2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
9 use Sub::Name 'subname';
12 our $VERSION = '0.22';
13 our $AUTHORITY = 'cpan:STEVAN';
15 use Moose::Meta::Method::Accessor;
16 use Moose::Util::TypeConstraints ();
18 use base 'Class::MOP::Attribute';
20 # options which are not directly used
21 # but we store them for metadata purposes
22 __PACKAGE__->meta->add_attribute('isa' => (reader => '_isa_metadata'));
23 __PACKAGE__->meta->add_attribute('does' => (reader => '_does_metadata'));
24 __PACKAGE__->meta->add_attribute('is' => (reader => '_is_metadata'));
26 # these are actual options for the attrs
27 __PACKAGE__->meta->add_attribute('required' => (reader => 'is_required' ));
28 __PACKAGE__->meta->add_attribute('lazy' => (reader => 'is_lazy' ));
29 __PACKAGE__->meta->add_attribute('lazy_build' => (reader => 'is_lazy_build' ));
30 __PACKAGE__->meta->add_attribute('coerce' => (reader => 'should_coerce' ));
31 __PACKAGE__->meta->add_attribute('weak_ref' => (reader => 'is_weak_ref' ));
32 __PACKAGE__->meta->add_attribute('auto_deref' => (reader => 'should_auto_deref'));
33 __PACKAGE__->meta->add_attribute('type_constraint' => (
34 reader => 'type_constraint',
35 predicate => 'has_type_constraint',
37 __PACKAGE__->meta->add_attribute('trigger' => (
39 predicate => 'has_trigger',
41 __PACKAGE__->meta->add_attribute('handles' => (
43 predicate => 'has_handles',
45 __PACKAGE__->meta->add_attribute('documentation' => (
46 reader => 'documentation',
47 predicate => 'has_documentation',
51 # we need to have a ->does method in here to
52 # more easily support traits, and the introspection
53 # of those traits. So in order to do this we
54 # just alias Moose::Object's version of it.
56 *does = \&Moose::Object::does;
59 my ($class, $name, %options) = @_;
60 $class->_process_options($name, \%options);
61 return $class->SUPER::new($name, %options);
64 sub clone_and_inherit_options {
65 my ($self, %options) = @_;
66 # you can change default, required, coerce, documentation and lazy
68 foreach my $legal_option (qw(default coerce required documentation lazy handles builder)) {
69 if (exists $options{$legal_option}) {
70 $actual_options{$legal_option} = $options{$legal_option};
71 delete $options{$legal_option};
77 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
78 $type_constraint = $options{isa};
81 $type_constraint = Moose::Util::TypeConstraints::find_or_create_type_constraint(
84 (defined $type_constraint)
85 || confess "Could not find the type constraint '" . $options{isa} . "'";
88 $actual_options{type_constraint} = $type_constraint;
94 if (blessed($options{does}) && $options{does}->isa('Moose::Meta::TypeConstraint')) {
95 $type_constraint = $options{does};
98 $type_constraint = Moose::Util::TypeConstraints::find_or_create_type_constraint(
101 (defined $type_constraint)
102 || confess "Could not find the type constraint '" . $options{does} . "'";
105 $actual_options{type_constraint} = $type_constraint;
106 delete $options{does};
109 (scalar keys %options == 0)
110 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
111 $self->clone(%actual_options);
114 sub _process_options {
115 my ($class, $name, $options) = @_;
117 if (exists $options->{is}) {
118 if ($options->{is} eq 'ro') {
119 $options->{reader} ||= $name;
120 (!exists $options->{trigger})
121 || confess "Cannot have a trigger on a read-only attribute $name";
123 elsif ($options->{is} eq 'rw') {
124 $options->{accessor} = $name;
125 ((reftype($options->{trigger}) || '') eq 'CODE')
126 || confess "Trigger must be a CODE ref"
127 if exists $options->{trigger};
130 confess "I do not understand this option (is => " . $options->{is} . ") on attribute $name"
134 if (exists $options->{isa}) {
135 if (exists $options->{does}) {
136 if (eval { $options->{isa}->can('does') }) {
137 ($options->{isa}->does($options->{does}))
138 || confess "Cannot have an isa option and a does option if the isa does not do the does on attribute $name";
141 confess "Cannot have an isa option which cannot ->does() on attribute $name";
145 # allow for anon-subtypes here ...
146 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
147 $options->{type_constraint} = $options->{isa};
150 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
152 parent => Moose::Util::TypeConstraints::find_type_constraint('Object'),
153 constraint => sub { $_[0]->isa($options->{isa}) }
158 elsif (exists $options->{does}) {
159 # allow for anon-subtypes here ...
