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 $type_constraint->check($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);
288 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
291 $meta_instance->set_slot_value($instance, $attr_name, $value);
293 if (ref $value && $self->is_weak_ref) {
294 $meta_instance->weaken_slot_value($instance, $attr_name);
297 if ($self->has_trigger) {
298 $self->trigger->($instance, $value, $self);
303 my ($self, $instance) = @_;
305 if ($self->is_lazy) {
306 unless ($self->has_value($instance)) {
307 if ($self->has_default) {
308 my $default = $self->default($instance);
309 $self->set_initial_value($instance, $default);
311 if ( $self->has_builder ){
312 if (my $builder = $instance->can($self->builder)){
313 $self->set_initial_value($instance, $instance->$builder);
316 confess(blessed($instance)
317 . " does not support builder method '"
319 . "' for attribute '"
325 $self->set_initial_value($instance, undef);
330 if ($self->should_auto_deref) {
332 my $type_constraint = $self->type_constraint;
334 if ($type_constraint->is_a_type_of('ArrayRef')) {
335 my $rv = $self->SUPER::get_value($instance);
336 return unless defined $rv;
337 return wantarray ? @{ $rv } : $rv;
339 elsif ($type_constraint->is_a_type_of('HashRef')) {
340 my $rv = $self->SUPER::get_value($instance);
341 return unless defined $rv;
342 return wantarray ? %{ $rv } : $rv;
345 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
351 return $self->SUPER::get_value($instance);
355 ## installing accessors
357 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
359 sub install_accessors {
361 $self->SUPER::install_accessors(@_);
363 if ($self->has_handles) {
366 # Here we canonicalize the 'handles' option
367 # this will sort out any details and always
368 # return an hash of methods which we want
369 # to delagate to, see that method for details
370 my %handles = $self->_canonicalize_handles();
372 # find the accessor method for this attribute
373 my $accessor = $self->get_read_method_ref;
374 # then unpack it if we need too ...
375 $accessor = $accessor->body if blessed $accessor;
377 # install the delegation ...
378 my $associated_class = $self->associated_class;
379 foreach my $handle (keys %handles) {
380 my $method_to_call = $handles{$handle};
381 my $class_name = $associated_class->name;
382 my $name = "${class_name}::${handle}";
384 (!$associated_class->has_method($handle))
385 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
388 # handles is not allowed to delegate
389 # any of these methods, as they will
390 # override the ones in your class, which
391 # is almost certainly not what you want.
393 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
394 #cluck("Not delegating method '$handle' because it is a core method") and
395 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
397 if ((reftype($method_to_call) || '') eq 'CODE') {
398 $associated_class->add_method($handle => subname $name, $method_to_call);
401 $associated_class->add_method($handle => subname $name, sub {
402 my $proxy = (shift)->$accessor();
405 || confess "Cannot delegate $handle to $method_to_call because " .
406 "the value of " . $self->name . " is not defined";
407 goto &{ $proxy->can($method_to_call) || return };
416 # private methods to help delegation ...
418 sub _canonicalize_handles {
420 my $handles = $self->handles;
421 if (my $handle_type = ref($handles)) {
422 if ($handle_type eq 'HASH') {
425 elsif ($handle_type eq 'ARRAY') {
426 return map { $_ => $_ } @{$handles};
428 elsif ($handle_type eq 'Regexp') {
429 ($self->has_type_constraint)
430 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
431 return map { ($_ => $_) }
432 grep { /$handles/ } $self->_get_delegate_method_list;
434 elsif ($handle_type eq 'CODE') {
435 return $handles->($self, $self->_find_delegate_metaclass);
438 confess "Unable to canonicalize the 'handles' option with $handles";
442 my $role_meta = eval { $handles->meta };
444 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
447 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
448 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
450 return map { $_ => $_ } (
451 $role_meta->get_method_list,
452 $role_meta->get_required_method_list
457 sub _find_delegate_metaclass {
459 if (my $class = $self->_isa_metadata) {
460 # if the class does have
461 # a meta method, use it
462 return $class->meta if $class->can('meta');
463 # otherwise we might be
464 # dealing with a non-Moose
465 # class, and need to make
467 return Moose::Meta::Class->initialize($class);
469 elsif (my $role = $self->_does_metadata) {
470 # our role will always have
475 confess "Cannot find delegate metaclass for attribute " . $self->name;
479 sub _get_delegate_method_list {
481 my $meta = $self->_find_delegate_metaclass;
482 if ($meta->isa('Class::MOP::Class')) {
483 return map { $_->{name} } # NOTE: !never! delegate &meta
484 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
485 $meta->compute_all_applicable_methods;
487 elsif ($meta->isa('Moose::Meta::Role')) {
488 return $meta->get_method_list;
491 confess "Unable to recognize the delegate metaclass '$meta'";
503 Moose::Meta::Attribute - The Moose attribute metaclass
507 This is a subclass of L<Class::MOP::Attribute> with Moose specific
510 For the most part, the only time you will ever encounter an
511 instance of this class is if you are doing some serious deep
512 introspection. To really understand this class, you need to refer
513 to the L<Class::MOP::Attribute> documentation.
