2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
11 our $VERSION = '0.12';
12 our $AUTHORITY = 'cpan:STEVAN';
14 use Moose::Meta::Method::Accessor;
15 use Moose::Util::TypeConstraints ();
17 use base 'Class::MOP::Attribute';
19 # options which are not directly used
20 # but we store them for metadata purposes
21 __PACKAGE__->meta->add_attribute('isa' => (reader => '_isa_metadata'));
22 __PACKAGE__->meta->add_attribute('does' => (reader => '_does_metadata'));
23 __PACKAGE__->meta->add_attribute('is' => (reader => '_is_metadata'));
25 # these are actual options for the attrs
26 __PACKAGE__->meta->add_attribute('required' => (reader => 'is_required' ));
27 __PACKAGE__->meta->add_attribute('lazy' => (reader => 'is_lazy' ));
28 __PACKAGE__->meta->add_attribute('coerce' => (reader => 'should_coerce' ));
29 __PACKAGE__->meta->add_attribute('weak_ref' => (reader => 'is_weak_ref' ));
30 __PACKAGE__->meta->add_attribute('auto_deref' => (reader => 'should_auto_deref'));
31 __PACKAGE__->meta->add_attribute('type_constraint' => (
32 reader => 'type_constraint',
33 predicate => 'has_type_constraint',
35 __PACKAGE__->meta->add_attribute('trigger' => (
37 predicate => 'has_trigger',
39 __PACKAGE__->meta->add_attribute('handles' => (
41 predicate => 'has_handles',
43 __PACKAGE__->meta->add_attribute('documentation' => (
44 reader => 'documentation',
45 predicate => 'has_documentation',
49 my ($class, $name, %options) = @_;
50 $class->_process_options($name, \%options);
51 return $class->SUPER::new($name, %options);
54 sub clone_and_inherit_options {
55 my ($self, %options) = @_;
56 # you can change default, required, coerce, documentation and lazy
58 foreach my $legal_option (qw(default coerce required documentation lazy)) {
59 if (exists $options{$legal_option}) {
60 $actual_options{$legal_option} = $options{$legal_option};
61 delete $options{$legal_option};
65 # handles can only be added, not changed
66 if ($options{handles}) {
67 confess "You can only add the 'handles' option, you cannot change it"
68 if $self->has_handles;
69 $actual_options{handles} = $options{handles};
70 delete $options{handles};
73 # isa can be changed, but only if the
74 # new type is a subtype
77 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
78 $type_constraint = $options{isa};
81 $type_constraint = Moose::Util::TypeConstraints::find_type_constraint($options{isa});
82 (defined $type_constraint)
83 || confess "Could not find the type constraint '" . $options{isa} . "'";
86 # check here to see if the new type
87 # is a subtype of the old one
88 ($type_constraint->is_subtype_of($self->type_constraint->name))
89 || confess "New type constraint setting must be a subtype of inherited one"
90 # iff we have a type constraint that is ...
91 if $self->has_type_constraint;
93 $actual_options{type_constraint} = $type_constraint;
96 (scalar keys %options == 0)
97 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
98 $self->clone(%actual_options);
101 sub _process_options {
102 my ($class, $name, $options) = @_;
104 if (exists $options->{is}) {
105 if ($options->{is} eq 'ro') {
106 $options->{reader} ||= $name;
107 (!exists $options->{trigger})
108 || confess "Cannot have a trigger on a read-only attribute";
110 elsif ($options->{is} eq 'rw') {
111 $options->{accessor} = $name;
112 ((reftype($options->{trigger}) || '') eq 'CODE')
113 || confess "Trigger must be a CODE ref"
114 if exists $options->{trigger};
117 confess "I do not understand this option (is => " . $options->{is} . ")"
121 if (exists $options->{isa}) {
123 if (exists $options->{does}) {
124 if (eval { $options->{isa}->can('does') }) {
125 ($options->{isa}->does($options->{does}))
126 || confess "Cannot have an isa option and a does option if the isa does not do the does";
129 confess "Cannot have an isa option which cannot ->does()";
133 # allow for anon-subtypes here ...
134 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
135 $options->{type_constraint} = $options->{isa};
138 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
141 parent => Moose::Util::TypeConstraints::find_type_constraint('Object'),
142 constraint => sub { $_[0]->isa($options->{isa}) }
147 elsif (exists $options->{does}) {
148 # allow for anon-subtypes here ...
149 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
150 $options->{type_constraint} = $options->{isa};
153 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
156 parent => Moose::Util::TypeConstraints::find_type_constraint('Role'),
157 constraint => sub { $_[0]->does($options->{does}) }
163 if (exists $options->{coerce} && $options->{coerce}) {
164 (exists $options->{type_constraint})
165 || confess "You cannot have coercion without specifying a type constraint";
166 confess "You cannot have a weak reference to a coerced value"
167 if $options->{weak_ref};
170 if (exists $options->{auto_deref} && $options->{auto_deref}) {
171 (exists $options->{type_constraint})
172 || confess "You cannot auto-dereference without specifying a type constraint";
173 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
174 $options->{type_constraint}->is_a_type_of('HashRef'))
175 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef";
178 if (exists $options->{lazy} && $options->{lazy}) {
179 (exists $options->{default})
180 || confess "You cannot have lazy attribute without specifying a default value for it";
184 sub initialize_instance_slot {
185 my ($self, $meta_instance, $instance, $params) = @_;
186 my $init_arg = $self->init_arg();
187 # try to fetch the init arg from the %params ...
