Source

RubyLearning / ProjectTrak / vendor / rails / activerecord / lib / active_record / validations.rb

Full commit
   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
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
module ActiveRecord
  # Raised by <tt>save!</tt> and <tt>create!</tt> when the record is invalid.  Use the
  # +record+ method to retrieve the record which did not validate.
  #   begin
  #     complex_operation_that_calls_save!_internally
  #   rescue ActiveRecord::RecordInvalid => invalid
  #     puts invalid.record.errors
  #   end
  class RecordInvalid < ActiveRecordError
    attr_reader :record
    def initialize(record)
      @record = record
      super("Validation failed: #{@record.errors.full_messages.join(", ")}")
    end
  end

  # Active Record validation is reported to and from this object, which is used by Base#save to
  # determine whether the object is in a valid state to be saved. See usage example in Validations.
  class Errors
    include Enumerable
    
    class << self
      def default_error_messages
        ActiveSupport::Deprecation.warn("ActiveRecord::Errors.default_error_messages has been deprecated. Please use I18n.translate('activerecord.errors.messages').")
        I18n.translate 'activerecord.errors.messages'
      end
    end

    def initialize(base) # :nodoc:
      @base, @errors = base, {}
    end

    # Adds an error to the base object instead of any particular attribute. This is used
    # to report errors that don't tie to any specific attribute, but rather to the object
    # as a whole. These error messages don't get prepended with any field name when iterating
    # with +each_full+, so they should be complete sentences.
    def add_to_base(msg)
      add(:base, msg)
    end

    # Adds an error message (+messsage+) to the +attribute+, which will be returned on a call to <tt>on(attribute)</tt>
    # for the same attribute and ensure that this error object returns false when asked if <tt>empty?</tt>. More than one
    # error can be added to the same +attribute+ in which case an array will be returned on a call to <tt>on(attribute)</tt>.
    # If no +messsage+ is supplied, :invalid is assumed.
    # If +message+ is a Symbol, it will be translated, using the appropriate scope (see translate_error).
    def add(attribute, message = nil, options = {})
      message ||= :invalid
      message = generate_message(attribute, message, options) if message.is_a?(Symbol)
      @errors[attribute.to_s] ||= []
      @errors[attribute.to_s] << message
    end

    # Will add an error message to each of the attributes in +attributes+ that is empty.
    def add_on_empty(attributes, custom_message = nil)
      for attr in [attributes].flatten
        value = @base.respond_to?(attr.to_s) ? @base.send(attr.to_s) : @base[attr.to_s]
        is_empty = value.respond_to?(:empty?) ? value.empty? : false
        add(attr, :empty, :default => custom_message) unless !value.nil? && !is_empty
      end
    end

    # Will add an error message to each of the attributes in +attributes+ that is blank (using Object#blank?).
    def add_on_blank(attributes, custom_message = nil)
      for attr in [attributes].flatten
        value = @base.respond_to?(attr.to_s) ? @base.send(attr.to_s) : @base[attr.to_s]
        add(attr, :blank, :default => custom_message) if value.blank?
      end
    end
    
    # Translates an error message in it's default scope (<tt>activerecord.errrors.messages</tt>).
    # Error messages are first looked up in <tt>models.MODEL.attributes.ATTRIBUTE.MESSAGE</tt>, if it's not there, 
    # it's looked up in <tt>models.MODEL.MESSAGE</tt> and if that is not there it returns the translation of the 
    # default message (e.g. <tt>activerecord.errors.messages.MESSAGE</tt>). The translated model name, 
    # translated attribute name and the value are available for interpolation.
    #
    # When using inheritence in your models, it will check all the inherited models too, but only if the model itself
    # hasn't been found. Say you have <tt>class Admin < User; end</tt> and you wanted the translation for the <tt>:blank</tt>
    # error +message+ for the <tt>title</tt> +attribute+, it looks for these translations:
    # 
    # <ol>
    # <li><tt>activerecord.errors.models.admin.attributes.title.blank</tt></li>
    # <li><tt>activerecord.errors.models.admin.blank</tt></li>
    # <li><tt>activerecord.errors.models.user.attributes.title.blank</tt></li>
    # <li><tt>activerecord.errors.models.user.blank</tt></li>
    # <li><tt>activerecord.errors.messages.blank</tt></li>
    # <li>any default you provided through the +options+ hash (in the activerecord.errors scope)</li>
    # </ol>
    def generate_message(attribute, message = :invalid, options = {})

      message, options[:default] = options[:default], message if options[:default].is_a?(Symbol)

      defaults = @base.class.self_and_descendents_from_active_record.map do |klass| 
        [ :"models.#{klass.name.underscore}.attributes.#{attribute}.#{message}", 
          :"models.#{klass.name.underscore}.#{message}" ]
      end
      
      defaults << options.delete(:default)
      defaults = defaults.compact.flatten << :"messages.#{message}"

      key = defaults.shift
      value = @base.respond_to?(attribute) ? @base.send(attribute) : nil

      options = { :default => defaults,
        :model => @base.class.human_name,
        :attribute => @base.class.human_attribute_name(attribute.to_s),
        :value => value,
        :scope => [:activerecord, :errors]
      }.merge(options)

