2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
11 our $VERSION = '0.14';
12 our $AUTHORITY = 'cpan:STEVAN';
14 use Moose::Meta::Method::Accessor;
15 use Moose::Util::TypeConstraints ();
17 use base 'Class::MOP::Attribute';
19 # options which are not directly used
20 # but we store them for metadata purposes
21 __PACKAGE__->meta->add_attribute('isa' => (reader => '_isa_metadata'));
22 __PACKAGE__->meta->add_attribute('does' => (reader => '_does_metadata'));
23 __PACKAGE__->meta->add_attribute('is' => (reader => '_is_metadata'));
25 # these are actual options for the attrs
26 __PACKAGE__->meta->add_attribute('required' => (reader => 'is_required' ));
27 __PACKAGE__->meta->add_attribute('lazy' => (reader => 'is_lazy' ));
28 __PACKAGE__->meta->add_attribute('lazy_build' => (reader => 'is_lazy_build' ));
29 __PACKAGE__->meta->add_attribute('coerce' => (reader => 'should_coerce' ));
30 __PACKAGE__->meta->add_attribute('weak_ref' => (reader => 'is_weak_ref' ));
31 __PACKAGE__->meta->add_attribute('auto_deref' => (reader => 'should_auto_deref'));
32 __PACKAGE__->meta->add_attribute('type_constraint' => (
33 reader => 'type_constraint',
34 predicate => 'has_type_constraint',
36 __PACKAGE__->meta->add_attribute('trigger' => (
38 predicate => 'has_trigger',
40 __PACKAGE__->meta->add_attribute('handles' => (
42 predicate => 'has_handles',
44 __PACKAGE__->meta->add_attribute('documentation' => (
45 reader => 'documentation',
46 predicate => 'has_documentation',
50 my ($class, $name, %options) = @_;
51 $class->_process_options($name, \%options);
52 return $class->SUPER::new($name, %options);
55 sub clone_and_inherit_options {
56 my ($self, %options) = @_;
57 # you can change default, required, coerce, documentation and lazy
59 foreach my $legal_option (qw(default coerce required documentation lazy)) {
60 if (exists $options{$legal_option}) {
61 $actual_options{$legal_option} = $options{$legal_option};
62 delete $options{$legal_option};
66 # handles can only be added, not changed
67 if ($options{handles}) {
68 confess "You can only add the 'handles' option, you cannot change it"
69 if $self->has_handles;
70 $actual_options{handles} = $options{handles};
71 delete $options{handles};
74 # isa can be changed, but only if the
75 # new type is a subtype
78 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
79 $type_constraint = $options{isa};
82 $type_constraint = Moose::Util::TypeConstraints::find_type_constraint($options{isa});
83 (defined $type_constraint)
84 || confess "Could not find the type constraint '" . $options{isa} . "'";
87 # check here to see if the new type
88 # is a subtype of the old one
89 ($type_constraint->is_subtype_of($self->type_constraint->name))
90 || confess "New type constraint setting must be a subtype of inherited one"
91 # iff we have a type constraint that is ...
92 if $self->has_type_constraint;
94 $actual_options{type_constraint} = $type_constraint;
97 (scalar keys %options == 0)
98 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
99 $self->clone(%actual_options);
102 sub _process_options {
103 my ($class, $name, $options) = @_;
105 if (exists $options->{is}) {
106 if ($options->{is} eq 'ro') {
107 $options->{reader} ||= $name;
108 (!exists $options->{trigger})
109 || confess "Cannot have a trigger on a read-only attribute";
111 elsif ($options->{is} eq 'rw') {
112 $options->{accessor} = $name;
113 ((reftype($options->{trigger}) || '') eq 'CODE')
114 || confess "Trigger must be a CODE ref"
115 if exists $options->{trigger};
118 confess "I do not understand this option (is => " . $options->{is} . ")"
122 if (exists $options->{isa}) {
124 if (exists $options->{does}) {
125 if (eval { $options->{isa}->can('does') }) {
126 ($options->{isa}->does($options->{does}))
127 || confess "Cannot have an isa option and a does option if the isa does not do the does";
130 confess "Cannot have an isa option which cannot ->does()";
134 # allow for anon-subtypes here ...
