rails--rails/activemodel/lib/active_model/validations/length.rb

module ActiveModel

  # == Active \Model Length \Validator
  module Validations
    class LengthValidator < EachValidator # :nodoc:
      MESSAGES  = { :is => :wrong_length, :minimum => :too_short, :maximum => :too_long }.freeze
      CHECKS    = { :is => :==, :minimum => :>=, :maximum => :<= }.freeze

      RESERVED_OPTIONS  = [:minimum, :maximum, :within, :is, :tokenizer, :too_short, :too_long]

      def initialize(options)
        if range = (options.delete(:in) || options.delete(:within))
          raise ArgumentError, ":in and :within must be a Range" unless range.is_a?(Range)
          options[:minimum], options[:maximum] = range.min, range.max
        end

        if options[:allow_blank] == false && options[:minimum].nil? && options[:is].nil?
          options[:minimum] = 1
        end

        super
      end

      def check_validity!
        keys = CHECKS.keys & options.keys

        if keys.empty?
          raise ArgumentError, 'Range unspecified. Specify the :in, :within, :maximum, :minimum, or :is option.'
        end

        keys.each do |key|
          value = options[key]

          unless (value.is_a?(Integer) && value >= 0) || value == Float::INFINITY
            raise ArgumentError, ":#{key} must be a nonnegative Integer or Infinity"
          end
        end
      end

      def validate_each(record, attribute, value)
        value = tokenize(value)
        value_length = value.respond_to?(:length) ? value.length : value.to_s.length
        errors_options = options.except(*RESERVED_OPTIONS)

        CHECKS.each do |key, validity_check|
          next unless check_value = options[key]

          if !value.nil? || skip_nil_check?(key)
            next if value_length.send(validity_check, check_value)
          end

          errors_options[:count] = check_value

          default_message = options[MESSAGES[key]]
          errors_options[:message] ||= default_message if default_message

          record.errors.add(attribute, MESSAGES[key], errors_options)
        end
      end

      private

      def tokenize(value)
        if options[:tokenizer] && value.kind_of?(String)
          options[:tokenizer].call(value)
        end || value
      end

      def skip_nil_check?(key)
        key == :maximum && options[:allow_nil].nil? && options[:allow_blank].nil?
      end
    end

    module HelperMethods

      # 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 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 :essay, minimum: 100, too_short: 'Your essay must be at least 100 words.',
      #                         tokenizer: ->(str) { str.scan(/\w+/) }
      #   end
      #
      # Configuration options:
      # * <tt>:minimum</tt> - The minimum size of the attribute.
      # * <tt>:maximum</tt> - The maximum size of the attribute. Allows +nil+ by
      #   default if not used with :minimum.
      # * <tt>:is</tt> - The exact size of the attribute.
      # * <tt>:within</tt> - A range specifying the minimum and maximum size of
      #   the attribute.
      # * <tt>:in</tt> - A synonym (or alias) for <tt>:within</tt>.
      # * <tt>:allow_nil</tt> - Attribute may be +nil+; skip validation.
      # * <tt>:allow_blank</tt> - Attribute may be blank; skip validation.
      # * <tt>:too_long</tt> - The error message if the attribute goes over the
      #   maximum (default is: "is too long (maximum is %{count} characters)").
      # * <tt>:too_short</tt> - The error message if the attribute goes under the
      #   minimum (default is: "is too short (min is %{count} characters)").
      # * <tt>:wrong_length</tt> - The error message if using the <tt>:is</tt>
      #   method and the attribute is the wrong size (default is: "is the wrong
      #   length (should be %{count} characters)").
      # * <tt>:message</tt> - The error message to use for a <tt>:minimum</tt>,
      #   <tt>:maximum</tt>, or <tt>:is</tt> violation. An alias of the appropriate
      #   <tt>too_long</tt>/<tt>too_short</tt>/<tt>wrong_length</tt> message.
      # * <tt>:tokenizer</tt> - Specifies how to split up the attribute string.
      #   (e.g. <tt>tokenizer: ->(str) { str.scan(/\w+/) }</tt> to count words
      #   as in above example). Defaults to <tt>->(value) { value.split(//) }</tt>
      #   which counts individual characters.
      #
      # There is also a list of default options supported by every validator:
      # +:if+, +:unless+, +:on+ and +:strict+.
      # See <tt>ActiveModel::Validation#validates</tt> for more information
      def validates_length_of(*attr_names)
        validates_with LengthValidator, _merge_attributes(attr_names)
      end

      alias_method :validates_size_of, :validates_length_of
    end
  end
end