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 $type_constraint = Moose::Util::TypeConstraints::find_or_create_isa_type_constraint($options{isa});
82 (defined $type_constraint)
83 || confess "Could not find the type constraint '" . $options{isa} . "'";
86 $actual_options{type_constraint} = $type_constraint;
92 if (blessed($options{does}) && $options{does}->isa('Moose::Meta::TypeConstraint')) {
93 $type_constraint = $options{does};
96 $type_constraint = Moose::Util::TypeConstraints::find_or_create_does_type_constraint($options{does});
97 (defined $type_constraint)
98 || confess "Could not find the type constraint '" . $options{does} . "'";
101 $actual_options{type_constraint} = $type_constraint;
102 delete $options{does};
105 (scalar keys %options == 0)
106 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
107 $self->clone(%actual_options);
110 sub _process_options {
111 my ($class, $name, $options) = @_;
113 if (exists $options->{is}) {
114 if ($options->{is} eq 'ro') {
115 $options->{reader} ||= $name;
116 (!exists $options->{trigger})
117 || confess "Cannot have a trigger on a read-only attribute $name";
119 elsif ($options->{is} eq 'rw') {
120 $options->{accessor} = $name;
121 ((reftype($options->{trigger}) || '') eq 'CODE')
122 || confess "Trigger must be a CODE ref"
123 if exists $options->{trigger};
126 confess "I do not understand this option (is => " . $options->{is} . ") on attribute $name"
130 if (exists $options->{isa}) {
131 if (exists $options->{does}) {
132 if (eval { $options->{isa}->can('does') }) {
133 ($options->{isa}->does($options->{does}))
134 || confess "Cannot have an isa option and a does option if the isa does not do the does on attribute $name";
137 confess "Cannot have an isa option which cannot ->does() on attribute $name";
141 # allow for anon-subtypes here ...
142 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
143 $options->{type_constraint} = $options->{isa};
146 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_isa_type_constraint($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 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_does_type_constraint($options->{does});
159 if (exists $options->{coerce} && $options->{coerce}) {
160 (exists $options->{type_constraint})
161 || confess "You cannot have coercion without specifying a type constraint on attribute $name";
162 confess "You cannot have a weak reference to a coerced value on attribute $name"
163 if $options->{weak_ref};
166 if (exists $options->{auto_deref} && $options->{auto_deref}) {
167 (exists $options->{type_constraint})
168 || confess "You cannot auto-dereference without specifying a type constraint on attribute $name";
169 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
170 $options->{type_constraint}->is_a_type_of('HashRef'))
171 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef on attribute $name";
174 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
175 confess("You can not use lazy_build and default for the same attribute $name")
176 if exists $options->{default};
177 $options->{lazy} = 1;
178 $options->{required} = 1;
179 $options->{builder} ||= "_build_${name}";
181 $options->{clearer} ||= "_clear${name}";
182 $options->{predicate} ||= "_has${name}";
185 $options->{clearer} ||= "clear_${name}";
186 $options->{predicate} ||= "has_${name}";
190 if (exists $options->{lazy} && $options->{lazy}) {
191 (exists $options->{default} || defined $options->{builder} )
192 || confess "You cannot have lazy attribute ($name) without specifying a default value for it";
195 if ( $options->{required} && !( ( !exists $options->{init_arg} || defined $options->{init_arg} ) || exists $options->{default} || defined $options->{builder} ) ) {
196 confess "You cannot have a required attribute ($name) without a default, builder, or an init_arg";
201 sub initialize_instance_slot {
202 my ($self, $meta_instance, $instance, $params) = @_;
203 my $init_arg = $self->init_arg();
204 # try to fetch the init arg from the %params ...
208 if ( defined($init_arg) and exists $params->{$init_arg}) {
209 $val = $params->{$init_arg};
213 # skip it if it's lazy
214 return if $self->is_lazy;
215 # and die if it's required and doesn't have a default value
216 confess "Attribute (" . $self->name . ") is required"
217 if $self->is_required && !$self->has_default && !$self->has_builder;
219 # if nothing was in the %params, we can use the
220 # attribute's default value (if it has one)
221 if ($self->has_default) {
222 $val = $self->default($instance);
225 elsif ($self->has_builder) {
226 if (my $builder = $instance->can($self->builder)){
227 $val = $instance->$builder;
231 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
236 return unless $value_is_set;
238 if ($self->has_type_constraint) {
239 my $type_constraint = $self->type_constraint;
240 if ($self->should_coerce && $type_constraint->has_coercion) {
241 $val = $type_constraint->coerce($val);
243 $type_constraint->check($val)
244 || confess "Attribute ("
246 . ") does not pass the type constraint because: "
247 . $type_constraint->get_message($val);
250 $self->set_initial_value($instance, $val);
251 $meta_instance->weaken_slot_value($instance, $self->name)
252 if ref $val && $self->is_weak_ref;
258 # this duplicates too much code from
259 # Class::MOP::Attribute, we need to
260 # refactor these bits eventually.
