2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
9 use Sub::Name 'subname';
12 our $VERSION = '0.18';
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 (defined($type_constraint->check($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 && $self->is_weak_ref;
265 my ($self, $instance, $value) = @_;
267 my $attr_name = $self->name;
269 if ($self->is_required) {
271 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
274 if ($self->has_type_constraint) {
276 my $type_constraint = $self->type_constraint;
278 if ($self->should_coerce) {
279 $value = $type_constraint->coerce($value);
281 $type_constraint->_compiled_type_constraint->($value)
282 || confess "Attribute ("
284 . ") does not pass the type constraint because "
285 . $type_constraint->get_message($value)
289 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
292 $meta_instance->set_slot_value($instance, $attr_name, $value);
294 if (ref $value && $self->is_weak_ref) {
295 $meta_instance->weaken_slot_value($instance, $attr_name);
298 if ($self->has_trigger) {
299 $self->trigger->($instance, $value, $self);
304 my ($self, $instance) = @_;
306 if ($self->is_lazy) {
307 unless ($self->has_value($instance)) {
308 if ($self->has_default) {
309 my $default = $self->default($instance);
310 $self->set_initial_value($instance, $default);
312 if ( $self->has_builder ){
313 if (my $builder = $instance->can($self->builder)){
314 $self->set_initial_value($instance, $instance->$builder);
317 confess(blessed($instance)
318 . " does not support builder method '"
320 . "' for attribute '"
326 $self->set_initial_value($instance, undef);
331 if ($self->should_auto_deref) {
333 my $type_constraint = $self->type_constraint;
335 if ($type_constraint->is_a_type_of('ArrayRef')) {
336 my $rv = $self->SUPER::get_value($instance);
337 return unless defined $rv;
338 return wantarray ? @{ $rv } : $rv;
340 elsif ($type_constraint->is_a_type_of('HashRef')) {
341 my $rv = $self->SUPER::get_value($instance);
342 return unless defined $rv;
343 return wantarray ? %{ $rv } : $rv;
346 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
352 return $self->SUPER::get_value($instance);
356 ## installing accessors
358 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
360 sub install_accessors {
362 $self->SUPER::install_accessors(@_);
364 if ($self->has_handles) {
367 # Here we canonicalize the 'handles' option
368 # this will sort out any details and always
369 # return an hash of methods which we want
370 # to delagate to, see that method for details
371 my %handles = $self->_canonicalize_handles();
373 # find the accessor method for this attribute
374 my $accessor = $self->get_read_method_ref;
375 # then unpack it if we need too ...
376 $accessor = $accessor->body if blessed $accessor;
378 # install the delegation ...
379 my $associated_class = $self->associated_class;
380 foreach my $handle (keys %handles) {
381 my $method_to_call = $handles{$handle};
382 my $class_name = $associated_class->name;
383 my $name = "${class_name}::${handle}";
385 (!$associated_class->has_method($handle))
386 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
389 # handles is not allowed to delegate
390 # any of these methods, as they will
391 # override the ones in your class, which
392 # is almost certainly not what you want.
394 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
395 #cluck("Not delegating method '$handle' because it is a core method") and
396 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
398 if ((reftype($method_to_call) || '') eq 'CODE') {
399 $associated_class->add_method($handle => subname $name, $method_to_call);
402 $associated_class->add_method($handle => subname $name, sub {
403 my $proxy = (shift)->$accessor();
406 || confess "Cannot delegate $handle to $method_to_call because " .
407 "the value of " . $self->name . " is not defined";
408 goto &{ $proxy->can($method_to_call) || return };
417 # private methods to help delegation ...
