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 (" .
254 $type_constraint->name .
257 ? overload::StrVal($val)
262 $meta_instance->set_slot_value($instance, $self->name, $val);
263 $meta_instance->weaken_slot_value($instance, $self->name)
264 if ref $val && $self->is_weak_ref;
270 my ($self, $instance, $value) = @_;
272 my $attr_name = $self->name;
274 if ($self->is_required) {
276 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
279 if ($self->has_type_constraint) {
281 my $type_constraint = $self->type_constraint;
283 if ($self->should_coerce) {
284 $value = $type_constraint->coerce($value);
286 $type_constraint->_compiled_type_constraint->($value)
287 || confess "Attribute ($attr_name) does not pass the type constraint ("
288 . $type_constraint->name
291 ? ("'" . overload::StrVal($value) . "'")
296 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
299 $meta_instance->set_slot_value($instance, $attr_name, $value);
301 if (ref $value && $self->is_weak_ref) {
302 $meta_instance->weaken_slot_value($instance, $attr_name);
305 if ($self->has_trigger) {
306 $self->trigger->($instance, $value, $self);
311 my ($self, $instance) = @_;
313 if ($self->is_lazy) {
314 unless ($self->has_value($instance)) {
315 if ($self->has_default) {
316 my $default = $self->default($instance);
317 $self->set_value($instance, $default);
319 if ( $self->has_builder ){
320 if (my $builder = $instance->can($self->builder)){
321 $self->set_value($instance, $instance->$builder);
324 confess(blessed($instance)
325 . " does not support builder method '"
327 . "' for attribute '"
333 $self->set_value($instance, undef);
338 if ($self->should_auto_deref) {
340 my $type_constraint = $self->type_constraint;
342 if ($type_constraint->is_a_type_of('ArrayRef')) {
343 my $rv = $self->SUPER::get_value($instance);
344 return unless defined $rv;
345 return wantarray ? @{ $rv } : $rv;
347 elsif ($type_constraint->is_a_type_of('HashRef')) {
348 my $rv = $self->SUPER::get_value($instance);
349 return unless defined $rv;
350 return wantarray ? %{ $rv } : $rv;
353 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
359 return $self->SUPER::get_value($instance);
363 ## installing accessors
365 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
367 sub install_accessors {
369 $self->SUPER::install_accessors(@_);
371 if ($self->has_handles) {
374 # Here we canonicalize the 'handles' option
375 # this will sort out any details and always
376 # return an hash of methods which we want
377 # to delagate to, see that method for details
378 my %handles = $self->_canonicalize_handles();
380 # find the accessor method for this attribute
381 my $accessor = $self->get_read_method_ref;
382 # then unpack it if we need too ...
383 $accessor = $accessor->body if blessed $accessor;
385 # install the delegation ...
386 my $associated_class = $self->associated_class;
387 foreach my $handle (keys %handles) {
388 my $method_to_call = $handles{$handle};
389 my $class_name = $associated_class->name;
390 my $name = "${class_name}::${handle}";
392 (!$associated_class->has_method($handle))
393 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
396 # handles is not allowed to delegate
397 # any of these methods, as they will
398 # override the ones in your class, which
399 # is almost certainly not what you want.
401 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
402 #cluck("Not delegating method '$handle' because it is a core method") and
403 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
405 if ((reftype($method_to_call) || '') eq 'CODE') {
406 $associated_class->add_method($handle => subname $name, $method_to_call);
409 $associated_class->add_method($handle => subname $name, sub {
410 my $proxy = (shift)->$accessor();
413 || confess "Cannot delegate $handle to $method_to_call because " .
414 "the value of " . $self->name . " is not defined";
415 goto &{ $proxy->can($method_to_call) || return };
424 # private methods to help delegation ...