190 if (exists $params->{$init_arg}) {
191 $val = $params->{$init_arg};
193 if (!defined $val && $self->is_required) {
194 confess "Attribute (" . $self->name . ") is required and cannot be undef";
198 # skip it if it's lazy
199 return if $self->is_lazy;
200 # and die if it's required and doesn't have a default value
201 confess "Attribute (" . $self->name . ") is required"
202 if $self->is_required && !$self->has_default;
205 # if nothing was in the %params, we can use the
206 # attribute's default value (if it has one)
207 if (!defined $val && $self->has_default) {
208 $val = $self->default($instance);
211 if (defined $val || $self->has_default) {
212 if ($self->has_type_constraint) {
213 my $type_constraint = $self->type_constraint;
214 if ($self->should_coerce && $type_constraint->has_coercion) {
215 $val = $type_constraint->coerce($val);
217 (defined($type_constraint->check($val)))
218 || confess "Attribute (" .
220 ") does not pass the type constraint (" .
221 $type_constraint->name .
224 ? (blessed($val) && overload::Overloaded($val)
225 ? overload::StrVal($val)
232 $meta_instance->set_slot_value($instance, $self->name, $val);
233 $meta_instance->weaken_slot_value($instance, $self->name)
234 if ref $val && $self->is_weak_ref;
240 my ($self, $instance, $value) = @_;
242 my $attr_name = $self->name;
244 if ($self->is_required) {
246 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
249 if ($self->has_type_constraint) {
251 my $type_constraint = $self->type_constraint;
253 if ($self->should_coerce) {
254 $value = $type_constraint->coerce($value);
256 defined($type_constraint->_compiled_type_constraint->($value))
257 || confess "Attribute ($attr_name) does not pass the type constraint ("
258 . $type_constraint->name
262 (blessed($value) && overload::Overloaded($value)
263 ? overload::StrVal($value)
270 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
273 $meta_instance->set_slot_value($instance, $attr_name, $value);
275 if (ref $value && $self->is_weak_ref) {
276 $meta_instance->weaken_slot_value($instance, $attr_name);
279 if ($self->has_trigger) {
280 $self->trigger->($instance, $value, $self);
285 my ($self, $instance) = @_;
287 if ($self->is_lazy) {
288 unless ($self->has_value($instance)) {
289 if ($self->has_default) {
290 my $default = $self->default($instance);
291 $self->set_value($instance, $default);
294 $self->set_value($instance, undef);
299 if ($self->should_auto_deref) {
301 my $type_constraint = $self->type_constraint;
303 if ($type_constraint->is_a_type_of('ArrayRef')) {
304 my $rv = $self->SUPER::get_value($instance);
305 return unless defined $rv;
306 return wantarray ? @{ $rv } : $rv;
308 elsif ($type_constraint->is_a_type_of('HashRef')) {
309 my $rv = $self->SUPER::get_value($instance);
310 return unless defined $rv;
311 return wantarray ? %{ $rv } : $rv;
314 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
320 return $self->SUPER::get_value($instance);
324 ## installing accessors
326 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
328 sub install_accessors {
330 $self->SUPER::install_accessors(@_);
332 if ($self->has_handles) {
335 # Here we canonicalize the 'handles' option
336 # this will sort out any details and always
337 # return an hash of methods which we want
338 # to delagate to, see that method for details
339 my %handles = $self->_canonicalize_handles();
341 # find the name of the accessor for this attribute
342 my $accessor_name = $self->reader || $self->accessor;
343 (defined $accessor_name)
344 || confess "You cannot install delegation without a reader or accessor for the attribute";
346 # make sure we handle HASH accessors correctly
347 ($accessor_name) = keys %{$accessor_name}
348 if ref($accessor_name) eq 'HASH';
350 # install the delegation ...
351 my $associated_class = $self->associated_class;
352 foreach my $handle (keys %handles) {
353 my $method_to_call = $handles{$handle};
355 (!$associated_class->has_method($handle))
356 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
359 # handles is not allowed to delegate
360 # any of these methods, as they will
361 # override the ones in your class, which
362 # is almost certainly not what you want.
363 next if $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
365 if ((reftype($method_to_call) || '') eq 'CODE') {
366 $associated_class->add_method($handle => $method_to_call);
369 $associated_class->add_method($handle => sub {
371 # we should check for lack of
372 # a callable return value from
374 my $proxy = (shift)->$accessor_name();
376 goto &{ $proxy->can($method_to_call)};
385 # private methods to help delegation ...
