This file is indexed.

/usr/lib/perl5/Class/MOP/Attribute.pm is in libmoose-perl 2.0401-1.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
package Class::MOP::Attribute;
BEGIN {
  $Class::MOP::Attribute::AUTHORITY = 'cpan:STEVAN';
}
{
  $Class::MOP::Attribute::VERSION = '2.0401';
}

use strict;
use warnings;

use Class::MOP::Method::Accessor;

use Carp         'confess';
use Scalar::Util 'blessed', 'weaken';
use Try::Tiny;

use base 'Class::MOP::Object', 'Class::MOP::Mixin::AttributeCore';

# NOTE: (meta-circularity)
# This method will be replaced in the
# boostrap section of Class::MOP, by
# a new version which uses the
# &Class::MOP::Class::construct_instance
# method to build an attribute meta-object
# which itself is described with attribute
# meta-objects.
#     - Ain't meta-circularity grand? :)
sub new {
    my ( $class, @args ) = @_;

    unshift @args, "name" if @args % 2 == 1;
    my %options = @args;

    my $name = $options{name};

    (defined $name)
        || confess "You must provide a name for the attribute";

    $options{init_arg} = $name
        if not exists $options{init_arg};
    if(exists $options{builder}){
        confess("builder must be a defined scalar value which is a method name")
            if ref $options{builder} || !(defined $options{builder});
        confess("Setting both default and builder is not allowed.")
            if exists $options{default};
    } else {
        ($class->is_default_a_coderef(\%options))
            || confess("References are not allowed as default values, you must ".
                       "wrap the default of '$name' in a CODE reference (ex: sub { [] } and not [])")
                if exists $options{default} && ref $options{default};
    }
    if( $options{required} and not( defined($options{builder}) || defined($options{init_arg}) || exists $options{default} ) ) {
        confess("A required attribute must have either 'init_arg', 'builder', or 'default'");
    }

    $class->_new(\%options);
}

sub _new {
    my $class = shift;

    return Class::MOP::Class->initialize($class)->new_object(@_)
        if $class ne __PACKAGE__;

    my $options = @_ == 1 ? $_[0] : {@_};

    bless {
        'name'               => $options->{name},
        'accessor'           => $options->{accessor},
        'reader'             => $options->{reader},
        'writer'             => $options->{writer},
        'predicate'          => $options->{predicate},
        'clearer'            => $options->{clearer},
        'builder'            => $options->{builder},
        'init_arg'           => $options->{init_arg},
        exists $options->{default}
            ? ('default'     => $options->{default})
            : (),
        'initializer'        => $options->{initializer},
        'definition_context' => $options->{definition_context},
        # keep a weakened link to the
        # class we are associated with
        'associated_class' => undef,
        # and a list of the methods
        # associated with this attr
        'associated_methods' => [],
        # this let's us keep track of
        # our order inside the associated
        # class
        'insertion_order'    => undef,
    }, $class;
}

# NOTE:
# this is a primative (and kludgy) clone operation
# for now, it will be replaced in the Class::MOP
# bootstrap with a proper one, however we know
# that this one will work fine for now.
sub clone {
    my $self    = shift;
    my %options = @_;
    (blessed($self))
        || confess "Can only clone an instance";
    return bless { %{$self}, %options } => ref($self);
}

sub initialize_instance_slot {
    my ($self, $meta_instance, $instance, $params) = @_;
    my $init_arg = $self->{'init_arg'};

    # try to fetch the init arg from the %params ...

    # if nothing was in the %params, we can use the
    # attribute's default value (if it has one)
    if(defined $init_arg and exists $params->{$init_arg}){
        $self->_set_initial_slot_value(
            $meta_instance,
            $instance,
            $params->{$init_arg},
        );
    }
    elsif (exists $self->{'default'}) {
        $self->_set_initial_slot_value(
            $meta_instance,
            $instance,
            $self->default($instance),
        );
    }
    elsif (defined( my $builder = $self->{'builder'})) {
        if ($builder = $instance->can($builder)) {
            $self->_set_initial_slot_value(
                $meta_instance,
                $instance,
                $instance->$builder,
            );
        }
        else {
            confess(ref($instance)." does not support builder method '". $self->{'builder'} ."' for attribute '" . $self->name . "'");
        }
    }
}

sub _set_initial_slot_value {
    my ($self, $meta_instance, $instance, $value) = @_;

    my $slot_name = $self->name;

    return $meta_instance->set_slot_value($instance, $slot_name, $value)
        unless $self->has_initializer;

    my $callback = $self->_make_initializer_writer_callback(
        $meta_instance, $instance, $slot_name
    );

    my $initializer = $self->initializer;

