gistfile1.rb

  ATTRIBUTES_ORDERED_FOR_CREATING_GUIDS = [:guid, :url, :content, :summary]
  def self.guid_from_entry(entry)
    def entry.can_make_guid_with?(symbol)
      respond_to?(symbol) && send(symbol).present?
    end
    def entry.make_guid_from(symbol)
      Digest::MD5.hexdigest(send(symbol))
    end

    ATTRIBUTES_ORDERED_FOR_CREATING_GUIDS.each do |symbol|
      entry.make_guid_from(symbol) if entry.can_make_guid_with?(symbol)
    end
  end