Add {get,set}_raw_value methods
[gitmo/Class-MOP.git] / lib / Class / MOP / Attribute.pm
CommitLineData
8b978dd5 1
2package Class::MOP::Attribute;
3
4use strict;
5use warnings;
6
ba38bf08 7use Class::MOP::Method::Accessor;
8
2eb717d5 9use Carp 'confess';
9b522fc4 10use Scalar::Util 'blessed', 'weaken';
2eb717d5 11
436d2a84 12our $VERSION = '0.93';
d519662a 13$VERSION = eval $VERSION;
f0480c45 14our $AUTHORITY = 'cpan:STEVAN';
8b978dd5 15
b1897d4d 16use base 'Class::MOP::Object';
17
727919c5 18# NOTE: (meta-circularity)
1d68af04 19# This method will be replaced in the
20# boostrap section of Class::MOP, by
21# a new version which uses the
727919c5 22# &Class::MOP::Class::construct_instance
23# method to build an attribute meta-object
24# which itself is described with attribute
1d68af04 25# meta-objects.
727919c5 26# - Ain't meta-circularity grand? :)
8b978dd5 27sub new {
649efb63 28 my ( $class, @args ) = @_;
29
30 unshift @args, "name" if @args % 2 == 1;
31 my %options = @args;
32
33 my $name = $options{name};
1d68af04 34
d9330488 35 (defined $name)
8b978dd5 36 || confess "You must provide a name for the attribute";
1d68af04 37
38 $options{init_arg} = $name
5659d76e 39 if not exists $options{init_arg};
1d68af04 40 if(exists $options{builder}){
41 confess("builder must be a defined scalar value which is a method name")
42 if ref $options{builder} || !(defined $options{builder});
43 confess("Setting both default and builder is not allowed.")
44 if exists $options{default};
8fe581e5 45 } else {
46 (is_default_a_coderef(\%options))
47 || confess("References are not allowed as default values, you must ".
3c0a8087 48 "wrap the default of '$name' in a CODE reference (ex: sub { [] } and not [])")
8fe581e5 49 if exists $options{default} && ref $options{default};
1d68af04 50 }
2e877f58 51 if( $options{required} and not( defined($options{builder}) || defined($options{init_arg}) || exists $options{default} ) ) {
52 confess("A required attribute must have either 'init_arg', 'builder', or 'default'");
53 }
8683db0e 54
cb75020f 55 $class->_new(\%options);
4b698b1a 56}
57
58sub _new {
0bfc85b8 59 my $class = shift;
ec9e38e5 60
61 return Class::MOP::Class->initialize($class)->new_object(@_)
812d58f9 62 if $class ne __PACKAGE__;
ec9e38e5 63
0bfc85b8 64 my $options = @_ == 1 ? $_[0] : {@_};
4b698b1a 65
8b978dd5 66 bless {
d9d99689 67 'name' => $options->{name},
68 'accessor' => $options->{accessor},
69 'reader' => $options->{reader},
70 'writer' => $options->{writer},
71 'predicate' => $options->{predicate},
72 'clearer' => $options->{clearer},
73 'builder' => $options->{builder},
74 'init_arg' => $options->{init_arg},
75 'default' => $options->{default},
76 'initializer' => $options->{initializer},
77 'definition_context' => $options->{definition_context},
1d68af04 78 # keep a weakened link to the
9ec169fe 79 # class we are associated with
8683db0e 80 'associated_class' => undef,
1d68af04 81 # and a list of the methods
3545c727 82 # associated with this attr
8683db0e 83 'associated_methods' => [],
dc9d420c 84 # this let's us keep track of
85 # our order inside the associated
86 # class
87 'insertion_order' => undef,
0bfc85b8 88 }, $class;
8b978dd5 89}
90
7b31baf4 91# NOTE:
1d68af04 92# this is a primative (and kludgy) clone operation
16e960bd 93# for now, it will be replaced in the Class::MOP
1d68af04 94# bootstrap with a proper one, however we know
5659d76e 95# that this one will work fine for now.
96sub clone {
97 my $self = shift;
98 my %options = @_;
99 (blessed($self))
100 || confess "Can only clone an instance";
b3fa93c7 101 return bless { %{$self}, %options } => ref($self);
5659d76e 102}
103
bd4e03f9 104sub initialize_instance_slot {
f892c0f0 105 my ($self, $meta_instance, $instance, $params) = @_;
8683db0e 106 my $init_arg = $self->{'init_arg'};
107
bd4e03f9 108 # try to fetch the init arg from the %params ...
