Hello,
I have recently converted a Pylons app from SQLObject to SQLAlchemy
0.3.10. Conversion went quite well.
I need to serialize access to some of my objects, so I've looked into
extending MapperExtension as described at [1] to add a mutex on load.
First, I define an extension and instantiate it:
--------
from sqlalchemy.orm import MapperExtension
import mutex
class MutexExtension(MapperExtension):
def create_instance(self, mapper, selectcontext, row, class_):
self.mutex = mutex.mutex()
return None
mutexext = MutexExtension()
-------
My mapper setup looks like this:
switch_mapper = mapper (Switch, switch_table,
extension=[mutexext.mutexext, sac.ext],
properties={'ports':sqla.relation(SwitchPort)})
When I try to fetch objects from the database, I get a exception
setting
self.entity_name:
Module sqlalchemy.orm.mapper:1485 in _instance
<< instance = self._create_instance(context.session)
else:
instance._entity_name = self.entity_name
if self.__should_log_debug:
self.__log_debug("_instance(): created new
instance %s identity %s" % (mapperutil.instance_str(instance),
%str(identitykey)))>>
instance._entity_name = self.entity_name
exceptions.AttributeError: 'NoneType' object has no attribute
'_entity_name'
What did I do wrong?
Thanks,
Ross
[1]
http://www.sqlalchemy.org/docs/03/adv_datamapping.html#advdatamapping_extending
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