160 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
161 $options->{type_constraint} = $options->{does};
164 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
165 $options->{does} => {
166 parent => Moose::Util::TypeConstraints::find_type_constraint('Role'),
168 Moose::Util::does_role($_[0], $options->{does})
175 if (exists $options->{coerce} && $options->{coerce}) {
176 (exists $options->{type_constraint})
177 || confess "You cannot have coercion without specifying a type constraint on attribute $name";
178 confess "You cannot have a weak reference to a coerced value on attribute $name"
179 if $options->{weak_ref};
182 if (exists $options->{auto_deref} && $options->{auto_deref}) {
183 (exists $options->{type_constraint})
184 || confess "You cannot auto-dereference without specifying a type constraint on attribute $name";
185 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
186 $options->{type_constraint}->is_a_type_of('HashRef'))
187 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef on attribute $name";
190 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
191 confess("You can not use lazy_build and default for the same attribute $name")
192 if exists $options->{default};
193 $options->{lazy} = 1;
194 $options->{required} = 1;
195 $options->{builder} ||= "_build_${name}";
197 $options->{clearer} ||= "_clear${name}";
198 $options->{predicate} ||= "_has${name}";
201 $options->{clearer} ||= "clear_${name}";
202 $options->{predicate} ||= "has_${name}";
206 if (exists $options->{lazy} && $options->{lazy}) {
207 (exists $options->{default} || defined $options->{builder} )
208 || confess "You cannot have lazy attribute ($name) without specifying a default value for it";
211 if ( $options->{required} && !( ( !exists $options->{init_arg} || defined $options->{init_arg} ) || exists $options->{default} || defined $options->{builder} ) ) {
212 confess "You cannot have a required attribute ($name) without a default, builder, or an init_arg";
217 sub initialize_instance_slot {
218 my ($self, $meta_instance, $instance, $params) = @_;
219 my $init_arg = $self->init_arg();
220 # try to fetch the init arg from the %params ...
224 if ( defined($init_arg) and exists $params->{$init_arg}) {
225 $val = $params->{$init_arg};
229 # skip it if it's lazy
230 return if $self->is_lazy;
231 # and die if it's required and doesn't have a default value
232 confess "Attribute (" . $self->name . ") is required"
233 if $self->is_required && !$self->has_default && !$self->has_builder;
235 # if nothing was in the %params, we can use the
236 # attribute's default value (if it has one)
237 if ($self->has_default) {
238 $val = $self->default($instance);
241 elsif ($self->has_builder) {
242 if (my $builder = $instance->can($self->builder)){
243 $val = $instance->$builder;
247 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
252 return unless $value_is_set;
254 if ($self->has_type_constraint) {
255 my $type_constraint = $self->type_constraint;
256 if ($self->should_coerce && $type_constraint->has_coercion) {
257 $val = $type_constraint->coerce($val);
259 $type_constraint->check($val)
260 || confess "Attribute ("
262 . ") does not pass the type constraint because: "
263 . $type_constraint->get_message($val);
266 $self->set_initial_value($instance, $val);
267 $meta_instance->weaken_slot_value($instance, $self->name)
268 if ref $val && $self->is_weak_ref;
274 # this duplicates too much code from
275 # Class::MOP::Attribute, we need to
276 # refactor these bits eventually.
