Module ActiveRecord::Validations::ClassMethods
In: vendor/rails/activerecord/lib/active_record/validations.rb

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.

Methods

Constants

DEFAULT_VALIDATION_OPTIONS = { :on => :save, :allow_nil => false, :allow_blank => false, :message => nil
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

Public Instance methods

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 342
342:       def condition_block?(condition)
343:         condition.respond_to?("call") && (condition.arity == 1 || condition.arity == -1)
344:       end

Creates an object just like Base.create but calls save! instead of save so an exception is raised if the record is invalid.

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 904
904:       def create!(attributes = nil)
905:         if attributes.is_a?(Array)
906:           attributes.collect { |attr| create!(attr) }
907:         else
908:           object = new(attributes)
909:           object.save!
910:           object
911:         end
912:       end

Determine from the given condition (whether a block, procedure, method or string) whether or not to validate the record. See validates_each.

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 348
348:       def evaluate_condition(condition, record)
349:         case condition
350:           when Symbol; record.send(condition)
351:           when String; eval(condition, record.send(:binding))
352:           else
353:             if condition_block?(condition)
354:               condition.call(record)
355:             else
356:               raise(
357:                 ActiveRecordError,
358:                 "Validations need to be either a symbol, string (to be eval'ed), proc/method, or " +
359:                 "class implementing a static validation method"
360:               )
361:             end
362:           end
363:       end

Adds a validation method or block to the class. This is useful when overriding the validate instance method becomes too unwieldly and you‘re looking for more descriptive declaration of your validations.

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.

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 327
327:       def validate(*methods, &block)
328:         methods << block if block_given?
329:         write_inheritable_set(:validate, methods)
330:       end

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 332
332:       def validate_on_create(*methods, &block)
333:         methods << block if block_given?
334:         write_inheritable_set(:validate_on_create, methods)
335:       end

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 337
337:       def validate_on_update(*methods, &block)
338:         methods << block if block_given?
339:         write_inheritable_set(:validate_on_update, methods)
340:       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:

  • message - A custom error message (default is: "must be accepted")
  • on - Specifies when this validation is active (default is :save, other options :create, :update)
  • allow_nil - Skip validation if attribute is nil. (default is true)
  • accept - 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.
  • if - 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.
  • unless - 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.

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 462
462:       def validates_acceptance_of(*attr_names)
463:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:accepted], :on => :save, :allow_nil => true, :accept => "1" }
464:         configuration.update(attr_names.extract_options!)
465: 
466:         db_cols = begin
467:           column_names
468:         rescue ActiveRecord::StatementInvalid
469:           []
470:         end
471:         names = attr_names.reject { |name| db_cols.include?(name.to_s) }
472:         attr_accessor(*names)
473: 
474:         validates_each(attr_names,configuration) do |record, attr_name, value|
475:           record.errors.add(attr_name, configuration[:message]) unless value == configuration[:accept]
476:         end
477:       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:

  • message - A custom error message (default is: "is invalid")
  • on Specifies when this validation is active (default is :save, other options :create, :update)
  • if - 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.
  • unless - 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.

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 824
824:       def validates_associated(*attr_names)
825:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:invalid], :on => :save }
826:         configuration.update(attr_names.extract_options!)
827: 
828:         validates_each(attr_names, configuration) do |record, attr_name, value|
829:           record.errors.add(attr_name, configuration[:message]) unless
830:             (value.is_a?(Array) ? value : [value]).inject(true) { |v, r| (r.nil? || r.valid?) && v }
831:         end
832:       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 acccessors 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:

  • message - A custom error message (default is: "doesn‘t match confirmation")
  • on - Specifies when this validation is active (default is :save, other options :create, :update)
  • if - 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.
  • unless - 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.

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 428
428:       def validates_confirmation_of(*attr_names)
429:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:confirmation], :on => :save }
430:         configuration.update(attr_names.extract_options!)
431: 
432:         attr_accessor(*(attr_names.map { |n| "#{n}_confirmation" }))
433: 
434:         validates_each(attr_names, configuration) do |record, attr_name, value|
435:           record.errors.add(attr_name, configuration[:message]) unless record.send("#{attr_name}_confirmation").nil? or value == record.send("#{attr_name}_confirmation")
436:         end
437:       end

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:

  • on - Specifies when this validation is active (default is :save, other options :create, :update)
  • allow_nil - Skip validation if attribute is nil.
  • allow_blank - Skip validation if attribute is blank.
  • if - 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.
  • unless - 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.

