1 package Mouse::Meta::Attribute;
2 use Mouse::Util qw(:meta); # enables strict and warnings
6 use Mouse::Meta::TypeConstraint;
7 use Mouse::Meta::Method::Accessor;
11 my($class, $name, $args) = @_;
14 # XXX: for backward compatibility (with method modifiers)
15 if($class->can('canonicalize_args') != \&canonicalize_args){
16 %{$args} = $class->canonicalize_args($name, %{$args});
19 # taken from Class::MOP::Attribute::new
22 or $class->throw_error('You must provide a name for the attribute');
24 if(!exists $args->{init_arg}){
25 $args->{init_arg} = $name;
28 # 'required' requires eigher 'init_arg', 'builder', or 'default'
29 my $can_be_required = defined( $args->{init_arg} );
31 if(exists $args->{builder}){
33 # Moose refuses a CODE ref builder, but Mouse doesn't for backward compatibility
34 # This feature will be changed in a future. (gfx)
35 $class->throw_error('builder must be a defined scalar value which is a method name')
36 #if ref $args->{builder} || !defined $args->{builder};
37 if !defined $args->{builder};
41 elsif(exists $args->{default}){
42 if(ref $args->{default} && ref($args->{default}) ne 'CODE'){
43 $class->throw_error("References are not allowed as default values, you must "
44 . "wrap the default of '$name' in a CODE reference (ex: sub { [] } and not [])");
49 if( $args->{required} && !$can_be_required ) {
50 $class->throw_error("You cannot have a required attribute ($name) without a default, builder, or an init_arg");
53 # taken from Mouse::Meta::Attribute->new and _process_args->
55 if(exists $args->{is}){
59 $args->{reader} ||= $name;
62 if(exists $args->{writer}){
63 $args->{reader} ||= $name;
66 $args->{accessor} ||= $name;
70 # do nothing, but don't complain (later) about missing methods
73 $is = 'undef' if !defined $is;
74 $class->throw_error("I do not understand this option (is => $is) on attribute ($name)");
79 if(exists $args->{isa}){
80 $args->{type_constraint} = Mouse::Util::TypeConstraints::find_or_create_isa_type_constraint($args->{isa});
82 elsif(exists $args->{does}){
84 # $args->{type_constraint} = Mouse::Util::TypeConstraints::find_or_create_does_type_constraint($args->{does});
86 $tc = $args->{type_constraint};
90 || $class->throw_error("You cannot have coercion without specifying a type constraint on attribute ($name)");
93 && $class->throw_error("You cannot have a weak reference to a coerced value on attribute ($name)");
96 if ($args->{lazy_build}) {
97 exists($args->{default})
98 && $class->throw_error("You can not use lazy_build and default for the same attribute ($name)");
101 $args->{builder} ||= "_build_${name}";
103 $args->{clearer} ||= "_clear${name}";
104 $args->{predicate} ||= "_has${name}";
107 $args->{clearer} ||= "clear_${name}";
108 $args->{predicate} ||= "has_${name}";
112 if ($args->{auto_deref}) {
114 || $class->throw_error("You cannot auto-dereference without specifying a type constraint on attribute ($name)");
116 ( $tc->is_a_type_of('ArrayRef') || $tc->is_a_type_of('HashRef') )
117 || $class->throw_error("You cannot auto-dereference anything other than a ArrayRef or HashRef on attribute ($name)");
120 if (exists $args->{trigger}) {
121 ('CODE' eq ref $args->{trigger})