      I18n.translate(key, options)
    end

    # Returns true if the specified +attribute+ has errors associated with it.
    #
    #   class Company < ActiveRecord::Base
    #     validates_presence_of :name, :address, :email
    #     validates_length_of :name, :in => 5..30
    #   end
    #
    #   company = Company.create(:address => '123 First St.')
    #   company.errors.invalid?(:name)      # => true
    #   company.errors.invalid?(:address)   # => false
    def invalid?(attribute)
      !@errors[attribute.to_s].nil?
    end

    # Returns +nil+, if no errors are associated with the specified +attribute+.
    # Returns the error message, if one error is associated with the specified +attribute+.
    # Returns an array of error messages, if more than one error is associated with the specified +attribute+.
    #
    #   class Company < ActiveRecord::Base
    #     validates_presence_of :name, :address, :email
    #     validates_length_of :name, :in => 5..30
    #   end
    #
    #   company = Company.create(:address => '123 First St.')
    #   company.errors.on(:name)      # => ["is too short (minimum is 5 characters)", "can't be blank"]
    #   company.errors.on(:email)     # => "can't be blank"
    #   company.errors.on(:address)   # => nil
    def on(attribute)
      errors = @errors[attribute.to_s]
      return nil if errors.nil?
      errors.size == 1 ? errors.first : errors
    end

    alias :[] :on

    # Returns errors assigned to the base object through +add_to_base+ according to the normal rules of <tt>on(attribute)</tt>.
    def on_base
      on(:base)
    end

    # Yields each attribute and associated message per error added.
    #
    #   class Company < ActiveRecord::Base
    #     validates_presence_of :name, :address, :email
    #     validates_length_of :name, :in => 5..30
    #   end
    #
    #   company = Company.create(:address => '123 First St.')
    #   company.errors.each{|attr,msg| puts "#{attr} - #{msg}" }
    #   # => name - is too short (minimum is 5 characters)
    #   #    name - can't be blank
    #   #    address - can't be blank
    def each
      @errors.each_key { |attr| @errors[attr].each { |msg| yield attr, msg } }
    end

    # Yields each full error message added. So <tt>Person.errors.add("first_name", "can't be empty")</tt> will be returned
    # through iteration as "First name can't be empty".
    #
    #   class Company < ActiveRecord::Base
    #     validates_presence_of :name, :address, :email
    #     validates_length_of :name, :in => 5..30
    #   end
    #
    #   company = Company.create(:address => '123 First St.')
    #   company.errors.each_full{|msg| puts msg }
    #   # => Name is too short (minimum is 5 characters)
    #   #    Name can't be blank
    #   #    Address can't be blank
    def each_full
      full_messages.each { |msg| yield msg }
    end

    # Returns all the full error messages in an array.
    #
    #   class Company < ActiveRecord::Base
    #     validates_presence_of :name, :address, :email
    #     validates_length_of :name, :in => 5..30
    #   end
    #
    #   company = Company.create(:address => '123 First St.')
    #   company.errors.full_messages # =>
    #     ["Name is too short (minimum is 5 characters)", "Name can't be blank", "Address can't be blank"]
    def full_messages(options = {})
      full_messages = []

      @errors.each_key do |attr|
        @errors[attr].each do |message|
          next unless message

          if attr == "base"
            full_messages << message
          else
            #key = :"activerecord.att.#{@base.class.name.underscore.to_sym}.#{attr}" 
            attr_name = @base.class.human_attribute_name(attr)
            full_messages << attr_name + ' ' + message
          end
        end
      end
      full_messages
    end 

    # Returns true if no errors have been added.
    def empty?
      @errors.empty?
    end

    # Removes all errors that have been added.
    def clear
      @errors = {}
    end

    # Returns the total number of errors added. Two errors added to the same attribute will be counted as such.
    def size
      @errors.values.inject(0) { |error_count, attribute| error_count + attribute.size }
    end

    alias_method :count, :size
    alias_method :length, :size

    # Returns an XML representation of this error object.
    #
    #   class Company < ActiveRecord::Base
    #     validates_presence_of :name, :address, :email
    #     validates_length_of :name, :in => 5..30
    #   end
    #
    #   company = Company.create(:address => '123 First St.')
    #   company.errors.to_xml
    #   # =>  <?xml version="1.0" encoding="UTF-8"?>
    #   #     <errors>
    #   #       <error>Name is too short (minimum is 5 characters)</error>
    #   #       <error>Name can't be blank</error>
    #   #       <error>Address can't be blank</error>
    #   #     </errors>
    def to_xml(options={})
      options[:root] ||= "errors"
      options[:indent] ||= 2
      options[:builder] ||= Builder::XmlMarkup.new(:indent => options[:indent])

      options[:builder].instruct! unless options.delete(:skip_instruct)
      options[:builder].errors do |e|
        full_messages.each { |msg| e.error(msg) }
      end
    end
    
