2 package Mouse::Meta::Attribute;
7 use Scalar::Util 'blessed';
13 my $name = $args{name};
15 $args{init_arg} = $name
16 unless exists $args{init_arg};
20 if ($args{lazy_build}) {
21 confess("You can not use lazy_build and default for the same attribute $name")
22 if exists $args{default};
25 $args{builder} ||= "_build_${name}";
27 $args{clearer} ||= "_clear${name}";
28 $args{predicate} ||= "_has${name}";
31 $args{clearer} ||= "clear_${name}";
32 $args{predicate} ||= "has_${name}";
39 sub name { $_[0]->{name} }
40 sub class { $_[0]->{class} }
41 sub _is_metadata { $_[0]->{is} }
42 sub is_required { $_[0]->{required} }
43 sub default { $_[0]->{default} }
44 sub is_lazy { $_[0]->{lazy} }
45 sub predicate { $_[0]->{predicate} }
46 sub clearer { $_[0]->{clearer} }
47 sub handles { $_[0]->{handles} }
48 sub is_weak_ref { $_[0]->{weak_ref} }
49 sub init_arg { $_[0]->{init_arg} }
50 sub type_constraint { $_[0]->{type_constraint} }
51 sub trigger { $_[0]->{trigger} }
52 sub builder { $_[0]->{builder} }
53 sub should_auto_deref { $_[0]->{auto_deref} }
55 sub has_default { exists $_[0]->{default} }
56 sub has_predicate { exists $_[0]->{predicate} }
57 sub has_clearer { exists $_[0]->{clearer} }
58 sub has_handles { exists $_[0]->{handles} }
59 sub has_type_constraint { exists $_[0]->{type_constraint} }
60 sub has_trigger { exists $_[0]->{trigger} }
61 sub has_builder { exists $_[0]->{builder} }
64 $_[0]->{_create_args} = $_[1] if @_ > 1;
68 sub generate_accessor {
69 my $attribute = shift;
71 my $name = $attribute->name;
73 my $default = $attribute->default;
74 my $trigger = $attribute->trigger;
75 my $type = $attribute->type_constraint;
76 my $constraint = $attribute->find_type_constraint;
77 my $builder = $attribute->builder;
82 if ($attribute->_is_metadata eq 'rw') {
83 $accessor .= 'if (@_) {
88 my $display = defined($_) ? overload::StrVal($_) : "undef";
89 Carp::confess("Attribute ($name) does not pass the type constraint because: Validation failed for \'$type\' failed with value $display") unless $constraint->();
93 $accessor .= '$self->{$key} = $_;';
95 if ($attribute->is_weak_ref) {
96 $accessor .= 'Scalar::Util::weaken($self->{$key}) if ref($self->{$key});';
100 $accessor .= '$trigger->($self, $_, $attribute);';
106 $accessor .= 'confess "Cannot assign a value to a read-only accessor" if @_;';
109 if ($attribute->is_lazy) {
110 $accessor .= '$self->{$key} = ';
112 $accessor .= $attribute->has_builder
114 : ref($default) eq 'CODE'
115 ? '$default->($self)'
118 $accessor .= ' if !exists($self->{$key});';
121 if ($attribute->should_auto_deref) {
122 if ($attribute->type_constraint eq 'ArrayRef') {
123 $accessor .= 'if (wantarray) {
124 return @{ $self->{$key} || [] };
128 $accessor .= 'if (wantarray) {
129 return %{ $self->{$key} || {} };
134 $accessor .= 'return $self->{$key};
137 return eval $accessor;
140 sub generate_predicate {
141 my $attribute = shift;
142 my $key = $attribute->name;
144 my $predicate = 'sub { exists($_[0]->{$key}) }';
146 return eval $predicate;
149 sub generate_clearer {
150 my $attribute = shift;
151 my $key = $attribute->name;
153 my $predicate = 'sub { delete($_[0]->{$key}) }';
155 return eval $predicate;
158 sub generate_handles {
159 my $attribute = shift;
160 my $reader = $attribute->name;
161 my %handles = $attribute->_canonicalize_handles($attribute->handles);
165 for my $local_method (keys %handles) {
166 my $remote_method = $handles{$local_method};
170 $self->$reader->$remote_method(@_)
173 $method_map{$local_method} = eval $method;
180 my ($self, $class, $name, %args) = @_;
183 $args{class} = $class;
185 $self->validate_args($name, %args);
187 $args{type_constraint} = delete $args{isa}
188 if exists $args{isa};
190 my $attribute = $self->new(%args);
191 $attribute->_create_args(\%args);
193 my $meta = $class->meta;
195 $meta->add_attribute($attribute);
197 # install an accessor
198 if ($attribute->_is_metadata eq 'rw' || $attribute->_is_metadata eq 'ro') {
199 my $accessor = $attribute->generate_accessor;
201 *{ $class . '::' . $name } = $accessor;
204 for my $method (qw/predicate clearer/) {
205 my $predicate = "has_$method";