    # most things will just want to set a value, so make it first arg
    $instance->$initializer($value, $callback, $self);
}

sub _make_initializer_writer_callback {
    my $self = shift;
    my ($meta_instance, $instance, $slot_name) = @_;

    return sub {
        $meta_instance->set_slot_value($instance, $slot_name, $_[0]);
    };
}

sub get_read_method  {
    my $self   = shift;
    my $reader = $self->reader || $self->accessor;
    # normal case ...
    return $reader unless ref $reader;
    # the HASH ref case
    my ($name) = %$reader;
    return $name;
}

sub get_write_method {
    my $self   = shift;
    my $writer = $self->writer || $self->accessor;
    # normal case ...
    return $writer unless ref $writer;
    # the HASH ref case
    my ($name) = %$writer;
    return $name;
}

sub get_read_method_ref {
    my $self = shift;
    if ((my $reader = $self->get_read_method) && $self->associated_class) {
        return $self->associated_class->get_method($reader);
    }
    else {
        my $code = sub { $self->get_value(@_) };
        if (my $class = $self->associated_class) {
            return $class->method_metaclass->wrap(
                $code,
                package_name => $class->name,
                name         => '__ANON__'
            );
        }
        else {
            return $code;
        }
    }
}

sub get_write_method_ref {
    my $self = shift;
    if ((my $writer = $self->get_write_method) && $self->associated_class) {
        return $self->associated_class->get_method($writer);
    }
    else {
        my $code = sub { $self->set_value(@_) };
        if (my $class = $self->associated_class) {
            return $class->method_metaclass->wrap(
                $code,
                package_name => $class->name,
                name         => '__ANON__'
            );
        }
        else {
            return $code;
        }
    }
}

# slots

sub slots { (shift)->name }

# class association

sub attach_to_class {
    my ($self, $class) = @_;
    (blessed($class) && $class->isa('Class::MOP::Class'))
        || confess "You must pass a Class::MOP::Class instance (or a subclass)";
    weaken($self->{'associated_class'} = $class);
}

sub detach_from_class {
    my $self = shift;
    $self->{'associated_class'} = undef;
}

# method association

sub associate_method {
    my ($self, $method) = @_;
    push @{$self->{'associated_methods'}} => $method;
}

## Slot management

sub set_initial_value {
    my ($self, $instance, $value) = @_;
    $self->_set_initial_slot_value(
        Class::MOP::Class->initialize(ref($instance))->get_meta_instance,
        $instance,
        $value
    );
}

sub set_value { shift->set_raw_value(@_) }

sub set_raw_value {
    my $self = shift;
    my ($instance, $value) = @_;

    my $mi = Class::MOP::Class->initialize(ref($instance))->get_meta_instance;
    return $mi->set_slot_value($instance, $self->name, $value);
}

sub _inline_set_value {
    my $self = shift;
    return $self->_inline_instance_set(@_) . ';';
}

sub _inline_instance_set {
    my $self = shift;
    my ($instance, $value) = @_;

    my $mi = $self->associated_class->get_meta_instance;
    return $mi->inline_set_slot_value($instance, $self->name, $value);
}

sub get_value { shift->get_raw_value(@_) }

sub get_raw_value {
    my $self = shift;
    my ($instance) = @_;

    my $mi = Class::MOP::Class->initialize(ref($instance))->get_meta_instance;
    return $mi->get_slot_value($instance, $self->name);
}

sub _inline_get_value {
    my $self = shift;
    return $self->_inline_instance_get(@_) . ';';
}

sub _inline_instance_get {
    my $self = shift;
    my ($instance) = @_;

    my $mi = $self->associated_class->get_meta_instance;
    return $mi->inline_get_slot_value($instance, $self->name);
}

sub has_value {
    my $self = shift;
    my ($instance) = @_;

    my $mi = Class::MOP::Class->initialize(ref($instance))->get_meta_instance;
    return $mi->is_slot_initialized($instance, $self->name);
}

sub _inline_has_value {
    my $self = shift;
    return $self->_inline_instance_has(@_) . ';';
}

sub _inline_instance_has {
    my $self = shift;
    my ($instance) = @_;

    my $mi = $self->associated_class->get_meta_instance;
    return $mi->inline_is_slot_initialized($instance, $self->name);
}

sub clear_value {
    my $self = shift;
    my ($instance) = @_;

    my $mi = Class::MOP::Class->initialize(ref($instance))->get_meta_instance;
    return $mi->deinitialize_slot($instance, $self->name);
}

sub _inline_clear_value {
    my $self = shift;
    return $self->_inline_instance_clear(@_) . ';';
}

sub _inline_instance_clear {
    my $self = shift;
    my ($instance) = @_;

    my $mi = $self->associated_class->get_meta_instance;
    return $mi->inline_deinitialize_slot($instance, $self->name);
}