122 || $class->throw_error("Trigger must be a CODE ref on attribute ($name)");
126 (exists $args->{default} || defined $args->{builder})
127 || $class->throw_error("You cannot have lazy attribute ($name) without specifying a default value for it");
137 my %args = (@_ == 1) ? %{ $_[0] } : @_;
139 $class->_process_options($name, \%args);
143 my $self = bless \%args, $class;
146 if($class ne __PACKAGE__){
147 $class->meta->_initialize_object($self, \%args);
150 # XXX: there is no fast way to check attribute validity
154 # Carp::cluck("Found unknown argument(s) passed to '$name' attribute constructor in '$class': @bad");
162 sub name { $_[0]->{name} }
163 sub associated_class { $_[0]->{associated_class} }
165 sub accessor { $_[0]->{accessor} }
166 sub reader { $_[0]->{reader} }
167 sub writer { $_[0]->{writer} }
168 sub predicate { $_[0]->{predicate} }
169 sub clearer { $_[0]->{clearer} }
170 sub handles { $_[0]->{handles} }
172 sub _is_metadata { $_[0]->{is} }
173 sub is_required { $_[0]->{required} }
174 sub default { $_[0]->{default} }
175 sub is_lazy { $_[0]->{lazy} }
176 sub is_lazy_build { $_[0]->{lazy_build} }
177 sub is_weak_ref { $_[0]->{weak_ref} }
178 sub init_arg { $_[0]->{init_arg} }
179 sub type_constraint { $_[0]->{type_constraint} }
181 sub trigger { $_[0]->{trigger} }
182 sub builder { $_[0]->{builder} }
183 sub should_auto_deref { $_[0]->{auto_deref} }
184 sub should_coerce { $_[0]->{coerce} }
188 sub has_accessor { exists $_[0]->{accessor} }
189 sub has_reader { exists $_[0]->{reader} }
190 sub has_writer { exists $_[0]->{writer} }
191 sub has_predicate { exists $_[0]->{predicate} }
192 sub has_clearer { exists $_[0]->{clearer} }
193 sub has_handles { exists $_[0]->{handles} }
195 sub has_default { exists $_[0]->{default} }
196 sub has_type_constraint { exists $_[0]->{type_constraint} }
197 sub has_trigger { exists $_[0]->{trigger} }
198 sub has_builder { exists $_[0]->{builder} }
200 sub has_read_method { exists $_[0]->{reader} || exists $_[0]->{accessor} }
201 sub has_write_method { exists $_[0]->{writer} || exists $_[0]->{accessor} }
203 sub _create_args { # DEPRECATED
204 $_[0]->{_create_args} = $_[1] if @_ > 1;
205 $_[0]->{_create_args}
208 sub interpolate_class{
209 my($class, $args) = @_;
211 if(my $metaclass = delete $args->{metaclass}){
212 $class = Mouse::Util::resolve_metaclass_alias( Attribute => $metaclass );
216 if(my $traits_ref = delete $args->{traits}){
218 for (my $i = 0; $i < @{$traits_ref}; $i++) {
219 my $trait = Mouse::Util::resolve_metaclass_alias(Attribute => $traits_ref->[$i], trait => 1);
221 next if $class->does($trait);
223 push @traits, $trait;
226 push @traits, $traits_ref->[++$i]
227 if ref($traits_ref->[$i+1]);
231 $class = Mouse::Meta::Class->create_anon_class(
232 superclasses => [ $class ],
239 return( $class, @traits );
242 sub canonicalize_args{ # DEPRECATED
243 my ($self, $name, %args) = @_;
245 Carp::cluck("$self->canonicalize_args has been deprecated."
246 . "Use \$self->_process_options instead.")
253 my ($self, $class, $name, %args) = @_;
255 Carp::cluck("$self->create has been deprecated."
256 . "Use \$meta->add_attribute and \$attr->install_accessors instead.")