206 if ($attribute->$predicate) {
207 my $generator = "generate_$method";
208 my $coderef = $attribute->$generator;
210 *{ $class . '::' . $attribute->$method } = $coderef;
214 if ($attribute->has_handles) {
215 my $method_map = $attribute->generate_handles;
216 for my $method_name (keys %$method_map) {
218 *{ $class . '::' . $method_name } = $method_map->{$method_name};
230 confess "You cannot have lazy attribute ($name) without specifying a default value for it"
231 if $args{lazy} && !exists($args{default}) && !exists($args{builder});
233 confess "References are not allowed as default values, you must wrap the default of '$name' in a CODE reference (ex: sub { [] } and not [])"
234 if ref($args{default})
235 && ref($args{default}) ne 'CODE';
237 confess "You cannot auto-dereference without specifying a type constraint on attribute $name"
238 if $args{auto_deref} && !exists($args{isa});
240 confess "You cannot auto-dereference anything other than a ArrayRef or HashRef on attribute $name"
242 && $args{isa} ne 'ArrayRef'
243 && $args{isa} ne 'HashRef';
248 sub find_type_constraint {
250 my $type = $self->type_constraint;
254 my $checker = Mouse::TypeRegistry->optimized_constraints->{$type};
255 return $checker if $checker;
257 return sub { blessed($_) && blessed($_) eq $type };
260 sub verify_type_constraint {
264 my $type = $self->type_constraint
266 my $constraint = $self->find_type_constraint;
268 return 1 if $constraint->($_);
270 my $name = $self->name;
271 my $display = defined($_) ? overload::StrVal($_) : 'undef';
272 Carp::confess("Attribute ($name) does not pass the type constraint because: Validation failed for \'$type\' failed with value $display");
275 sub _canonicalize_handles {
279 if (ref($handles) eq 'HASH') {
282 elsif (ref($handles) eq 'ARRAY') {
283 return map { $_ => $_ } @$handles;
286 confess "Unable to canonicalize the 'handles' option with $handles";
294 my %args = ($self->get_parent_args($class, $name), @_);
296 $self->create($class, $name, %args);
299 sub get_parent_args {
304 for my $super ($class->meta->linearized_isa) {
305 my $super_attr = $super->can("meta") && $super->meta->get_attribute($name)
307 return %{ $super_attr->_create_args };
310 confess "Could not find an attribute by the name of '$name' to inherit from";
319 Mouse::Meta::Attribute - attribute metaclass
323 =head2 new %args -> Mouse::Meta::Attribute
325 Instantiates a new Mouse::Meta::Attribute. Does nothing else.
327 =head2 create OwnerClass, AttributeName, %args -> Mouse::Meta::Attribute
329 Creates a new attribute in OwnerClass. Accessors and helper methods are
330 installed. Some error checking is done.
332 =head2 name -> AttributeName
334 =head2 class -> OwnerClass
336 =head2 is_required -> Bool
338 =head2 default -> Item
340 =head2 has_default -> Bool
342 =head2 is_lazy -> Bool
344 =head2 predicate -> MethodName | Undef
346 =head2 has_predicate -> Bool
348 =head2 clearer -> MethodName | Undef
350 =head2 has_clearer -> Bool
352 =head2 handles -> { LocalName => RemoteName }
354 =head2 has_handles -> Bool
356 =head2 is_weak_ref -> Bool
358 =head2 init_arg -> Str
360 =head2 type_constraint -> Str
362 =head2 has_type_constraint -> Bool
364 =head2 trigger => CODE | Undef
366 =head2 has_trigger -> Bool
368 =head2 builder => MethodName | Undef
370 =head2 has_builder -> Bool
372 =head2 should_auto_deref -> Bool
374 Informational methods.
376 =head2 generate_accessor -> CODE
378 Creates a new code reference for the attribute's accessor.
380 =head2 generate_predicate -> CODE
382 Creates a new code reference for the attribute's predicate.
384 =head2 generate_clearer -> CODE
386 Creates a new code reference for the attribute's clearer.
388 =head2 generate_handles -> { MethodName => CODE }
390 Creates a new code reference for each of the attribute's handles methods.
392 =head2 find_type_constraint -> CODE
394 Returns a code reference which can be used to check that a given value passes
395 this attribute's type constraint;
397 =head2 verify_type_constraint Item -> 1 | ERROR
399 Checks that the given value passes this attribute's type constraint. Returns 1
400 on success, otherwise C<confess>es.