2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
9 use Sub::Name 'subname';
12 our $VERSION = '0.22';
13 our $AUTHORITY = 'cpan:STEVAN';
15 use Moose::Meta::Method::Accessor;
16 use Moose::Util::TypeConstraints ();
18 use base 'Class::MOP::Attribute';
20 # options which are not directly used
21 # but we store them for metadata purposes
22 __PACKAGE__->meta->add_attribute('isa' => (reader => '_isa_metadata'));
23 __PACKAGE__->meta->add_attribute('does' => (reader => '_does_metadata'));
24 __PACKAGE__->meta->add_attribute('is' => (reader => '_is_metadata'));
26 # these are actual options for the attrs
27 __PACKAGE__->meta->add_attribute('required' => (reader => 'is_required' ));
28 __PACKAGE__->meta->add_attribute('lazy' => (reader => 'is_lazy' ));
29 __PACKAGE__->meta->add_attribute('lazy_build' => (reader => 'is_lazy_build' ));
30 __PACKAGE__->meta->add_attribute('coerce' => (reader => 'should_coerce' ));
31 __PACKAGE__->meta->add_attribute('weak_ref' => (reader => 'is_weak_ref' ));
32 __PACKAGE__->meta->add_attribute('auto_deref' => (reader => 'should_auto_deref'));
33 __PACKAGE__->meta->add_attribute('type_constraint' => (
34 reader => 'type_constraint',
35 predicate => 'has_type_constraint',
37 __PACKAGE__->meta->add_attribute('trigger' => (
39 predicate => 'has_trigger',
41 __PACKAGE__->meta->add_attribute('handles' => (
43 predicate => 'has_handles',
45 __PACKAGE__->meta->add_attribute('documentation' => (
46 reader => 'documentation',
47 predicate => 'has_documentation',
51 my ($class, $name, %options) = @_;
52 $class->_process_options($name, \%options);
53 return $class->SUPER::new($name, %options);
56 sub clone_and_inherit_options {
57 my ($self, %options) = @_;
58 # you can change default, required, coerce, documentation and lazy
60 foreach my $legal_option (qw(default coerce required documentation lazy)) {
61 if (exists $options{$legal_option}) {
62 $actual_options{$legal_option} = $options{$legal_option};
63 delete $options{$legal_option};
67 # handles can only be added, not changed
68 if ($options{handles}) {
69 confess "You can only add the 'handles' option, you cannot change it"
70 if $self->has_handles;
71 $actual_options{handles} = $options{handles};
72 delete $options{handles};
75 # handles can only be added, not changed
76 if ($options{builder}) {
77 confess "You can only add the 'builder' option, you cannot change it"
78 if $self->has_builder;
79 $actual_options{builder} = $options{builder};
80 delete $options{builder};
83 # isa can be changed, but only if the
84 # new type is a subtype
87 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
88 $type_constraint = $options{isa};
91 $type_constraint = Moose::Util::TypeConstraints::find_or_create_type_constraint(
94 (defined $type_constraint)
95 || confess "Could not find the type constraint '" . $options{isa} . "'";
98 # check here to see if the new type
99 # is a subtype of the old one
100 ($type_constraint->is_subtype_of($self->type_constraint->name))
101 || confess "New type constraint setting must be a subtype of inherited one"
102 # iff we have a type constraint that is ...
103 if $self->has_type_constraint;
105 $actual_options{type_constraint} = $type_constraint;
106 delete $options{isa};
108 (scalar keys %options == 0)
109 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
110 $self->clone(%actual_options);
113 sub _process_options {
114 my ($class, $name, $options) = @_;
116 if (exists $options->{is}) {
117 if ($options->{is} eq 'ro') {
118 $options->{reader} ||= $name;
119 (!exists $options->{trigger})
120 || confess "Cannot have a trigger on a read-only attribute";
122 elsif ($options->{is} eq 'rw') {
123 $options->{accessor} = $name;
124 ((reftype($options->{trigger}) || '') eq 'CODE')
125 || confess "Trigger must be a CODE ref"
126 if exists $options->{trigger};
129 confess "I do not understand this option (is => " . $options->{is} . ")"
133 if (exists $options->{isa}) {
134 if (exists $options->{does}) {
135 if (eval { $options->{isa}->can('does') }) {
136 ($options->{isa}->does($options->{does}))
137 || confess "Cannot have an isa option and a does option if the isa does not do the does";
140 confess "Cannot have an isa option which cannot ->does()";
144 # allow for anon-subtypes here ...