517 =head2 Overridden methods
519 These methods override methods in L<Class::MOP::Attribute> and add
520 Moose specific features. You can safely assume though that they
521 will behave just as L<Class::MOP::Attribute> does.
527 =item B<initialize_instance_slot>
529 =item B<install_accessors>
531 =item B<accessor_metaclass>
537 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
542 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
544 Before setting the value, a check is made on the type constraint of
545 the attribute, if it has one, to see if the value passes it. If the
546 value fails to pass, the set operation dies with a L<Carp/confess>.
548 Any coercion to convert values is done before checking the type constraint.
550 To check a value against a type constraint before setting it, fetch the
551 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
552 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
553 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
558 =head2 Additional Moose features
560 Moose attributes support type-constraint checking, weak reference
561 creation and type coercion.
565 =item B<clone_and_inherit_options>
567 This is to support the C<has '+foo'> feature, it clones an attribute
568 from a superclass and allows a very specific set of changes to be made
571 =item B<has_type_constraint>
573 Returns true if this meta-attribute has a type constraint.
575 =item B<type_constraint>
577 A read-only accessor for this meta-attribute's type constraint. For
578 more information on what you can do with this, see the documentation
579 for L<Moose::Meta::TypeConstraint>.
583 Returns true if this meta-attribute performs delegation.
587 This returns the value which was passed into the handles option.
591 Returns true if this meta-attribute produces a weak reference.
595 Returns true if this meta-attribute is required to have a value.
599 Returns true if this meta-attribute should be initialized lazily.
601 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
603 =item B<is_lazy_build>
605 Returns true if this meta-attribute should be initialized lazily through
606 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
607 make your attribute required and lazy. In addition it will set the builder, clearer
608 and predicate options for you using the following convention.
610 #If your attribute name starts with an underscore:
611 has '_foo' => (lazy_build => 1);
613 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
615 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
617 #If your attribute name does not start with an underscore:
618 has 'foo' => (lazy_build => 1);
620 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
622 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
624 The reason for the different naming of the C<builder> is that the C<builder>
625 method is a private method while the C<clearer> and C<predicate> methods
628 NOTE: This means your class should provide a method whose name matches the value
629 of the builder part, in this case _build__foo or _build_foo.
631 =item B<should_coerce>
633 Returns true if this meta-attribute should perform type coercion.
635 =item B<should_auto_deref>
637 Returns true if this meta-attribute should perform automatic
640 NOTE: This can only be done for attributes whose type constraint is
641 either I<ArrayRef> or I<HashRef>.
645 Returns true if this meta-attribute has a trigger set.
649 This is a CODE reference which will be executed every time the
650 value of an attribute is assigned. The CODE ref will get two values,
651 the invocant and the new value. This can be used to handle I<basic>
652 bi-directional relations.
654 =item B<documentation>
656 This is a string which contains the documentation for this attribute.
657 It serves no direct purpose right now, but it might in the future
658 in some kind of automated documentation system perhaps.
660 =item B<has_documentation>
662 Returns true if this meta-attribute has any documentation.
668 All complex software has bugs lurking in it, and this module is no
669 exception. If you find a bug please either email me, or add the bug
674 Stevan Little E<lt>stevan@iinteractive.comE<gt>
676 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
678 =head1 COPYRIGHT AND LICENSE
680 Copyright 2006-2008 by Infinity Interactive, Inc.
682 L<http://www.iinteractive.com>
684 This library is free software; you can redistribute it and/or modify
685 it under the same terms as Perl itself.