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, :message => nil
ALL_RANGE_OPTIONS = [ :is, :within, :in, :minimum, :maximum ].freeze
Public Instance methods
condition_block?(condition)
     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 254
254:       def condition_block?(condition)
255:         condition.respond_to?("call") && (condition.arity == 1 || condition.arity == -1)
256:       end
create!(attributes = nil)

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

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 704
704:       def create!(attributes = nil)
705:         if attributes.is_a?(Array)
706:           attributes.collect { |attr| create!(attr) }
707:         else
708:           attributes.reverse_merge!(scope(:create)) if scoped?(:create)
709: 
710:           object = new(attributes)
711:           object.save!
712:           object
713:         end
714:       end
evaluate_condition(condition, record)

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

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 260
260:       def evaluate_condition(condition, record)
261:         case condition
262:           when Symbol: record.send(condition)
263:           when String: eval(condition, binding)
264:           else
265:             if condition_block?(condition)
266:               condition.call(record)
267:             else
268:               raise(
269:                 ActiveRecordError,
270:                 "Validations need to be either a symbol, string (to be eval'ed), proc/method, or " +
271:                 "class implementing a static validation method"
272:               )
273:             end
274:           end
275:       end
validate(*methods, &block)
     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 239
239:       def validate(*methods, &block)
240:         methods << block if block_given?
241:         write_inheritable_set(:validate, methods)
242:       end
validate_on_create(*methods, &block)
     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 244
244:       def validate_on_create(*methods, &block)
245:         methods << block if block_given?
246:         write_inheritable_set(:validate_on_create, methods)
247:       end
validate_on_update(*methods, &block)
     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 249
249:       def validate_on_update(*methods, &block)
250:         methods << block if block_given?
251:         write_inheritable_set(:validate_on_update, methods)
252:       end
validates_acceptance_of(*attr_names)

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:

  • message - A custom error message (default is: "must be accepted")
  • on - Specifies when this validation is active (default is :save, other options :create, :update)
  • accept - Specifies value that is considered accepted. The default value is a string "1", which

makes it easy to relate to an HTML checkbox.

  • 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.

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 359
359:       def validates_acceptance_of(*attr_names)
360:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:accepted], :on => :save, :allow_nil => true, :accept => "1" }
361:         configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)
362: 
363:         attr_accessor *attr_names
364: 
365:         validates_each(attr_names,configuration) do |record, attr_name, value|
366:           record.errors.add(attr_name, configuration[:message]) unless value == configuration[:accept]
367:         end
368:       end
validates_associated(*attr_names)

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:

  • 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.

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 654
654:       def validates_associated(*attr_names)
655:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:invalid], :on => :save }
656:         configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)
657: 
658:         validates_each(attr_names, configuration) do |record, attr_name, value|
659:           record.errors.add(attr_name, configuration[:message]) unless
660:             (value.is_a?(Array) ? value : [value]).all? { |r| r.nil? or r.valid? }
661:         end
662:       end
validates_confirmation_of(*attr_names)

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:

  • 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.

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 330
330:       def validates_confirmation_of(*attr_names)
331:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:confirmation], :on => :save }
332:         configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)
333: 
334:         attr_accessor *(attr_names.map { |n| "#{n}_confirmation" })
335: 
336:         validates_each(attr_names, configuration) do |record, attr_name, value|
337:           record.errors.add(attr_name, configuration[:message]) unless record.send("#{attr_name}_confirmation").nil? or value == record.send("#{attr_name}_confirmation")
338:         end
339:       end
validates_each(*attrs) {|record, attr, value| ...}

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.
  • 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.

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 291
291:       def validates_each(*attrs)
292:         options = attrs.last.is_a?(Hash) ? attrs.pop.symbolize_keys : {}
293:         attrs = attrs.flatten
294: 
295:         # Declare the validation.
296:         send(validation_method(options[:on] || :save)) do |record|
297:           # Don't validate when there is an :if condition and that condition is false
298:           unless options[:if] && !evaluate_condition(options[:if], record)
299:             attrs.each do |attr|
300:               value = record.send(attr)
301:               next if value.nil? && options[:allow_nil]
302:               yield record, attr, value
303:             end
304:           end
305:         end
306:       end
validates_exclusion_of(*attr_names)

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:

  • 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)
  • 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.

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 614
614:       def validates_exclusion_of(*attr_names)
615:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:exclusion], :on => :save }
616:         configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)
617: 
618:         enum = configuration[:in] || configuration[:within]
619: 
620:         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?")
621: 
622:         validates_each(attr_names, configuration) do |record, attr_name, value|
623:           record.errors.add(attr_name, configuration[:message]) if enum.include?(value)
624:         end
625:       end
validates_format_of(*attr_names)

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:

  • 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.

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 562
562:       def validates_format_of(*attr_names)
563:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:invalid], :on => :save, :with => nil }
564:         configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)
565: 
566:         raise(ArgumentError, "A regular expression must be supplied as the :with option of the configuration hash") unless configuration[:with].is_a?(Regexp)
567: 
568:         validates_each(attr_names, configuration) do |record, attr_name, value|
569:           record.errors.add(attr_name, configuration[:message]) unless value.to_s =~ configuration[:with]
570:         end
571:       end
validates_inclusion_of(*attr_names)

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:

  • 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)
  • 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.

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 587
587:       def validates_inclusion_of(*attr_names)
588:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:inclusion], :on => :save }
589:         configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)
590: 
591:         enum = configuration[:in] || configuration[:within]
592: 
593:         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?")
594: 
595:         validates_each(attr_names, configuration) do |record, attr_name, value|
596:           record.errors.add(attr_name, configuration[:message]) unless enum.include?(value)
597:         end
598:       end
validates_length_of(*attrs)

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:

  • 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.
  • 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.

