aboutsummaryrefslogtreecommitdiffstats
path: root/activerecord/lib/active_record/validations.rb
blob: 904153bf24917b1b5a52c878bcd12ac6bb21d98d (plain) (blame)
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
module ActiveRecord
  # Raised by save! and create! 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, *args)
      @record = record
      super(*args)
    end
  end

  # Active Record validation is reported to and from this object, which is used by Base#save to
  # determine whether the object in a valid state to be saved. See usage example in Validations.
  class Errors
    include Enumerable

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

    @@default_error_messages = {
      :inclusion => "is not included in the list",
      :exclusion => "is reserved",
      :invalid => "is invalid",
      :confirmation => "doesn't match confirmation",
      :accepted  => "must be accepted",
      :empty => "can't be empty",
      :blank => "can't be blank",
      :too_long => "is too long (max is %d characters)",
      :too_short => "is too short (min is %d characters)",
      :wrong_length => "is the wrong length (should be %d characters)",
      :taken => "has already been taken",
      :not_a_number => "is not a number"
    }

    # Holds a hash with all the default error messages, such that they can be replaced by your own copy or localizations.
    cattr_accessor :default_error_messages


    # 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 (+msg+) 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 +msg+ is supplied, "invalid" is assumed.
    def add(attribute, msg = @@default_error_messages[:invalid])
      @errors[attribute.to_s] = [] if @errors[attribute.to_s].nil?
      @errors[attribute.to_s] << msg
    end

    # Will add an error message to each of the attributes in +attributes+ that is empty.
    def add_on_empty(attributes, msg = @@default_error_messages[:empty])
      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, msg) 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, msg = @@default_error_messages[:blank])
      for attr in [attributes].flatten
        value = @base.respond_to?(attr.to_s) ? @base.send(attr.to_s) : @base[attr.to_s]
        add(attr, msg) if value.blank?
      end
    end

    # Will add an error message to each of the attributes in +attributes+ that has a length outside of the passed boundary +range+.
    # If the length is above the boundary, the too_long_msg message will be used. If below, the too_short_msg.
    def add_on_boundary_breaking(attributes, range, too_long_msg = @@default_error_messages[:too_long], too_short_msg = @@default_error_messages[:too_short])
      for attr in [attributes].flatten
        value = @base.respond_to?(attr.to_s) ? @base.send(attr.to_s) : @base[attr.to_s]
        add(attr, too_short_msg % range.begin) if value && value.length < range.begin
        add(attr, too_long_msg % range.end) if value && value.length > range.end
      end
    end

    alias :add_on_boundry_breaking :add_on_boundary_breaking

    # Returns true if the specified +attribute+ has errors associated with it.
    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+.
    def on(attribute)
      if @errors[attribute.to_s].nil?
        nil
      elsif @errors[attribute.to_s].length == 1
        @errors[attribute.to_s].first
      else
        @errors[attribute.to_s]
      end
    end

    alias :[] :on

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

    # Yields each attribute and associated message per error added.
    def each
      @errors.each_key { |attr| @errors[attr].each { |msg| yield attr, msg } }
    end

    # Yields each full error message added. So Person.errors.add("first_name", "can't be empty") will be returned
    # through iteration as "First name can't be empty".
    def each_full
      full_messages.each { |msg| yield msg }
    end

    # Returns all the full error messages in an array.
    def full_messages
      full_messages = []

      @errors.each_key do |attr|
        @errors[attr].each do |msg|
          next if msg.nil?

          if attr == "base"
            full_messages << msg
          else
            full_messages << @base.class.human_attribute_name(attr) + " " + msg
          end
        end
      end

      return full_messages
    end

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

    # Removes all the 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
    # with this as well.
    def count
      error_count = 0
      @errors.each_value { |attribute| error_count += attribute.length }
      error_count
    end
  end