## load em up ...

sub accessor_metaclass { 'Class::MOP::Method::Accessor' }

sub _process_accessors {
    my ($self, $type, $accessor, $generate_as_inline_methods) = @_;

    my $method_ctx = { %{ $self->definition_context || {} } };

    if (ref($accessor)) {
        (ref($accessor) eq 'HASH')
            || confess "bad accessor/reader/writer/predicate/clearer format, must be a HASH ref";
        my ($name, $method) = %{$accessor};

        $method_ctx->{description} = $self->_accessor_description($name, $type);

        $method = $self->accessor_metaclass->wrap(
            $method,
            attribute    => $self,
            package_name => $self->associated_class->name,
            name         => $name,
            associated_metaclass => $self->associated_class,
            definition_context => $method_ctx,
        );
        $self->associate_method($method);
        return ($name, $method);
    }
    else {
        my $inline_me = ($generate_as_inline_methods && $self->associated_class->instance_metaclass->is_inlinable);
        my $method;
        try {
            $method_ctx->{description} = $self->_accessor_description($accessor, $type);

            $method = $self->accessor_metaclass->new(
                attribute     => $self,
                is_inline     => $inline_me,
                accessor_type => $type,
                package_name  => $self->associated_class->name,
                name          => $accessor,
                associated_metaclass => $self->associated_class,
                definition_context => $method_ctx,
            );
        }
        catch {
            confess "Could not create the '$type' method for " . $self->name . " because : $_";
        };
        $self->associate_method($method);
        return ($accessor, $method);
    }
}

sub _accessor_description {
    my $self = shift;
    my ($name, $type) = @_;

    my $desc = "$type " . $self->associated_class->name . "::$name";
    if ( $name ne $self->name ) {
        $desc .= " of attribute " . $self->name;
    }

    return $desc;
}

sub install_accessors {
    my $self   = shift;
    my $inline = shift;
    my $class  = $self->associated_class;

    $class->add_method(
        $self->_process_accessors('accessor' => $self->accessor(), $inline)
    ) if $self->has_accessor();

    $class->add_method(
        $self->_process_accessors('reader' => $self->reader(), $inline)
    ) if $self->has_reader();

    $class->add_method(
        $self->_process_accessors('writer' => $self->writer(), $inline)
    ) if $self->has_writer();

    $class->add_method(
        $self->_process_accessors('predicate' => $self->predicate(), $inline)
    ) if $self->has_predicate();

    $class->add_method(
        $self->_process_accessors('clearer' => $self->clearer(), $inline)
    ) if $self->has_clearer();

    return;
}

{
    my $_remove_accessor = sub {
        my ($accessor, $class) = @_;
        if (ref($accessor) && ref($accessor) eq 'HASH') {
            ($accessor) = keys %{$accessor};
        }
        my $method = $class->get_method($accessor);
        $class->remove_method($accessor)
            if (ref($method) && $method->isa('Class::MOP::Method::Accessor'));
    };

    sub remove_accessors {
        my $self = shift;
        # TODO:
        # we really need to make sure to remove from the
        # associates methods here as well. But this is
        # such a slimly used method, I am not worried
        # about it right now.
        $_remove_accessor->($self->accessor(),  $self->associated_class()) if $self->has_accessor();
        $_remove_accessor->($self->reader(),    $self->associated_class()) if $self->has_reader();
        $_remove_accessor->($self->writer(),    $self->associated_class()) if $self->has_writer();
        $_remove_accessor->($self->predicate(), $self->associated_class()) if $self->has_predicate();
        $_remove_accessor->($self->clearer(),   $self->associated_class()) if $self->has_clearer();
        return;
    }

}

1;