278 sub _set_initial_slot_value {
279 my ($self, $meta_instance, $instance, $value) = @_;
281 my $slot_name = $self->name;
283 return $meta_instance->set_slot_value($instance, $slot_name, $value)
284 unless $self->has_initializer;
286 my ($type_constraint, $can_coerce);
287 if ($self->has_type_constraint) {
288 $type_constraint = $self->type_constraint;
289 $can_coerce = ($self->should_coerce && $type_constraint->has_coercion);
294 if ($type_constraint) {
295 $val = $type_constraint->coerce($val)
297 $type_constraint->check($val)
298 || confess "Attribute ("
300 . ") does not pass the type constraint because: "
301 . $type_constraint->get_message($val);
303 $meta_instance->set_slot_value($instance, $slot_name, $val);
306 my $initializer = $self->initializer;
308 # most things will just want to set a value, so make it first arg
309 $instance->$initializer($value, $callback, $self);
313 my ($self, $instance, $value) = @_;
315 my $attr_name = $self->name;
317 if ($self->is_required) {
319 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
322 if ($self->has_type_constraint) {
324 my $type_constraint = $self->type_constraint;
326 if ($self->should_coerce) {
327 $value = $type_constraint->coerce($value);
329 $type_constraint->_compiled_type_constraint->($value)
330 || confess "Attribute ("
332 . ") does not pass the type constraint because "
333 . $type_constraint->get_message($value);
336 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
339 $meta_instance->set_slot_value($instance, $attr_name, $value);
341 if (ref $value && $self->is_weak_ref) {
342 $meta_instance->weaken_slot_value($instance, $attr_name);
345 if ($self->has_trigger) {
346 $self->trigger->($instance, $value, $self);
351 my ($self, $instance) = @_;
353 if ($self->is_lazy) {
354 unless ($self->has_value($instance)) {
355 if ($self->has_default) {
356 my $default = $self->default($instance);
357 $self->set_initial_value($instance, $default);
359 if ( $self->has_builder ){
360 if (my $builder = $instance->can($self->builder)){
361 $self->set_initial_value($instance, $instance->$builder);
364 confess(blessed($instance)
365 . " does not support builder method '"
367 . "' for attribute '"
373 $self->set_initial_value($instance, undef);
378 if ($self->should_auto_deref) {
380 my $type_constraint = $self->type_constraint;
382 if ($type_constraint->is_a_type_of('ArrayRef')) {
383 my $rv = $self->SUPER::get_value($instance);
384 return unless defined $rv;
385 return wantarray ? @{ $rv } : $rv;
387 elsif ($type_constraint->is_a_type_of('HashRef')) {
388 my $rv = $self->SUPER::get_value($instance);
389 return unless defined $rv;
390 return wantarray ? %{ $rv } : $rv;
393 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
399 return $self->SUPER::get_value($instance);
403 ## installing accessors
405 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
407 sub install_accessors {
409 $self->SUPER::install_accessors(@_);
411 if ($self->has_handles) {
414 # Here we canonicalize the 'handles' option
415 # this will sort out any details and always
416 # return an hash of methods which we want
417 # to delagate to, see that method for details
418 my %handles = $self->_canonicalize_handles();
420 # find the accessor method for this attribute
421 my $accessor = $self->get_read_method_ref;
422 # then unpack it if we need too ...
423 $accessor = $accessor->body if blessed $accessor;
425 # install the delegation ...
426 my $associated_class = $self->associated_class;
427 foreach my $handle (keys %handles) {
428 my $method_to_call = $handles{$handle};
429 my $class_name = $associated_class->name;
430 my $name = "${class_name}::${handle}";
432 (!$associated_class->has_method($handle))
433 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
436 # handles is not allowed to delegate
437 # any of these methods, as they will
438 # override the ones in your class, which
439 # is almost certainly not what you want.
441 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
442 #cluck("Not delegating method '$handle' because it is a core method") and
443 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
445 if ((reftype($method_to_call) || '') eq 'CODE') {
446 $associated_class->add_method($handle => subname $name, $method_to_call);
450 # we used to do a goto here, but the
451 # goto didn't handle failure correctly
452 # (it just returned nothing), so I took
453 # that out. However, the more I thought
454 # about it, the less I liked it doing
455 # the goto, and I prefered the act of
456 # delegation being actually represented
457 # in the stack trace.
459 $associated_class->add_method($handle => subname $name, sub {
460 my $proxy = (shift)->$accessor();
462 || confess "Cannot delegate $handle to $method_to_call because " .
463 "the value of " . $self->name . " is not defined";
464 $proxy->$method_to_call(@_);
473 # private methods to help delegation ...
475 sub _canonicalize_handles {
477 my $handles = $self->handles;
478 if (my $handle_type = ref($handles)) {
479 if ($handle_type eq 'HASH') {
482 elsif ($handle_type eq 'ARRAY') {
483 return map { $_ => $_ } @{$handles};
485 elsif ($handle_type eq 'Regexp') {
486 ($self->has_type_constraint)
487 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
488 return map { ($_ => $_) }
489 grep { /$handles/ } $self->_get_delegate_method_list;
491 elsif ($handle_type eq 'CODE') {
492 return $handles->($self, $self->_find_delegate_metaclass);
495 confess "Unable to canonicalize the 'handles' option with $handles";
499 my $role_meta = eval { $handles->meta };
501 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
504 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
505 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
507 return map { $_ => $_ } (
508 $role_meta->get_method_list,
509 $role_meta->get_required_method_list
514 sub _find_delegate_metaclass {
516 if (my $class = $self->_isa_metadata) {
517 # if the class does have
518 # a meta method, use it
519 return $class->meta if $class->can('meta');
520 # otherwise we might be
521 # dealing with a non-Moose
522 # class, and need to make
524 return Moose::Meta::Class->initialize($class);
526 elsif (my $role = $self->_does_metadata) {
527 # our role will always have
532 confess "Cannot find delegate metaclass for attribute " . $self->name;
536 sub _get_delegate_method_list {
538 my $meta = $self->_find_delegate_metaclass;
539 if ($meta->isa('Class::MOP::Class')) {
540 return map { $_->{name} } # NOTE: !never! delegate &meta
541 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
542 $meta->compute_all_applicable_methods;
544 elsif ($meta->isa('Moose::Meta::Role')) {
545 return $meta->get_method_list;
548 confess "Unable to recognize the delegate metaclass '$meta'";
560 Moose::Meta::Attribute - The Moose attribute metaclass
564 This is a subclass of L<Class::MOP::Attribute> with Moose specific
567 For the most part, the only time you will ever encounter an
568 instance of this class is if you are doing some serious deep
569 introspection. To really understand this class, you need to refer
570 to the L<Class::MOP::Attribute> documentation.