This method is also aliased as validates_size_of
     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 438
438:       def validates_length_of(*attrs)
439:         # Merge given options with defaults.
440:         options = {
441:           :too_long     => ActiveRecord::Errors.default_error_messages[:too_long],
442:           :too_short    => ActiveRecord::Errors.default_error_messages[:too_short],
443:           :wrong_length => ActiveRecord::Errors.default_error_messages[:wrong_length]
444:         }.merge(DEFAULT_VALIDATION_OPTIONS)
445:         options.update(attrs.pop.symbolize_keys) if attrs.last.is_a?(Hash)
446: 
447:         # Ensure that one and only one range option is specified.
448:         range_options = ALL_RANGE_OPTIONS & options.keys
449:         case range_options.size
450:           when 0
451:             raise ArgumentError, 'Range unspecified.  Specify the :within, :maximum, :minimum, or :is option.'
452:           when 1
453:             # Valid number of options; do nothing.
454:           else
455:             raise ArgumentError, 'Too many range options specified.  Choose only one.'
456:         end
457: 
458:         # Get range option and value.
459:         option = range_options.first
460:         option_value = options[range_options.first]
461: 
462:         case option
463:           when :within, :in
464:             raise ArgumentError, ":#{option} must be a Range" unless option_value.is_a?(Range)
465: 
466:             too_short = options[:too_short] % option_value.begin
467:             too_long  = options[:too_long]  % option_value.end
468: 
469:             validates_each(attrs, options) do |record, attr, value|
470:               if value.nil? or value.split(//).size < option_value.begin
471:                 record.errors.add(attr, too_short)
472:               elsif value.split(//).size > option_value.end
473:                 record.errors.add(attr, too_long)
474:               end
475:             end
476:           when :is, :minimum, :maximum
477:             raise ArgumentError, ":#{option} must be a nonnegative Integer" unless option_value.is_a?(Integer) and option_value >= 0
478: 
479:             # Declare different validations per option.
480:             validity_checks = { :is => "==", :minimum => ">=", :maximum => "<=" }
481:             message_options = { :is => :wrong_length, :minimum => :too_short, :maximum => :too_long }
482: 
483:             message = (options[:message] || options[message_options[option]]) % option_value
484: 
485:             validates_each(attrs, options) do |record, attr, value|
486:               if value.kind_of?(String)
487:                 record.errors.add(attr, message) unless !value.nil? and value.split(//).size.method(validity_checks[option])[option_value]
488:               else
489:                 record.errors.add(attr, message) unless !value.nil? and value.size.method(validity_checks[option])[option_value]
490:               end
491:             end
492:         end
493:       end
validates_numericality_of(*attr_names)

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 /^[+\-]?\d+$/ (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
  • 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.

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 680
680:       def validates_numericality_of(*attr_names)
681:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:not_a_number], :on => :save,
682:                            :only_integer => false, :allow_nil => false }
683:         configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)
684: 
685:         if configuration[:only_integer]
686:           validates_each(attr_names,configuration) do |record, attr_name,value|
687:             record.errors.add(attr_name, configuration[:message]) unless record.send("#{attr_name}_before_type_cast").to_s =~ /^[+-]?\d+$/
688:           end
689:         else
690:           validates_each(attr_names,configuration) do |record, attr_name,value|
691:            next if configuration[:allow_nil] and record.send("#{attr_name}_before_type_cast").nil?
692:             begin
693:               Kernel.Float(record.send("#{attr_name}_before_type_cast").to_s)
694:             rescue ArgumentError, TypeError
695:               record.errors.add(attr_name, configuration[:message])
696:             end
697:           end
698:         end
699:       end
validates_presence_of(*attr_names)

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.

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.

Warning

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

 validate_presence_of :invoice_id

Not this:

 validate_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.

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 396
396:       def validates_presence_of(*attr_names)
397:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:blank], :on => :save }
398:         configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)
399: 
400:         # can't use validates_each here, because it cannot cope with nonexistent attributes,
401:         # while errors.add_on_empty can
402:         attr_names.each do |attr_name|
403:           send(validation_method(configuration[:on])) do |record|
404:             unless configuration[:if] and not evaluate_condition(configuration[:if], record)
405:               record.errors.add_on_blank(attr_name,configuration[:message])
406:             end
407:           end
408:         end
409:       end
validates_size_of(*attrs)
validates_uniqueness_of(*attr_names)

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:

  • 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.
  • 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.

     # File vendor/rails/activerecord/lib/active_record/validations.rb, line 522
522:       def validates_uniqueness_of(*attr_names)
523:         configuration = { :message => ActiveRecord::Errors.default_error_messages[:taken] }
524:         configuration.update(attr_names.pop) if attr_names.last.is_a?(Hash)
525: 
526:         validates_each(attr_names,configuration) do |record, attr_name, value|
527:           condition_sql = "#{record.class.table_name}.#{attr_name} #{attribute_condition(value)}"
528:           condition_params = [value]
529:           if scope = configuration[:scope]
530:             Array(scope).map do |scope_item|
531:               scope_value = record.send(scope_item)
532:               condition_sql << " AND #{record.class.table_name}.#{scope_item} #{attribute_condition(scope_value)}"
533:               condition_params << scope_value
534:             end
535:           end
536:           unless record.new_record?
537:             condition_sql << " AND #{record.class.table_name}.#{record.class.primary_key} <> ?"
538:             condition_params << record.send(:id)
539:           end
540:           if record.class.find(:first, :conditions => [condition_sql, *condition_params])
541:             record.errors.add(attr_name, configuration[:message])
542:           end
543:         end
544:       end