8d2d4c67 109
1d68af04 110 # if nothing was in the %params, we can use the
bd4e03f9 111 # attribute's default value (if it has one)
2e877f58 112 if(defined $init_arg and exists $params->{$init_arg}){
8ee74136 113 $self->_set_initial_slot_value(
114 $meta_instance,
0ab65f99 115 $instance,
0ab65f99 116 $params->{$init_arg},
0ab65f99 117 );
b7bdffc3 118 }
8683db0e 119 elsif (defined $self->{'default'}) {
8ee74136 120 $self->_set_initial_slot_value(
121 $meta_instance,
0ab65f99 122 $instance,
0ab65f99 123 $self->default($instance),
0ab65f99 124 );
b7bdffc3 125 }
8683db0e 126 elsif (defined( my $builder = $self->{'builder'})) {
b7bdffc3 127 if ($builder = $instance->can($builder)) {
8ee74136 128 $self->_set_initial_slot_value(
129 $meta_instance,
0ab65f99 130 $instance,
0ab65f99 131 $instance->$builder,
0ab65f99 132 );
b7bdffc3 133 }
134 else {
b3fa93c7 135 confess(ref($instance)." does not support builder method '". $self->{'builder'} ."' for attribute '" . $self->name . "'");
8fe581e5 136 }
1d68af04 137 }
bd4e03f9 138}
139
8ee74136 140sub _set_initial_slot_value {
141 my ($self, $meta_instance, $instance, $value) = @_;
142
143 my $slot_name = $self->name;
144
145 return $meta_instance->set_slot_value($instance, $slot_name, $value)
146 unless $self->has_initializer;
147
148 my $callback = sub {
149 $meta_instance->set_slot_value($instance, $slot_name, $_[0]);
150 };
151
152 my $initializer = $self->initializer;
153
154 # most things will just want to set a value, so make it first arg
155 $instance->$initializer($value, $callback, $self);
156}
157
5659d76e 158# NOTE:
1d68af04 159# the next bunch of methods will get bootstrapped
7b31baf4 160# away in the Class::MOP bootstrapping section
161
8683db0e 162sub associated_class { $_[0]->{'associated_class'} }
163sub associated_methods { $_[0]->{'associated_methods'} }
164
b3fa93c7 165sub has_accessor { defined($_[0]->{'accessor'}) }
166sub has_reader { defined($_[0]->{'reader'}) }
167sub has_writer { defined($_[0]->{'writer'}) }
168sub has_predicate { defined($_[0]->{'predicate'}) }
169sub has_clearer { defined($_[0]->{'clearer'}) }
170sub has_builder { defined($_[0]->{'builder'}) }
171sub has_init_arg { defined($_[0]->{'init_arg'}) }
172sub has_default { defined($_[0]->{'default'}) }
173sub has_initializer { defined($_[0]->{'initializer'}) }
dc9d420c 174sub has_insertion_order { defined($_[0]->{'insertion_order'}) }
8683db0e 175
d9d99689 176sub accessor { $_[0]->{'accessor'} }
177sub reader { $_[0]->{'reader'} }
178sub writer { $_[0]->{'writer'} }
179sub predicate { $_[0]->{'predicate'} }
180sub clearer { $_[0]->{'clearer'} }
181sub builder { $_[0]->{'builder'} }
182sub init_arg { $_[0]->{'init_arg'} }
183sub initializer { $_[0]->{'initializer'} }
184sub definition_context { $_[0]->{'definition_context'} }
dc9d420c 185sub insertion_order { $_[0]->{'insertion_order'} }
943cbe2d 186sub _set_insertion_order { $_[0]->{'insertion_order'} = $_[1] }
c50c603e 187
7b31baf4 188# end bootstrapped away method section.
189# (all methods below here are kept intact)
190
9e517e01 191sub has_read_method { $_[0]->has_reader || $_[0]->has_accessor }
192sub has_write_method { $_[0]->has_writer || $_[0]->has_accessor }
193
d14f6cbe 194sub get_read_method {
195 my $self = shift;
196 my $reader = $self->reader || $self->accessor;
197 # normal case ...
198 return $reader unless ref $reader;
199 # the HASH ref case
200 my ($name) = %$reader;
201 return $name;
202}
203
204sub get_write_method {
205 my $self = shift;
206 my $writer = $self->writer || $self->accessor;
207 # normal case ...