  end


  # Please do have a look at ActiveRecord::Validations::ClassMethods for a higher level of validations.
  #
  # Active Records implement validation by overwriting Base#validate (or the variations, +validate_on_create+ and
  # +validate_on_update+). Each of these methods can inspect the state of the object, which usually means ensuring
  # that a number of attributes have a certain value (such as not empty, within a given range, matching a certain regular expression).
  #
  # Example:
  #
  #   class Person < ActiveRecord::Base
  #     protected
  #       def validate
  #         errors.add_on_empty %w( first_name last_name )
  #         errors.add("phone_number", "has invalid format") unless phone_number =~ /[0-9]*/
  #       end
  #
  #       def validate_on_create # is only run the first time a new object is saved
  #         unless valid_discount?(membership_discount)
  #           errors.add("membership_discount", "has expired")
  #         end
  #       end
  #
  #       def validate_on_update
  #         errors.add_to_base("No changes have occurred") if unchanged_attributes?
  #       end
  #   end
  #
  #   person = Person.new("first_name" => "David", "phone_number" => "what?")
  #   person.save                         # => false (and doesn't do the save)
  #   person.errors.empty?                # => false
  #   person.errors.count                 # => 2
  #   person.errors.on "last_name"        # => "can't be empty"
  #   person.errors.on "phone_number"     # => "has invalid format"
  #   person.errors.each_full { |msg| puts msg }
  #                                       # => "Last name can't be empty\n" +
  #                                       #    "Phone number has invalid format"
  #
  #   person.attributes = { "last_name" => "Heinemeier", "phone_number" => "555-555" }
  #   person.save # => true (and person is now saved in the database)
  #
  # An Errors object is automatically created for every Active Record.
  module Validations
    VALIDATIONS = %w( validate validate_on_create validate_on_update )

    def self.included(base) # :nodoc:
      base.extend ClassMethods
      base.class_eval do
        alias_method_chain :save, :validation
        alias_method_chain :save!, :validation
      end

      base.send :include, ActiveSupport::Callbacks
      base.define_callbacks *VALIDATIONS
    end

    # Active Record classes can implement validations in several ways. The highest level, easiest to read,
    # and recommended approach is to use the declarative <tt>validates_..._of</tt> class methods (and
    # +validates_associated+) documented below. These are sufficient for most model validations.
    #
    # Slightly lower level is +validates_each+. It provides some of the same options as the purely declarative
    # validation methods, but like all the lower-level approaches it requires manually adding to the errors collection
    # when the record is invalid.
    #
    # At a yet lower level, a model can use the class methods +validate+, +validate_on_create+ and +validate_on_update+
    # to add validation methods or blocks. These are ActiveSupport::Callbacks and follow the same rules of inheritance
    # and chaining.
    #
    # The lowest level style is to define the instance methods +validate+, +validate_on_create+ and +validate_on_update+
    # as documented in ActiveRecord::Validations.
    #
    # == +validate+, +validate_on_create+ and +validate_on_update+ Class Methods
    #
    # Calls to these methods add a validation method or block to the class. Again, this approach is recommended
    # only when the higher-level methods documented below (<tt>validates_..._of</tt> and +validates_associated+) are
    # insufficient to handle the required validation.
    #
    # This can be done with a symbol pointing to a method:
    #
    #   class Comment < ActiveRecord::Base
    #     validate :must_be_friends
    #
    #     def must_be_friends
    #       errors.add_to_base("Must be friends to leave a comment") unless commenter.friend_of?(commentee)
    #     end
    #   end
    #
    # Or with a block which is passed the current record to be validated:
    #
    #   class Comment < ActiveRecord::Base
    #     validate do |comment|
    #       comment.must_be_friends
    #     end
    #
    #     def must_be_friends
    #       errors.add_to_base("Must be friends to leave a comment") unless commenter.friend_of?(commentee)
    #     end
    #   end
    #
    # This usage applies to +validate_on_create+ and +validate_on_update+ as well.
    module ClassMethods
      DEFAULT_VALIDATION_OPTIONS = {
        :on => :save,
        :allow_nil => false,
        :allow_blank => false,
        :message => nil
      }.freeze

      ALL_RANGE_OPTIONS = [ :is, :within, :in, :minimum, :maximum ].freeze
      ALL_NUMERICALITY_CHECKS = { :greater_than => '>', :greater_than_or_equal_to => '>=',
                                  :equal_to => '==', :less_than => '<', :less_than_or_equal_to => '<=',
                                  :odd => 'odd?', :even => 'even?' }.freeze

      # Validates each attribute against a block.
      #
      #   class Person < ActiveRecord::Base
      #     validates_each :first_name, :last_name do |record, attr, value|
      #       record.errors.add attr, 'starts with z.' if value[0] == ?z
      #     end
      #   end
      #
      # Options:
      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
      # * <tt>:allow_nil</tt> - Skip validation if attribute is +nil+.
      # * <tt>:allow_blank</tt> - Skip validation if attribute is blank.
      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      def validates_each(*attrs)
        options = attrs.extract_options!.symbolize_keys
        attrs   = attrs.flatten

        # Declare the validation.
        send(validation_method(options[:on] || :save), options) do |record|
          attrs.each do |attr|
            value = record.send(attr)
            next if (value.nil? && options[:allow_nil]) || (value.blank? && options[:allow_blank])
            yield record, attr, value
          end
        end
      end