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 383
383:       def validates_each(*attrs)
384:         options = attrs.extract_options!.symbolize_keys
385:         attrs   = attrs.flatten
386: 
387:         # Declare the validation.
388:         send(validation_method(options[:on] || :save)) do |record|
389:           # Don't validate when there is an :if condition and that condition is false or there is an :unless condition and that condition is true
390:           unless (options[:if] && !evaluate_condition(options[:if], record)) || (options[:unless] && evaluate_condition(options[:unless], record))
391:             attrs.each do |attr|
392:               value = record.send(attr)
393:               next if (value.nil? && options[:allow_nil]) || (value.blank? && options[:allow_blank])
394:               yield record, attr, value
395:             end
396:           end
397:         end
398:       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 %s is not allowed"
  end

Configuration options:

  • in - An enumerable object of items that the value shouldn‘t be part of
  • message - Specifies a customer error message (default is: "is reserved")
  • allow_nil - If set to true, skips this validation if the attribute is null (default is: false)
  • allow_blank - If set to true, skips this validation if the attribute is blank (default is: false)
  • if - 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.
  • unless - 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.

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 780
780:       def validates_exclusion_of(*attr_names)
781:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:exclusion], :on => :save }
782:         configuration.update(attr_names.extract_options!)
783: 
784:         enum = configuration[:in] || configuration[:within]
785: 
786:         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?")
787: 
788:         validates_each(attr_names, configuration) do |record, attr_name, value|
789:           record.errors.add(attr_name, configuration[:message] % value) if enum.include?(value)
790:         end
791:       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 \A and \Z to match the start and end of the string, ^ and $ match the start/end of a line.

A regular expression must be provided or else an exception will be raised.

Configuration options:

  • message - A custom error message (default is: "is invalid")
  • with - The regular expression used to validate the format with (note: must be supplied!)
  • on Specifies when this validation is active (default is :save, other options :create, :update)
  • if - 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.
  • unless - 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.

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 718
718:       def validates_format_of(*attr_names)
719:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:invalid], :on => :save, :with => nil }
720:         configuration.update(attr_names.extract_options!)
721: 
722:         raise(ArgumentError, "A regular expression must be supplied as the :with option of the configuration hash") unless configuration[:with].is_a?(Regexp)
723: 
724:         validates_each(attr_names, configuration) do |record, attr_name, value|
725:           record.errors.add(attr_name, configuration[:message]) unless value.to_s =~ configuration[:with]
726:         end
727:       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 %s is not included in the list"
  end

Configuration options:

  • in - An enumerable object of available items
  • message - Specifies a customer error message (default is: "is not included in the list")
  • allow_nil - If set to true, skips this validation if the attribute is null (default is: false)
  • allow_blank - If set to true, skips this validation if the attribute is blank (default is: false)
  • if - 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.
  • unless - 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.

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 748
748:       def validates_inclusion_of(*attr_names)
749:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:inclusion], :on => :save }
750:         configuration.update(attr_names.extract_options!)
751: 
752:         enum = configuration[:in] || configuration[:within]
753: 
754:         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?")
755: 
756:         validates_each(attr_names, configuration) do |record, attr_name, value|
757:           record.errors.add(attr_name, configuration[:message] % value) unless enum.include?(value)
758:         end
759:       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 :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 %d character"
    validates_length_of :smurf_leader, :is=>4, :message=>"papa is spelled with %d characters... don't play me."
  end

Configuration options:

  • minimum - The minimum size of the attribute
  • maximum - The maximum size of the attribute
  • is - The exact size of the attribute
  • within - A range specifying the minimum and maximum size of the attribute
  • in - A synonym(or alias) for :within
  • allow_nil - Attribute may be nil; skip validation.
  • allow_blank - Attribute may be blank; skip validation.
  • too_long - The error message if the attribute goes over the maximum (default is: "is too long (maximum is %d characters)")
  • too_short - The error message if the attribute goes under the minimum (default is: "is too short (min is %d characters)")
  • wrong_length - 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)")
  • message - The error message to use for a :minimum, :maximum, or :is violation. An alias of the appropriate too_long/too_short/wrong_length message
  • on - Specifies when this validation is active (default is :save, other options :create, :update)
  • if - 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.
  • unless - 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.