208 return $writer unless ref $writer;
209 # the HASH ref case
210 my ($name) = %$writer;
211 return $name;
212}
b25109b1 213
5da16d1b 214sub get_read_method_ref {
215 my $self = shift;
742fb371 216 if ((my $reader = $self->get_read_method) && $self->associated_class) {
5da16d1b 217 return $self->associated_class->get_method($reader);
218 }
219 else {
def5c0b5 220 my $code = sub { $self->get_value(@_) };
221 if (my $class = $self->associated_class) {
222 return $class->method_metaclass->wrap(
223 $code,
224 package_name => $class->name,
225 name => '__ANON__'
226 );
227 }
228 else {
229 return $code;
230 }
5da16d1b 231 }
232}
233
234sub get_write_method_ref {
235 my $self = shift;
d14f6cbe 236 if ((my $writer = $self->get_write_method) && $self->associated_class) {
742fb371 237 return $self->associated_class->get_method($writer);
5da16d1b 238 }
239 else {
def5c0b5 240 my $code = sub { $self->set_value(@_) };
241 if (my $class = $self->associated_class) {
242 return $class->method_metaclass->wrap(
243 $code,
244 package_name => $class->name,
245 name => '__ANON__'
246 );
247 }
248 else {
249 return $code;
250 }
5da16d1b 251 }
252}
253
1d68af04 254sub is_default_a_coderef {
ed337aad 255 my ($value) = $_[0]->{'default'};
256 return unless ref($value);
257 return ref($value) eq 'CODE' || (blessed($value) && $value->isa('Class::MOP::Method'));
c0cbf4d9 258}
259
1d68af04 260sub default {
c0cbf4d9 261 my ($self, $instance) = @_;
9363ea89 262 if (defined $instance && $self->is_default_a_coderef) {
1d68af04 263 # if the default is a CODE ref, then
727919c5 264 # we pass in the instance and default
1d68af04 265 # can return a value based on that
727919c5 266 # instance. Somewhat crude, but works.
8683db0e 267 return $self->{'default'}->($instance);
1d68af04 268 }
8683db0e 269 $self->{'default'};
c50c603e 270}
8b978dd5 271
c57c8b10 272# slots
273
274sub slots { (shift)->name }
275
1d68af04 276# class association
727919c5 277
9ec169fe 278sub attach_to_class {
279 my ($self, $class) = @_;
280 (blessed($class) && $class->isa('Class::MOP::Class'))
281 || confess "You must pass a Class::MOP::Class instance (or a subclass)";
8683db0e 282 weaken($self->{'associated_class'} = $class);
9ec169fe 283}
284
285sub detach_from_class {
286 my $self = shift;
8683db0e 287 $self->{'associated_class'} = undef;
9ec169fe 288}
289
1d68af04 290# method association
3545c727 291
292sub associate_method {
293 my ($self, $method) = @_;
8683db0e 294 push @{$self->{'associated_methods'}} => $method;
3545c727 295}
296
16e960bd 297## Slot management
298
ef91a0e2 299sub set_initial_value {
300 my ($self, $instance, $value) = @_;
e76b01fb 301 $self->_set_initial_slot_value(
b3fa93c7 302 Class::MOP::Class->initialize(ref($instance))->get_meta_instance,
8ee74136 303 $instance,
304 $value
305 );
ef91a0e2 306}
307
7e5efe15 308sub set_value { shift->set_raw_value(@_) }
309sub get_value { shift->get_raw_value(@_) }
310
311sub set_raw_value {
1396f86b 312 my ($self, $instance, $value) = @_;
16e960bd 313
b3fa93c7 314 Class::MOP::Class->initialize(ref($instance))
da34f054 315 ->get_meta_instance
316 ->set_slot_value($instance, $self->name, $value);
16e960bd 317}
318
7e5efe15 319sub get_raw_value {
1396f86b 320 my ($self, $instance) = @_;
16e960bd 321
b3fa93c7 322 Class::MOP::Class->initialize(ref($instance))
da34f054 323 ->get_meta_instance
324 ->get_slot_value($instance, $self->name);
16e960bd 325}
326
3545c727 327sub has_value {
328 my ($self, $instance) = @_;
1d68af04 329
b3fa93c7 330 Class::MOP::Class->initialize(ref($instance))
da34f054 331 ->get_meta_instance
332 ->is_slot_initialized($instance, $self->name);
3545c727 333}
334
335sub clear_value {
336 my ($self, $instance) = @_;
1d68af04 337
b3fa93c7 338 Class::MOP::Class->initialize(ref($instance))
da34f054 339 ->get_meta_instance
340 ->deinitialize_slot($instance, $self->name);
3545c727 341}
342
ba38bf08 343## load em up ...