135 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
136 $options->{type_constraint} = $options->{isa};
139 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
141 parent => Moose::Util::TypeConstraints::find_type_constraint('Object'),
142 constraint => sub { $_[0]->isa($options->{isa}) }
147 elsif (exists $options->{does}) {
148 # allow for anon-subtypes here ...
149 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
150 $options->{type_constraint} = $options->{isa};
153 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
154 $options->{does} => {
155 parent => Moose::Util::TypeConstraints::find_type_constraint('Role'),
156 constraint => sub { $_[0]->does($options->{does}) }
162 if (exists $options->{coerce} && $options->{coerce}) {
163 (exists $options->{type_constraint})
164 || confess "You cannot have coercion without specifying a type constraint";
165 confess "You cannot have a weak reference to a coerced value"
166 if $options->{weak_ref};
169 if (exists $options->{auto_deref} && $options->{auto_deref}) {
170 (exists $options->{type_constraint})
171 || confess "You cannot auto-dereference without specifying a type constraint";
172 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
173 $options->{type_constraint}->is_a_type_of('HashRef'))
174 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef";
177 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
178 confess("You can not use lazy_build and default for the same attribute")
179 if exists $options->{default};
180 $options->{lazy} = 1;
181 $options->{required} = 1;
182 $options->{builder} ||= "_build_${name}";
184 $options->{clearer} ||= "_clear${name}";
185 $options->{predicate} ||= "_has${name}";
187 $options->{clearer} ||= "clear_${name}";
188 $options->{predicate} ||= "has_${name}";
192 if (exists $options->{lazy} && $options->{lazy}) {
193 (exists $options->{default} || exists $options->{builder} )
194 || confess "You cannot have lazy attribute without specifying a default value for it";
199 sub initialize_instance_slot {
200 my ($self, $meta_instance, $instance, $params) = @_;
201 my $init_arg = $self->init_arg();
202 # try to fetch the init arg from the %params ...
206 if (exists $params->{$init_arg}) {
207 $val = $params->{$init_arg};
211 # skip it if it's lazy
212 return if $self->is_lazy;
213 # and die if it's required and doesn't have a default value
214 confess "Attribute (" . $self->name . ") is required"
215 if $self->is_required && !$self->has_default && !$self->has_builder;
217 # if nothing was in the %params, we can use the
218 # attribute's default value (if it has one)
219 if ($self->has_default) {
220 $val = $self->default($instance);
222 } elsif ($self->has_builder) {
223 if(my $builder = $instance->can($self->builder)){
224 $val = $instance->$builder;
227 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
232 return unless $value_is_set;
234 if ($self->has_type_constraint) {
235 my $type_constraint = $self->type_constraint;
236 if ($self->should_coerce && $type_constraint->has_coercion) {
237 $val = $type_constraint->coerce($val);
239 (defined($type_constraint->check($val)))
240 || confess "Attribute (" .
242 ") does not pass the type constraint (" .
243 $type_constraint->name .