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 557
557:       def validates_length_of(*attrs)
558:         # Merge given options with defaults.
559:         options = {
560:           :too_long     => ActiveRecord::Errors.default_error_messages[:too_long],
561:           :too_short    => ActiveRecord::Errors.default_error_messages[:too_short],
562:           :wrong_length => ActiveRecord::Errors.default_error_messages[:wrong_length]
563:         }.merge(DEFAULT_VALIDATION_OPTIONS)
564:         options.update(attrs.extract_options!.symbolize_keys)
565: 
566:         # Ensure that one and only one range option is specified.
567:         range_options = ALL_RANGE_OPTIONS & options.keys
568:         case range_options.size
569:           when 0
570:             raise ArgumentError, 'Range unspecified.  Specify the :within, :maximum, :minimum, or :is option.'
571:           when 1
572:             # Valid number of options; do nothing.
573:           else
574:             raise ArgumentError, 'Too many range options specified.  Choose only one.'
575:         end
576: 
577:         # Get range option and value.
578:         option = range_options.first
579:         option_value = options[range_options.first]
580: 
581:         case option
582:           when :within, :in
583:             raise ArgumentError, ":#{option} must be a Range" unless option_value.is_a?(Range)
584: 
585:             too_short = options[:too_short] % option_value.begin
586:             too_long  = options[:too_long]  % option_value.end
587: 
588:             validates_each(attrs, options) do |record, attr, value|
589:               if value.nil? or value.split(//).size < option_value.begin
590:                 record.errors.add(attr, too_short)
591:               elsif value.split(//).size > option_value.end
592:                 record.errors.add(attr, too_long)
593:               end
594:             end
595:           when :is, :minimum, :maximum
596:             raise ArgumentError, ":#{option} must be a nonnegative Integer" unless option_value.is_a?(Integer) and option_value >= 0
597: 
598:             # Declare different validations per option.
599:             validity_checks = { :is => "==", :minimum => ">=", :maximum => "<=" }
600:             message_options = { :is => :wrong_length, :minimum => :too_short, :maximum => :too_long }
601: 
602:             message = (options[:message] || options[message_options[option]]) % option_value
603: 
604:             validates_each(attrs, options) do |record, attr, value|
605:               if value.kind_of?(String)
606:                 record.errors.add(attr, message) unless !value.nil? and value.split(//).size.method(validity_checks[option])[option_value]
607:               else
608:                 record.errors.add(attr, message) unless !value.nil? and value.size.method(validity_checks[option])[option_value]
609:               end
610:             end
611:         end
612:       end

Validates whether the value of the specified attribute is numeric by trying to convert it to a float with Kernel.Float (if integer is false) or applying it to the regular expression /\A[+\-]?\d+\Z/ (if integer is set to true).

  class Person < ActiveRecord::Base
    validates_numericality_of :value, :on => :create
  end

Configuration options:

  • message - A custom error message (default is: "is not a number")
  • on Specifies when this validation is active (default is :save, other options :create, :update)
  • only_integer Specifies whether the value has to be an integer, e.g. an integral value (default is false)
  • allow_nil Skip validation if attribute is nil (default is false). Notice that for fixnum and float columns empty strings are converted to nil
  • greater_than Specifies the value must be greater than the supplied value
  • greater_than_or_equal_to Specifies the value must be greater than or equal the supplied value
  • equal_to Specifies the value must be equal to the supplied value
  • less_than Specifies the value must be less than the supplied value
  • less_than_or_equal_to Specifies the value must be less than or equal the supplied value
  • odd Specifies the value must be an odd number
  • even Specifies the value must be an even number
  • if - 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.
  • unless - 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.

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 860
860:       def validates_numericality_of(*attr_names)
861:         configuration = { :on => :save, :only_integer => false, :allow_nil => false }
862:         configuration.update(attr_names.extract_options!)
863: 
864: 
865:         numericality_options = ALL_NUMERICALITY_CHECKS.keys & configuration.keys
866: 
867:         (numericality_options - [ :odd, :even ]).each do |option|
868:           raise ArgumentError, ":#{option} must be a number" unless configuration[option].is_a?(Numeric)
869:         end
870: 
871:         validates_each(attr_names,configuration) do |record, attr_name, value|
872:           raw_value = record.send("#{attr_name}_before_type_cast") || value
873: 
874:           next if configuration[:allow_nil] and raw_value.nil?
875: 
876:           if configuration[:only_integer]
877:             unless raw_value.to_s =~ /\A[+-]?\d+\Z/
878:               record.errors.add(attr_name, configuration[:message] || ActiveRecord::Errors.default_error_messages[:not_a_number])
879:               next
880:             end
881:             raw_value = raw_value.to_i
882:           else
883:            begin
884:               raw_value = Kernel.Float(raw_value.to_s)
885:             rescue ArgumentError, TypeError
886:               record.errors.add(attr_name, configuration[:message] || ActiveRecord::Errors.default_error_messages[:not_a_number])
887:               next
888:             end
889:           end
890: 
891:           numericality_options.each do |option|
892:             case option
893:               when :odd, :even
894:                 record.errors.add(attr_name, configuration[:message] || ActiveRecord::Errors.default_error_messages[option]) unless raw_value.to_i.method(ALL_NUMERICALITY_CHECKS[option])[]
895:               else
896:                 record.errors.add(attr_name, configuration[:message] || (ActiveRecord::Errors.default_error_messages[option] % configuration[option])) unless raw_value.method(ALL_NUMERICALITY_CHECKS[option])[configuration[option]]
897:             end
898:           end
899:         end
900:       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:

