->add_method($handle => $method_to_call);
395 $associated_class->add_method($handle => sub {
397 # we should check for lack of
398 # a callable return value from
400 my $proxy = (shift)->$accessor_name();
402 goto &{ $proxy->can($method_to_call)};
411 # private methods to help delegation ...
413 sub _canonicalize_handles {
415 my $handles = $self->handles;
416 if (my $handle_type = ref($handles)) {
417 if ($handle_type eq 'HASH') {
420 elsif ($handle_type eq 'ARRAY') {
421 return map { $_ => $_ } @{$handles};
423 elsif ($handle_type eq 'Regexp') {
424 ($self->has_type_constraint)
425 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
426 return map { ($_ => $_) }
427 grep { /$handles/ } $self->_get_delegate_method_list;
429 elsif ($handle_type eq 'CODE') {
430 return $handles->($self, $self->_find_delegate_metaclass);
433 confess "Unable to canonicalize the 'handles' option with $handles";
437 my $role_meta = eval { $handles->meta };
439 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
442 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
443 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
445 return map { $_ => $_ } (
446 $role_meta->get_method_list,
447 $role_meta->get_required_method_list
452 sub _find_delegate_metaclass {
454 if (my $class = $self->_isa_metadata) {
455 # if the class does have
456 # a meta method, use it
457 return $class->meta if $class->can('meta');
458 # otherwise we might be
459 # dealing with a non-Moose
460 # class, and need to make
462 return Moose::Meta::Class->initialize($class);
464 elsif (my $role = $self->_does_metadata) {
465 # our role will always have
470 confess "Cannot find delegate metaclass for attribute " . $self->name;
474 sub _get_delegate_method_list {
476 my $meta = $self->_find_delegate_metaclass;
477 if ($meta->isa('Class::MOP::Class')) {
478 return map { $_->{name} } # NOTE: !never! delegate &meta
479 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
480 $meta->compute_all_applicable_methods;
482 elsif ($meta->isa('Moose::Meta::Role')) {
483 return $meta->get_method_list;
486 confess "Unable to recognize the delegate metaclass '$meta'";
498 Moose::Meta::Attribute - The Moose attribute metaclass
502 This is a subclass of L<Class::MOP::Attribute> with Moose specific
505 For the most part, the only time you will ever encounter an
506 instance of this class is if you are doing some serious deep
507 introspection. To really understand this class, you need to refer
508 to the L<Class::MOP::Attribute> documentation.
512 =head2 Overridden methods
514 These methods override methods in L<Class::MOP::Attribute> and add
515 Moose specific features. You can safely assume though that they
516 will behave just as L<Class::MOP::Attribute> does.
522 =item B<initialize_instance_slot>
524 =item B<install_accessors>
526 =item B<accessor_metaclass>
532 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
537 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
539 Before setting the value, a check is made on the type constraint of
540 the attribute, if it has one, to see if the value passes it. If the
541 value fails to pass, the set operation dies with a L<Carp/confess>.
543 Any coercion to convert values is done before checking the type constraint.
545 To check a value against a type constraint before setting it, fetch the
546 attribute instance using L<Moose::Meta::Attribute/find_attribute_by_name>,
547 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
548 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
553 =head2 Additional Moose features
555 Moose attributes support type-constraint checking, weak reference
556 creation and type coercion.
560 =item B<clone_and_inherit_options>
562 This is to support the C<has '+foo'> feature, it clones an attribute
563 from a superclass and allows a very specific set of changes to be made
566 =item B<has_type_constraint>
568 Returns true if this meta-attribute has a type constraint.
570 =item B<type_constraint>
572 A read-only accessor for this meta-attribute's type constraint. For
573 more information on what you can do with this, see the documentation
574 for L<Moose::Meta::TypeConstraint>.
578 Returns true if this meta-attribute performs delegation.
582 This returns the value which was passed into the handles option.
586 Returns true if this meta-attribute produces a weak reference.
590 Returns true if this meta-attribute is required to have a value.
594 Returns true if this meta-attribute should be initialized lazily.
596 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
598 =item B<is_lazy_build>
600 Returns true if this meta-attribute should be initialized lazily through
601 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
602 make your attribute required and lazy. In addition it will set the builder, clearer
603 and predicate options for you using the following convention.
605 #If your attribute name starts with an underscore:
606 has '_foo' => (lazy_build => 1);
608 has '_foo' => (lazy => 1, required => 1, builder => '_build_foo', predicate => '_has_foo', clearer => '_clear_foo');
610 has '_foo' => (lazy => 1, required => 1, builder => '_build_foo', default => sub{shift->_build_foo}, clearer => '_clear_foo');
612 #If your attribute name does not start with an underscore:
613 has 'foo' => (lazy => 1, required => 1, builder => 'build_foo', predicate => 'has_foo', clearer => 'clear_foo');
615 has '_foo' => (lazy => 1, required => 1, builder => '_build_foo', default => sub{shift->build_foo}, clearer => '_clear_foo');
617 NOTE: This means your class should provide a method whose name matches the value
618 of the builder part, in this case _build_foo or build_foo.
620 =item B<should_coerce>
622 Returns true if this meta-attribute should perform type coercion.
624 =item B<should_auto_deref>
626 Returns true if this meta-attribute should perform automatic
629 NOTE: This can only be done for attributes whose type constraint is
630 either I<ArrayRef> or I<HashRef>.
634 Returns true if this meta-attribute has a trigger set.
638 This is a CODE reference which will be executed every time the
639 value of an attribute is assigned. The CODE ref will get two values,
640 the invocant and the new value. This can be used to handle I<basic>
641 bi-directional relations.
643 =item B<documentation>
645 This is a string which contains the documentation for this attribute.
646 It serves no direct purpose right now, but it might in the future
647 in some kind of automated documentation system perhaps.
649 =item B<has_documentation>
651 Returns true if this meta-attribute has any documentation.
657 All complex software has bugs lurking in it, and this module is no
658 exception. If you find a bug please either email me, or add the bug
663 Stevan Little E<lt>stevan@iinteractive.comE<gt>
665 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
667 =head1 COPYRIGHT AND LICENSE
669 Copyright 2006, 2007 by Infinity Interactive, Inc.
671 L<http://www.iinteractive.com>
673 This library is free software; you can redistribute it and/or modify
674 it under the same terms as Perl itself.