419 sub _canonicalize_handles {
421 my $handles = $self->handles;
422 if (my $handle_type = ref($handles)) {
423 if ($handle_type eq 'HASH') {
426 elsif ($handle_type eq 'ARRAY') {
427 return map { $_ => $_ } @{$handles};
429 elsif ($handle_type eq 'Regexp') {
430 ($self->has_type_constraint)
431 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
432 return map { ($_ => $_) }
433 grep { /$handles/ } $self->_get_delegate_method_list;
435 elsif ($handle_type eq 'CODE') {
436 return $handles->($self, $self->_find_delegate_metaclass);
439 confess "Unable to canonicalize the 'handles' option with $handles";
443 my $role_meta = eval { $handles->meta };
445 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
448 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
449 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
451 return map { $_ => $_ } (
452 $role_meta->get_method_list,
453 $role_meta->get_required_method_list
458 sub _find_delegate_metaclass {
460 if (my $class = $self->_isa_metadata) {
461 # if the class does have
462 # a meta method, use it
463 return $class->meta if $class->can('meta');
464 # otherwise we might be
465 # dealing with a non-Moose
466 # class, and need to make
468 return Moose::Meta::Class->initialize($class);
470 elsif (my $role = $self->_does_metadata) {
471 # our role will always have
476 confess "Cannot find delegate metaclass for attribute " . $self->name;
480 sub _get_delegate_method_list {
482 my $meta = $self->_find_delegate_metaclass;
483 if ($meta->isa('Class::MOP::Class')) {
484 return map { $_->{name} } # NOTE: !never! delegate &meta
485 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
486 $meta->compute_all_applicable_methods;
488 elsif ($meta->isa('Moose::Meta::Role')) {
489 return $meta->get_method_list;
492 confess "Unable to recognize the delegate metaclass '$meta'";
504 Moose::Meta::Attribute - The Moose attribute metaclass
508 This is a subclass of L<Class::MOP::Attribute> with Moose specific
511 For the most part, the only time you will ever encounter an
512 instance of this class is if you are doing some serious deep
513 introspection. To really understand this class, you need to refer
514 to the L<Class::MOP::Attribute> documentation.
518 =head2 Overridden methods
520 These methods override methods in L<Class::MOP::Attribute> and add
521 Moose specific features. You can safely assume though that they
522 will behave just as L<Class::MOP::Attribute> does.
528 =item B<initialize_instance_slot>
530 =item B<install_accessors>
532 =item B<accessor_metaclass>
538 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
543 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
545 Before setting the value, a check is made on the type constraint of
546 the attribute, if it has one, to see if the value passes it. If the
547 value fails to pass, the set operation dies with a L<Carp/confess>.
549 Any coercion to convert values is done before checking the type constraint.
551 To check a value against a type constraint before setting it, fetch the
552 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
553 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
554 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
559 =head2 Additional Moose features
561 Moose attributes support type-constraint checking, weak reference
562 creation and type coercion.
566 =item B<clone_and_inherit_options>
568 This is to support the C<has '+foo'> feature, it clones an attribute
569 from a superclass and allows a very specific set of changes to be made
572 =item B<has_type_constraint>
574 Returns true if this meta-attribute has a type constraint.
576 =item B<type_constraint>
578 A read-only accessor for this meta-attribute's type constraint. For
579 more information on what you can do with this, see the documentation
580 for L<Moose::Meta::TypeConstraint>.
584 Returns true if this meta-attribute performs delegation.
588 This returns the value which was passed into the handles option.
592 Returns true if this meta-attribute produces a weak reference.
596 Returns true if this meta-attribute is required to have a value.
600 Returns true if this meta-attribute should be initialized lazily.
602 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
604 =item B<is_lazy_build>
606 Returns true if this meta-attribute should be initialized lazily through
607 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
608 make your attribute required and lazy. In addition it will set the builder, clearer
609 and predicate options for you using the following convention.
611 #If your attribute name starts with an underscore:
612 has '_foo' => (lazy_build => 1);
614 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
616 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
618 #If your attribute name does not start with an underscore:
619 has 'foo' => (lazy_build => 1);
621 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
623 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
625 The reason for the different naming of the C<builder> is that the C<builder>
626 method is a private method while the C<clearer> and C<predicate> methods
629 NOTE: This means your class should provide a method whose name matches the value
630 of the builder part, in this case _build__foo or _build_foo.
632 =item B<should_coerce>
634 Returns true if this meta-attribute should perform type coercion.
636 =item B<should_auto_deref>
638 Returns true if this meta-attribute should perform automatic
641 NOTE: This can only be done for attributes whose type constraint is
642 either I<ArrayRef> or I<HashRef>.
646 Returns true if this meta-attribute has a trigger set.
650 This is a CODE reference which will be executed every time the
651 value of an attribute is assigned. The CODE ref will get two values,
652 the invocant and the new value. This can be used to handle I<basic>
653 bi-directional relations.
655 =item B<documentation>
657 This is a string which contains the documentation for this attribute.
658 It serves no direct purpose right now, but it might in the future
659 in some kind of automated documentation system perhaps.
661 =item B<has_documentation>
663 Returns true if this meta-attribute has any documentation.
669 All complex software has bugs lurking in it, and this module is no
670 exception. If you find a bug please either email me, or add the bug
675 Stevan Little E<lt>stevan@iinteractive.comE<gt>
677 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
679 =head1 COPYRIGHT AND LICENSE
681 Copyright 2006-2008 by Infinity Interactive, Inc.
683 L<http://www.iinteractive.com>
685 This library is free software; you can redistribute it and/or modify
686 it under the same terms as Perl itself.