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);
440 $associated_class->add_method($handle => subname $name, sub {
441 my $proxy = (shift)->$accessor();
443 || confess "Cannot delegate $handle to $method_to_call because " .
444 "the value of " . $self->name . " is not defined";
445 $proxy->$method_to_call(@_);
454 # private methods to help delegation ...
456 sub _canonicalize_handles {
458 my $handles = $self->handles;
459 if (my $handle_type = ref($handles)) {
460 if ($handle_type eq 'HASH') {
463 elsif ($handle_type eq 'ARRAY') {
464 return map { $_ => $_ } @{$handles};
466 elsif ($handle_type eq 'Regexp') {
467 ($self->has_type_constraint)
468 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
469 return map { ($_ => $_) }
470 grep { /$handles/ } $self->_get_delegate_method_list;
472 elsif ($handle_type eq 'CODE') {
473 return $handles->($self, $self->_find_delegate_metaclass);
476 confess "Unable to canonicalize the 'handles' option with $handles";
480 my $role_meta = eval { $handles->meta };
482 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
485 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
486 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
488 return map { $_ => $_ } (
489 $role_meta->get_method_list,
490 $role_meta->get_required_method_list
495 sub _find_delegate_metaclass {
497 if (my $class = $self->_isa_metadata) {
498 # if the class does have
499 # a meta method, use it
500 return $class->meta if $class->can('meta');
501 # otherwise we might be
502 # dealing with a non-Moose
503 # class, and need to make
505 return Moose::Meta::Class->initialize($class);
507 elsif (my $role = $self->_does_metadata) {
508 # our role will always have
513 confess "Cannot find delegate metaclass for attribute " . $self->name;
517 sub _get_delegate_method_list {
519 my $meta = $self->_find_delegate_metaclass;
520 if ($meta->isa('Class::MOP::Class')) {
521 return map { $_->{name} } # NOTE: !never! delegate &meta
522 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
523 $meta->compute_all_applicable_methods;
525 elsif ($meta->isa('Moose::Meta::Role')) {
526 return $meta->get_method_list;
529 confess "Unable to recognize the delegate metaclass '$meta'";
541 Moose::Meta::Attribute - The Moose attribute metaclass
545 This is a subclass of L<Class::MOP::Attribute> with Moose specific
548 For the most part, the only time you will ever encounter an
549 instance of this class is if you are doing some serious deep
550 introspection. To really understand this class, you need to refer
551 to the L<Class::MOP::Attribute> documentation.
555 =head2 Overridden methods
557 These methods override methods in L<Class::MOP::Attribute> and add
558 Moose specific features. You can safely assume though that they
559 will behave just as L<Class::MOP::Attribute> does.
565 =item B<initialize_instance_slot>
567 =item B<install_accessors>
569 =item B<accessor_metaclass>
575 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
580 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
582 Before setting the value, a check is made on the type constraint of
583 the attribute, if it has one, to see if the value passes it. If the
584 value fails to pass, the set operation dies with a L<Carp/confess>.
586 Any coercion to convert values is done before checking the type constraint.
588 To check a value against a type constraint before setting it, fetch the
589 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
590 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
591 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
596 =head2 Additional Moose features
598 Moose attributes support type-constraint checking, weak reference
599 creation and type coercion.
603 =item B<clone_and_inherit_options>
605 This is to support the C<has '+foo'> feature, it clones an attribute
606 from a superclass and allows a very specific set of changes to be made
609 =item B<has_type_constraint>
611 Returns true if this meta-attribute has a type constraint.
613 =item B<type_constraint>
615 A read-only accessor for this meta-attribute's type constraint. For
616 more information on what you can do with this, see the documentation
617 for L<Moose::Meta::TypeConstraint>.
621 Returns true if this meta-attribute performs delegation.
625 This returns the value which was passed into the handles option.
629 Returns true if this meta-attribute produces a weak reference.
633 Returns true if this meta-attribute is required to have a value.
637 Returns true if this meta-attribute should be initialized lazily.
639 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
641 =item B<is_lazy_build>
643 Returns true if this meta-attribute should be initialized lazily through
644 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
645 make your attribute required and lazy. In addition it will set the builder, clearer
646 and predicate options for you using the following convention.
648 #If your attribute name starts with an underscore:
649 has '_foo' => (lazy_build => 1);
651 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
653 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
655 #If your attribute name does not start with an underscore:
656 has 'foo' => (lazy_build => 1);
658 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
660 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
662 The reason for the different naming of the C<builder> is that the C<builder>
663 method is a private method while the C<clearer> and C<predicate> methods
666 NOTE: This means your class should provide a method whose name matches the value
667 of the builder part, in this case _build__foo or _build_foo.
669 =item B<should_coerce>
671 Returns true if this meta-attribute should perform type coercion.
673 =item B<should_auto_deref>
675 Returns true if this meta-attribute should perform automatic
678 NOTE: This can only be done for attributes whose type constraint is
679 either I<ArrayRef> or I<HashRef>.
683 Returns true if this meta-attribute has a trigger set.
687 This is a CODE reference which will be executed every time the
688 value of an attribute is assigned. The CODE ref will get two values,
689 the invocant and the new value. This can be used to handle I<basic>
690 bi-directional relations.
692 =item B<documentation>
694 This is a string which contains the documentation for this attribute.
695 It serves no direct purpose right now, but it might in the future
696 in some kind of automated documentation system perhaps.
698 =item B<has_documentation>
700 Returns true if this meta-attribute has any documentation.
706 All complex software has bugs lurking in it, and this module is no
707 exception. If you find a bug please either email me, or add the bug
712 Stevan Little E<lt>stevan@iinteractive.comE<gt>
714 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
716 =head1 COPYRIGHT AND LICENSE
718 Copyright 2006-2008 by Infinity Interactive, Inc.
720 L<http://www.iinteractive.com>
722 This library is free software; you can redistribute it and/or modify
723 it under the same terms as Perl itself.