# ABSTRACT: Attribute Meta Object



=pod

=head1 NAME

Class::MOP::Attribute - Attribute Meta Object

=head1 VERSION

version 2.0401

=head1 SYNOPSIS

  Class::MOP::Attribute->new(
      foo => (
          accessor  => 'foo',           # dual purpose get/set accessor
          predicate => 'has_foo',       # predicate check for defined-ness
          init_arg  => '-foo',          # class->new will look for a -foo key
          default   => 'BAR IS BAZ!'    # if no -foo key is provided, use this
      )
  );

  Class::MOP::Attribute->new(
      bar => (
          reader    => 'bar',           # getter
          writer    => 'set_bar',       # setter
          predicate => 'has_bar',       # predicate check for defined-ness
          init_arg  => ':bar',          # class->new will look for a :bar key
                                        # no default value means it is undef
      )
  );

=head1 DESCRIPTION

The Attribute Protocol is almost entirely an invention of
C<Class::MOP>. Perl 5 does not have a consistent notion of
attributes. There are so many ways in which this is done, and very few
(if any) are easily discoverable by this module.

With that said, this module attempts to inject some order into this
chaos, by introducing a consistent API which can be used to create
object attributes.

=head1 METHODS

=head2 Creation

=over 4

=item B<< Class::MOP::Attribute->new($name, ?%options) >>

An attribute must (at the very least), have a C<$name>. All other
C<%options> are added as key-value pairs.

=over 8

=item * init_arg

This is a string value representing the expected key in an
initialization hash. For instance, if we have an C<init_arg> value of
C<-foo>, then the following code will Just Work.

  MyClass->meta->new_object( -foo => 'Hello There' );

If an init_arg is not assigned, it will automatically use the
attribute's name. If C<init_arg> is explicitly set to C<undef>, the
attribute cannot be specified during initialization.

=item * builder

This provides the name of a method that will be called to initialize
the attribute. This method will be called on the object after it is
constructed. It is expected to return a valid value for the attribute.

=item * default

This can be used to provide an explicit default for initializing the
attribute. If the default you provide is a subroutine reference, then
this reference will be called I<as a method> on the object.

If the value is a simple scalar (string or number), then it can be
just passed as is. However, if you wish to initialize it with a HASH
or ARRAY ref, then you need to wrap that inside a subroutine
reference:

  Class::MOP::Attribute->new(
      'foo' => (
          default => sub { [] },
      )
  );

  # or ...

  Class::MOP::Attribute->new(
      'foo' => (
          default => sub { {} },
      )
  );

If you wish to initialize an attribute with a subroutine reference
itself, then you need to wrap that in a subroutine as well:

  Class::MOP::Attribute->new(
      'foo' => (
          default => sub {
              sub { print "Hello World" }
          },
      )
  );

And lastly, if the value of your attribute is dependent upon some
other aspect of the instance structure, then you can take advantage of
the fact that when the C<default> value is called as a method:

  Class::MOP::Attribute->new(
      'object_identity' => (
          default => sub { Scalar::Util::refaddr( $_[0] ) },
      )
  );

Note that there is no guarantee that attributes are initialized in any
particular order, so you cannot rely on the value of some other
attribute when generating the default.

=item * initializer

This option can be either a method name or a subroutine
reference. This method will be called when setting the attribute's
value in the constructor. Unlike C<default> and C<builder>, the
initializer is only called when a value is provided to the
constructor. The initializer allows you to munge this value during
object construction.

The initializer is called as a method with three arguments. The first
is the value that was passed to the constructor. The second is a
subroutine reference that can be called to actually set the
attribute's value, and the last is the associated
C<Class::MOP::Attribute> object.

This contrived example shows an initializer that sets the attribute to
twice the given value.

  Class::MOP::Attribute->new(
      'doubled' => (
          initializer => sub {
              my ( $self, $value, $set, $attr ) = @_;
              $set->( $value * 2 );
          },
      )
  );

Since an initializer can be a method name, you can easily make
attribute initialization use the writer:

  Class::MOP::Attribute->new(
      'some_attr' => (
          writer      => 'some_attr',
          initializer => 'some_attr',
      )
  );

Your writer (actually, a wrapper around the writer, using
L<method modifications|Moose::Manual::MethodModifiers>) will need to examine
C<@_> and determine under which
context it is being called:

  around 'some_attr' => sub {
      my $orig = shift;
      my $self = shift;
      # $value is not defined if being called as a reader
      # $setter and $attr are only defined if being called as an initializer
      my ($value, $setter, $attr) = @_;

      # the reader behaves normally
      return $self->$orig if not @_;

      # mutate $value as desired
      # $value = <something($value);

      # if called as an initializer, set the value and we're done
      return $setter->($row) if $setter;

      # otherwise, call the real writer with the new value
      $self->$orig($row);
  };

=back

The C<accessor>, C<reader>, C<writer>, C<predicate> and C<clearer>
options all accept the same parameters. You can provide the name of
the method, in which case an appropriate default method will be
generated for you. Or instead you can also provide hash reference
containing exactly one key (the method name) and one value. The value
should be a subroutine reference, which will be installed as the
method itself.