263 sub _coerce_and_verify {
264 my($self, $value, $instance) = @_;
266 my $type_constraint = $self->{type_constraint};
268 return $value if !$type_constraint;
270 if ($self->should_coerce && $type_constraint->has_coercion) {
271 $value = $type_constraint->coerce($value);
274 return $value if $type_constraint->check($value);
276 $self->verify_against_type_constraint($value);
281 sub verify_against_type_constraint {
282 my ($self, $value) = @_;
284 my $type_constraint = $self->{type_constraint};
285 return 1 if !$type_constraint;;
286 return 1 if $type_constraint->check($value);
288 $self->verify_type_constraint_error($self->name, $value, $type_constraint);
291 sub verify_type_constraint_error {
292 my($self, $name, $value, $type) = @_;
293 $self->throw_error("Attribute ($name) does not pass the type constraint because: " . $type->get_message($value));
296 sub coerce_constraint { # DEPRECATED
297 my $type = $_[0]->{type_constraint}
300 Carp::cluck("coerce_constraint() has been deprecated, which was an internal utility anyway");
302 return Mouse::Util::TypeConstraints->typecast_constraints($_[0]->associated_class->name, $type, $_[1]);
305 sub clone_and_inherit_options{
306 my($self, %args) = @_;
308 my($attribute_class, @traits) = ref($self)->interpolate_class(\%args);
310 $args{traits} = \@traits if @traits;
311 return $attribute_class->new($self->name, %{$self}, %args);
314 sub clone_parent { # DEPRECATED
318 my %args = ($self->get_parent_args($class, $name), @_);
320 Carp::cluck("$self->clone_parent has been deprecated."
321 . "Use \$meta->add_attribute and \$attr->install_accessors instead.")
324 $self->clone_and_inherited_args($class, $name, %args);
327 sub get_parent_args { # DEPRECATED
332 for my $super ($class->linearized_isa) {
333 my $super_attr = $super->can("meta") && $super->meta->get_attribute($name)
335 return %{ $super_attr->_create_args };
338 $self->throw_error("Could not find an attribute by the name of '$name' to inherit from");
342 sub get_read_method { # DEPRECATED
343 $_[0]->{reader} || $_[0]->{accessor}
345 sub get_write_method { # DEPRECATED
346 $_[0]->{writer} || $_[0]->{accessor}
349 sub get_read_method_ref{
352 $self->{_read_method_ref} ||= do{
353 my $metaclass = $self->associated_class
354 or $self->throw_error('No asocciated class for ' . $self->name);
356 my $reader = $self->{reader} || $self->{accessor};
358 $metaclass->name->can($reader);
361 $self->accessor_metaclass->_generate_reader($self, $metaclass);
366 sub get_write_method_ref{
369 $self->{_write_method_ref} ||= do{
370 my $metaclass = $self->associated_class
371 or $self->throw_error('No asocciated class for ' . $self->name);
373 my $reader = $self->{writer} || $self->{accessor};
375 $metaclass->name->can($reader);
378 $self->accessor_metaclass->_generate_writer($self, $metaclass);
383 sub _canonicalize_handles {
384 my($self, $handles) = @_;
386 if (ref($handles) eq 'HASH') {
389 elsif (ref($handles) eq 'ARRAY') {
390 return map { $_ => $_ } @$handles;
393 $self->throw_error("Unable to canonicalize the 'handles' option with $handles");
398 sub associate_method{
399 my ($attribute, $method) = @_;
400 $attribute->{associated_methods}++;
404 sub accessor_metaclass(){ 'Mouse::Meta::Method::Accessor' }
406 sub install_accessors{
409 my $metaclass = $attribute->{associated_class};
410 my $accessor_class = $attribute->accessor_metaclass;
412 foreach my $type(qw(accessor reader writer predicate clearer)){
413 if(exists $attribute->{$type}){
414 my $generator = '_generate_' . $type;
415 my $code = $accessor_class->$generator($attribute, $metaclass);
416 $metaclass->add_method($attribute->{$type} => $code);
417 $attribute->associate_method($code);
422 if(exists $attribute->{handles}){
423 my %handles = $attribute->_canonicalize_handles($attribute->{handles});
424 my $reader = $attribute->get_read_method_ref;
426 while(my($handle_name, $method_to_call) = each %handles){
427 my $code = $accessor_class->_generate_delegation($attribute, $metaclass,
428 $reader, $handle_name, $method_to_call);
430 $metaclass->add_method($handle_name => $code);
431 $attribute->associate_method($code);
436 if($attribute->can('create') != \&create){
437 # backword compatibility
438 $attribute->create($metaclass, $attribute->name, %{$attribute});
447 my $metaclass = (ref $self && $self->associated_class) || 'Mouse::Meta::Class';
448 $metaclass->throw_error(@_, depth => 1);
