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 $options{handles};
75 # isa can be changed, but only if the
76 # new type is a subtype
79 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
80 $type_constraint = $options{isa};
83 $type_constraint = Moose::Util::TypeConstraints::find_or_create_type_constraint(
86 (defined $type_constraint)
87 || confess "Could not find the type constraint '" . $options{isa} . "'";
90 # check here to see if the new type
91 # is a subtype of the old one
92 ($type_constraint->is_subtype_of($self->type_constraint->name))
93 || confess "New type constraint setting must be a subtype of inherited one"
94 # iff we have a type constraint that is ...
95 if $self->has_type_constraint;
97 $actual_options{type_constraint} = $type_constraint;
100 (scalar keys %options == 0)
101 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
102 $self->clone(%actual_options);
105 sub _process_options {
106 my ($class, $name, $options) = @_;
108 if (exists $options->{is}) {
109 if ($options->{is} eq 'ro') {
110 $options->{reader} ||= $name;
111 (!exists $options->{trigger})
112 || confess "Cannot have a trigger on a read-only attribute";
114 elsif ($options->{is} eq 'rw') {
115 $options->{accessor} = $name;
116 ((reftype($options->{trigger}) || '') eq 'CODE')
117 || confess "Trigger must be a CODE ref"
118 if exists $options->{trigger};
121 confess "I do not understand this option (is => " . $options->{is} . ")"
125 if (exists $options->{isa}) {
126 if (exists $options->{does}) {
127 if (eval { $options->{isa}->can('does') }) {
128 ($options->{isa}->does($options->{does}))
129 || confess "Cannot have an isa option and a does option if the isa does not do the does";
132 confess "Cannot have an isa option which cannot ->does()";
136 # allow for anon-subtypes here ...
137 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
138 $options->{type_constraint} = $options->{isa};
141 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
143 parent => Moose::Util::TypeConstraints::find_type_constraint('Object'),
144 constraint => sub { $_[0]->isa($options->{isa}) }
149 elsif (exists $options->{does}) {
150 # allow for anon-subtypes here ...
151 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
152 $options->{type_constraint} = $options->{does};
155 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
156 $options->{does} => {
157 parent => Moose::Util::TypeConstraints::find_type_constraint('Role'),
159 Moose::Util::does_role($_[0], $options->{does})
166 if (exists $options->{coerce} && $options->{coerce}) {
167 (exists $options->{type_constraint})
168 || confess "You cannot have coercion without specifying a type constraint";
169 confess "You cannot have a weak reference to a coerced value"
170 if $options->{weak_ref};
173 if (exists $options->{auto_deref} && $options->{auto_deref}) {
174 (exists $options->{type_constraint})
175 || confess "You cannot auto-dereference without specifying a type constraint";
176 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
177 $options->{type_constraint}->is_a_type_of('HashRef'))
178 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef";
181 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
182 confess("You can not use lazy_build and default for the same attribute")
183 if exists $options->{default};
184 $options->{lazy} = 1;
185 $options->{required} = 1;
186 $options->{builder} ||= "_build_${name}";
188 $options->{clearer} ||= "_clear${name}";
189 $options->{predicate} ||= "_has${name}";
192 $options->{clearer} ||= "clear_${name}";
193 $options->{predicate} ||= "has_${name}";
197 if (exists $options->{lazy} && $options->{lazy}) {
198 (exists $options->{default} || defined $options->{builder} )
199 || confess "You cannot have lazy attribute without specifying a default value for it";
202 if ( $options->{required} && !( ( !exists $options->{init_arg} || defined $options->{init_arg} ) || exists $options->{default} || defined $options->{builder} ) ) {
203 confess "You cannot have a required attribute without a default, builder, or an init_arg";
208 sub initialize_instance_slot {
209 my ($self, $meta_instance, $instance, $params) = @_;
210 my $init_arg = $self->init_arg();
211 # try to fetch the init arg from the %params ...