c0cbf4d9 344
ba38bf08 345sub accessor_metaclass { 'Class::MOP::Method::Accessor' }
c0cbf4d9 346
45a183fb 347sub _process_accessors {
c0cbf4d9 348 my ($self, $type, $accessor, $generate_as_inline_methods) = @_;
d9d99689 349
350 my $method_ctx;
351
352 if ( my $ctx = $self->definition_context ) {
353 $method_ctx = { %$ctx };
354 }
355
9b522fc4 356 if (ref($accessor)) {
357 (ref($accessor) eq 'HASH')
7d28758b 358 || confess "bad accessor/reader/writer/predicate/clearer format, must be a HASH ref";
4d47b77f 359 my ($name, $method) = %{$accessor};
4c105333 360 $method = $self->accessor_metaclass->wrap(
361 $method,
362 package_name => $self->associated_class->name,
363 name => $name,
d9d99689 364 definition_context => $method_ctx,
4c105333 365 );
3545c727 366 $self->associate_method($method);
1d68af04 367 return ($name, $method);
2eb717d5 368 }
9ec169fe 369 else {
1d68af04 370 my $inline_me = ($generate_as_inline_methods && $self->associated_class->instance_metaclass->is_inlinable);
ba38bf08 371 my $method;
372 eval {
d9d99689 373 if ( $method_ctx ) {
374 my $desc = "accessor $accessor";
375 if ( $accessor ne $self->name ) {
376 $desc .= " of attribute " . $self->name;
377 }
378
379 $method_ctx->{description} = $desc;
380 }
381
ba38bf08 382 $method = $self->accessor_metaclass->new(
383 attribute => $self,
d90b42a6 384 is_inline => $inline_me,
ba38bf08 385 accessor_type => $type,
4c105333 386 package_name => $self->associated_class->name,
387 name => $accessor,
d9d99689 388 definition_context => $method_ctx,
1d68af04 389 );
ba38bf08 390 };
1d68af04 391 confess "Could not create the '$type' method for " . $self->name . " because : $@" if $@;
3545c727 392 $self->associate_method($method);
ba38bf08 393 return ($accessor, $method);
1d68af04 394 }
9ec169fe 395}
396
397sub install_accessors {
c0cbf4d9 398 my $self = shift;
399 my $inline = shift;
400 my $class = $self->associated_class;
1d68af04 401
9ec169fe 402 $class->add_method(
45a183fb 403 $self->_process_accessors('accessor' => $self->accessor(), $inline)
9ec169fe 404 ) if $self->has_accessor();
405
1d68af04 406 $class->add_method(
45a183fb 407 $self->_process_accessors('reader' => $self->reader(), $inline)
9ec169fe 408 ) if $self->has_reader();
409
410 $class->add_method(
45a183fb 411 $self->_process_accessors('writer' => $self->writer(), $inline)
9ec169fe 412 ) if $self->has_writer();
413
414 $class->add_method(
45a183fb 415 $self->_process_accessors('predicate' => $self->predicate(), $inline)
9ec169fe 416 ) if $self->has_predicate();
1d68af04 417
7d28758b 418 $class->add_method(
45a183fb 419 $self->_process_accessors('clearer' => $self->clearer(), $inline)
7d28758b 420 ) if $self->has_clearer();
1d68af04 421
9ec169fe 422 return;
2eb717d5 423}
424
b51af7f9 425{
426 my $_remove_accessor = sub {
427 my ($accessor, $class) = @_;
9b522fc4 428 if (ref($accessor) && ref($accessor) eq 'HASH') {
c50c603e 429 ($accessor) = keys %{$accessor};
1d68af04 430 }
431 my $method = $class->get_method($accessor);
432 $class->remove_method($accessor)
b3fa93c7 433 if (ref($method) && $method->isa('Class::MOP::Method::Accessor'));
b51af7f9 434 };
1d68af04 435
b51af7f9 436 sub remove_accessors {
9ec169fe 437 my $self = shift;
2367814a 438 # TODO:
1d68af04 439 # we really need to make sure to remove from the
440 # associates methods here as well. But this is
441 # such a slimly used method, I am not worried
2367814a 442 # about it right now.
9ec169fe 443 $_remove_accessor->($self->accessor(), $self->associated_class()) if $self->has_accessor();
444 $_remove_accessor->($self->reader(), $self->associated_class()) if $self->has_reader();
445 $_remove_accessor->($self->writer(), $self->associated_class()) if $self->has_writer();
446 $_remove_accessor->($self->predicate(), $self->associated_class()) if $self->has_predicate();
7d28758b 447 $_remove_accessor->($self->clearer(), $self->associated_class()) if $self->has_clearer();
1d68af04 448 return;
b51af7f9 449 }
450
8b978dd5 451}
452
4531;
454
455__END__
456
457=pod
458
1d68af04 459=head1 NAME
8b978dd5 460
461Class::MOP::Attribute - Attribute Meta Object
462
463=head1 SYNOPSIS
1d68af04 464
2e23f7dc 465 Class::MOP::Attribute->new(
466 foo => (
467 accessor => 'foo', # dual purpose get/set accessor
468 predicate => 'has_foo', # predicate check for defined-ness
469 init_arg => '-foo', # class->new will look for a -foo key
470 default => 'BAR IS BAZ!' # if no -foo key is provided, use this
471 )
472 );
473
474 Class::MOP::Attribute->new(
475 bar => (
476 reader => 'bar', # getter
477 writer => 'set_bar', # setter
478 predicate => 'has_bar', # predicate check for defined-ness
479 init_arg => ':bar', # class->new will look for a :bar key
480 # no default value means it is undef
481 )
482 );
8b978dd5 483
484=head1 DESCRIPTION
485
2e23f7dc 486The Attribute Protocol is almost entirely an invention of
487C<Class::MOP>. Perl 5 does not have a consistent notion of
488attributes. There are so many ways in which this is done, and very few
489(if any) are easily discoverable by this module.
