Validates that the specified attributes are blank (as defined by Object#blank?). Happens by default on save.

class Person < ActiveRecord::Base
  validates_absence_of :first_name
end

The first_name attribute must be in the object and it must be blank.

Configuration options:

• :message - A custom error message (default is: “must be blank”).

There is also a list of default options supported by every validator: :if, :unless, :on, :allow_nil, :allow_blank, and :strict. See ActiveModel::Validations#validates for more information

# File activemodel/lib/active_model/validations/absence.rb, line 26
def validates_absence_of(*attr_names)
  validates_with AbsenceValidator, _merge_attributes(attr_names)
end

Encapsulates the pattern of wanting to validate the acceptance of a terms of service check box (or similar agreement).

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”).

• :accept - Specifies a value that is considered accepted. Also accepts an array of possible values. The default value is an array [“1”, true], which makes it easy to relate to an HTML checkbox. This should be set to, or include, true if you are validating a database column, since the attribute is typecast from “1” to true before validation.

There is also a list of default options supported by every validator: :if, :unless, :on, :allow_nil, :allow_blank, and :strict. See ActiveModel::Validations#validates for more information.

# File activemodel/lib/active_model/validations/acceptance.rb, line 99
def validates_acceptance_of(*attr_names)
  validates_with AcceptanceValidator, _merge_attributes(attr_names)
end

Encapsulates the pattern of wanting to validate a password or email address field with a confirmation.

Model:
  class Person < ActiveRecord::Base
    validates_confirmation_of :user_name, :password
    validates_confirmation_of :email_address,
                              message: 'should match confirmation'
  end

View:
  <%= password_field "person", "password" %>
  <%= password_field "person", "password_confirmation" %>

The added password_confirmation attribute is virtual; it exists only as an in-memory attribute for validating the password. To achieve this, the validation adds accessors to the model for the confirmation attribute.

NOTE: This check is performed only if password_confirmation is not nil. 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 %{translated_attribute_name}”).

• :case_sensitive - Looks for an exact match. Ignored by non-text columns (true by default).

There is also a list of default options supported by every validator: :if, :unless, :on, :allow_nil, :allow_blank, and :strict. See ActiveModel::Validations#validates for more information

# File activemodel/lib/active_model/validations/confirmation.rb, line 73
def validates_confirmation_of(*attr_names)
  validates_with ConfirmationValidator, _merge_attributes(attr_names)
end

Validates that the value of the specified attribute is not in a particular enumerable object.

class Person < ActiveRecord::Base
  validates_exclusion_of :username, in: %w( admin superuser ), message: "You don't belong here"
  validates_exclusion_of :age, in: 30..60, message: 'This site is only for under 30 and over 60'
  validates_exclusion_of :format, in: %w( mov avi ), message: "extension %{value} is not allowed"
  validates_exclusion_of :password, in: ->(person) { [person.username, person.first_name] },
                         message: 'should not be the same as your username or first name'
  validates_exclusion_of :karma, in: :reserved_karmas
end

Configuration options:

• :in - An enumerable object of items that the value shouldn't be part of. This can be supplied as a proc, lambda or symbol which returns an enumerable. If the enumerable is a numerical, time or datetime range the test is performed with Range#cover?, otherwise with include?. When using a proc or lambda the instance under validation is passed as an argument.

• :within - A synonym(or alias) for :in Range#cover?, otherwise with include?.

• :message - Specifies a custom error message (default is: “is reserved”).

There is also a list of default options supported by every validator: :if, :unless, :on, :allow_nil, :allow_blank, and :strict. See ActiveModel::Validations#validates for more information

# File activemodel/lib/active_model/validations/exclusion.rb, line 42
def validates_exclusion_of(*attr_names)
  validates_with ExclusionValidator, _merge_attributes(attr_names)
end

Validates whether the value of the specified attribute is of the correct form, going by the regular expression provided. You can require that the attribute matches the regular expression:

class Person < ActiveRecord::Base
  validates_format_of :email, with: /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i, on: :create
end

Alternatively, you can require that the specified attribute does not match the regular expression:

class Person < ActiveRecord::Base
  validates_format_of :email, without: /NOSPAM/
end

You can also provide a proc or lambda which will determine the regular expression that will be used to validate the attribute.

class Person < ActiveRecord::Base
  # Admin can have number as a first letter in their screen name
  validates_format_of :screen_name,
                      with: ->(person) { person.admin? ? /\A[a-z0-9][a-z0-9_\-]*\z/i : /\A[a-z][a-z0-9_\-]*\z/i }
end

Note: use \A and \z to match the start and end of the string, ^ and $ match the start/end of a line.