262 sub _set_initial_slot_value {
263 my ($self, $meta_instance, $instance, $value) = @_;
265 my $slot_name = $self->name;
267 return $meta_instance->set_slot_value($instance, $slot_name, $value)
268 unless $self->has_initializer;
270 my ($type_constraint, $can_coerce);
271 if ($self->has_type_constraint) {
272 $type_constraint = $self->type_constraint;
273 $can_coerce = ($self->should_coerce && $type_constraint->has_coercion);
278 if ($type_constraint) {
279 $val = $type_constraint->coerce($val)
281 $type_constraint->check($val)
282 || confess "Attribute ("
284 . ") does not pass the type constraint because: "
285 . $type_constraint->get_message($val);
287 $meta_instance->set_slot_value($instance, $slot_name, $val);
290 my $initializer = $self->initializer;
292 # most things will just want to set a value, so make it first arg
293 $instance->$initializer($value, $callback, $self);
297 my ($self, $instance, $value) = @_;
299 my $attr_name = $self->name;
301 if ($self->is_required) {
303 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
306 if ($self->has_type_constraint) {
308 my $type_constraint = $self->type_constraint;
310 if ($self->should_coerce) {
311 $value = $type_constraint->coerce($value);
313 $type_constraint->_compiled_type_constraint->($value)
314 || confess "Attribute ("
316 . ") does not pass the type constraint because "
317 . $type_constraint->get_message($value);
320 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
323 $meta_instance->set_slot_value($instance, $attr_name, $value);
325 if (ref $value && $self->is_weak_ref) {
326 $meta_instance->weaken_slot_value($instance, $attr_name);
329 if ($self->has_trigger) {
330 $self->trigger->($instance, $value, $self);
335 my ($self, $instance) = @_;
337 if ($self->is_lazy) {
338 unless ($self->has_value($instance)) {
339 if ($self->has_default) {
340 my $default = $self->default($instance);
341 $self->set_initial_value($instance, $default);
343 if ( $self->has_builder ){
344 if (my $builder = $instance->can($self->builder)){
345 $self->set_initial_value($instance, $instance->$builder);
348 confess(blessed($instance)
349 . " does not support builder method '"
351 . "' for attribute '"
357 $self->set_initial_value($instance, undef);
362 if ($self->should_auto_deref) {
364 my $type_constraint = $self->type_constraint;
366 if ($type_constraint->is_a_type_of('ArrayRef')) {
367 my $rv = $self->SUPER::get_value($instance);
368 return unless defined $rv;
369 return wantarray ? @{ $rv } : $rv;
371 elsif ($type_constraint->is_a_type_of('HashRef')) {
372 my $rv = $self->SUPER::get_value($instance);
373 return unless defined $rv;
374 return wantarray ? %{ $rv } : $rv;
377 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
383 return $self->SUPER::get_value($instance);
387 ## installing accessors
389 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
391 sub install_accessors {
393 $self->SUPER::install_accessors(@_);
395 if ($self->has_handles) {
398 # Here we canonicalize the 'handles' option
399 # this will sort out any details and always
400 # return an hash of methods which we want
401 # to delagate to, see that method for details
402 my %handles = $self->_canonicalize_handles();
404 # find the accessor method for this attribute
405 my $accessor = $self->get_read_method_ref;
406 # then unpack it if we need too ...
407 $accessor = $accessor->body if blessed $accessor;
409 # install the delegation ...
410 my $associated_class = $self->associated_class;
411 foreach my $handle (keys %handles) {
412 my $method_to_call = $handles{$handle};
413 my $class_name = $associated_class->name;
414 my $name = "${class_name}::${handle}";
416 (!$associated_class->has_method($handle))
417 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
420 # handles is not allowed to delegate
421 # any of these methods, as they will
422 # override the ones in your class, which
423 # is almost certainly not what you want.
425 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
426 #cluck("Not delegating method '$handle' because it is a core method") and
427 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
429 if ((reftype($method_to_call) || '') eq 'CODE') {
430 $associated_class->add_method($handle => subname $name, $method_to_call);
434 # we used to do a goto here, but the
435 # goto didn't handle failure correctly
436 # (it just returned nothing), so I took
437 # that out. However, the more I thought
438 # about it, the less I liked it doing
439 # the goto, and I prefered the act of
440 # delegation being actually represented
441 # in the stack trace.
443 $associated_class->add_method($handle => subname $name, sub {
444 my $proxy = (shift)->$accessor();
446 || confess "Cannot delegate $handle to $method_to_call because " .
447 "the value of " . $self->name . " is not defined";
448 $proxy->$method_to_call(@_);
457 # private methods to help delegation ...