552e3d24 490
2e23f7dc 491With that said, this module attempts to inject some order into this
1d68af04 492chaos, by introducing a consistent API which can be used to create
fe122940 493object attributes.
552e3d24 494
495=head1 METHODS
496
497=head2 Creation
498
499=over 4
500
2e23f7dc 501=item B<< Class::MOP::Attribute->new($name, ?%options) >>
fe122940 502
1d68af04 503An attribute must (at the very least), have a C<$name>. All other
2e23f7dc 504C<%options> are added as key-value pairs.
fe122940 505
2e23f7dc 506=over 8
fe122940 507
76187047 508=item * init_arg
fe122940 509
2e23f7dc 510This is a string value representing the expected key in an
511initialization hash. For instance, if we have an C<init_arg> value of
512C<-foo>, then the following code will Just Work.
fe122940 513
d69fb6b3 514 MyClass->meta->new_object( -foo => 'Hello There' );
fe122940 515
2e23f7dc 516If an init_arg is not assigned, it will automatically use the
517attribute's name. If C<init_arg> is explicitly set to C<undef>, the
518attribute cannot be specified during initialization.
7b31baf4 519
76187047 520=item * builder
1d68af04 521
2e23f7dc 522This provides the name of a method that will be called to initialize
523the attribute. This method will be called on the object after it is
524constructed. It is expected to return a valid value for the attribute.
fe122940 525
76187047 526=item * default
4c4a6c41 527
2e23f7dc 528This can be used to provide an explicit default for initializing the
529attribute. If the default you provide is a subroutine reference, then
530this reference will be called I<as a method> on the object.
4c4a6c41 531
2e23f7dc 532If the value is a simple scalar (string or number), then it can be
533just passed as is. However, if you wish to initialize it with a HASH
534or ARRAY ref, then you need to wrap that inside a subroutine
535reference:
fe122940 536
2e23f7dc 537 Class::MOP::Attribute->new(
538 'foo' => (
539 default => sub { [] },
540 )
541 );
1d68af04 542
543 # or ...
544
2e23f7dc 545 Class::MOP::Attribute->new(
546 'foo' => (
547 default => sub { {} },
548 )
549 );
550
551If you wish to initialize an attribute with a subroutine reference
552itself, then you need to wrap that in a subroutine as well:
553
554 Class::MOP::Attribute->new(
555 'foo' => (
556 default => sub {
557 sub { print "Hello World" }
558 },
559 )
560 );
561
562And lastly, if the value of your attribute is dependent upon some
563other aspect of the instance structure, then you can take advantage of
564the fact that when the C<default> value is called as a method:
565
566 Class::MOP::Attribute->new(
567 'object_identity' => (
568 default => sub { Scalar::Util::refaddr( $_[0] ) },
569 )
570 );
571
572Note that there is no guarantee that attributes are initialized in any
573particular order, so you cannot rely on the value of some other
574attribute when generating the default.
fe122940 575
76187047 576=item * initializer
0ef07b33 577
2e23f7dc 578This option can be either a method name or a subroutine
579reference. This method will be called when setting the attribute's
580value in the constructor. Unlike C<default> and C<builder>, the
581initializer is only called when a value is provided to the
582constructor. The initializer allows you to munge this value during
583object construction.
584
585The initializer is called as a method with three arguments. The first
586is the value that was passed to the constructor. The second is a
587subroutine reference that can be called to actually set the
588attribute's value, and the last is the associated
589C<Class::MOP::Attribute> object.
590
591This contrived example shows an initializer that sets the attribute to
592twice the given value.
