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->{isa};
155 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
156 $options->{does} => {
157 parent => Moose::Util::TypeConstraints::find_type_constraint('Role'),
158 constraint => sub { $_[0]->does($options->{does}) }
164 if (exists $options->{coerce} && $options->{coerce}) {
165 (exists $options->{type_constraint})
166 || confess "You cannot have coercion without specifying a type constraint";
167 confess "You cannot have a weak reference to a coerced value"
168 if $options->{weak_ref};
171 if (exists $options->{auto_deref} && $options->{auto_deref}) {
172 (exists $options->{type_constraint})
173 || confess "You cannot auto-dereference without specifying a type constraint";
174 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
175 $options->{type_constraint}->is_a_type_of('HashRef'))
176 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef";
179 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
180 confess("You can not use lazy_build and default for the same attribute")
181 if exists $options->{default};
182 $options->{lazy} = 1;
183 $options->{required} = 1;
184 $options->{builder} ||= "_build_${name}";
186 $options->{clearer} ||= "_clear${name}";
187 $options->{predicate} ||= "_has${name}";
190 $options->{clearer} ||= "clear_${name}";
191 $options->{predicate} ||= "has_${name}";
195 if (exists $options->{lazy} && $options->{lazy}) {
196 (exists $options->{default} || exists $options->{builder} )
197 || confess "You cannot have lazy attribute without specifying a default value for it";
202 sub initialize_instance_slot {
203 my ($self, $meta_instance, $instance, $params) = @_;
204 my $init_arg = $self->init_arg();
205 # try to fetch the init arg from the %params ...
209 if (exists $params->{$init_arg}) {
210 $val = $params->{$init_arg};
214 # skip it if it's lazy
215 return if $self->is_lazy;
216 # and die if it's required and doesn't have a default value
217 confess "Attribute (" . $self->name . ") is required"
218 if $self->is_required && !$self->has_default && !$self->has_builder;
220 # if nothing was in the %params, we can use the
221 # attribute's default value (if it has one)
222 if ($self->has_default) {
223 $val = $self->default($instance);
226 elsif ($self->has_builder) {
227 if (my $builder = $instance->can($self->builder)){
228 $val = $instance->$builder;
232 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
237 return unless $value_is_set;
239 if ($self->has_type_constraint) {
240 my $type_constraint = $self->type_constraint;
241 if ($self->should_coerce && $type_constraint->has_coercion) {
242 $val = $type_constraint->coerce($val);
244 (defined($type_constraint->check($val)))
245 || confess "Attribute (" .
247 ") does not pass the type constraint (" .
248 $type_constraint->name .
251 ? overload::StrVal($val)
256 $meta_instance->set_slot_value($instance, $self->name, $val);
257 $meta_instance->weaken_slot_value($instance, $self->name)
258 if ref $val && $self->is_weak_ref;
264 my ($self, $instance, $value) = @_;
266 my $attr_name = $self->name;
268 if ($self->is_required) {
270 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
273 if ($self->has_type_constraint) {
275 my $type_constraint = $self->type_constraint;
277 if ($self->should_coerce) {
278 $value = $type_constraint->coerce($value);
280 $type_constraint->_compiled_type_constraint->($value)
281 || confess "Attribute ($attr_name) does not pass the type constraint ("
282 . $type_constraint->name
285 ? ("'" . overload::StrVal($value) . "'")
290 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
293 $meta_instance->set_slot_value($instance, $attr_name, $value);
295 if (ref $value && $self->is_weak_ref) {
296 $meta_instance->weaken_slot_value($instance, $attr_name);
299 if ($self->has_trigger) {
300 $self->trigger->($instance, $value, $self);
305 my ($self, $instance) = @_;
307 if ($self->is_lazy) {
308 unless ($self->has_value($instance)) {
309 if ($self->has_default) {
310 my $default = $self->default($instance);
311 $self->set_value($instance, $default);
313 if ( $self->has_builder ){
314 if (my $builder = $instance->can($self->builder)){
315 $self->set_value($instance, $instance->$builder);
318 confess(blessed($instance)
319 . " does not support builder method '"
321 . "' for attribute '"
327 $self->set_value($instance, undef);
332 if ($self->should_auto_deref) {
334 my $type_constraint = $self->type_constraint;
