On Oct 16, 7:42 pm, Michael Bayer <[EMAIL PROTECTED]> wrote:
> On Oct 16, 2007, at 1:30 PM, [EMAIL PROTECTED] wrote:
> > Am I really supposed to save/flush/clear/query my objects to get the
> > correct mappings?
> > Or is this a bug?
>
> the advised pattern here is the
> "association object" pattern described in the docs:
> http://www.sqlalchemy.org/docs/04/
> mappers.html#advdatamapping_relation_patterns_association
Ah, great. Thank you for your advice!
Using the association proxy
http://www.sqlalchemy.org/docs/04/plugins.html#plugins_associationproxy
I can also easily access the entities without explicitly using the
association:
u1 = User("test user 1")
e1 = Event("test event 1")
u1.events.append(e1) # association automatically created
u2 = User("test user 2")
e2 = Event("test event 2")
p2 = Participation(user=u2, event=e2, status=42) # explicit creation
of the association
Modified code for classes and mappers:
from sqlalchemy.ext.associationproxy import association_proxy
class User(object):
def __init__(self, name=None):
self.name = name
events = association_proxy('participations', 'event',
creator=lambda e: Participation(event=e))
class Event(object):
def __init__(self, title=None):
self.title = title
users = association_proxy('participations', 'user', creator=lambda
u: Participation(user=u))
class Participation(object):
def __init__(self, event=None, user=None, status=0):
self.event = event
self.user = user
self.status = status
mapper(User, user_table,
properties=dict(
participations=relation(Participation, backref='user'),
)
)
mapper(Participation, participation_table,
properties=dict(
user=relation(User, backref='participations')
)
)
mapper(Event, event_table,
properties=dict(
participations=relation(Participation, backref='event'),
)
)
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