  # 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.
  #
  # Please do have a look at ActiveRecord::Validations::ClassMethods for a higher level of validations.
  module Validations
    VALIDATIONS = %w( validate validate_on_create validate_on_update )

    def self.append_features(base) # :nodoc:
      super
      base.extend ClassMethods
      base.class_eval do
        alias_method :save_without_validation, :save
        alias_method :save, :save_with_validation

        alias_method :update_attribute_without_validation_skipping, :update_attribute
        alias_method :update_attribute, :update_attribute_with_validation_skipping
      end
    end

    # All of the following validations are defined in the class scope of the model that you're interested in validating.
    # They offer a more declarative way of specifying when the model is valid and when it is not. It is recommended to use
    # these over the low-level calls to validate and validate_on_create when possible.
    module ClassMethods
      DEFAULT_VALIDATION_OPTIONS = {
        :on => :save,
        :allow_nil => false,
        :message => nil
      }.freeze

      ALL_RANGE_OPTIONS = [ :is, :within, :in, :minimum, :maximum ].freeze

      def validate(*methods, &block)
        methods << block if block_given?
        write_inheritable_set(:validate, methods)
      end

      def validate_on_create(*methods, &block)
        methods << block if block_given?
        write_inheritable_set(:validate_on_create, methods)
      end

      def validate_on_update(*methods, &block)
        methods << block if block_given?
        write_inheritable_set(:validate_on_update, methods)
      end

      def condition_block?(condition)
        condition.respond_to?("call") && (condition.arity == 1 || condition.arity == -1)
      end

      # Determine from the given condition (whether a block, procedure, method or string)
      # whether or not to validate the record.  See #validates_each.
      def evaluate_condition(condition, record)
        case condition
          when Symbol: record.send(condition)
          when String: eval(condition, binding)
          else
            if condition_block?(condition)
              condition.call(record)
            else
              raise(
                ActiveRecordError,
                "Validations need to be either a symbol, string (to be eval'ed), proc/method, or " +
                "class implementing a static validation method"
              )
            end
          end
      end

      # Validates each attribute against a block.
      #
      #   class Person < ActiveRecord::Base
      #     validates_each :first_name, :last_name do |record, attr|
      #       record.errors.add attr, 'starts with z.' if attr[0] == ?z
      #     end
      #   end
      #
      # Options:
      # * <tt>on</tt> - Specifies when this validation is active (default is :save, other options :create, :update)
      # * <tt>allow_nil</tt> - Skip validation if attribute is nil.
      # * <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.
      def validates_each(*attrs)
        options = attrs.last.is_a?(Hash) ? attrs.pop.symbolize_keys : {}
        attrs = attrs.flatten

        # Declare the validation.
        send(validation_method(options[:on] || :save)) do |record|
          # Don't validate when there is an :if condition and that condition is false
          unless options[:if] && !evaluate_condition(options[:if], record)
            attrs.each do |attr|
              value = record.send(attr)
              next if value.nil? && options[:allow_nil]
              yield record, attr, value
            end
          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 person has to already have a password attribute (a column in the people table), but the password_confirmation is virtual.
      # It exists only as an in-memory variable for validating the password. This check is performed only if password_confirmation
      # is not nil and by default on save.
      #
      # 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 :save, other options :create, :update)
      # * <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.
      def validates_confirmation_of(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:confirmation], :on => :save }
        configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)

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

        validates_each(attr_names, configuration) do |record, attr_name, value|
          record.errors.add(attr_name, configuration[:message]) unless record.send("#{attr_name}_confirmation").nil? or value == record.send("#{attr_name}_confirmation")
        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
      #
      # The terms_of_service attribute is entirely virtual. No database column is needed. 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 :save, other options :create, :update)
      # * <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.
      # * <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.
      def validates_acceptance_of(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:accepted], :on => :save, :allow_nil => true, :accept => "1" }
        configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)

        attr_accessor *attr_names

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

      # Validates that the specified attributes are not blank (as defined by Object#blank?). Happens by default on save.
      #
      # 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 :save, other options :create, :update)
      # * <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.
      def validates_presence_of(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:blank], :on => :save }
        configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)

