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

require 'active_support/core_ext/range'

module ActiveModel
  module Validations
    module Clusivity #:nodoc:
      ERROR_MESSAGE = "An object with the method #include? or a proc, lambda or symbol is required, " \
                      "and must be supplied as the :in (or :within) option of the configuration hash"

      def check_validity!
        unless delimiter.respond_to?(:include?) || delimiter.respond_to?(:call) || delimiter.respond_to?(:to_sym)
          raise ArgumentError, ERROR_MESSAGE
        end
      end

    private

      def include?(record, value)
        members = if delimiter.respond_to?(:call)
                    delimiter.call(record)
                  elsif delimiter.respond_to?(:to_sym)
                    record.send(delimiter)
                  else
                    delimiter
                  end

        members.send(inclusion_method(members), value)
      end

      def delimiter
        @delimiter ||= options[:in] || options[:within]
      end

      # In Ruby 1.9 <tt>Range#include?</tt> on non-number-or-time-ish ranges checks all
      # possible values in the range for equality, which is slower but more accurate.
      # <tt>Range#cover?</tt> uses the previous logic of comparing a value with the range
      # endpoints, which is fast but is only accurate on Numeric, Time, or DateTime ranges.
      def inclusion_method(enumerable)
        return :include? unless enumerable.is_a?(Range)
        case enumerable.first
        when Numeric, Time, DateTime
          :cover?
        else
          :include?
        end
      end
    end
  end
end