def touch(name = nil)
      now = DateTime.now
      self.updated_at = now
      attributes[name] = now if name
      save
    end
def touch(name = nil)
      now = DateTime.now
      self.updated_at = now
      attributes[name] = now if name
      save
    end
Set updated_at and any passed in field to current DateTime. Useful for things like last_login_at, etc.