593
594 Class::MOP::Attribute->new(
595 'doubled' => (
596 initializer => sub {
ea62c8ab 597 my ( $self, $value, $set, $attr ) = @_;
2e23f7dc 598 $set->( $value * 2 );
599 },
600 )
601 );
602
603Since an initializer can be a method name, you can easily make
0ef07b33 604attribute initialization use the writer:
605
2e23f7dc 606 Class::MOP::Attribute->new(
607 'some_attr' => (
608 writer => 'some_attr',
609 initializer => 'some_attr',
610 )
611 );
0ef07b33 612
2e23f7dc 613Your writer will need to examine C<@_> and determine under which
614context it is being called.
127d39a7 615
fe122940 616=back
617
2e23f7dc 618The C<accessor>, C<reader>, C<writer>, C<predicate> and C<clearer>
619options all accept the same parameters. You can provide the name of
620the method, in which case an appropriate default method will be
621generated for you. Or instead you can also provide hash reference
622containing exactly one key (the method name) and one value. The value
623should be a subroutine reference, which will be installed as the
624method itself.
59e7697f 625
76187047 626=over 8
59e7697f 627
76187047 628=item * accessor
59e7697f 629
2e23f7dc 630An C<accessor> is a standard Perl-style read/write accessor. It will
631return the value of the attribute, and if a value is passed as an
632argument, it will assign that value to the attribute.
fe122940 633
2e23f7dc 634Note that C<undef> is a legitimate value, so this will work:
fe122940 635
636 $object->set_something(undef);
637
76187047 638=item * reader
59e7697f 639
2e23f7dc 640This is a basic read-only accessor. It returns the value of the
641attribute.
fe122940 642
76187047 643=item * writer
59e7697f 644
1d68af04 645This is a basic write accessor, it accepts a single argument, and
2e23f7dc 646assigns that value to the attribute.
59e7697f 647
2e23f7dc 648Note that C<undef> is a legitimate value, so this will work:
59e7697f 649
2e23f7dc 650 $object->set_something(undef);
fe122940 651
76187047 652=item * predicate
fe122940 653
2e23f7dc 654The predicate method returns a boolean indicating whether or not the
655attribute has been explicitly set.
07dca7e3 656
2e23f7dc 657Note that the predicate returns true even if the attribute was set to
658a false value (C<0> or C<undef>).
07dca7e3 659
76187047 660=item * clearer
7d28758b 661
2e23f7dc 662This method will uninitialize the attribute. After an attribute is
663cleared, its C<predicate> will return false.
7d28758b 664
76187047 665=item * definition_context
f8813817 666
667Mostly, this exists as a hook for the benefit of Moose.
668
669This option should be a hash reference containing several keys which
670will be used when inlining the attribute's accessors. The keys should
671include C<line>, the line number where the attribute was created, and
672either C<file> or C<description>.
673
674This information will ultimately be used when eval'ing inlined
675accessor code so that error messages report a useful line and file
676name.
677
59e7697f 678=back
552e3d24 679
2e23f7dc 680=item B<< $attr->clone(%options) >>
bd4e03f9 681
2e23f7dc 682This clones the attribute. Any options you provide will override the
683settings of the original attribute. You can change the name of the new
684attribute by passing a C<name> key in C<%options>.
127d39a7 685
2e23f7dc 686=back
bd4e03f9 687
2e23f7dc 688=head2 Informational
127d39a7 689
2e23f7dc 690These are all basic read-only accessors for the values passed into
691the constructor.
552e3d24 692
2e23f7dc 693=over 4
16e960bd 694
2e23f7dc 695=item B<< $attr->name >>
2367814a 696
76187047 697Returns the attribute's name.
698
2e23f7dc 699=item B<< $attr->accessor >>
2367814a 700
2e23f7dc 701=item B<< $attr->reader >>
16e960bd 702
2e23f7dc 703=item B<< $attr->writer >>
16e960bd 704
2e23f7dc 705=item B<< $attr->predicate >>
16e960bd 706
2e23f7dc 707=item B<< $attr->clearer >>
c0921932 708
2e23f7dc 709The C<accessor>, C<reader>, C<writer>, C<predicate>, and C<clearer>
710methods all return exactly what was passed to the constructor, so it
a6710c60 711can be either a string containing a method name, or a hash reference.
c0921932 712
2e23f7dc 713=item B<< $attr->initializer >>
16e960bd 714
a6710c60 715Returns the initializer as passed to the constructor, so this may be
2e23f7dc 716either a method name or a subroutine reference.
16e960bd 717
2e23f7dc 718=item B<< $attr->init_arg >>
3545c727 719
2e23f7dc 720=item B<< $attr->is_default_a_coderef >>
2367814a 721
2e23f7dc 722=item B<< $attr->default($instance) >>
3545c727 723
2e23f7dc 724The C<$instance> argument is optional. If you don't pass it, the
725return value for this method is exactly what was passed to the
726constructor, either a simple scalar or a subroutine reference.