  • message - A custom error message (default is: "can‘t be blank")
  • on - Specifies when this validation is active (default is :save, other options :create, :update)
  • if - 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.
  • unless - 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.

Warning

Validate the presence of the foreign key, not the instance variable itself. Do this:

 validates_presence_of :invoice_id

Not this:

 validates_presence_of :invoice

If you validate the presence of the associated object, you will get failures on saves when both the parent object and the child object are new.

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 512
512:       def validates_presence_of(*attr_names)
513:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:blank], :on => :save }
514:         configuration.update(attr_names.extract_options!)
515: 
516:         # can't use validates_each here, because it cannot cope with nonexistent attributes,
517:         # while errors.add_on_empty can
518:         send(validation_method(configuration[:on])) do |record|
519:           unless (configuration[:if] && !evaluate_condition(configuration[:if], record)) || (configuration[:unless] && evaluate_condition(configuration[:unless], record))
520:             record.errors.add_on_blank(attr_names, configuration[:message])
521:           end
522:         end
523:       end
validates_size_of(*attrs)

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.

Because this check is performed outside the database there is still a chance that duplicate values will be inserted in two parallel transactions. To guarantee against this you should create a unique index on the field. See create_index for more information.

Configuration options:

  • message - Specifies a custom error message (default is: "has already been taken")
  • scope - One or more columns by which to limit the scope of the uniquness constraint.
  • case_sensitive - Looks for an exact match. Ignored by non-text columns (true by default).
  • allow_nil - If set to true, skips this validation if the attribute is null (default is: false)
  • allow_blank - If set to true, skips this validation if the attribute is blank (default is: false)
  • if - 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.
  • unless - 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.

[Source]

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 650
650:       def validates_uniqueness_of(*attr_names)
651:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:taken], :case_sensitive => true }
652:         configuration.update(attr_names.extract_options!)
653: 
654:         validates_each(attr_names,configuration) do |record, attr_name, value|
655:           if value.nil? || (configuration[:case_sensitive] || !columns_hash[attr_name.to_s].text?)
656:             condition_sql = "#{record.class.table_name}.#{attr_name} #{attribute_condition(value)}"
657:             condition_params = [value]
658:           else
659:             condition_sql = "LOWER(#{record.class.table_name}.#{attr_name}) #{attribute_condition(value)}"
660:             condition_params = [value.downcase]
661:           end
662: 
663:           if scope = configuration[:scope]
664:             Array(scope).map do |scope_item|
665:               scope_value = record.send(scope_item)
666:               condition_sql << " AND #{record.class.table_name}.#{scope_item} #{attribute_condition(scope_value)}"
667:               condition_params << scope_value
668:             end
669:           end
670: 
671:           unless record.new_record?
672:             condition_sql << " AND #{record.class.table_name}.#{record.class.primary_key} <> ?"
673:             condition_params << record.send(:id)
674:           end
675: 
676:           # The check for an existing value should be run from a class that
677:           # isn't abstract. This means working down from the current class
678:           # (self), to the first non-abstract class. Since classes don't know
679:           # their subclasses, we have to build the hierarchy between self and
680:           # the record's class.
681:           class_hierarchy = [record.class]
682:           while class_hierarchy.first != self
683:             class_hierarchy.insert(0, class_hierarchy.first.superclass)
684:           end
685: 
686:           # Now we can work our way down the tree to the first non-abstract
687:           # class (which has a database table to query from).
688:           finder_class = class_hierarchy.detect { |klass| !klass.abstract_class? }
689: 
690:           if finder_class.find(:first, :conditions => [condition_sql, *condition_params])
691:             record.errors.add(attr_name, configuration[:message])
692:           end
693:         end
694:       end

[Validate]