459 sub _canonicalize_handles {
461 my $handles = $self->handles;
462 if (my $handle_type = ref($handles)) {
463 if ($handle_type eq 'HASH') {
466 elsif ($handle_type eq 'ARRAY') {
467 return map { $_ => $_ } @{$handles};
469 elsif ($handle_type eq 'Regexp') {
470 ($self->has_type_constraint)
471 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
472 return map { ($_ => $_) }
473 grep { /$handles/ } $self->_get_delegate_method_list;
475 elsif ($handle_type eq 'CODE') {
476 return $handles->($self, $self->_find_delegate_metaclass);
479 confess "Unable to canonicalize the 'handles' option with $handles";
483 my $role_meta = eval { $handles->meta };
485 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
488 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
489 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
491 return map { $_ => $_ } (
492 $role_meta->get_method_list,
493 $role_meta->get_required_method_list
498 sub _find_delegate_metaclass {
500 if (my $class = $self->_isa_metadata) {
501 # if the class does have
502 # a meta method, use it
503 return $class->meta if $class->can('meta');
504 # otherwise we might be
505 # dealing with a non-Moose
506 # class, and need to make
508 return Moose::Meta::Class->initialize($class);
510 elsif (my $role = $self->_does_metadata) {
511 # our role will always have
516 confess "Cannot find delegate metaclass for attribute " . $self->name;
520 sub _get_delegate_method_list {
522 my $meta = $self->_find_delegate_metaclass;
523 if ($meta->isa('Class::MOP::Class')) {
524 return map { $_->{name} } # NOTE: !never! delegate &meta
525 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
526 $meta->compute_all_applicable_methods;
528 elsif ($meta->isa('Moose::Meta::Role')) {
529 return $meta->get_method_list;
532 confess "Unable to recognize the delegate metaclass '$meta'";
544 Moose::Meta::Attribute - The Moose attribute metaclass
548 This is a subclass of L<Class::MOP::Attribute> with Moose specific
551 For the most part, the only time you will ever encounter an
552 instance of this class is if you are doing some serious deep
553 introspection. To really understand this class, you need to refer
554 to the L<Class::MOP::Attribute> documentation.
558 =head2 Overridden methods
560 These methods override methods in L<Class::MOP::Attribute> and add
561 Moose specific features. You can safely assume though that they
562 will behave just as L<Class::MOP::Attribute> does.
570 =item B<initialize_instance_slot>
572 =item B<install_accessors>
574 =item B<accessor_metaclass>
580 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
585 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
587 Before setting the value, a check is made on the type constraint of
588 the attribute, if it has one, to see if the value passes it. If the
589 value fails to pass, the set operation dies with a L<Carp/confess>.
591 Any coercion to convert values is done before checking the type constraint.
593 To check a value against a type constraint before setting it, fetch the
594 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
595 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
596 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
601 =head2 Additional Moose features
603 Moose attributes support type-constraint checking, weak reference
604 creation and type coercion.
608 =item B<clone_and_inherit_options>
610 This is to support the C<has '+foo'> feature, it clones an attribute
611 from a superclass and allows a very specific set of changes to be made
614 =item B<has_type_constraint>
616 Returns true if this meta-attribute has a type constraint.
618 =item B<type_constraint>
620 A read-only accessor for this meta-attribute's type constraint. For
621 more information on what you can do with this, see the documentation
622 for L<Moose::Meta::TypeConstraint>.
626 Returns true if this meta-attribute performs delegation.
630 This returns the value which was passed into the handles option.
634 Returns true if this meta-attribute produces a weak reference.
638 Returns true if this meta-attribute is required to have a value.
642 Returns true if this meta-attribute should be initialized lazily.
644 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
646 =item B<is_lazy_build>
648 Returns true if this meta-attribute should be initialized lazily through
649 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
650 make your attribute required and lazy. In addition it will set the builder, clearer
651 and predicate options for you using the following convention.
653 #If your attribute name starts with an underscore:
654 has '_foo' => (lazy_build => 1);
656 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
658 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
660 #If your attribute name does not start with an underscore:
661 has 'foo' => (lazy_build => 1);
663 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
665 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
667 The reason for the different naming of the C<builder> is that the C<builder>
668 method is a private method while the C<clearer> and C<predicate> methods
671 NOTE: This means your class should provide a method whose name matches the value
672 of the builder part, in this case _build__foo or _build_foo.
674 =item B<should_coerce>
676 Returns true if this meta-attribute should perform type coercion.
678 =item B<should_auto_deref>
680 Returns true if this meta-attribute should perform automatic
683 NOTE: This can only be done for attributes whose type constraint is
684 either I<ArrayRef> or I<HashRef>.
688 Returns true if this meta-attribute has a trigger set.
692 This is a CODE reference which will be executed every time the
693 value of an attribute is assigned. The CODE ref will get two values,
694 the invocant and the new value. This can be used to handle I<basic>
695 bi-directional relations.
697 =item B<documentation>
699 This is a string which contains the documentation for this attribute.
700 It serves no direct purpose right now, but it might in the future
701 in some kind of automated documentation system perhaps.
703 =item B<has_documentation>
705 Returns true if this meta-attribute has any documentation.
711 All complex software has bugs lurking in it, and this module is no
712 exception. If you find a bug please either email me, or add the bug
717 Stevan Little E<lt>stevan@iinteractive.comE<gt>
719 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
721 =head1 COPYRIGHT AND LICENSE
723 Copyright 2006-2008 by Infinity Interactive, Inc.
725 L<http://www.iinteractive.com>
727 This library is free software; you can redistribute it and/or modify
728 it under the same terms as Perl itself.