457 Mouse::Meta::Attribute - The Mouse attribute metaclass
461 =head2 C<< new(%options) -> Mouse::Meta::Attribute >>
463 Instantiates a new Mouse::Meta::Attribute. Does nothing else.
465 It adds the following options to the constructor:
469 =item C<< is => 'ro', 'rw', 'bare' >>
471 This provides a shorthand for specifying the C<reader>, C<writer>, or
472 C<accessor> names. If the attribute is read-only ('ro') then it will
473 have a C<reader> method with the same attribute as the name.
475 If it is read-write ('rw') then it will have an C<accessor> method
476 with the same name. If you provide an explicit C<writer> for a
477 read-write attribute, then you will have a C<reader> with the same
478 name as the attribute, and a C<writer> with the name you provided.
480 Use 'bare' when you are deliberately not installing any methods
481 (accessor, reader, etc.) associated with this attribute; otherwise,
482 Moose will issue a deprecation warning when this attribute is added to a
485 =item C<< isa => Type >>
487 This option accepts a type. The type can be a string, which should be
488 a type name. If the type name is unknown, it is assumed to be a class
491 This option can also accept a L<Moose::Meta::TypeConstraint> object.
493 If you I<also> provide a C<does> option, then your C<isa> option must
494 be a class name, and that class must do the role specified with
497 =item C<< does => Role >>
499 This is short-hand for saying that the attribute's type must be an
500 object which does the named role.
502 B<This option is not yet supported.>
504 =item C<< coerce => Bool >>
506 This option is only valid for objects with a type constraint
507 (C<isa>). If this is true, then coercions will be applied whenever
508 this attribute is set.
510 You can make both this and the C<weak_ref> option true.
512 =item C<< trigger => CodeRef >>
514 This option accepts a subroutine reference, which will be called after
515 the attribute is set.
517 =item C<< required => Bool >>
519 An attribute which is required must be provided to the constructor. An
520 attribute which is required can also have a C<default> or C<builder>,
521 which will satisfy its required-ness.
523 A required attribute must have a C<default>, C<builder> or a
524 non-C<undef> C<init_arg>
526 =item C<< lazy => Bool >>
528 A lazy attribute must have a C<default> or C<builder>. When an
529 attribute is lazy, the default value will not be calculated until the
532 =item C<< weak_ref => Bool >>
534 If this is true, the attribute's value will be stored as a weak
537 =item C<< auto_deref => Bool >>
539 If this is true, then the reader will dereference the value when it is
540 called. The attribute must have a type constraint which defines the
541 attribute as an array or hash reference.
543 =item C<< lazy_build => Bool >>
545 Setting this to true makes the attribute lazy and provides a number of
553 is equivalent to this:
558 builder => '_build_size',
559 clearer => 'clear_size',
560 predicate => 'has_size',
565 =head2 C<< associate_method(Method) >>
567 Associates a method with the attribute. Typically, this is called internally
568 when an attribute generates its accessors.
570 Currently the argument I<Method> is ignored in Mouse.
572 =head2 C<< verify_against_type_constraint(Item) -> TRUE | ERROR >>
574 Checks that the given value passes this attribute's type constraint. Returns C<true>
575 on success, otherwise C<confess>es.
577 =head2 C<< clone_and_inherit_options(options) -> Mouse::Meta::Attribute >>
579 Creates a new attribute in the owner class, inheriting options from parent classes.
580 Accessors and helper methods are installed. Some error checking is done.
582 =head2 C<< get_read_method_ref >>
\r
584 =head2 C<< get_write_method_ref >>
\r
586 Returns the subroutine reference of a method suitable for reading or
\r
587 writing the attribute's value in the associated class. These methods
\r
588 always return a subroutine reference, regardless of whether or not the
\r
589 attribute is read- or write-only.
593 L<Moose::Meta::Attribute>
595 L<Class::MOP::Attribute>