246 ? (blessed($val) && overload::Overloaded($val)
247 ? overload::StrVal($val)
253 $meta_instance->set_slot_value($instance, $self->name, $val);
254 $meta_instance->weaken_slot_value($instance, $self->name)
255 if ref $val && $self->is_weak_ref;
261 my ($self, $instance, $value) = @_;
263 my $attr_name = $self->name;
265 if ($self->is_required) {
267 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
270 if ($self->has_type_constraint) {
272 my $type_constraint = $self->type_constraint;
274 if ($self->should_coerce) {
275 $value = $type_constraint->coerce($value);
277 defined($type_constraint->_compiled_type_constraint->($value))
278 || confess "Attribute ($attr_name) does not pass the type constraint ("
279 . $type_constraint->name
283 (blessed($value) && overload::Overloaded($value)
284 ? overload::StrVal($value)
291 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
294 $meta_instance->set_slot_value($instance, $attr_name, $value);
296 if (ref $value && $self->is_weak_ref) {
297 $meta_instance->weaken_slot_value($instance, $attr_name);
300 if ($self->has_trigger) {
301 $self->trigger->($instance, $value, $self);
306 my ($self, $instance) = @_;
308 if ($self->is_lazy) {
309 unless ($self->has_value($instance)) {
310 if ($self->has_default) {
311 my $default = $self->default($instance);
312 $self->set_value($instance, $default);
314 if ( $self->has_builder ){
315 if(my $builder = $instance->can($self->builder)){
316 $self->set_value($instance, $instance->$builder);
318 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
321 $self->set_value($instance, undef);
326 if ($self->should_auto_deref) {
328 my $type_constraint = $self->type_constraint;
330 if ($type_constraint->is_a_type_of('ArrayRef')) {
331 my $rv = $self->SUPER::get_value($instance);
332 return unless defined $rv;
333 return wantarray ? @{ $rv } : $rv;
335 elsif ($type_constraint->is_a_type_of('HashRef')) {
336 my $rv = $self->SUPER::get_value($instance);
337 return unless defined $rv;
338 return wantarray ? %{ $rv } : $rv;
341 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
347 return $self->SUPER::get_value($instance);
351 ## installing accessors
353 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
355 sub install_accessors {
357 $self->SUPER::install_accessors(@_);
359 if ($self->has_handles) {
362 # Here we canonicalize the 'handles' option
363 # this will sort out any details and always
364 # return an hash of methods which we want
365 # to delagate to, see that method for details
366 my %handles = $self->_canonicalize_handles();
368 # find the name of the accessor for this attribute
369 my $accessor_name = $self->reader || $self->accessor;
370 (defined $accessor_name)
371 || confess "You cannot install delegation without a reader or accessor for the attribute";
373 # make sure we handle HASH accessors correctly
374 ($accessor_name) = keys %{$accessor_name}
375 if ref($accessor_name) eq 'HASH';
377 # install the delegation ...
378 my $associated_class = $self->associated_class;
379 foreach my $handle (keys %handles) {
380 my $method_to_call = $handles{$handle};
382 (!$associated_class->has_method($handle))
383 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
386 # handles is not allowed to delegate
387 # any of these methods, as they will
388 # override the ones in your class, which
389 # is almost certainly not what you want.
390 next if $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
392 if ((reftype($method_to_call) || '') eq 'CODE') {
393 $associated_class->add_method($handle => $method_to_call);
396 $associated_class->add_method($handle => sub {
398 # we should check for lack of
399 # a callable return value from
401 my $proxy = (shift)->$accessor_name();
403 goto &{ $proxy->can($method_to_call)};
412 # private methods to help delegation ...
414 sub _canonicalize_handles {
416 my $handles = $self->handles;
417 if (my $handle_type = ref($handles)) {
418 if ($handle_type eq 'HASH') {
421 elsif ($handle_type eq 'ARRAY') {
422 return map { $_ => $_ } @{$handles};
424 elsif ($handle_type eq 'Regexp') {
425 ($self->has_type_constraint)
426 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
427 return map { ($_ => $_) }
428 grep { /$handles/ } $self->_get_delegate_method_list;
430 elsif ($handle_type eq 'CODE') {
431 return $handles->($self, $self->_find_delegate_metaclass);
434 confess "Unable to canonicalize the 'handles' option with $handles";
438 my $role_meta = eval { $handles->meta };
440 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
443 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
444 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
446 return map { $_ => $_ } (
447 $role_meta->get_method_list,
448 $role_meta->get_required_method_list
453 sub _find_delegate_metaclass {
455 if (my $class = $self->_isa_metadata) {
456 # if the class does have
457 # a meta method, use it
458 return $class->meta if $class->can('meta');
459 # otherwise we might be
460 # dealing with a non-Moose
461 # class, and need to make
463 return Moose::Meta::Class->initialize($class);
465 elsif (my $role = $self->_does_metadata) {
466 # our role will always have
471 confess "Cannot find delegate metaclass for attribute " . $self->name;
475 sub _get_delegate_method_list {
477 my $meta = $self->_find_delegate_metaclass;
478 if ($meta->isa('Class::MOP::Class')) {
479 return map { $_->{name} } # NOTE: !never! delegate &meta
480 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
481 $meta->compute_all_applicable_methods;
483 elsif ($meta->isa('Moose::Meta::Role')) {
484 return $meta->get_method_list;
487 confess "Unable to recognize the delegate metaclass '$meta'";
499 Moose::Meta::Attribute - The Moose attribute metaclass
503 This is a subclass of L<Class::MOP::Attribute> with Moose specific
506 For the most part, the only time you will ever encounter an
507 instance of this class is if you are doing some serious deep
508 introspection. To really understand this class, you need to refer
509 to the L<Class::MOP::Attribute> documentation.