145 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
146 $options->{type_constraint} = $options->{isa};
149 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
151 parent => Moose::Util::TypeConstraints::find_type_constraint('Object'),
152 constraint => sub { $_[0]->isa($options->{isa}) }
157 elsif (exists $options->{does}) {
158 # allow for anon-subtypes here ...
159 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
160 $options->{type_constraint} = $options->{does};
163 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
164 $options->{does} => {
165 parent => Moose::Util::TypeConstraints::find_type_constraint('Role'),
167 Moose::Util::does_role($_[0], $options->{does})
174 if (exists $options->{coerce} && $options->{coerce}) {
175 (exists $options->{type_constraint})
176 || confess "You cannot have coercion without specifying a type constraint";
177 confess "You cannot have a weak reference to a coerced value"
178 if $options->{weak_ref};
181 if (exists $options->{auto_deref} && $options->{auto_deref}) {
182 (exists $options->{type_constraint})
183 || confess "You cannot auto-dereference without specifying a type constraint";
184 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
185 $options->{type_constraint}->is_a_type_of('HashRef'))
186 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef";
189 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
190 confess("You can not use lazy_build and default for the same attribute")
191 if exists $options->{default};
192 $options->{lazy} = 1;
193 $options->{required} = 1;
194 $options->{builder} ||= "_build_${name}";
196 $options->{clearer} ||= "_clear${name}";
197 $options->{predicate} ||= "_has${name}";
200 $options->{clearer} ||= "clear_${name}";
201 $options->{predicate} ||= "has_${name}";
205 if (exists $options->{lazy} && $options->{lazy}) {
206 (exists $options->{default} || defined $options->{builder} )
207 || confess "You cannot have lazy attribute without specifying a default value for it";
210 if ( $options->{required} && !( ( !exists $options->{init_arg} || defined $options->{init_arg} ) || exists $options->{default} || defined $options->{builder} ) ) {
211 confess "You cannot have a required attribute without a default, builder, or an init_arg";
216 sub initialize_instance_slot {
217 my ($self, $meta_instance, $instance, $params) = @_;
218 my $init_arg = $self->init_arg();
219 # try to fetch the init arg from the %params ...
223 if ( defined($init_arg) and exists $params->{$init_arg}) {
224 $val = $params->{$init_arg};
228 # skip it if it's lazy
229 return if $self->is_lazy;
230 # and die if it's required and doesn't have a default value
231 confess "Attribute (" . $self->name . ") is required"
232 if $self->is_required && !$self->has_default && !$self->has_builder;
234 # if nothing was in the %params, we can use the
235 # attribute's default value (if it has one)
236 if ($self->has_default) {
237 $val = $self->default($instance);
240 elsif ($self->has_builder) {
241 if (my $builder = $instance->can($self->builder)){
242 $val = $instance->$builder;
246 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
251 return unless $value_is_set;
253 if ($self->has_type_constraint) {
254 my $type_constraint = $self->type_constraint;
255 if ($self->should_coerce && $type_constraint->has_coercion) {
256 $val = $type_constraint->coerce($val);
258 $type_constraint->check($val)
259 || confess "Attribute ("
261 . ") does not pass the type constraint because: "
262 . $type_constraint->get_message($val);
265 $self->set_initial_value($instance, $val);
266 $meta_instance->weaken_slot_value($instance, $self->name)
267 if ref $val && $self->is_weak_ref;
273 # this duplicates too much code from
274 # Class::MOP::Attribute, we need to
275 # refactor these bits eventually.
