gistfile1.txt

class InclusionWithBlockValidator < ActiveModel::EachValidator
  def validate_each(object, attribute, value)
    begin
      enum = options[:in].call
      raise unless enum.kind_of?(Enumerable)
    rescue 
      raise "value of :in option at inclusion_with_block validator " + 
            "must be a block those return enumerable object"
    end
    unless enum.include?(value)
      object.errors[attribute] << (options[:message] || 
        I18n.t(:'activerecord.errors.messages.inclusion'))
    end
  end
end