215 if ( defined($init_arg) and exists $params->{$init_arg}) {
216 $val = $params->{$init_arg};
220 # skip it if it's lazy
221 return if $self->is_lazy;
222 # and die if it's required and doesn't have a default value
223 confess "Attribute (" . $self->name . ") is required"
224 if $self->is_required && !$self->has_default && !$self->has_builder;
226 # if nothing was in the %params, we can use the
227 # attribute's default value (if it has one)
228 if ($self->has_default) {
229 $val = $self->default($instance);
232 elsif ($self->has_builder) {
233 if (my $builder = $instance->can($self->builder)){
234 $val = $instance->$builder;
238 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
243 return unless $value_is_set;
245 if ($self->has_type_constraint) {
246 my $type_constraint = $self->type_constraint;
247 if ($self->should_coerce && $type_constraint->has_coercion) {
248 $val = $type_constraint->coerce($val);
250 $type_constraint->check($val)
251 || confess "Attribute ("
253 . ") does not pass the type constraint because: "
254 . $type_constraint->get_message($val);
257 $self->set_initial_value($instance, $val);
258 $meta_instance->weaken_slot_value($instance, $self->name)
259 if ref $val && $self->is_weak_ref;
265 # this duplicates too much code from
266 # Class::MOP::Attribute, we need to
267 # refactor these bits eventually.
269 sub _set_initial_slot_value {
270 my ($self, $meta_instance, $instance, $value) = @_;
272 my $slot_name = $self->name;
274 return $meta_instance->set_slot_value($instance, $slot_name, $value)
275 unless $self->has_initializer;
277 my ($type_constraint, $can_coerce);
278 if ($self->has_type_constraint) {
279 $type_constraint = $self->type_constraint;
280 $can_coerce = ($self->should_coerce && $type_constraint->has_coercion);
285 if ($type_constraint) {
286 $val = $type_constraint->coerce($val)
288 $type_constraint->check($val)
289 || confess "Attribute ("
291 . ") does not pass the type constraint because: "
292 . $type_constraint->get_message($val);
294 $meta_instance->set_slot_value($instance, $slot_name, $val);
297 my $initializer = $self->initializer;
299 # most things will just want to set a value, so make it first arg
300 $instance->$initializer($value, $callback, $self);
304 my ($self, $instance, $value) = @_;
306 my $attr_name = $self->name;
308 if ($self->is_required) {
310 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
313 if ($self->has_type_constraint) {
315 my $type_constraint = $self->type_constraint;
317 if ($self->should_coerce) {
318 $value = $type_constraint->coerce($value);
320 $type_constraint->_compiled_type_constraint->($value)
321 || confess "Attribute ("
323 . ") does not pass the type constraint because "
324 . $type_constraint->get_message($value);
327 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
330 $meta_instance->set_slot_value($instance, $attr_name, $value);
332 if (ref $value && $self->is_weak_ref) {
333 $meta_instance->weaken_slot_value($instance, $attr_name);
336 if ($self->has_trigger) {
337 $self->trigger->($instance, $value, $self);
342 my ($self, $instance) = @_;
344 if ($self->is_lazy) {
345 unless ($self->has_value($instance)) {
346 if ($self->has_default) {
347 my $default = $self->default($instance);
348 $self->set_initial_value($instance, $default);
350 if ( $self->has_builder ){
351 if (my $builder = $instance->can($self->builder)){
352 $self->set_initial_value($instance, $instance->$builder);
355 confess(blessed($instance)
356 . " does not support builder method '"
358 . "' for attribute '"
364 $self->set_initial_value($instance, undef);
369 if ($self->should_auto_deref) {
371 my $type_constraint = $self->type_constraint;
373 if ($type_constraint->is_a_type_of('ArrayRef')) {
374 my $rv = $self->SUPER::get_value($instance);
375 return unless defined $rv;
376 return wantarray ? @{ $rv } : $rv;
378 elsif ($type_constraint->is_a_type_of('HashRef')) {
379 my $rv = $self->SUPER::get_value($instance);
380 return unless defined $rv;
381 return wantarray ? %{ $rv } : $rv;
384 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
390 return $self->SUPER::get_value($instance);
394 ## installing accessors
396 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
398 sub install_accessors {
400 $self->SUPER::install_accessors(@_);
402 if ($self->has_handles) {
405 # Here we canonicalize the 'handles' option
406 # this will sort out any details and always
407 # return an hash of methods which we want
408 # to delagate to, see that method for details
409 my %handles = $self->_canonicalize_handles();
411 # find the accessor method for this attribute
412 my $accessor = $self->get_read_method_ref;
413 # then unpack it if we need too ...