277 sub _set_initial_slot_value {
278 my ($self, $meta_instance, $instance, $value) = @_;
280 my $slot_name = $self->name;
282 return $meta_instance->set_slot_value($instance, $slot_name, $value)
283 unless $self->has_initializer;
285 my ($type_constraint, $can_coerce);
286 if ($self->has_type_constraint) {
287 $type_constraint = $self->type_constraint;
288 $can_coerce = ($self->should_coerce && $type_constraint->has_coercion);
293 if ($type_constraint) {
294 $val = $type_constraint->coerce($val)
296 $type_constraint->check($val)
297 || confess "Attribute ("
299 . ") does not pass the type constraint because: "
300 . $type_constraint->get_message($val);
302 $meta_instance->set_slot_value($instance, $slot_name, $val);
305 my $initializer = $self->initializer;
307 # most things will just want to set a value, so make it first arg
308 $instance->$initializer($value, $callback, $self);
312 my ($self, $instance, $value) = @_;
314 my $attr_name = $self->name;
316 if ($self->is_required) {
318 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
321 if ($self->has_type_constraint) {
323 my $type_constraint = $self->type_constraint;
325 if ($self->should_coerce) {
326 $value = $type_constraint->coerce($value);
328 $type_constraint->_compiled_type_constraint->($value)
329 || confess "Attribute ("
331 . ") does not pass the type constraint because "
332 . $type_constraint->get_message($value);
335 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
338 $meta_instance->set_slot_value($instance, $attr_name, $value);
340 if (ref $value && $self->is_weak_ref) {
341 $meta_instance->weaken_slot_value($instance, $attr_name);
344 if ($self->has_trigger) {
345 $self->trigger->($instance, $value, $self);
350 my ($self, $instance) = @_;
352 if ($self->is_lazy) {
353 unless ($self->has_value($instance)) {
354 if ($self->has_default) {
355 my $default = $self->default($instance);
356 $self->set_initial_value($instance, $default);
358 if ( $self->has_builder ){
359 if (my $builder = $instance->can($self->builder)){
360 $self->set_initial_value($instance, $instance->$builder);
363 confess(blessed($instance)
364 . " does not support builder method '"
366 . "' for attribute '"
372 $self->set_initial_value($instance, undef);
377 if ($self->should_auto_deref) {
379 my $type_constraint = $self->type_constraint;
381 if ($type_constraint->is_a_type_of('ArrayRef')) {
382 my $rv = $self->SUPER::get_value($instance);
383 return unless defined $rv;
384 return wantarray ? @{ $rv } : $rv;
386 elsif ($type_constraint->is_a_type_of('HashRef')) {
387 my $rv = $self->SUPER::get_value($instance);
388 return unless defined $rv;
389 return wantarray ? %{ $rv } : $rv;
392 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
398 return $self->SUPER::get_value($instance);
402 ## installing accessors
404 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
406 sub install_accessors {
408 $self->SUPER::install_accessors(@_);
410 if ($self->has_handles) {
413 # Here we canonicalize the 'handles' option
414 # this will sort out any details and always
415 # return an hash of methods which we want
416 # to delagate to, see that method for details
417 my %handles = $self->_canonicalize_handles();
419 # find the accessor method for this attribute
420 my $accessor = $self->get_read_method_ref;
421 # then unpack it if we need too ...
422 $accessor = $accessor->body if blessed $accessor;
424 # install the delegation ...
425 my $associated_class = $self->associated_class;
426 foreach my $handle (keys %handles) {
427 my $method_to_call = $handles{$handle};
428 my $class_name = $associated_class->name;
429 my $name = "${class_name}::${handle}";
431 (!$associated_class->has_method($handle))
432 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
435 # handles is not allowed to delegate
436 # any of these methods, as they will
437 # override the ones in your class, which
438 # is almost certainly not what you want.
440 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
441 #cluck("Not delegating method '$handle' because it is a core method") and
442 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
444 if ((reftype($method_to_call) || '') eq 'CODE') {
445 $associated_class->add_method($handle => subname $name, $method_to_call);
449 # we used to do a goto here, but the
450 # goto didn't handle failure correctly
451 # (it just returned nothing), so I took
452 # that out. However, the more I thought
453 # about it, the less I liked it doing
454 # the goto, and I prefered the act of
455 # delegation being actually represented
456 # in the stack trace.
458 $associated_class->add_method($handle => subname $name, sub {
459 my $proxy = (shift)->$accessor();
461 || confess "Cannot delegate $handle to $method_to_call because " .
462 "the value of " . $self->name . " is not defined";
463 $proxy->$method_to_call(@_);
472 # private methods to help delegation ...