        # can't use validates_each here, because it cannot cope with nonexistent attributes,
        # while errors.add_on_empty can
        attr_names.each do |attr_name|
          send(validation_method(configuration[:on])) do |record|
            unless configuration[:if] and not evaluate_condition(configuration[:if], record)
              record.errors.add_on_blank(attr_name,configuration[:message])
            end
          end
        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 %d if you don't mind"
      #     validates_length_of :fax, :in => 7..32, :allow_nil => 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 %d character"
      #     validates_length_of :smurf_leader, :is=>4, :message=>"papa is spelled with %d characters... don't play me."
      #   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 :within
      # * <tt>allow_nil</tt> - Attribute may be nil; skip validation.
      #
      # * <tt>too_long</tt> - The error message if the attribute goes over the maximum (default is: "is too long (max is %d characters)")
      # * <tt>too_short</tt> - The error message if the attribute goes under the minimum (default is: "is too short (min is %d characters)")
      # * <tt>wrong_length</tt> - The error message if using the :is method and the attribute is the wrong size (default is: "is the wrong length (should be %d characters)")
      # * <tt>message</tt> - The error message to use for a :minimum, :maximum, or :is violation.  An alias of the appropriate too_long/too_short/wrong_length message
      # * <tt>on</tt> - Specifies when this validation is active (default is :save, other options :create, :update)
      # * <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.
      def validates_length_of(*attrs)
        # Merge given options with defaults.
        options = {
          :too_long     => ActiveRecord::Errors.default_error_messages[:too_long],
          :too_short    => ActiveRecord::Errors.default_error_messages[:too_short],
          :wrong_length => ActiveRecord::Errors.default_error_messages[:wrong_length]
        }.merge(DEFAULT_VALIDATION_OPTIONS)
        options.update(attrs.pop.symbolize_keys) if attrs.last.is_a?(Hash)

        # 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)

          too_short = options[:too_short] % option_value.begin
          too_long  = options[:too_long]  % option_value.end

          validates_each(attrs, options) do |record, attr, value|
            if value.nil? or value.size < option_value.begin
              record.errors.add(attr, too_short)
            elsif value.size > option_value.end
              record.errors.add(attr, too_long)
            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 }

          message = (options[:message] || options[message_options[option]]) % option_value

          validates_each(attrs, options) do |record, attr, value|
            record.errors.add(attr, message) unless !value.nil? and value.size.method(validity_checks[option])[option_value]
          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
      #
      # 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> - Ensures that the uniqueness is restricted to a condition of "scope = record.scope"
      # * <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.
      def validates_uniqueness_of(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:taken] }
        configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)

        if scope = configuration[:scope]
          validates_each(attr_names,configuration) do |record, attr_name, value|
            record.errors.add(attr_name, configuration[:message]) if record.class.find(:first, :conditions => (record.new_record? ? ["#{attr_name} = ? AND #{scope} = ?", record.send(attr_name), record.send(scope)] : ["#{attr_name} = ? AND #{record.class.primary_key} <> ? AND #{scope} = ?", record.send(attr_name), record.send(:id), record.send(scope)]))
          end
        else
          validates_each(attr_names,configuration) do |record, attr_name, value|
            record.errors.add(attr_name, configuration[:message]) if record.class.find(:first, :conditions => (record.new_record? ? ["#{attr_name} = ?", record.send(attr_name)] : ["#{attr_name} = ? AND #{record.class.primary_key} <> ?", record.send(attr_name), record.send(:id) ] ))
          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 => /^([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})$/i, :on => :create
      #   end
      #
      # 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>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 :save, other options :create, :update)
      # * <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.
      def validates_format_of(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:invalid], :on => :save, :with => nil }
        configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)

        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|
          record.errors.add(attr_name, configuration[:message]) unless value.to_s =~ configuration[:with]
        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
      #   end
      #
      # Configuration options:
      # * <tt>in</tt> - An enumerable object of available items
      # * <tt>message</tt> - Specifies a customer 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 null (default is: false)
      # * <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.
      def validates_inclusion_of(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:inclusion], :on => :save }
        configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)