      # Encapsulates the pattern of wanting to validate a password or email address field with a confirmation. Example:
      #
      #   Model:
      #     class Person < ActiveRecord::Base
      #       validates_confirmation_of :user_name, :password
      #       validates_confirmation_of :email_address, :message => "should match confirmation"
      #     end
      #
      #   View:
      #     <%= password_field "person", "password" %>
      #     <%= password_field "person", "password_confirmation" %>
      #
      # The added +password_confirmation+ attribute is virtual; it exists only as an in-memory attribute for validating the password.
      # To achieve this, the validation adds accessors to the model for the confirmation attribute. NOTE: This check is performed
      # only if +password_confirmation+ is not +nil+, and by default only on save. To require confirmation, make sure to add a presence
      # check for the confirmation attribute:
      #
      #   validates_presence_of :password_confirmation, :if => :password_changed?
      #
      # Configuration options:
      # * <tt>:message</tt> - A custom error message (default is: "doesn't match confirmation").
      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      def validates_confirmation_of(*attr_names)
        configuration = { :on => :save }
        configuration.update(attr_names.extract_options!)

        attr_accessor(*(attr_names.map { |n| "#{n}_confirmation" }))

        validates_each(attr_names, configuration) do |record, attr_name, value|
          unless record.send("#{attr_name}_confirmation").nil? or value == record.send("#{attr_name}_confirmation")
            record.errors.add(attr_name, :confirmation, :default => configuration[:message]) 
          end
        end
      end

      # Encapsulates the pattern of wanting to validate the acceptance of a terms of service check box (or similar agreement). Example:
      #
      #   class Person < ActiveRecord::Base
      #     validates_acceptance_of :terms_of_service
      #     validates_acceptance_of :eula, :message => "must be abided"
      #   end
      #
      # If the database column does not exist, the +terms_of_service+ attribute is entirely virtual. This check is
      # performed only if +terms_of_service+ is not +nil+ and by default on save.
      #
      # Configuration options:
      # * <tt>:message</tt> - A custom error message (default is: "must be accepted").
      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
      # * <tt>:allow_nil</tt> - Skip validation if attribute is +nil+ (default is true).
      # * <tt>:accept</tt> - Specifies value that is considered accepted.  The default value is a string "1", which
      #   makes it easy to relate to an HTML checkbox. This should be set to +true+ if you are validating a database
      #   column, since the attribute is typecast from "1" to +true+ before validation.
      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      def validates_acceptance_of(*attr_names)
        configuration = { :on => :save, :allow_nil => true, :accept => "1" }
        configuration.update(attr_names.extract_options!)

        db_cols = begin
          column_names
        rescue Exception # To ignore both statement and connection errors
          []
        end
        names = attr_names.reject { |name| db_cols.include?(name.to_s) }
        attr_accessor(*names)

        validates_each(attr_names,configuration) do |record, attr_name, value|
          unless value == configuration[:accept]
            record.errors.add(attr_name, :accepted, :default => configuration[:message]) 
          end
        end
      end

      # Validates that the specified attributes are not blank (as defined by Object#blank?). Happens by default on save. Example:
      #
      #   class Person < ActiveRecord::Base
      #     validates_presence_of :first_name
      #   end
      #
      # The first_name attribute must be in the object and it cannot be blank.
      #
      # If you want to validate the presence of a boolean field (where the real values are true and false),
      # you will want to use validates_inclusion_of :field_name, :in => [true, false]
      # This is due to the way Object#blank? handles boolean values. false.blank? # => true
      #
      # Configuration options:
      # * <tt>message</tt> - A custom error message (default is: "can't be blank").
      # * <tt>on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
      # * <tt>if</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   occur (e.g. :if => :allow_validation, or :if => Proc.new { |user| user.signup_step > 2 }).  The
      #   method, proc or string should return or evaluate to a true or false value.
      # * <tt>unless</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   not occur (e.g. :unless => :skip_validation, or :unless => Proc.new { |user| user.signup_step <= 2 }).  The
      #   method, proc or string should return or evaluate to a true or false value.
      #
      def validates_presence_of(*attr_names)
        configuration = { :on => :save }
        configuration.update(attr_names.extract_options!)

        # can't use validates_each here, because it cannot cope with nonexistent attributes,
        # while errors.add_on_empty can
        send(validation_method(configuration[:on]), configuration) do |record|
          record.errors.add_on_blank(attr_names, configuration[:message])
        end
      end