=over 8

=item * accessor

An C<accessor> is a standard Perl-style read/write accessor. It will
return the value of the attribute, and if a value is passed as an
argument, it will assign that value to the attribute.

Note that C<undef> is a legitimate value, so this will work:

  $object->set_something(undef);

=item * reader

This is a basic read-only accessor. It returns the value of the
attribute.

=item * writer

This is a basic write accessor, it accepts a single argument, and
assigns that value to the attribute.

Note that C<undef> is a legitimate value, so this will work:

  $object->set_something(undef);

=item * predicate

The predicate method returns a boolean indicating whether or not the
attribute has been explicitly set.

Note that the predicate returns true even if the attribute was set to
a false value (C<0> or C<undef>).

=item * clearer

This method will uninitialize the attribute. After an attribute is
cleared, its C<predicate> will return false.

=item * definition_context

Mostly, this exists as a hook for the benefit of Moose.

This option should be a hash reference containing several keys which
will be used when inlining the attribute's accessors. The keys should
include C<line>, the line number where the attribute was created, and
either C<file> or C<description>.

This information will ultimately be used when eval'ing inlined
accessor code so that error messages report a useful line and file
name.

=back

=item B<< $attr->clone(%options) >>

This clones the attribute. Any options you provide will override the
settings of the original attribute. You can change the name of the new
attribute by passing a C<name> key in C<%options>.

=back

=head2 Informational

These are all basic read-only accessors for the values passed into
the constructor.

=over 4

=item B<< $attr->name >>

Returns the attribute's name.

=item B<< $attr->accessor >>

=item B<< $attr->reader >>

=item B<< $attr->writer >>

=item B<< $attr->predicate >>

=item B<< $attr->clearer >>

The C<accessor>, C<reader>, C<writer>, C<predicate>, and C<clearer>
methods all return exactly what was passed to the constructor, so it
can be either a string containing a method name, or a hash reference.

=item B<< $attr->initializer >>

Returns the initializer as passed to the constructor, so this may be
either a method name or a subroutine reference.

=item B<< $attr->init_arg >>

=item B<< $attr->is_default_a_coderef >>

=item B<< $attr->default($instance) >>

The C<$instance> argument is optional. If you don't pass it, the
return value for this method is exactly what was passed to the
constructor, either a simple scalar or a subroutine reference.

If you I<do> pass an C<$instance> and the default is a subroutine
reference, then the reference is called as a method on the
C<$instance> and the generated value is returned.

=item B<< $attr->slots >>

Return a list of slots required by the attribute. This is usually just
one, the name of the attribute.

A slot is the name of the hash key used to store the attribute in an
object instance.

=item B<< $attr->get_read_method >>

=item B<< $attr->get_write_method >>

Returns the name of a method suitable for reading or writing the value
of the attribute in the associated class.

If an attribute is read- or write-only, then these methods can return
C<undef> as appropriate.

=item B<< $attr->has_read_method >>

=item B<< $attr->has_write_method >>

This returns a boolean indicating whether the attribute has a I<named>
read or write method.

=item B<< $attr->get_read_method_ref >>

=item B<< $attr->get_write_method_ref >>

Returns the subroutine reference of a method suitable for reading or
writing the attribute's value in the associated class. These methods
always return a subroutine reference, regardless of whether or not the
attribute is read- or write-only.

=item B<< $attr->insertion_order >>

If this attribute has been inserted into a class, this returns a zero
based index regarding the order of insertion.

=back

=head2 Informational predicates

These are all basic predicate methods for the values passed into C<new>.

=over 4

=item B<< $attr->has_accessor >>

=item B<< $attr->has_reader >>

=item B<< $attr->has_writer >>

=item B<< $attr->has_predicate >>

=item B<< $attr->has_clearer >>

=item B<< $attr->has_initializer >>

=item B<< $attr->has_init_arg >>

This will be I<false> if the C<init_arg> was set to C<undef>.

