2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
11 our $VERSION = '0.15';
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_or_create_type_constraint(
85 (defined $type_constraint)
86 || confess "Could not find the type constraint '" . $options{isa} . "'";
89 # check here to see if the new type
90 # is a subtype of the old one
91 ($type_constraint->is_subtype_of($self->type_constraint->name))
92 || confess "New type constraint setting must be a subtype of inherited one"
93 # iff we have a type constraint that is ...
94 if $self->has_type_constraint;
96 $actual_options{type_constraint} = $type_constraint;
99 (scalar keys %options == 0)
100 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
101 $self->clone(%actual_options);
104 sub _process_options {
105 my ($class, $name, $options) = @_;
107 if (exists $options->{is}) {
108 if ($options->{is} eq 'ro') {
109 $options->{reader} ||= $name;
110 (!exists $options->{trigger})
111 || confess "Cannot have a trigger on a read-only attribute";
113 elsif ($options->{is} eq 'rw') {
114 $options->{accessor} = $name;
115 ((reftype($options->{trigger}) || '') eq 'CODE')
116 || confess "Trigger must be a CODE ref"
117 if exists $options->{trigger};
120 confess "I do not understand this option (is => " . $options->{is} . ")"
124 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}";
189 $options->{clearer} ||= "clear_${name}";
190 $options->{predicate} ||= "has_${name}";
194 if (exists $options->{lazy} && $options->{lazy}) {
195 (exists $options->{default} || exists $options->{builder} )
196 || confess "You cannot have lazy attribute without specifying a default value for it";
201 sub initialize_instance_slot {
202 my ($self, $meta_instance, $instance, $params) = @_;
203 my $init_arg = $self->init_arg();
204 # try to fetch the init arg from the %params ...
208 if (exists $params->{$init_arg}) {
209 $val = $params->{$init_arg};
213 # skip it if it's lazy
214 return if $self->is_lazy;
215 # and die if it's required and doesn't have a default value
216 confess "Attribute (" . $self->name . ") is required"
217 if $self->is_required && !$self->has_default && !$self->has_builder;
219 # if nothing was in the %params, we can use the
220 # attribute's default value (if it has one)
221 if ($self->has_default) {
222 $val = $self->default($instance);
224 } elsif ($self->has_builder) {
225 if(my $builder = $instance->can($self->builder)){
226 $val = $instance->$builder;
229 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
234 return unless $value_is_set;
236 if ($self->has_type_constraint) {
237 my $type_constraint = $self->type_constraint;
238 if ($self->should_coerce && $type_constraint->has_coercion) {
239 $val = $type_constraint->coerce($val);
241 (defined($type_constraint->check($val)))
242 || confess "Attribute (" .
244 ") does not pass the type constraint (" .
245 $type_constraint->name .
248 ? (blessed($val) && overload::Overloaded($val)
249 ? overload::StrVal($val)
255 $meta_instance->set_slot_value($instance, $self->name, $val);
256 $meta_instance->weaken_slot_value($instance, $self->name)
257 if ref $val && $self->is_weak_ref;
263 my ($self, $instance, $value) = @_;
265 my $attr_name = $self->name;
267 if ($self->is_required) {
269 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
272 if ($self->has_type_constraint) {
274 my $type_constraint = $self->type_constraint;
276 if ($self->should_coerce) {
277 $value = $type_constraint->coerce($value);
279 defined($type_constraint->_compiled_type_constraint->($value))
280 || confess "Attribute ($attr_name) does not pass the type constraint ("
281 . $type_constraint->name
285 (blessed($value) && overload::Overloaded($value)
286 ? overload::StrVal($value)
293 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
296 $meta_instance->set_slot_value($instance, $attr_name, $value);
298 if (ref $value && $self->is_weak_ref) {
299 $meta_instance->weaken_slot_value($instance, $attr_name);
302 if ($self->has_trigger) {
303 $self->trigger->($instance, $value, $self);
308 my ($self, $instance) = @_;
310 if ($self->is_lazy) {
311 unless ($self->has_value($instance)) {
312 if ($self->has_default) {
313 my $default = $self->default($instance);
314 $self->set_value($instance, $default);
316 if ( $self->has_builder ){
317 if(my $builder = $instance->can($self->builder)){
318 $self->set_value($instance, $instance->$builder);
