def []=(namespace = :default, index, value)
      obj = get_setting(namespace, index)
      if obj
        obj.instance_eval do
          write_attribute(setting_value_field, value)
        end
        obj.save
        write_cache(obj)
      else
        obj = write_cache(self.create(setting_name_field => index, setting_namespace_field => namespace, setting_value_field => value))
      end
    end
def []=(namespace = :default, index, value)
      obj = get_setting(namespace, index)
      if obj
        obj.instance_eval do
          write_attribute(setting_value_field, value)
        end
        obj.save
        write_cache(obj)
      else
        obj = write_cache(self.create(setting_name_field => index, setting_namespace_field => namespace, setting_value_field => value))
      end
    end
:call-seq:
   Model[:key] = value -> value
   Model[:namespace, :key] = value -> value

 Sets the value for +:key+ to +value+ and commits the new value to
 the database. If +:namespace+ is given, the key is set in that
 namespace only, if +:namespace+ is not given then +:default+ is
 used.