426 sub _canonicalize_handles {
428 my $handles = $self->handles;
429 if (my $handle_type = ref($handles)) {
430 if ($handle_type eq 'HASH') {
433 elsif ($handle_type eq 'ARRAY') {
434 return map { $_ => $_ } @{$handles};
436 elsif ($handle_type eq 'Regexp') {
437 ($self->has_type_constraint)
438 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
439 return map { ($_ => $_) }
440 grep { /$handles/ } $self->_get_delegate_method_list;
442 elsif ($handle_type eq 'CODE') {
443 return $handles->($self, $self->_find_delegate_metaclass);
446 confess "Unable to canonicalize the 'handles' option with $handles";
450 my $role_meta = eval { $handles->meta };
452 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
455 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
456 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
458 return map { $_ => $_ } (
459 $role_meta->get_method_list,
460 $role_meta->get_required_method_list
465 sub _find_delegate_metaclass {
467 if (my $class = $self->_isa_metadata) {
468 # if the class does have
469 # a meta method, use it
470 return $class->meta if $class->can('meta');
471 # otherwise we might be
472 # dealing with a non-Moose
473 # class, and need to make
475 return Moose::Meta::Class->initialize($class);
477 elsif (my $role = $self->_does_metadata) {
478 # our role will always have
483 confess "Cannot find delegate metaclass for attribute " . $self->name;
487 sub _get_delegate_method_list {
489 my $meta = $self->_find_delegate_metaclass;
490 if ($meta->isa('Class::MOP::Class')) {
491 return map { $_->{name} } # NOTE: !never! delegate &meta
492 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
493 $meta->compute_all_applicable_methods;
495 elsif ($meta->isa('Moose::Meta::Role')) {
496 return $meta->get_method_list;
499 confess "Unable to recognize the delegate metaclass '$meta'";
511 Moose::Meta::Attribute - The Moose attribute metaclass
515 This is a subclass of L<Class::MOP::Attribute> with Moose specific
518 For the most part, the only time you will ever encounter an
519 instance of this class is if you are doing some serious deep
520 introspection. To really understand this class, you need to refer
521 to the L<Class::MOP::Attribute> documentation.
525 =head2 Overridden methods
527 These methods override methods in L<Class::MOP::Attribute> and add
528 Moose specific features. You can safely assume though that they
529 will behave just as L<Class::MOP::Attribute> does.
535 =item B<initialize_instance_slot>
537 =item B<install_accessors>
539 =item B<accessor_metaclass>
545 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
550 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
552 Before setting the value, a check is made on the type constraint of
553 the attribute, if it has one, to see if the value passes it. If the
554 value fails to pass, the set operation dies with a L<Carp/confess>.
556 Any coercion to convert values is done before checking the type constraint.
558 To check a value against a type constraint before setting it, fetch the
559 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
560 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
561 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
566 =head2 Additional Moose features
568 Moose attributes support type-constraint checking, weak reference
569 creation and type coercion.
573 =item B<clone_and_inherit_options>
575 This is to support the C<has '+foo'> feature, it clones an attribute
576 from a superclass and allows a very specific set of changes to be made
579 =item B<has_type_constraint>
581 Returns true if this meta-attribute has a type constraint.
583 =item B<type_constraint>
585 A read-only accessor for this meta-attribute's type constraint. For
586 more information on what you can do with this, see the documentation
587 for L<Moose::Meta::TypeConstraint>.
591 Returns true if this meta-attribute performs delegation.
595 This returns the value which was passed into the handles option.
599 Returns true if this meta-attribute produces a weak reference.
603 Returns true if this meta-attribute is required to have a value.
607 Returns true if this meta-attribute should be initialized lazily.
609 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
611 =item B<is_lazy_build>
613 Returns true if this meta-attribute should be initialized lazily through
614 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
615 make your attribute required and lazy. In addition it will set the builder, clearer
616 and predicate options for you using the following convention.
618 #If your attribute name starts 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 #If your attribute name does not start with an underscore:
626 has 'foo' => (lazy_build => 1);
628 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
630 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
632 The reason for the different naming of the C<builder> is that the C<builder>
633 method is a private method while the C<clearer> and C<predicate> methods
636 NOTE: This means your class should provide a method whose name matches the value
637 of the builder part, in this case _build__foo or _build_foo.
639 =item B<should_coerce>
641 Returns true if this meta-attribute should perform type coercion.
643 =item B<should_auto_deref>
645 Returns true if this meta-attribute should perform automatic
648 NOTE: This can only be done for attributes whose type constraint is
649 either I<ArrayRef> or I<HashRef>.
653 Returns true if this meta-attribute has a trigger set.
657 This is a CODE reference which will be executed every time the
658 value of an attribute is assigned. The CODE ref will get two values,
659 the invocant and the new value. This can be used to handle I<basic>
660 bi-directional relations.
662 =item B<documentation>
664 This is a string which contains the documentation for this attribute.
665 It serves no direct purpose right now, but it might in the future
666 in some kind of automated documentation system perhaps.
668 =item B<has_documentation>
670 Returns true if this meta-attribute has any documentation.
676 All complex software has bugs lurking in it, and this module is no
677 exception. If you find a bug please either email me, or add the bug
682 Stevan Little E<lt>stevan@iinteractive.comE<gt>
684 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
686 =head1 COPYRIGHT AND LICENSE
688 Copyright 2006-2008 by Infinity Interactive, Inc.
690 L<http://www.iinteractive.com>
692 This library is free software; you can redistribute it and/or modify
693 it under the same terms as Perl itself.