      # Validates that the specified attribute matches the length restrictions supplied. Only one option can be used at a time:
      #
      #   class Person < ActiveRecord::Base
      #     validates_length_of :first_name, :maximum=>30
      #     validates_length_of :last_name, :maximum=>30, :message=>"less than {{count}} if you don't mind"
      #     validates_length_of :fax, :in => 7..32, :allow_nil => true
      #     validates_length_of :phone, :in => 7..32, :allow_blank => true
      #     validates_length_of :user_name, :within => 6..20, :too_long => "pick a shorter name", :too_short => "pick a longer name"
      #     validates_length_of :fav_bra_size, :minimum => 1, :too_short => "please enter at least {{count}} character"
      #     validates_length_of :smurf_leader, :is => 4, :message => "papa is spelled with {{count}} characters... don't play me."
      #     validates_length_of :essay, :minimum => 100, :too_short => "Your essay must be at least {{count}} words."), :tokenizer => lambda {|str| str.scan(/\w+/) }
      #   end
      #
      # Configuration options:
      # * <tt>:minimum</tt> - The minimum size of the attribute.
      # * <tt>:maximum</tt> - The maximum size of the attribute.
      # * <tt>:is</tt> - The exact size of the attribute.
      # * <tt>:within</tt> - A range specifying the minimum and maximum size of the attribute.
      # * <tt>:in</tt> - A synonym(or alias) for <tt>:within</tt>.
      # * <tt>:allow_nil</tt> - Attribute may be +nil+; skip validation.
      # * <tt>:allow_blank</tt> - Attribute may be blank; skip validation.
      # * <tt>:too_long</tt> - The error message if the attribute goes over the maximum (default is: "is too long (maximum is {{count}} characters)").
      # * <tt>:too_short</tt> - The error message if the attribute goes under the minimum (default is: "is too short (min is {{count}} characters)").
      # * <tt>:wrong_length</tt> - The error message if using the <tt>:is</tt> method and the attribute is the wrong size (default is: "is the wrong length (should be {{count}} characters)").
      # * <tt>:message</tt> - The error message to use for a <tt>:minimum</tt>, <tt>:maximum</tt>, or <tt>:is</tt> violation.  An alias of the appropriate <tt>too_long</tt>/<tt>too_short</tt>/<tt>wrong_length</tt> message.
      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      # * <tt>:tokenizer</tt> - Specifies how to split up the attribute string. (e.g. <tt>:tokenizer => lambda {|str| str.scan(/\w+/)}</tt> to
      #   count words as in above example.)
      #   Defaults to <tt>lambda{ |value| value.split(//) }</tt> which counts individual characters.
      def validates_length_of(*attrs)
        # Merge given options with defaults.
        options = {
          :tokenizer => lambda {|value| value.split(//)}
        }.merge(DEFAULT_VALIDATION_OPTIONS)
        options.update(attrs.extract_options!.symbolize_keys)

        # Ensure that one and only one range option is specified.
        range_options = ALL_RANGE_OPTIONS & options.keys
        case range_options.size
          when 0
            raise ArgumentError, 'Range unspecified.  Specify the :within, :maximum, :minimum, or :is option.'
          when 1
            # Valid number of options; do nothing.
          else
            raise ArgumentError, 'Too many range options specified.  Choose only one.'
        end

        # Get range option and value.
        option = range_options.first
        option_value = options[range_options.first]

        case option
          when :within, :in
            raise ArgumentError, ":#{option} must be a Range" unless option_value.is_a?(Range)

            validates_each(attrs, options) do |record, attr, value|
              value = options[:tokenizer].call(value) if value.kind_of?(String)
              if value.nil? or value.size < option_value.begin
                record.errors.add(attr, :too_short, :default => options[:too_short], :count => option_value.begin)
              elsif value.size > option_value.end
                record.errors.add(attr, :too_long, :default => options[:too_long], :count => option_value.end)
              end
            end
          when :is, :minimum, :maximum
            raise ArgumentError, ":#{option} must be a nonnegative Integer" unless option_value.is_a?(Integer) and option_value >= 0

            # Declare different validations per option.
            validity_checks = { :is => "==", :minimum => ">=", :maximum => "<=" }
            message_options = { :is => :wrong_length, :minimum => :too_short, :maximum => :too_long }

            validates_each(attrs, options) do |record, attr, value|
              value = options[:tokenizer].call(value) if value.kind_of?(String)
              unless !value.nil? and value.size.method(validity_checks[option])[option_value]
                key = message_options[option]
                custom_message = options[:message] || options[key]
                record.errors.add(attr, key, :default => custom_message, :count => option_value) 
              end
            end
        end
      end