2367814a 727
2e23f7dc 728If you I<do> pass an C<$instance> and the default is a subroutine
729reference, then the reference is called as a method on the
730C<$instance> and the generated value is returned.
16e960bd 731
2e23f7dc 732=item B<< $attr->slots >>
552e3d24 733
2e23f7dc 734Return a list of slots required by the attribute. This is usually just
735one, the name of the attribute.
fe122940 736
2e23f7dc 737A slot is the name of the hash key used to store the attribute in an
738object instance.
552e3d24 739
2e23f7dc 740=item B<< $attr->get_read_method >>
552e3d24 741
2e23f7dc 742=item B<< $attr->get_write_method >>
552e3d24 743
2e23f7dc 744Returns the name of a method suitable for reading or writing the value
745of the attribute in the associated class.
552e3d24 746
2e23f7dc 747If an attribute is read- or write-only, then these methods can return
748C<undef> as appropriate.
552e3d24 749
2e23f7dc 750=item B<< $attr->has_read_method >>
c50c603e 751
2e23f7dc 752=item B<< $attr->has_write_method >>
7d28758b 753
2e23f7dc 754This returns a boolean indicating whether the attribute has a I<named>
755read or write method.
0ab65f99 756
2e23f7dc 757=item B<< $attr->get_read_method_ref >>
552e3d24 758
2e23f7dc 759=item B<< $attr->get_write_method_ref >>
495af518 760
2e23f7dc 761Returns the subroutine reference of a method suitable for reading or
762writing the attribute's value in the associated class. These methods
763always return a subroutine reference, regardless of whether or not the
764attribute is read- or write-only.
765
eeff7496 766=item B<< $attr->insertion_order >>
767
768If this attribute has been inserted into a class, this returns a zero
769based index regarding the order of insertion.
770
2e23f7dc 771=back
fe122940 772
2e23f7dc 773=head2 Informational predicates
92d2abfa 774
2e23f7dc 775These are all basic predicate methods for the values passed into C<new>.
552e3d24 776
2e23f7dc 777=over 4
c57c8b10 778
2e23f7dc 779=item B<< $attr->has_accessor >>
c57c8b10 780
2e23f7dc 781=item B<< $attr->has_reader >>
b25109b1 782
2e23f7dc 783=item B<< $attr->has_writer >>
b25109b1 784
2e23f7dc 785=item B<< $attr->has_predicate >>
5da16d1b 786
2e23f7dc 787=item B<< $attr->has_clearer >>
5da16d1b 788
2e23f7dc 789=item B<< $attr->has_initializer >>
5da16d1b 790
2e23f7dc 791=item B<< $attr->has_init_arg >>
5da16d1b 792
2e23f7dc 793This will be I<false> if the C<init_arg> was set to C<undef>.
b25109b1 794
2e23f7dc 795=item B<< $attr->has_default >>
9e517e01 796
2e23f7dc 797This will be I<false> if the C<default> was set to C<undef>, since
798C<undef> is the default C<default> anyway.
9e517e01 799
2e23f7dc 800=item B<< $attr->has_builder >>
9e517e01 801
eeff7496 802=item B<< $attr->has_insertion_order >>
803
804This will be I<false> if this attribute has not be inserted into a class
805
552e3d24 806=back
807
2e23f7dc 808=head2 Value management
552e3d24 809
a6710c60 810These methods are basically "back doors" to the instance, and can be
2e23f7dc 811used to bypass the regular accessors, but still stay within the MOP.
812
813These methods are not for general use, and should only be used if you
814really know what you are doing.
fe122940 815
552e3d24 816=over 4
817
2e23f7dc 818=item B<< $attr->initialize_instance_slot($meta_instance, $instance, $params) >>
819
820This method is used internally to initialize the attribute's slot in
821the object C<$instance>.
822
823The C<$params> is a hash reference of the values passed to the object
824constructor.
825
826It's unlikely that you'll need to call this method yourself.
552e3d24 827
2e23f7dc 828=item B<< $attr->set_value($instance, $value) >>
552e3d24 829
2e23f7dc 830Sets the value without going through the accessor. Note that this
831works even with read-only attributes.
552e3d24 832
7e5efe15 833=item B<< $attr->set_raw_value($instance, $value) >>
834
835Sets the value with no side effects such as a trigger.
836
837This doesn't actually apply to Class::MOP attributes, only to subclasses.
838
2e23f7dc 839=item B<< $attr->set_initial_value($instance, $value) >>
c50c603e 840
2e23f7dc 841Sets the value without going through the accessor. This method is only
842called when the instance is first being initialized.