320 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
323 $self->set_value($instance, undef);
328 if ($self->should_auto_deref) {
330 my $type_constraint = $self->type_constraint;
332 if ($type_constraint->is_a_type_of('ArrayRef')) {
333 my $rv = $self->SUPER::get_value($instance);
334 return unless defined $rv;
335 return wantarray ? @{ $rv } : $rv;
337 elsif ($type_constraint->is_a_type_of('HashRef')) {
338 my $rv = $self->SUPER::get_value($instance);
339 return unless defined $rv;
340 return wantarray ? %{ $rv } : $rv;
343 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
349 return $self->SUPER::get_value($instance);
353 ## installing accessors
355 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
357 sub install_accessors {
359 $self->SUPER::install_accessors(@_);
361 if ($self->has_handles) {
364 # Here we canonicalize the 'handles' option
365 # this will sort out any details and always
366 # return an hash of methods which we want
367 # to delagate to, see that method for details
368 my %handles = $self->_canonicalize_handles();
370 # find the accessor method for this attribute
371 my $accessor = $self->get_read_method_ref;
372 # then unpack it if we need too ...
373 $accessor = $accessor->body if blessed $accessor;
375 # install the delegation ...
376 my $associated_class = $self->associated_class;
377 foreach my $handle (keys %handles) {
378 my $method_to_call = $handles{$handle};
380 (!$associated_class->has_method($handle))
381 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
384 # handles is not allowed to delegate
385 # any of these methods, as they will
386 # override the ones in your class, which
387 # is almost certainly not what you want.
388 next if $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
390 if ((reftype($method_to_call) || '') eq 'CODE') {
391 $associated_class->add_method($handle => $method_to_call);
394 $associated_class->add_method($handle => sub {
396 # we should check for lack of
397 # a callable return value from
399 my $proxy = (shift)->$accessor();
401 goto &{ $proxy->can($method_to_call) };
410 # private methods to help delegation ...
412 sub _canonicalize_handles {
414 my $handles = $self->handles;
415 if (my $handle_type = ref($handles)) {
416 if ($handle_type eq 'HASH') {
419 elsif ($handle_type eq 'ARRAY') {
420 return map { $_ => $_ } @{$handles};
422 elsif ($handle_type eq 'Regexp') {
423 ($self->has_type_constraint)
424 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
425 return map { ($_ => $_) }
426 grep { /$handles/ } $self->_get_delegate_method_list;
428 elsif ($handle_type eq 'CODE') {
429 return $handles->($self, $self->_find_delegate_metaclass);
432 confess "Unable to canonicalize the 'handles' option with $handles";
436 my $role_meta = eval { $handles->meta };
438 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
441 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
442 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
444 return map { $_ => $_ } (
445 $role_meta->get_method_list,
446 $role_meta->get_required_method_list
451 sub _find_delegate_metaclass {
453 if (my $class = $self->_isa_metadata) {
454 # if the class does have
455 # a meta method, use it
456 return $class->meta if $class->can('meta');
457 # otherwise we might be
458 # dealing with a non-Moose
459 # class, and need to make
461 return Moose::Meta::Class->initialize($class);
463 elsif (my $role = $self->_does_metadata) {
464 # our role will always have
469 confess "Cannot find delegate metaclass for attribute " . $self->name;
473 sub _get_delegate_method_list {
475 my $meta = $self->_find_delegate_metaclass;
476 if ($meta->isa('Class::MOP::Class')) {
477 return map { $_->{name} } # NOTE: !never! delegate &meta
478 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
479 $meta->compute_all_applicable_methods;
481 elsif ($meta->isa('Moose::Meta::Role')) {
482 return $meta->get_method_list;
485 confess "Unable to recognize the delegate metaclass '$meta'";
497 Moose::Meta::Attribute - The Moose attribute metaclass
501 This is a subclass of L<Class::MOP::Attribute> with Moose specific
504 For the most part, the only time you will ever encounter an
505 instance of this class is if you are doing some serious deep
506 introspection. To really understand this class, you need to refer
507 to the L<Class::MOP::Attribute> documentation.