=item B<< $attr->has_default >>

This will be I<false> if the C<default> was set to C<undef>, since
C<undef> is the default C<default> anyway.

=item B<< $attr->has_builder >>

=item B<< $attr->has_insertion_order >>

This will be I<false> if this attribute has not be inserted into a class

=back

=head2 Value management

These methods are basically "back doors" to the instance, and can be
used to bypass the regular accessors, but still stay within the MOP.

These methods are not for general use, and should only be used if you
really know what you are doing.

=over 4

=item B<< $attr->initialize_instance_slot($meta_instance, $instance, $params) >>

This method is used internally to initialize the attribute's slot in
the object C<$instance>.

The C<$params> is a hash reference of the values passed to the object
constructor.

It's unlikely that you'll need to call this method yourself.

=item B<< $attr->set_value($instance, $value) >>

Sets the value without going through the accessor. Note that this
works even with read-only attributes.

=item B<< $attr->set_raw_value($instance, $value) >>

Sets the value with no side effects such as a trigger.

This doesn't actually apply to Class::MOP attributes, only to subclasses.

=item B<< $attr->set_initial_value($instance, $value) >>

Sets the value without going through the accessor. This method is only
called when the instance is first being initialized.

=item B<< $attr->get_value($instance) >>

Returns the value without going through the accessor. Note that this
works even with write-only accessors.

=item B<< $attr->get_raw_value($instance) >>

Returns the value without any side effects such as lazy attributes.

Doesn't actually apply to Class::MOP attributes, only to subclasses.

=item B<< $attr->has_value($instance) >>

Return a boolean indicating whether the attribute has been set in
C<$instance>. This how the default C<predicate> method works.

=item B<< $attr->clear_value($instance) >>

This will clear the attribute's value in C<$instance>. This is what
the default C<clearer> calls.

Note that this works even if the attribute does not have any
associated read, write or clear methods.

=back

=head2 Class association

These methods allow you to manage the attributes association with
the class that contains it. These methods should not be used
lightly, nor are they very magical, they are mostly used internally
and by metaclass instances.

=over 4

=item B<< $attr->associated_class >>

This returns the C<Class::MOP::Class> with which this attribute is
associated, if any.

=item B<< $attr->attach_to_class($metaclass) >>

This method stores a weakened reference to the C<$metaclass> object
internally.

This method does not remove the attribute from its old class,
nor does it create any accessors in the new class.

It is probably best to use the L<Class::MOP::Class> C<add_attribute>
method instead.

=item B<< $attr->detach_from_class >>

This method removes the associate metaclass object from the attribute
it has one.

This method does not remove the attribute itself from the class, or
remove its accessors.

It is probably best to use the L<Class::MOP::Class>
C<remove_attribute> method instead.

=back

=head2 Attribute Accessor generation

=over 4

=item B<< $attr->accessor_metaclass >>

Accessor methods are generated using an accessor metaclass. By
default, this is L<Class::MOP::Method::Accessor>. This method returns
the name of the accessor metaclass that this attribute uses.

=item B<< $attr->associate_method($method) >>

This associates a L<Class::MOP::Method> object with the
attribute. Typically, this is called internally when an attribute
generates its accessors.

=item B<< $attr->associated_methods >>

This returns the list of methods which have been associated with the
attribute.

=item B<< $attr->install_accessors >>

This method generates and installs code the attributes various
accessors. It is typically called from the L<Class::MOP::Class>
C<add_attribute> method.

=item B<< $attr->remove_accessors >>

This method removes all of the accessors associated with the
attribute.

This does not currently remove methods from the list returned by
C<associated_methods>.

=item B<< $attr->inline_get >>

=item B<< $attr->inline_set >>

=item B<< $attr->inline_has >>

=item B<< $attr->inline_clear >>

These methods return a code snippet suitable for inlining the relevant
operation. They expect strings containing variable names to be used in the
inlining, like C<'$self'> or C<'$_[1]'>.

=back

=head2 Introspection

=over 4

=item B<< Class::MOP::Attribute->meta >>

This will return a L<Class::MOP::Class> instance for this class.

It should also be noted that L<Class::MOP> will actually bootstrap
this module by installing a number of attribute meta-objects into its
metaclass.

=back

=head1 AUTHOR

Moose is maintained by the Moose Cabal, along with the help of many contributors. See L<Moose/CABAL> and L<Moose/CONTRIBUTORS> for details.

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2011 by Infinity Interactive, Inc..

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut


__END__