513 =head2 Overridden methods
515 These methods override methods in L<Class::MOP::Attribute> and add
516 Moose specific features. You can safely assume though that they
517 will behave just as L<Class::MOP::Attribute> does.
523 =item B<initialize_instance_slot>
525 =item B<install_accessors>
527 =item B<accessor_metaclass>
533 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
538 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
540 Before setting the value, a check is made on the type constraint of
541 the attribute, if it has one, to see if the value passes it. If the
542 value fails to pass, the set operation dies with a L<Carp/confess>.
544 Any coercion to convert values is done before checking the type constraint.
546 To check a value against a type constraint before setting it, fetch the
547 attribute instance using L<Moose::Meta::Attribute/find_attribute_by_name>,
548 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
549 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
554 =head2 Additional Moose features
556 Moose attributes support type-constraint checking, weak reference
557 creation and type coercion.
561 =item B<clone_and_inherit_options>
563 This is to support the C<has '+foo'> feature, it clones an attribute
564 from a superclass and allows a very specific set of changes to be made
567 =item B<has_type_constraint>
569 Returns true if this meta-attribute has a type constraint.
571 =item B<type_constraint>
573 A read-only accessor for this meta-attribute's type constraint. For
574 more information on what you can do with this, see the documentation
575 for L<Moose::Meta::TypeConstraint>.
579 Returns true if this meta-attribute performs delegation.
583 This returns the value which was passed into the handles option.
587 Returns true if this meta-attribute produces a weak reference.
591 Returns true if this meta-attribute is required to have a value.
595 Returns true if this meta-attribute should be initialized lazily.
597 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
599 =item B<is_lazy_build>
601 Returns true if this meta-attribute should be initialized lazily through
602 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
603 make your attribute required and lazy. In addition it will set the builder, clearer
604 and predicate options for you using the following convention.
606 #If your attribute name starts with an underscore:
607 has '_foo' => (lazy_build => 1);
609 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
611 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
613 #If your attribute name does not start with an underscore:
614 has 'foo' => (lazy_build => 1);
616 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
618 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
620 The reason for the different naming of the C<builder> is that the C<builder>
621 method is a private method while the C<clearer> and C<predicate> methods
624 NOTE: This means your class should provide a method whose name matches the value
625 of the builder part, in this case _build__foo or _build_foo.
627 =item B<should_coerce>
629 Returns true if this meta-attribute should perform type coercion.
631 =item B<should_auto_deref>
633 Returns true if this meta-attribute should perform automatic
636 NOTE: This can only be done for attributes whose type constraint is
637 either I<ArrayRef> or I<HashRef>.
641 Returns true if this meta-attribute has a trigger set.
645 This is a CODE reference which will be executed every time the
646 value of an attribute is assigned. The CODE ref will get two values,
647 the invocant and the new value. This can be used to handle I<basic>
648 bi-directional relations.
650 =item B<documentation>
652 This is a string which contains the documentation for this attribute.
653 It serves no direct purpose right now, but it might in the future
654 in some kind of automated documentation system perhaps.
656 =item B<has_documentation>
658 Returns true if this meta-attribute has any documentation.
664 All complex software has bugs lurking in it, and this module is no
665 exception. If you find a bug please either email me, or add the bug
670 Stevan Little E<lt>stevan@iinteractive.comE<gt>
672 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
674 =head1 COPYRIGHT AND LICENSE
676 Copyright 2006, 2007 by Infinity Interactive, Inc.
678 L<http://www.iinteractive.com>
680 This library is free software; you can redistribute it and/or modify
681 it under the same terms as Perl itself.