7d28758b 843
2e23f7dc 844=item B<< $attr->get_value($instance) >>
0ab65f99 845
2e23f7dc 846Returns the value without going through the accessor. Note that this
847works even with write-only accessors.
552e3d24 848
7e5efe15 849=item B<< $sttr->get_raw_value($instance) >>
850
851Returns the value without any side effects such as lazy attributes.
852
853Doesn't actually apply to Class::MOP attributes, only to subclasses.
854
2e23f7dc 855=item B<< $attr->has_value($instance) >>
552e3d24 856
2e23f7dc 857Return a boolean indicating whether the attribute has been set in
858C<$instance>. This how the default C<predicate> method works.
859
860=item B<< $attr->clear_value($instance) >>
861
862This will clear the attribute's value in C<$instance>. This is what
863the default C<clearer> calls.
864
865Note that this works even if the attribute does not have any
866associated read, write or clear methods.
bf731086 867
552e3d24 868=back
869
9ec169fe 870=head2 Class association
871
1d68af04 872These methods allow you to manage the attributes association with
873the class that contains it. These methods should not be used
2367814a 874lightly, nor are they very magical, they are mostly used internally
875and by metaclass instances.
876
9ec169fe 877=over 4
878
2e23f7dc 879=item B<< $attr->associated_class >>
880
881This returns the C<Class::MOP::Class> with which this attribute is
882associated, if any.
883
884=item B<< $attr->attach_to_class($metaclass) >>
9ec169fe 885
2e23f7dc 886This method stores a weakened reference to the C<$metaclass> object
887internally.
2367814a 888
2e23f7dc 889This method does not remove the attribute from its old class,
890nor does it create any accessors in the new class.
9ec169fe 891
2e23f7dc 892It is probably best to use the L<Class::MOP::Class> C<add_attribute>
893method instead.
2367814a 894
2e23f7dc 895=item B<< $attr->detach_from_class >>
9ec169fe 896
2e23f7dc 897This method removes the associate metaclass object from the attribute
898it has one.
899
900This method does not remove the attribute itself from the class, or
901remove its accessors.
902
903It is probably best to use the L<Class::MOP::Class>
904C<remove_attribute> method instead.
2367814a 905
9ec169fe 906=back
907
552e3d24 908=head2 Attribute Accessor generation
909
910=over 4
911
2e23f7dc 912=item B<< $attr->accessor_metaclass >>
ba38bf08 913
2e23f7dc 914Accessor methods are generated using an accessor metaclass. By
915default, this is L<Class::MOP::Method::Accessor>. This method returns
2367814a 916the name of the accessor metaclass that this attribute uses.
917
2e23f7dc 918=item B<< $attr->associate_method($method) >>
2367814a 919
2e23f7dc 920This associates a L<Class::MOP::Method> object with the
921attribute. Typically, this is called internally when an attribute
922generates its accessors.
3545c727 923
2e23f7dc 924=item B<< $attr->associated_methods >>
3545c727 925
2e23f7dc 926This returns the list of methods which have been associated with the
927attribute.
2367814a 928
2e23f7dc 929=item B<< $attr->install_accessors >>
2eb717d5 930
2e23f7dc 931This method generates and installs code the attributes various
932accessors. It is typically called from the L<Class::MOP::Class>
933C<add_attribute> method.
2eb717d5 934
2e23f7dc 935=item B<< $attr->remove_accessors >>
2eb717d5 936
2e23f7dc 937This method removes all of the accessors associated with the
938attribute.
2eb717d5 939
2e23f7dc 940This does not currently remove methods from the list returned by
941C<associated_methods>.
2367814a 942
2eb717d5 943=back
944
945=head2 Introspection
946
947=over 4
552e3d24 948
45b4c423 949=item B<< Class::MOP::Attribute->meta >>
552e3d24 950
2e23f7dc 951This will return a L<Class::MOP::Class> instance for this class.
fe122940 952
2e23f7dc 953It should also be noted that L<Class::MOP> will actually bootstrap
954this module by installing a number of attribute meta-objects into its
955metaclass.
fe122940 956
552e3d24 957=back
958
1a09d9cc 959=head1 AUTHORS
8b978dd5 960
a2e85e6c 961Stevan Little E<lt>stevan@iinteractive.comE<gt>
8b978dd5 962
963=head1 COPYRIGHT AND LICENSE
964
070bb6c9 965Copyright 2006-2009 by Infinity Interactive, Inc.
8b978dd5 966
967L<http://www.iinteractive.com>
968
969This library is free software; you can redistribute it and/or modify
1d68af04 970it under the same terms as Perl itself.
8b978dd5 971
16e960bd 972=cut
973
7d28758b 974