      alias_method :validates_size_of, :validates_length_of


      # Validates whether the value of the specified attributes are unique across the system. Useful for making sure that only one user
      # can be named "davidhh".
      #
      #   class Person < ActiveRecord::Base
      #     validates_uniqueness_of :user_name, :scope => :account_id
      #   end
      #
      # It can also validate whether the value of the specified attributes are unique based on multiple scope parameters.  For example,
      # making sure that a teacher can only be on the schedule once per semester for a particular class.
      #
      #   class TeacherSchedule < ActiveRecord::Base
      #     validates_uniqueness_of :teacher_id, :scope => [:semester_id, :class_id]
      #   end
      #
      # When the record is created, a check is performed to make sure that no record exists in the database with the given value for the specified
      # attribute (that maps to a column). When the record is updated, the same check is made but disregarding the record itself.
      #
      # Configuration options:
      # * <tt>:message</tt> - Specifies a custom error message (default is: "has already been taken").
      # * <tt>:scope</tt> - One or more columns by which to limit the scope of the uniqueness constraint.
      # * <tt>:case_sensitive</tt> - Looks for an exact match. Ignored by non-text columns (+true+ by default).
      # * <tt>:allow_nil</tt> - If set to true, skips this validation if the attribute is +nil+ (default is +false+).
      # * <tt>:allow_blank</tt> - If set to true, skips this validation if the attribute is blank (default is +false+).
      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      #
      # === Concurrency and integrity
      #
      # Using this validation method in conjunction with ActiveRecord::Base#save
      # does not guarantee the absence of duplicate record insertions, because
      # uniqueness checks on the application level are inherently prone to race
      # conditions. For example, suppose that two users try to post a Comment at
      # the same time, and a Comment's title must be unique. At the database-level,
      # the actions performed by these users could be interleaved in the following manner:
      #
      #               User 1                 |               User 2
      #  ------------------------------------+--------------------------------------
      #  # User 1 checks whether there's     |
      #  # already a comment with the title  |
      #  # 'My Post'. This is not the case.  |
      #  SELECT * FROM comments              |
      #  WHERE title = 'My Post'             |
      #                                      |
      #                                      | # User 2 does the same thing and also
      #                                      | # infers that his title is unique.
      #                                      | SELECT * FROM comments
      #                                      | WHERE title = 'My Post'
      #                                      |
      #  # User 1 inserts his comment.       |
      #  INSERT INTO comments                |
      #  (title, content) VALUES             |
      #  ('My Post', 'hi!')                  |
      #                                      |
      #                                      | # User 2 does the same thing.
      #                                      | INSERT INTO comments
      #                                      | (title, content) VALUES
      #                                      | ('My Post', 'hello!')
      #                                      |
      #                                      | # ^^^^^^
      #                                      | # Boom! We now have a duplicate
      #                                      | # title!
      #
      # This could even happen if you use transactions with the 'serializable'
      # isolation level. There are several ways to get around this problem:
      # - By locking the database table before validating, and unlocking it after
      #   saving. However, table locking is very expensive, and thus not
      #   recommended.
      # - By locking a lock file before validating, and unlocking it after saving.
      #   This does not work if you've scaled your Rails application across
      #   multiple web servers (because they cannot share lock files, or cannot
      #   do that efficiently), and thus not recommended.
      # - Creating a unique index on the field, by using
      #   ActiveRecord::ConnectionAdapters::SchemaStatements#add_index. In the
      #   rare case that a race condition occurs, the database will guarantee
      #   the field's uniqueness.
      #   
      #   When the database catches such a duplicate insertion,
      #   ActiveRecord::Base#save will raise an ActiveRecord::StatementInvalid
      #   exception. You can either choose to let this error propagate (which
      #   will result in the default Rails exception page being shown), or you
      #   can catch it and restart the transaction (e.g. by telling the user
      #   that the title already exists, and asking him to re-enter the title).
      #   This technique is also known as optimistic concurrency control:
      #   http://en.wikipedia.org/wiki/Optimistic_concurrency_control
      #   
      #   Active Record currently provides no way to distinguish unique
      #   index constraint errors from other types of database errors, so you
      #   will have to parse the (database-specific) exception message to detect
      #   such a case.
      def validates_uniqueness_of(*attr_names)
        configuration = { :case_sensitive => true }
        configuration.update(attr_names.extract_options!)

        validates_each(attr_names,configuration) do |record, attr_name, value|
          # The check for an existing value should be run from a class that
          # isn't abstract. This means working down from the current class
          # (self), to the first non-abstract class. Since classes don't know
          # their subclasses, we have to build the hierarchy between self and
          # the record's class.
          class_hierarchy = [record.class]
          while class_hierarchy.first != self
            class_hierarchy.insert(0, class_hierarchy.first.superclass)
          end

          # Now we can work our way down the tree to the first non-abstract
          # class (which has a database table to query from).
          finder_class = class_hierarchy.detect { |klass| !klass.abstract_class? }

          is_text_column = finder_class.columns_hash[attr_name.to_s].text?

          if value.nil?
            comparison_operator = "IS ?"
          elsif is_text_column
            comparison_operator = "#{connection.case_sensitive_equality_operator} ?"
            value = value.to_s
          else
            comparison_operator = "= ?"
          end

          sql_attribute = "#{record.class.quoted_table_name}.#{connection.quote_column_name(attr_name)}"

          if value.nil? || (configuration[:case_sensitive] || !is_text_column)
            condition_sql = "#{sql_attribute} #{comparison_operator}"
            condition_params = [value]
          else
            condition_sql = "LOWER(#{sql_attribute}) #{comparison_operator}"
            condition_params = [value.mb_chars.downcase]
          end

          if scope = configuration[:scope]
            Array(scope).map do |scope_item|
              scope_value = record.send(scope_item)
              condition_sql << " AND #{record.class.quoted_table_name}.#{scope_item} #{attribute_condition(scope_value)}"
              condition_params << scope_value
            end
          end

          unless record.new_record?
            condition_sql << " AND #{record.class.quoted_table_name}.#{record.class.primary_key} <> ?"
            condition_params << record.send(:id)
          end

          finder_class.with_exclusive_scope do
            if finder_class.exists?([condition_sql, *condition_params])
              record.errors.add(attr_name, :taken, :default => configuration[:message], :value => value)
            end
          end
        end
      end