414 $accessor = $accessor->body if blessed $accessor;
416 # install the delegation ...
417 my $associated_class = $self->associated_class;
418 foreach my $handle (keys %handles) {
419 my $method_to_call = $handles{$handle};
420 my $class_name = $associated_class->name;
421 my $name = "${class_name}::${handle}";
423 (!$associated_class->has_method($handle))
424 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
427 # handles is not allowed to delegate
428 # any of these methods, as they will
429 # override the ones in your class, which
430 # is almost certainly not what you want.
432 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
433 #cluck("Not delegating method '$handle' because it is a core method") and
434 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
436 if ((reftype($method_to_call) || '') eq 'CODE') {
437 $associated_class->add_method($handle => subname $name, $method_to_call);
441 # we used to do a goto here, but the
442 # goto didn't handle failure correctly
443 # (it just returned nothing), so I took
444 # that out. However, the more I thought
445 # about it, the less I liked it doing
446 # the goto, and I prefered the act of
447 # delegation being actually represented
448 # in the stack trace.
450 $associated_class->add_method($handle => subname $name, sub {
451 my $proxy = (shift)->$accessor();
453 || confess "Cannot delegate $handle to $method_to_call because " .
454 "the value of " . $self->name . " is not defined";
455 $proxy->$method_to_call(@_);
464 # private methods to help delegation ...
466 sub _canonicalize_handles {
468 my $handles = $self->handles;
469 if (my $handle_type = ref($handles)) {
470 if ($handle_type eq 'HASH') {
473 elsif ($handle_type eq 'ARRAY') {
474 return map { $_ => $_ } @{$handles};
476 elsif ($handle_type eq 'Regexp') {
477 ($self->has_type_constraint)
478 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
479 return map { ($_ => $_) }
480 grep { /$handles/ } $self->_get_delegate_method_list;
482 elsif ($handle_type eq 'CODE') {
483 return $handles->($self, $self->_find_delegate_metaclass);
486 confess "Unable to canonicalize the 'handles' option with $handles";
490 my $role_meta = eval { $handles->meta };
492 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
495 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
496 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
498 return map { $_ => $_ } (
499 $role_meta->get_method_list,
500 $role_meta->get_required_method_list
505 sub _find_delegate_metaclass {
507 if (my $class = $self->_isa_metadata) {
508 # if the class does have
509 # a meta method, use it
510 return $class->meta if $class->can('meta');
511 # otherwise we might be
512 # dealing with a non-Moose
513 # class, and need to make
515 return Moose::Meta::Class->initialize($class);
517 elsif (my $role = $self->_does_metadata) {
518 # our role will always have
523 confess "Cannot find delegate metaclass for attribute " . $self->name;
527 sub _get_delegate_method_list {
529 my $meta = $self->_find_delegate_metaclass;
530 if ($meta->isa('Class::MOP::Class')) {
531 return map { $_->{name} } # NOTE: !never! delegate &meta
532 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
533 $meta->compute_all_applicable_methods;
535 elsif ($meta->isa('Moose::Meta::Role')) {
536 return $meta->get_method_list;
539 confess "Unable to recognize the delegate metaclass '$meta'";
551 Moose::Meta::Attribute - The Moose attribute metaclass
555 This is a subclass of L<Class::MOP::Attribute> with Moose specific
558 For the most part, the only time you will ever encounter an
559 instance of this class is if you are doing some serious deep
560 introspection. To really understand this class, you need to refer
561 to the L<Class::MOP::Attribute> documentation.
