Hi Hector,
If I'm not mistaken, everywhere you wrote
(MyObject.id==MyObject.containerId),
you meant to write: (Container.id==MyObject.containerId).
Instead of the backref technique, why not just create the MyObject--
>Container relationship a single time in your MyObject class. That
should be able to coexist with your first code example (with no
backrefs).
On Nov 11, 8:16 am, Hector Blanco <white.li...@gmail.com> wrote:
> I have a class that has two relationships to the same type of objects.
> One of the relationships will store objects of type "VR" and the other
> objects with a type "CC". One object can only be in one of the lists
> (relationships) at the same time:
>
> This is the "container" class and its two relationships:
>
> class Container(rdb.Model):
> rdb.metadata(metadata)
> rdb.tablename("containers")
>
> id = Column("id", Integer, primary_key=True)
>
> relation1 = relationship("MyObject",
> uselist=True,
> primaryjoin=lambda: and_((MyObject.id ==
> MyObject.containerId),
> (MyObject._type == "VR")),
> cascade="all, delete, delete-orphan"
> )
>
> relation2 = relationship("MyObject",
> uselist=True,
> primaryjoin=lambda: and_((MyObject.id ==
> MyObject.containerId),
> (MyObject._type == "CC")),
> cascade="all, delete, delete-orphan"
> )
>
> I don't think there's need to mention, but, MyObject.containerId is
> a ForeignKey "pointing" to the Container.id.
>
> I'd like to know if there's a way to create a backref so I will be
> able to access the "container" through the "MyObject" class. The idea
> would be having something like:
>
> relation1 = relationship("MyObject",
> uselist=True,
> primaryjoin=lambda: and_((MyObject.id ==
> MyObject.containerId),
> (MyObject._type == "VR")),
> cascade="all, delete, delete-orphan",
> backref=backref('container', order_by=id)
> )
>
> relation2 = relationship("MyObject",
> uselist=True,
> primaryjoin=lambda: and_((MyObject.id ==
> MyObject.containerId),
> (MyObject._type == "CC")),
> cascade="all, delete, delete-orphan",
> backref=backref('container', order_by=id)
> )
>
> But of course, that fails because it's trying to add two ".container"
> fields to the "MyObject" class.
>
> I have also seen that you can define "joins" in the backref, but I
> haven't been able to find examples about how to define it. And I am
> still not very sure that that would allow me to have to backrefs with
> the same name/identifier.
>
> I just need to know if it's even possible having two backrefs with the
> same name. Actually, a "you really got the whole concept wrong" may
> help too (if that's the case) . If it's doable, does any of you know
> where can I find examples of "advanced" backref usage? With primary
> joins, secondary joins and all that juicy stuff...
>
> Thank you in advance!!
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