Shoot!! It works!! :D :D
---------------------- Parent.py (extract) ----------------------
# . . .
child1 = relationship(
"Child",
uselist=True,
primaryjoin=lambda: and_((Parent.id == Child.parent_id),
(Child.type
== "VR")),
collection_class=lambda: ZepConnector("VR")
)
child2 = relationship(
"Child",
uselist=True,
primaryjoin=lambda: and_((Parent.id == Child.parent_id),
(Child.type
== "CC")),
collection_class=lambda: ZepConnector("CC")
)
-----------------------
Do you know any documentation where I can understand "why"? Conor
already mentioned
(http://groups.google.com/group/sqlalchemy/msg/d8fbbbff6d961332) the
importance of using lambdas, strings... to avoid mistakes,
------ Quote: ---------
In SQLAlchemy you get around circular dependencies by:
* Using strings as the target of ForeignKey()
* Using class name strings as the target of a relation (declarative
only)
* Using strings or callables as primaryjoin/secondaryjoin arguments
in a relationship()
---------------------------------
but I'd like to understand a little bit more how does it work (what's
going on internally) so I won't make similar errors in the future.
Thank you so much...
2010/11/9 Michael Bayer <mike...@zzzcomputing.com>:
>
> On Nov 8, 2010, at 6:36 PM, Hector Blanco wrote:
>
>> methods that I have implemented and that need to be there. That would
>> be the "ZepConnector" (and, for purposes of the example, it's method
>> foo() it's the one I need to use). As you can see in the following
>> lines, I randomly test its availability in the addChild1() method of
>> the Parent.
>>
>> child1 = relationship(
>> "Child",
>> uselist=True,
>> primaryjoin=lambda: and_((Parent.id == Child.parent_id),
>> (Child.type
>> == "VR")),
>> collection_class=ZepConnector("VR")
>> )
>
> So this is incorrect - collection_class takes a class or other callable as an
> argument that will produce an instance of your collection. The ZepConnector
> source you have below indicates that ZepConnector("VR") is an instance of the
> collection. You need to use a lambda: there. The other errors you're
> getting would appear to extend from that (and is also why __init__ is called
> on ZepConnector - you're calling it yourself).
>
>
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