387 sub _canonicalize_handles {
389 my $handles = $self->handles;
390 if (my $handle_type = ref($handles)) {
391 if ($handle_type eq 'HASH') {
394 elsif ($handle_type eq 'ARRAY') {
395 return map { $_ => $_ } @{$handles};
397 elsif ($handle_type eq 'Regexp') {
398 ($self->has_type_constraint)
399 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
400 return map { ($_ => $_) }
401 grep { /$handles/ } $self->_get_delegate_method_list;
403 elsif ($handle_type eq 'CODE') {
404 return $handles->($self, $self->_find_delegate_metaclass);
407 confess "Unable to canonicalize the 'handles' option with $handles";
411 my $role_meta = eval { $handles->meta };
413 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
416 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
417 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
419 return map { $_ => $_ } (
420 $role_meta->get_method_list,
421 $role_meta->get_required_method_list
426 sub _find_delegate_metaclass {
428 if (my $class = $self->_isa_metadata) {
429 # if the class does have
430 # a meta method, use it
431 return $class->meta if $class->can('meta');
432 # otherwise we might be
433 # dealing with a non-Moose
434 # class, and need to make
436 return Moose::Meta::Class->initialize($class);
438 elsif (my $role = $self->_does_metadata) {
439 # our role will always have
444 confess "Cannot find delegate metaclass for attribute " . $self->name;
448 sub _get_delegate_method_list {
450 my $meta = $self->_find_delegate_metaclass;
451 if ($meta->isa('Class::MOP::Class')) {
452 return map { $_->{name} } # NOTE: !never! delegate &meta
453 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
454 $meta->compute_all_applicable_methods;
456 elsif ($meta->isa('Moose::Meta::Role')) {
457 return $meta->get_method_list;
460 confess "Unable to recognize the delegate metaclass '$meta'";
472 Moose::Meta::Attribute - The Moose attribute metaclass
476 This is a subclass of L<Class::MOP::Attribute> with Moose specific
479 For the most part, the only time you will ever encounter an
480 instance of this class is if you are doing some serious deep
481 introspection. To really understand this class, you need to refer
482 to the L<Class::MOP::Attribute> documentation.
486 =head2 Overridden methods
488 These methods override methods in L<Class::MOP::Attribute> and add
489 Moose specific features. You can safely assume though that they
490 will behave just as L<Class::MOP::Attribute> does.
496 =item B<initialize_instance_slot>
498 =item B<install_accessors>
500 =item B<accessor_metaclass>
506 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
511 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
513 Before setting the value, a check is made on the type constraint of
514 the attribute, if it has one, to see if the value passes it. If the
515 value fails to pass, the set operation dies with a L<Carp/confess>.
517 Any coercion to convert values is done before checking the type constraint.
519 To check a value against a type constraint before setting it, fetch the
520 attribute instance using L<Moose::Meta::Attribute/find_attribute_by_name>,
521 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
522 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
527 =head2 Additional Moose features
529 Moose attributes support type-constraint checking, weak reference
530 creation and type coercion.
534 =item B<clone_and_inherit_options>
536 This is to support the C<has '+foo'> feature, it clones an attribute
537 from a superclass and allows a very specific set of changes to be made
540 =item B<has_type_constraint>
542 Returns true if this meta-attribute has a type constraint.
544 =item B<type_constraint>
546 A read-only accessor for this meta-attribute's type constraint. For
547 more information on what you can do with this, see the documentation
548 for L<Moose::Meta::TypeConstraint>.
552 Returns true if this meta-attribute performs delegation.
556 This returns the value which was passed into the handles option.
560 Returns true if this meta-attribute produces a weak reference.
564 Returns true if this meta-attribute is required to have a value.
568 Returns true if this meta-attribute should be initialized lazily.
570 NOTE: lazy attributes, B<must> have a C<default> field set.
572 =item B<should_coerce>
574 Returns true if this meta-attribute should perform type coercion.
576 =item B<should_auto_deref>
578 Returns true if this meta-attribute should perform automatic
581 NOTE: This can only be done for attributes whose type constraint is
582 either I<ArrayRef> or I<HashRef>.
586 Returns true if this meta-attribute has a trigger set.
590 This is a CODE reference which will be executed every time the
591 value of an attribute is assigned. The CODE ref will get two values,
592 the invocant and the new value. This can be used to handle I<basic>
593 bi-directional relations.
595 =item B<documentation>
597 This is a string which contains the documentation for this attribute.
598 It serves no direct purpose right now, but it might in the future
599 in some kind of automated documentation system perhaps.
601 =item B<has_documentation>
603 Returns true if this meta-attribute has any documentation.
609 All complex software has bugs lurking in it, and this module is no
610 exception. If you find a bug please either email me, or add the bug
615 Stevan Little E<lt>stevan@iinteractive.comE<gt>
617 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
619 =head1 COPYRIGHT AND LICENSE
621 Copyright 2006, 2007 by Infinity Interactive, Inc.
623 L<http://www.iinteractive.com>
625 This library is free software; you can redistribute it and/or modify
626 it under the same terms as Perl itself.