[Source]

# File activerecord/lib/active_record/validations.rb, line 316
      def condition_block?(condition)
        condition.respond_to?("call") && (condition.arity == 1 || condition.arity == -1)
      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 activerecord/lib/active_record/validations.rb, line 844
      def create!(attributes = nil)
        if attributes.is_a?(Array)
          attributes.collect { |attr| create!(attr) }
        else
          object = new(attributes)
          object.save!
          object
        end
      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 activerecord/lib/active_record/validations.rb, line 322
      def evaluate_condition(condition, record)
        case condition
          when Symbol; record.send(condition)
          when String; eval(condition, record.send(: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

[Source]

# File activerecord/lib/active_record/validations.rb, line 301
      def validate(*methods, &block)
        methods << block if block_given?
        write_inheritable_set(:validate, methods)
      end

[Source]

# File activerecord/lib/active_record/validations.rb, line 306
      def validate_on_create(*methods, &block)
        methods << block if block_given?
        write_inheritable_set(:validate_on_create, methods)
      end

[Source]

# File activerecord/lib/active_record/validations.rb, line 311
      def validate_on_update(*methods, &block)
        methods << block if block_given?
        write_inheritable_set(:validate_on_update, methods)
      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:

• 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.
• 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 activerecord/lib/active_record/validations.rb, line 432
      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.extract_options!)

        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 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.
• 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 activerecord/lib/active_record/validations.rb, line 764
      def validates_associated(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:invalid], :on => :save }
        configuration.update(attr_names.extract_options!)

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

• 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 activerecord/lib/active_record/validations.rb, line 399
      def validates_confirmation_of(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:confirmation], :on => :save }
        configuration.update(attr_names.extract_options!)

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

        validates_each(attr_names, configuration) do |record, attr_name, value|
          record.errors.add(attr_name, configuration[:message]) unless record.send("#{attr_name}_confirmation").nil? or value == record.send("#{attr_name}_confirmation")
        end
      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 activerecord/lib/active_record/validations.rb, line 357
      def validates_each(*attrs)
        options = attrs.extract_options!.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 or there is an :unless condition and that condition is true
          unless (options[:if] && !evaluate_condition(options[:if], record)) || (options[:unless] && evaluate_condition(options[:unless], record))
            attrs.each do |attr|
              value = record.send(attr)
              next if (value.nil? && options[:allow_nil]) || (value.blank? && options[:allow_blank])
              yield record, attr, value
            end
          end
        end
      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:

• 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 activerecord/lib/active_record/validations.rb, line 721
      def validates_exclusion_of(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:exclusion], :on => :save }
        configuration.update(attr_names.extract_options!)

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

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

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

Validates whether the value of the specified attribute is of the correct form by matching it against the regular expression provided.

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

Note: use \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 activerecord/lib/active_record/validations.rb, line 661
      def validates_format_of(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:invalid], :on => :save, :with => nil }
        configuration.update(attr_names.extract_options!)

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

        validates_each(attr_names, configuration) do |record, attr_name, value|
          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:

• 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 activerecord/lib/active_record/validations.rb, line 690
      def validates_inclusion_of(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:inclusion], :on => :save }
        configuration.update(attr_names.extract_options!)

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

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

        validates_each(attr_names, configuration) do |record, attr_name, value|
          record.errors.add(attr_name, configuration[:message]) unless enum.include?(value)
        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 :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 activerecord/lib/active_record/validations.rb, line 521
      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.extract_options!.symbolize_keys)

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

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

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

            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.split(//).size < option_value.begin
                record.errors.add(attr, too_short)
              elsif value.split(//).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|
              if value.kind_of?(String)
                record.errors.add(attr, message) unless !value.nil? and value.split(//).size.method(validity_checks[option])[option_value]
              else
                record.errors.add(attr, message) unless !value.nil? and value.size.method(validity_checks[option])[option_value]
              end
            end
        end
      end

Validates whether the value of the specified attribute is numeric by trying to convert it to a float with Kernel.Float (if 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 activerecord/lib/active_record/validations.rb, line 800
      def validates_numericality_of(*attr_names)
        configuration = { :on => :save, :only_integer => false, :allow_nil => false }
        configuration.update(attr_names.extract_options!)


        numericality_options = ALL_NUMERICALITY_CHECKS.keys & configuration.keys

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

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

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

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

          numericality_options.each do |option|
            case option
              when :odd, :even
                record.errors.add(attr_name, configuration[:message] || ActiveRecord::Errors.default_error_messages[option]) unless raw_value.to_i.method(ALL_NUMERICALITY_CHECKS[option])[]
              else
                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]]
            end
          end
        end
      end

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

  class Person < ActiveRecord::Base
    validates_presence_of :first_name
  end

The first_name attribute must be in the object and it cannot be blank.

If you want to validate the presence of a boolean field (where the real values are true and false), you will want to use validates_inclusion_of :field_name, :in => [true, false] This is due to the way Object#blank? handles boolean values. false.blank? # => true

Configuration options:

• 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 activerecord/lib/active_record/validations.rb, line 476
      def validates_presence_of(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:blank], :on => :save }
        configuration.update(attr_names.extract_options!)

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

Alias for validates_length_of

Validates whether the value of the specified attributes are unique across the system. Useful for making sure that only one user can be named "davidhh".

  class Person < ActiveRecord::Base
    validates_uniqueness_of :user_name, :scope => :account_id
  end

It can also validate whether the value of the specified attributes are unique based on multiple scope parameters. For example, making sure that a teacher can only be on the schedule once per semester for a particular class.

  class TeacherSchedule < ActiveRecord::Base
    validates_uniqueness_of :teacher_id, :scope => [:semester_id, :class_id]
  end

When the record is created, a check is performed to make sure that no record exists in the database with the given value for the specified attribute (that maps to a column). When the record is updated, the same check is made but disregarding the record itself.

Configuration options:

• 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 activerecord/lib/active_record/validations.rb, line 610
      def validates_uniqueness_of(*attr_names)
        configuration = { :message => ActiveRecord::Errors.default_error_messages[:taken], :case_sensitive => true }
        configuration.update(attr_names.extract_options!)

        validates_each(attr_names,configuration) do |record, attr_name, value|
          if value.nil? || (configuration[:case_sensitive] || !columns_hash[attr_name.to_s].text?)
            condition_sql = "#{record.class.table_name}.#{attr_name} #{attribute_condition(value)}"
            condition_params = [value]
          else
            condition_sql = "LOWER(#{record.class.table_name}.#{attr_name}) #{attribute_condition(value)}"
            condition_params = [value.downcase]
          end
          if scope = configuration[:scope]
            Array(scope).map do |scope_item|
              scope_value = record.send(scope_item)
              condition_sql << " AND #{record.class.table_name}.#{scope_item} #{attribute_condition(scope_value)}"
              condition_params << scope_value
            end
          end
          unless record.new_record?
            condition_sql << " AND #{record.class.table_name}.#{record.class.primary_key} <> ?"
            condition_params << record.send(:id)
          end
          if record.class.find(:first, :conditions => [condition_sql, *condition_params])
            record.errors.add(attr_name, configuration[:message])
          end
        end
      end

[Source]

# File activerecord/lib/active_record/validations.rb, line 861
        def validation_method(on)
          case on
            when :save   then :validate
            when :create then :validate_on_create
            when :update then :validate_on_update
          end
        end

[Source]

# File activerecord/lib/active_record/validations.rb, line 856
        def write_inheritable_set(key, methods)
          existing_methods = read_inheritable_attribute(key) || []
          write_inheritable_attribute(key, existing_methods | methods)
        end