      # Validates whether the value of the specified attribute is of the correct form by matching it against the regular expression
      # provided.
      #
      #   class Person < ActiveRecord::Base
      #     validates_format_of :email, :with => /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i, :on => :create
      #   end
      #
      # Note: use <tt>\A</tt> and <tt>\Z</tt> to match the start and end of the string, <tt>^</tt> and <tt>$</tt> match the start/end of a line.
      #
      # A regular expression must be provided or else an exception will be raised.
      #
      # Configuration options:
      # * <tt>:message</tt> - A custom error message (default is: "is invalid").
      # * <tt>:allow_nil</tt> - If set to true, skips this validation if the attribute is +nil+ (default is +false+).
      # * <tt>:allow_blank</tt> - If set to true, skips this validation if the attribute is blank (default is +false+).
      # * <tt>:with</tt> - The regular expression used to validate the format with (note: must be supplied!).
      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      def validates_format_of(*attr_names)
        configuration = { :on => :save, :with => nil }
        configuration.update(attr_names.extract_options!)

        raise(ArgumentError, "A regular expression must be supplied as the :with option of the configuration hash") unless configuration[:with].is_a?(Regexp)

        validates_each(attr_names, configuration) do |record, attr_name, value|
          unless value.to_s =~ configuration[:with]
            record.errors.add(attr_name, :invalid, :default => configuration[:message], :value => value) 
          end
        end
      end

      # Validates whether the value of the specified attribute is available in a particular enumerable object.
      #
      #   class Person < ActiveRecord::Base
      #     validates_inclusion_of :gender, :in => %w( m f ), :message => "woah! what are you then!??!!"
      #     validates_inclusion_of :age, :in => 0..99
      #     validates_inclusion_of :format, :in => %w( jpg gif png ), :message => "extension {{value}} is not included in the list"
      #   end
      #
      # Configuration options:
      # * <tt>:in</tt> - An enumerable object of available items.
      # * <tt>:message</tt> - Specifies a custom error message (default is: "is not included in the list").
      # * <tt>:allow_nil</tt> - If set to true, skips this validation if the attribute is +nil+ (default is +false+).
      # * <tt>:allow_blank</tt> - If set to true, skips this validation if the attribute is blank (default is +false+).
      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      def validates_inclusion_of(*attr_names)
        configuration = { :on => :save }
        configuration.update(attr_names.extract_options!)

        enum = configuration[:in] || configuration[:within]

        raise(ArgumentError, "An object with the method include? is required must be supplied as the :in option of the configuration hash") unless enum.respond_to?(:include?)

        validates_each(attr_names, configuration) do |record, attr_name, value|
          unless enum.include?(value)
            record.errors.add(attr_name, :inclusion, :default => configuration[:message], :value => value) 
          end
        end
      end

      # Validates that the value of the specified attribute is not in a particular enumerable object.
      #
      #   class Person < ActiveRecord::Base
      #     validates_exclusion_of :username, :in => %w( admin superuser ), :message => "You don't belong here"
      #     validates_exclusion_of :age, :in => 30..60, :message => "This site is only for under 30 and over 60"
      #     validates_exclusion_of :format, :in => %w( mov avi ), :message => "extension {{value}} is not allowed"
      #   end
      #
      # Configuration options:
      # * <tt>:in</tt> - An enumerable object of items that the value shouldn't be part of.
      # * <tt>:message</tt> - Specifies a custom error message (default is: "is reserved").
      # * <tt>:allow_nil</tt> - If set to true, skips this validation if the attribute is +nil+ (default is +false+).
      # * <tt>:allow_blank</tt> - If set to true, skips this validation if the attribute is blank (default is +false+).
      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      def validates_exclusion_of(*attr_names)
        configuration = { :on => :save }
        configuration.update(attr_names.extract_options!)

        enum = configuration[:in] || configuration[:within]

        raise(ArgumentError, "An object with the method include? is required must be supplied as the :in option of the configuration hash") unless enum.respond_to?(:include?)

        validates_each(attr_names, configuration) do |record, attr_name, value|
          if enum.include?(value)
            record.errors.add(attr_name, :exclusion, :default => configuration[:message], :value => value) 
          end
        end
      end

      # Validates whether the associated object or objects are all valid themselves. Works with any kind of association.
      #
      #   class Book < ActiveRecord::Base
      #     has_many :pages
      #     belongs_to :library
      #
      #     validates_associated :pages, :library
      #   end
      #
      # Warning: If, after the above definition, you then wrote:
      #
      #   class Page < ActiveRecord::Base
      #     belongs_to :book
      #
      #     validates_associated :book
      #   end
      #
      # this would specify a circular dependency and cause infinite recursion.
      #
      # NOTE: This validation will not fail if the association hasn't been assigned. If you want to ensure that the association
      # is both present and guaranteed to be valid, you also need to use +validates_presence_of+.
      #
      # Configuration options:
      # * <tt>:message</tt> - A custom error message (default is: "is invalid")
      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      def validates_associated(*attr_names)
        configuration = { :on => :save }
        configuration.update(attr_names.extract_options!)