336 if ($type_constraint->is_a_type_of('ArrayRef')) {
337 my $rv = $self->SUPER::get_value($instance);
338 return unless defined $rv;
339 return wantarray ? @{ $rv } : $rv;
341 elsif ($type_constraint->is_a_type_of('HashRef')) {
342 my $rv = $self->SUPER::get_value($instance);
343 return unless defined $rv;
344 return wantarray ? %{ $rv } : $rv;
347 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
353 return $self->SUPER::get_value($instance);
357 ## installing accessors
359 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
361 sub install_accessors {
363 $self->SUPER::install_accessors(@_);
365 if ($self->has_handles) {
368 # Here we canonicalize the 'handles' option
369 # this will sort out any details and always
370 # return an hash of methods which we want
371 # to delagate to, see that method for details
372 my %handles = $self->_canonicalize_handles();
374 # find the accessor method for this attribute
375 my $accessor = $self->get_read_method_ref;
376 # then unpack it if we need too ...
377 $accessor = $accessor->body if blessed $accessor;
379 # install the delegation ...
380 my $associated_class = $self->associated_class;
381 foreach my $handle (keys %handles) {
382 my $method_to_call = $handles{$handle};
383 my $class_name = $associated_class->name;
384 my $name = "${class_name}::${handle}";
386 (!$associated_class->has_method($handle))
387 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
390 # handles is not allowed to delegate
391 # any of these methods, as they will
392 # override the ones in your class, which
393 # is almost certainly not what you want.
395 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
396 #cluck("Not delegating method '$handle' because it is a core method") and
397 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
399 if ((reftype($method_to_call) || '') eq 'CODE') {
400 $associated_class->add_method($handle => subname $name, $method_to_call);
403 $associated_class->add_method($handle => subname $name, sub {
404 my $proxy = (shift)->$accessor();
407 || confess "Cannot delegate $handle to $method_to_call because " .
408 "the value of " . $self->name . " is not defined";
409 goto &{ $proxy->can($method_to_call) || return };
418 # private methods to help delegation ...
420 sub _canonicalize_handles {
422 my $handles = $self->handles;
423 if (my $handle_type = ref($handles)) {
424 if ($handle_type eq 'HASH') {
427 elsif ($handle_type eq 'ARRAY') {
428 return map { $_ => $_ } @{$handles};
430 elsif ($handle_type eq 'Regexp') {
431 ($self->has_type_constraint)
432 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
433 return map { ($_ => $_) }
434 grep { /$handles/ } $self->_get_delegate_method_list;
436 elsif ($handle_type eq 'CODE') {
437 return $handles->($self, $self->_find_delegate_metaclass);
440 confess "Unable to canonicalize the 'handles' option with $handles";
444 my $role_meta = eval { $handles->meta };
446 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
449 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
450 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
452 return map { $_ => $_ } (
453 $role_meta->get_method_list,
454 $role_meta->get_required_method_list
459 sub _find_delegate_metaclass {
461 if (my $class = $self->_isa_metadata) {
462 # if the class does have
463 # a meta method, use it
464 return $class->meta if $class->can('meta');
465 # otherwise we might be
466 # dealing with a non-Moose
467 # class, and need to make
469 return Moose::Meta::Class->initialize($class);
471 elsif (my $role = $self->_does_metadata) {
472 # our role will always have
477 confess "Cannot find delegate metaclass for attribute " . $self->name;
481 sub _get_delegate_method_list {
483 my $meta = $self->_find_delegate_metaclass;
484 if ($meta->isa('Class::MOP::Class')) {
485 return map { $_->{name} } # NOTE: !never! delegate &meta
486 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
487 $meta->compute_all_applicable_methods;
489 elsif ($meta->isa('Moose::Meta::Role')) {
490 return $meta->get_method_list;
493 confess "Unable to recognize the delegate metaclass '$meta'";
505 Moose::Meta::Attribute - The Moose attribute metaclass
509 This is a subclass of L<Class::MOP::Attribute> with Moose specific
512 For the most part, the only time you will ever encounter an
513 instance of this class is if you are doing some serious deep
514 introspection. To really understand this class, you need to refer
515 to the L<Class::MOP::Attribute> documentation.