565 =head2 Overridden methods
567 These methods override methods in L<Class::MOP::Attribute> and add
568 Moose specific features. You can safely assume though that they
569 will behave just as L<Class::MOP::Attribute> does.
575 =item B<initialize_instance_slot>
577 =item B<install_accessors>
579 =item B<accessor_metaclass>
585 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
590 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
592 Before setting the value, a check is made on the type constraint of
593 the attribute, if it has one, to see if the value passes it. If the
594 value fails to pass, the set operation dies with a L<Carp/confess>.
596 Any coercion to convert values is done before checking the type constraint.
598 To check a value against a type constraint before setting it, fetch the
599 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
600 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
601 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
606 =head2 Additional Moose features
608 Moose attributes support type-constraint checking, weak reference
609 creation and type coercion.
613 =item B<clone_and_inherit_options>
615 This is to support the C<has '+foo'> feature, it clones an attribute
616 from a superclass and allows a very specific set of changes to be made
619 =item B<has_type_constraint>
621 Returns true if this meta-attribute has a type constraint.
623 =item B<type_constraint>
625 A read-only accessor for this meta-attribute's type constraint. For
626 more information on what you can do with this, see the documentation
627 for L<Moose::Meta::TypeConstraint>.
631 Returns true if this meta-attribute performs delegation.
635 This returns the value which was passed into the handles option.
639 Returns true if this meta-attribute produces a weak reference.
643 Returns true if this meta-attribute is required to have a value.
647 Returns true if this meta-attribute should be initialized lazily.
649 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
651 =item B<is_lazy_build>
653 Returns true if this meta-attribute should be initialized lazily through
654 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
655 make your attribute required and lazy. In addition it will set the builder, clearer
656 and predicate options for you using the following convention.
658 #If your attribute name starts with an underscore:
659 has '_foo' => (lazy_build => 1);
661 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
663 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
665 #If your attribute name does not start with an underscore:
666 has 'foo' => (lazy_build => 1);
668 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
670 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
672 The reason for the different naming of the C<builder> is that the C<builder>
673 method is a private method while the C<clearer> and C<predicate> methods
676 NOTE: This means your class should provide a method whose name matches the value
677 of the builder part, in this case _build__foo or _build_foo.
679 =item B<should_coerce>
681 Returns true if this meta-attribute should perform type coercion.
683 =item B<should_auto_deref>
685 Returns true if this meta-attribute should perform automatic
688 NOTE: This can only be done for attributes whose type constraint is
689 either I<ArrayRef> or I<HashRef>.
693 Returns true if this meta-attribute has a trigger set.
697 This is a CODE reference which will be executed every time the
698 value of an attribute is assigned. The CODE ref will get two values,
699 the invocant and the new value. This can be used to handle I<basic>
700 bi-directional relations.
702 =item B<documentation>
704 This is a string which contains the documentation for this attribute.
705 It serves no direct purpose right now, but it might in the future
706 in some kind of automated documentation system perhaps.
708 =item B<has_documentation>
710 Returns true if this meta-attribute has any documentation.
716 All complex software has bugs lurking in it, and this module is no
717 exception. If you find a bug please either email me, or add the bug
722 Stevan Little E<lt>stevan@iinteractive.comE<gt>
724 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
726 =head1 COPYRIGHT AND LICENSE
728 Copyright 2006-2008 by Infinity Interactive, Inc.
730 L<http://www.iinteractive.com>
732 This library is free software; you can redistribute it and/or modify
733 it under the same terms as Perl itself.