        validates_each(attr_names, configuration) do |record, attr_name, value|
          unless (value.is_a?(Array) ? value : [value]).inject(true) { |v, r| (r.nil? || r.valid?) && v }
            record.errors.add(attr_name, :invalid, :default => configuration[:message], :value => value)
          end
        end
      end

      # Validates whether the value of the specified attribute is numeric by trying to convert it to
      # a float with Kernel.Float (if <tt>only_integer</tt> is false) or applying it to the regular expression
      # <tt>/\A[\+\-]?\d+\Z/</tt> (if <tt>only_integer</tt> is set to true).
      #
      #   class Person < ActiveRecord::Base
      #     validates_numericality_of :value, :on => :create
      #   end
      #
      # Configuration options:
      # * <tt>:message</tt> - A custom error message (default is: "is not a number").
      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
      # * <tt>:only_integer</tt> - Specifies whether the value has to be an integer, e.g. an integral value (default is +false+).
      # * <tt>:allow_nil</tt> - Skip validation if attribute is +nil+ (default is +false+). Notice that for fixnum and float columns empty strings are converted to +nil+.
      # * <tt>:greater_than</tt> - Specifies the value must be greater than the supplied value.
      # * <tt>:greater_than_or_equal_to</tt> - Specifies the value must be greater than or equal the supplied value.
      # * <tt>:equal_to</tt> - Specifies the value must be equal to the supplied value.
      # * <tt>:less_than</tt> - Specifies the value must be less than the supplied value.
      # * <tt>:less_than_or_equal_to</tt> - Specifies the value must be less than or equal the supplied value.
      # * <tt>:odd</tt> - Specifies the value must be an odd number.
      # * <tt>:even</tt> - Specifies the value must be an even number.
      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      def validates_numericality_of(*attr_names)
        configuration = { :on => :save, :only_integer => false, :allow_nil => false }
        configuration.update(attr_names.extract_options!)


        numericality_options = ALL_NUMERICALITY_CHECKS.keys & configuration.keys

        (numericality_options - [ :odd, :even ]).each do |option|
          raise ArgumentError, ":#{option} must be a number" unless configuration[option].is_a?(Numeric)
        end

        validates_each(attr_names,configuration) do |record, attr_name, value|
          raw_value = record.send("#{attr_name}_before_type_cast") || value

          next if configuration[:allow_nil] and raw_value.nil?

          if configuration[:only_integer]
            unless raw_value.to_s =~ /\A[+-]?\d+\Z/
              record.errors.add(attr_name, :not_a_number, :value => raw_value, :default => configuration[:message])
              next
            end
            raw_value = raw_value.to_i
          else
            begin
              raw_value = Kernel.Float(raw_value)
            rescue ArgumentError, TypeError
              record.errors.add(attr_name, :not_a_number, :value => raw_value, :default => configuration[:message])
              next
            end
          end

          numericality_options.each do |option|
            case option
              when :odd, :even
                unless raw_value.to_i.method(ALL_NUMERICALITY_CHECKS[option])[]
                  record.errors.add(attr_name, option, :value => raw_value, :default => configuration[:message]) 
                end
              else
                record.errors.add(attr_name, option, :default => configuration[:message], :value => raw_value, :count => configuration[option]) unless raw_value.method(ALL_NUMERICALITY_CHECKS[option])[configuration[option]]
            end
          end
        end
      end

      # Creates an object just like Base.create but calls save! instead of save
      # so an exception is raised if the record is invalid.
      def create!(attributes = nil, &block)
        if attributes.is_a?(Array)
          attributes.collect { |attr| create!(attr, &block) }
        else
          object = new(attributes)
          yield(object) if block_given?
          object.save!
          object
        end
      end

      private
        def validation_method(on)
          case on
            when :save   then :validate
            when :create then :validate_on_create
            when :update then :validate_on_update
          end
        end
    end

    # The validation process on save can be skipped by passing false. The regular Base#save method is
    # replaced with this when the validations module is mixed in, which it is by default.
    def save_with_validation(perform_validation = true)
      if perform_validation && valid? || !perform_validation
        save_without_validation
      else
        false
      end
    end

    # Attempts to save the record just like Base#save but will raise a RecordInvalid exception instead of returning false
    # if the record is not valid.
    def save_with_validation!
      if valid?
        save_without_validation!
      else
        raise RecordInvalid.new(self)
      end
    end

    # Runs +validate+ and +validate_on_create+ or +validate_on_update+ and returns true if no errors were added otherwise false.
    def valid?
      errors.clear

      run_callbacks(:validate)
      validate

      if new_record?
        run_callbacks(:validate_on_create)
        validate_on_create
      else
        run_callbacks(:validate_on_update)
        validate_on_update
      end

      errors.empty?
    end

    # Returns the Errors object that holds all information about attribute error messages.
    def errors
      @errors ||= Errors.new(self)
    end

    protected
      # Overwrite this method for validation checks on all saves and use <tt>Errors.add(field, msg)</tt> for invalid attributes.
      def validate #:doc:
      end

      # Overwrite this method for validation checks used only on creation.
      def validate_on_create #:doc:
      end

      # Overwrite this method for validation checks used only on updates.
      def validate_on_update # :doc:
      end
  end
end