519 =head2 Overridden methods
521 These methods override methods in L<Class::MOP::Attribute> and add
522 Moose specific features. You can safely assume though that they
523 will behave just as L<Class::MOP::Attribute> does.
529 =item B<initialize_instance_slot>
531 =item B<install_accessors>
533 =item B<accessor_metaclass>
539 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
544 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
546 Before setting the value, a check is made on the type constraint of
547 the attribute, if it has one, to see if the value passes it. If the
548 value fails to pass, the set operation dies with a L<Carp/confess>.
550 Any coercion to convert values is done before checking the type constraint.
552 To check a value against a type constraint before setting it, fetch the
553 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
554 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
555 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
560 =head2 Additional Moose features
562 Moose attributes support type-constraint checking, weak reference
563 creation and type coercion.
567 =item B<clone_and_inherit_options>
569 This is to support the C<has '+foo'> feature, it clones an attribute
570 from a superclass and allows a very specific set of changes to be made
573 =item B<has_type_constraint>
575 Returns true if this meta-attribute has a type constraint.
577 =item B<type_constraint>
579 A read-only accessor for this meta-attribute's type constraint. For
580 more information on what you can do with this, see the documentation
581 for L<Moose::Meta::TypeConstraint>.
585 Returns true if this meta-attribute performs delegation.
589 This returns the value which was passed into the handles option.
593 Returns true if this meta-attribute produces a weak reference.
597 Returns true if this meta-attribute is required to have a value.
601 Returns true if this meta-attribute should be initialized lazily.
603 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
605 =item B<is_lazy_build>
607 Returns true if this meta-attribute should be initialized lazily through
608 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
609 make your attribute required and lazy. In addition it will set the builder, clearer
610 and predicate options for you using the following convention.
612 #If your attribute name starts with an underscore:
613 has '_foo' => (lazy_build => 1);
615 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
617 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
619 #If your attribute name does not start with an underscore:
620 has 'foo' => (lazy_build => 1);
622 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
624 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
626 The reason for the different naming of the C<builder> is that the C<builder>
627 method is a private method while the C<clearer> and C<predicate> methods
630 NOTE: This means your class should provide a method whose name matches the value
631 of the builder part, in this case _build__foo or _build_foo.
633 =item B<should_coerce>
635 Returns true if this meta-attribute should perform type coercion.
637 =item B<should_auto_deref>
639 Returns true if this meta-attribute should perform automatic
642 NOTE: This can only be done for attributes whose type constraint is
643 either I<ArrayRef> or I<HashRef>.
647 Returns true if this meta-attribute has a trigger set.
651 This is a CODE reference which will be executed every time the
652 value of an attribute is assigned. The CODE ref will get two values,
653 the invocant and the new value. This can be used to handle I<basic>
654 bi-directional relations.
656 =item B<documentation>
658 This is a string which contains the documentation for this attribute.
659 It serves no direct purpose right now, but it might in the future
660 in some kind of automated documentation system perhaps.
662 =item B<has_documentation>
664 Returns true if this meta-attribute has any documentation.
670 All complex software has bugs lurking in it, and this module is no
671 exception. If you find a bug please either email me, or add the bug
676 Stevan Little E<lt>stevan@iinteractive.comE<gt>
678 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
680 =head1 COPYRIGHT AND LICENSE
682 Copyright 2006-2008 by Infinity Interactive, Inc.
684 L<http://www.iinteractive.com>
686 This library is free software; you can redistribute it and/or modify
687 it under the same terms as Perl itself.