Due to frequent misuse of ^ and $, you need to pass the multiline: true option in case you use any of these two anchors in the provided regular expression. In most cases, you should be using \A and \z.

You must pass either :with or :without as an option. In addition, both must be a regular expression or a proc or lambda, or else an exception will be raised.

Configuration options:

• :message - A custom error message (default is: “is invalid”).

• :with - Regular expression that if the attribute matches will result in a successful validation. This can be provided as a proc or lambda returning regular expression which will be called at runtime.

• :without - Regular expression that if the attribute does not match will result in a successful validation. This can be provided as a proc or lambda returning regular expression which will be called at runtime.

• :multiline - Set to true if your regular expression contains anchors that match the beginning or end of lines as opposed to the beginning or end of the string. These anchors are ^ and $.

There is also a list of default options supported by every validator: :if, :unless, :on, :allow_nil, :allow_blank, and :strict. See ActiveModel::Validations#validates for more information

# File activemodel/lib/active_model/validations/format.rb, line 108
def validates_format_of(*attr_names)
  validates_with FormatValidator, _merge_attributes(attr_names)
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 )
  validates_inclusion_of :age, in: 0..99
  validates_inclusion_of :format, in: %w( jpg gif png ), message: "extension %{value} is not included in the list"
  validates_inclusion_of :states, in: ->(person) { STATES[person.country] }
  validates_inclusion_of :karma, in: :available_karmas
end

Configuration options:

• :in - An enumerable object of available items. This can be supplied as a proc, lambda or symbol which returns an enumerable. If the enumerable is a numerical, time or datetime range the test is performed with Range#cover?, otherwise with include?. When using a proc or lambda the instance under validation is passed as an argument.

• :within - A synonym(or alias) for :in

• :message - Specifies a custom error message (default is: “is not included in the list”).

There is also a list of default options supported by every validator: :if, :unless, :on, :allow_nil, :allow_blank, and :strict. See ActiveModel::Validations#validates for more information

# File activemodel/lib/active_model/validations/inclusion.rb, line 40
def validates_inclusion_of(*attr_names)
  validates_with InclusionValidator, _merge_attributes(attr_names)
end

Validates that the specified attributes match the length restrictions supplied. Only one constraint option can be used at a time apart from :minimum and :maximum that can be combined together:

class Person < ActiveRecord::Base
  validates_length_of :first_name, maximum: 30
  validates_length_of :last_name, maximum: 30, message: "less than 30 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 :zip_code, minimum: 5, too_short: 'please enter at least 5 characters'
  validates_length_of :smurf_leader, is: 4, message: "papa is spelled with 4 characters... don't play me."
  validates_length_of :words_in_essay, minimum: 100, too_short: 'Your essay must be at least 100 words.'

  private

  def words_in_essay
    essay.scan(/\w+/)
  end
end

Constraint options:

• :minimum - The minimum size of the attribute.

• :maximum - The maximum size of the attribute. Allows nil by default if not used with :minimum.

• :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.

Other options:

• :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 %{count} characters)”).

• :too_short - The error message if the attribute goes under the minimum (default is: “is too short (minimum is %{count} 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 %{count} 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.

There is also a list of default options supported by every validator: :if, :unless, :on and :strict. See ActiveModel::Validations#validates for more information

# File activemodel/lib/active_model/validations/length.rb, line 114
def validates_length_of(*attr_names)
  validates_with LengthValidator, _merge_attributes(attr_names)
end

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

• :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 Integer 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.

• :other_than - Specifies the value must be other than the supplied value.

• :odd - Specifies the value must be an odd number.

• :even - Specifies the value must be an even number.

There is also a list of default options supported by every validator: :if, :unless, :on, :allow_nil, :allow_blank, and :strict . See ActiveModel::Validations#validates for more information

The following checks can also be supplied with a proc or a symbol which corresponds to a method:

• :greater_than

• :greater_than_or_equal_to

• :equal_to

• :less_than

• :less_than_or_equal_to

• :only_integer

For example:

class Person < ActiveRecord::Base
  validates_numericality_of :width, less_than: ->(person) { person.height }
  validates_numericality_of :width, greater_than: :minimum_weight
end

# File activemodel/lib/active_model/validations/numericality.rb, line 158
def validates_numericality_of(*attr_names)
  validates_with NumericalityValidator, _merge_attributes(attr_names)
end

Validates that the specified attributes are not blank (as defined by Object#blank?). Happens by default on save.

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”).

There is also a list of default options supported by every validator: :if, :unless, :on, :allow_nil, :allow_blank, and :strict. See ActiveModel::Validations#validates for more information

# File activemodel/lib/active_model/validations/presence.rb, line 33
def validates_presence_of(*attr_names)
  validates_with PresenceValidator, _merge_attributes(attr_names)
end