# File lib/active_record/validations.rb, line 556
      def validates_length_of(*attrs)
        # Merge given options with defaults.
        options = {
          :tokenizer => lambda {|value| value.split(//)}
        }.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)

            validates_each(attrs, options) do |record, attr, value|
              value = options[:tokenizer].call(value) if value.kind_of?(String)
              if value.nil? or value.size < option_value.begin
                record.errors.add(attr, :too_short, :default => options[:too_short], :count => option_value.begin)
              elsif value.size > option_value.end
                record.errors.add(attr, :too_long, :default => options[:too_long], :count => option_value.end)
              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 }

            validates_each(attrs, options) do |record, attr, value|
              value = options[:tokenizer].call(value) if value.kind_of?(String)
              unless !value.nil? and value.size.method(validity_checks[option])[option_value]
                key = message_options[option]
                custom_message = options[:message] || options[key]
                record.errors.add(attr, key, :default => custom_message, :count => option_value) 
              end
            end
        end
      end