511 =head2 Overridden methods
513 These methods override methods in L<Class::MOP::Attribute> and add
514 Moose specific features. You can safely assume though that they
515 will behave just as L<Class::MOP::Attribute> does.
521 =item B<initialize_instance_slot>
523 =item B<install_accessors>
525 =item B<accessor_metaclass>
531 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
536 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
538 Before setting the value, a check is made on the type constraint of
539 the attribute, if it has one, to see if the value passes it. If the
540 value fails to pass, the set operation dies with a L<Carp/confess>.
542 Any coercion to convert values is done before checking the type constraint.
544 To check a value against a type constraint before setting it, fetch the
545 attribute instance using L<Moose::Meta::Attribute/find_attribute_by_name>,
546 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
547 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
552 =head2 Additional Moose features
554 Moose attributes support type-constraint checking, weak reference
555 creation and type coercion.
559 =item B<clone_and_inherit_options>
561 This is to support the C<has '+foo'> feature, it clones an attribute
562 from a superclass and allows a very specific set of changes to be made
565 =item B<has_type_constraint>
567 Returns true if this meta-attribute has a type constraint.
569 =item B<type_constraint>
571 A read-only accessor for this meta-attribute's type constraint. For
572 more information on what you can do with this, see the documentation
573 for L<Moose::Meta::TypeConstraint>.
577 Returns true if this meta-attribute performs delegation.
581 This returns the value which was passed into the handles option.
585 Returns true if this meta-attribute produces a weak reference.
589 Returns true if this meta-attribute is required to have a value.
593 Returns true if this meta-attribute should be initialized lazily.
595 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
597 =item B<is_lazy_build>
599 Returns true if this meta-attribute should be initialized lazily through
600 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
601 make your attribute required and lazy. In addition it will set the builder, clearer
602 and predicate options for you using the following convention.
604 #If your attribute name starts with an underscore:
605 has '_foo' => (lazy_build => 1);
607 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
609 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
611 #If your attribute name does not start 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 The reason for the different naming of the C<builder> is that the C<builder>
619 method is a private method while the C<clearer> and C<predicate> methods
622 NOTE: This means your class should provide a method whose name matches the value
623 of the builder part, in this case _build__foo or _build_foo.
625 =item B<should_coerce>
627 Returns true if this meta-attribute should perform type coercion.
629 =item B<should_auto_deref>
631 Returns true if this meta-attribute should perform automatic
634 NOTE: This can only be done for attributes whose type constraint is
635 either I<ArrayRef> or I<HashRef>.
639 Returns true if this meta-attribute has a trigger set.
643 This is a CODE reference which will be executed every time the
644 value of an attribute is assigned. The CODE ref will get two values,
645 the invocant and the new value. This can be used to handle I<basic>
646 bi-directional relations.
648 =item B<documentation>
650 This is a string which contains the documentation for this attribute.
651 It serves no direct purpose right now, but it might in the future
652 in some kind of automated documentation system perhaps.
654 =item B<has_documentation>
656 Returns true if this meta-attribute has any documentation.
662 All complex software has bugs lurking in it, and this module is no
663 exception. If you find a bug please either email me, or add the bug
668 Stevan Little E<lt>stevan@iinteractive.comE<gt>
670 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
672 =head1 COPYRIGHT AND LICENSE
674 Copyright 2006, 2007 by Infinity Interactive, Inc.
676 L<http://www.iinteractive.com>
678 This library is free software; you can redistribute it and/or modify
679 it under the same terms as Perl itself.