574 =head2 Overridden methods
576 These methods override methods in L<Class::MOP::Attribute> and add
577 Moose specific features. You can safely assume though that they
578 will behave just as L<Class::MOP::Attribute> does.
586 =item B<initialize_instance_slot>
588 =item B<install_accessors>
590 =item B<accessor_metaclass>
596 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
601 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
603 Before setting the value, a check is made on the type constraint of
604 the attribute, if it has one, to see if the value passes it. If the
605 value fails to pass, the set operation dies with a L<Carp/confess>.
607 Any coercion to convert values is done before checking the type constraint.
609 To check a value against a type constraint before setting it, fetch the
610 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
611 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
612 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
617 =head2 Additional Moose features
619 Moose attributes support type-constraint checking, weak reference
620 creation and type coercion.
624 =item B<clone_and_inherit_options>
626 This is to support the C<has '+foo'> feature, it clones an attribute
627 from a superclass and allows a very specific set of changes to be made
630 =item B<has_type_constraint>
632 Returns true if this meta-attribute has a type constraint.
634 =item B<type_constraint>
636 A read-only accessor for this meta-attribute's type constraint. For
637 more information on what you can do with this, see the documentation
638 for L<Moose::Meta::TypeConstraint>.
642 Returns true if this meta-attribute performs delegation.
646 This returns the value which was passed into the handles option.
650 Returns true if this meta-attribute produces a weak reference.
654 Returns true if this meta-attribute is required to have a value.
658 Returns true if this meta-attribute should be initialized lazily.
660 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
662 =item B<is_lazy_build>
664 Returns true if this meta-attribute should be initialized lazily through
665 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
666 make your attribute required and lazy. In addition it will set the builder, clearer
667 and predicate options for you using the following convention.
669 #If your attribute name starts with an underscore:
670 has '_foo' => (lazy_build => 1);
672 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
674 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
676 #If your attribute name does not start with an underscore:
677 has 'foo' => (lazy_build => 1);
679 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
681 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
683 The reason for the different naming of the C<builder> is that the C<builder>
684 method is a private method while the C<clearer> and C<predicate> methods
687 NOTE: This means your class should provide a method whose name matches the value
688 of the builder part, in this case _build__foo or _build_foo.
690 =item B<should_coerce>
692 Returns true if this meta-attribute should perform type coercion.
694 =item B<should_auto_deref>
696 Returns true if this meta-attribute should perform automatic
699 NOTE: This can only be done for attributes whose type constraint is
700 either I<ArrayRef> or I<HashRef>.
704 Returns true if this meta-attribute has a trigger set.
708 This is a CODE reference which will be executed every time the
709 value of an attribute is assigned. The CODE ref will get two values,
710 the invocant and the new value. This can be used to handle I<basic>
711 bi-directional relations.
713 =item B<documentation>
715 This is a string which contains the documentation for this attribute.
716 It serves no direct purpose right now, but it might in the future
717 in some kind of automated documentation system perhaps.
719 =item B<has_documentation>
721 Returns true if this meta-attribute has any documentation.
727 All complex software has bugs lurking in it, and this module is no
728 exception. If you find a bug please either email me, or add the bug
733 Stevan Little E<lt>stevan@iinteractive.comE<gt>
735 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
737 =head1 COPYRIGHT AND LICENSE
739 Copyright 2006-2008 by Infinity Interactive, Inc.
741 L<http://www.iinteractive.com>
743 This library is free software; you can redistribute it and/or modify
744 it under the same terms as Perl itself.