474 sub _canonicalize_handles {
476 my $handles = $self->handles;
477 if (my $handle_type = ref($handles)) {
478 if ($handle_type eq 'HASH') {
481 elsif ($handle_type eq 'ARRAY') {
482 return map { $_ => $_ } @{$handles};
484 elsif ($handle_type eq 'Regexp') {
485 ($self->has_type_constraint)
486 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
487 return map { ($_ => $_) }
488 grep { /$handles/ } $self->_get_delegate_method_list;
490 elsif ($handle_type eq 'CODE') {
491 return $handles->($self, $self->_find_delegate_metaclass);
494 confess "Unable to canonicalize the 'handles' option with $handles";
498 my $role_meta = eval { $handles->meta };
500 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
503 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
504 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
506 return map { $_ => $_ } (
507 $role_meta->get_method_list,
508 $role_meta->get_required_method_list
513 sub _find_delegate_metaclass {
515 if (my $class = $self->_isa_metadata) {
516 # if the class does have
517 # a meta method, use it
518 return $class->meta if $class->can('meta');
519 # otherwise we might be
520 # dealing with a non-Moose
521 # class, and need to make
523 return Moose::Meta::Class->initialize($class);
525 elsif (my $role = $self->_does_metadata) {
526 # our role will always have
531 confess "Cannot find delegate metaclass for attribute " . $self->name;
535 sub _get_delegate_method_list {
537 my $meta = $self->_find_delegate_metaclass;
538 if ($meta->isa('Class::MOP::Class')) {
539 return map { $_->{name} } # NOTE: !never! delegate &meta
540 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
541 $meta->compute_all_applicable_methods;
543 elsif ($meta->isa('Moose::Meta::Role')) {
544 return $meta->get_method_list;
547 confess "Unable to recognize the delegate metaclass '$meta'";
559 Moose::Meta::Attribute - The Moose attribute metaclass
563 This is a subclass of L<Class::MOP::Attribute> with Moose specific
566 For the most part, the only time you will ever encounter an
567 instance of this class is if you are doing some serious deep
568 introspection. To really understand this class, you need to refer
569 to the L<Class::MOP::Attribute> documentation.
573 =head2 Overridden methods
575 These methods override methods in L<Class::MOP::Attribute> and add
576 Moose specific features. You can safely assume though that they
577 will behave just as L<Class::MOP::Attribute> does.
583 =item B<initialize_instance_slot>
585 =item B<install_accessors>
587 =item B<accessor_metaclass>
593 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
598 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
600 Before setting the value, a check is made on the type constraint of
601 the attribute, if it has one, to see if the value passes it. If the
602 value fails to pass, the set operation dies with a L<Carp/confess>.
604 Any coercion to convert values is done before checking the type constraint.
606 To check a value against a type constraint before setting it, fetch the
607 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
608 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
609 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
614 =head2 Additional Moose features
616 Moose attributes support type-constraint checking, weak reference
617 creation and type coercion.
621 =item B<clone_and_inherit_options>
623 This is to support the C<has '+foo'> feature, it clones an attribute
624 from a superclass and allows a very specific set of changes to be made
627 =item B<has_type_constraint>
629 Returns true if this meta-attribute has a type constraint.
631 =item B<type_constraint>
633 A read-only accessor for this meta-attribute's type constraint. For
634 more information on what you can do with this, see the documentation
635 for L<Moose::Meta::TypeConstraint>.
639 Returns true if this meta-attribute performs delegation.
643 This returns the value which was passed into the handles option.
647 Returns true if this meta-attribute produces a weak reference.
651 Returns true if this meta-attribute is required to have a value.
655 Returns true if this meta-attribute should be initialized lazily.
657 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
659 =item B<is_lazy_build>
661 Returns true if this meta-attribute should be initialized lazily through
662 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
663 make your attribute required and lazy. In addition it will set the builder, clearer
664 and predicate options for you using the following convention.
666 #If your attribute name starts with an underscore:
667 has '_foo' => (lazy_build => 1);
669 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
671 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
673 #If your attribute name does not start with an underscore:
674 has 'foo' => (lazy_build => 1);
676 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
678 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
680 The reason for the different naming of the C<builder> is that the C<builder>
681 method is a private method while the C<clearer> and C<predicate> methods
684 NOTE: This means your class should provide a method whose name matches the value
685 of the builder part, in this case _build__foo or _build_foo.
687 =item B<should_coerce>
689 Returns true if this meta-attribute should perform type coercion.
691 =item B<should_auto_deref>
693 Returns true if this meta-attribute should perform automatic
696 NOTE: This can only be done for attributes whose type constraint is
697 either I<ArrayRef> or I<HashRef>.
701 Returns true if this meta-attribute has a trigger set.
705 This is a CODE reference which will be executed every time the
706 value of an attribute is assigned. The CODE ref will get two values,
707 the invocant and the new value. This can be used to handle I<basic>
708 bi-directional relations.
710 =item B<documentation>
712 This is a string which contains the documentation for this attribute.
713 It serves no direct purpose right now, but it might in the future
714 in some kind of automated documentation system perhaps.
716 =item B<has_documentation>
718 Returns true if this meta-attribute has any documentation.
724 All complex software has bugs lurking in it, and this module is no
725 exception. If you find a bug please either email me, or add the bug
730 Stevan Little E<lt>stevan@iinteractive.comE<gt>
732 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
734 =head1 COPYRIGHT AND LICENSE
736 Copyright 2006-2008 by Infinity Interactive, Inc.
738 L<http://www.iinteractive.com>
740 This library is free software; you can redistribute it and/or modify
741 it under the same terms as Perl itself.