        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|
          record.errors.add(attr_name, configuration[:message]) unless enum.include?(value)
        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"
      #   end
      #
      # Configuration options:
      # * <tt>in</tt> - An enumerable object of items that the value shouldn't be part of
      # * <tt>message</tt> - Specifies a customer error message (default is: "is reserved")
      # * <tt>allow_nil</tt> - If set to true, skips this validation if the attribute is null (default is: false)
      # * <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.
      def validates_exclusion_of(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:exclusion], :on => :save }
        configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)

        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|
          record.errors.add(attr_name, configuration[:message]) if enum.include?(value)
        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>on</tt> Specifies when this validation is active (default is :save, other options :create, :update)
      # * <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.
      def validates_associated(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:invalid], :on => :save }
        configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)

        validates_each(attr_names, configuration) do |record, attr_name, value|
          record.errors.add(attr_name, configuration[:message]) unless
            (value.is_a?(Array) ? value : [value]).all? { |r| r.nil? or r.valid? }
        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>integer</tt> is false) or applying it to the regular expression
      # <tt>/^[\+\-]?\d+$/</tt> (if <tt>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 :save, other options :create, :update)
      # * <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>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.
      def validates_numericality_of(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:not_a_number], :on => :save,
                           :only_integer => false, :allow_nil => false }
        configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)

        if configuration[:only_integer]
          validates_each(attr_names,configuration) do |record, attr_name,value|
            record.errors.add(attr_name, configuration[:message]) unless record.send("#{attr_name}_before_type_cast").to_s =~ /^[+-]?\d+$/
          end
        else
          validates_each(attr_names,configuration) do |record, attr_name,value|
           next if configuration[:allow_nil] and record.send("#{attr_name}_before_type_cast").nil?
            begin
              Kernel.Float(record.send("#{attr_name}_before_type_cast").to_s)
            rescue ArgumentError, TypeError
              record.errors.add(attr_name, configuration[:message])
            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)
        if attributes.is_a?(Array)
          attributes.collect { |attr| create!(attr) }
        else
          attributes.reverse_merge!(scope(:create)) if scoped?(:create)

          object = new(attributes)
          object.save!
          object
        end
      end


      private
        def write_inheritable_set(key, methods)
          existing_methods = read_inheritable_attribute(key) || []
          write_inheritable_attribute(key, methods | existing_methods)
        end

        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
        true
      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!
      if valid?
        save(false)
      else
        raise RecordInvalid.new(self)
      end
    end

    # Updates a single attribute and saves the record without going through the normal validation procedure.
    # This is especially useful for boolean flags on existing records. The regular +update_attribute+ method
    # in Base is replaced with this when the validations module is mixed in, which it is by default.
    def update_attribute_with_validation_skipping(name, value)
      send(name.to_s + '=', value)
      save(false)
    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_validations(:validate)
      validate

      if new_record?
        run_validations(:validate_on_create)
        validate_on_create
      else
        run_validations(: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 Errors.add(field, msg) 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

    private
      def run_validations(validation_method)
        validations = self.class.read_inheritable_attribute(validation_method.to_sym)
        if validations.nil? then return end
        validations.each do |validation|
          if validation.is_a?(Symbol)
            self.send(validation)
          elsif validation.is_a?(String)
            eval(validation, binding)
          elsif validation_block?(validation)
            validation.call(self)
          elsif validation_class?(validation, validation_method)
            validation.send(validation_method, self)
          else
            raise(
              ActiveRecordError,
              "Validations need to be either a symbol, string (to be eval'ed), proc/method, or " +
              "class implementing a static validation method"
            )
          end
        end
      end

      def validation_block?(validation)
        validation.respond_to?("call") && (validation.arity == 1 || validation.arity == -1)
      end

      def validation_class?(validation, validation_method)
        validation.respond_to?(validation_method)
      end
  end
end