can you throw in the actual operations that fail in your test and I'll just run
it ? thanks.
On Mar 16, 2011, at 4:15 PM, Eric Ongerth wrote:
> I hope this makes sense, what I'm trying to do here. My naive first
> try at it was to just see if I could have the desired backref()s on
> either the A or C class, and manage to have the relationship go
> through the associationproxy. Probably I should be thinking of a
> technical reason why we would not expect that to work. So then I
> thought maybe the backrefs just need to be on the relationships
> defined on the B class. The above post was my third try, where I
> attempted to just make the whole setup symmetrical between A and C.
>
>
> On Mar 14, 4:44 pm, Eric Ongerth <ericonge...@gmail.com> wrote:
>> from sqlalchemy import Unicode, Integer, Column, create_engine,
>> ForeignKey
>> from sqlalchemy.orm import relationship, Session
>> from sqlalchemy.orm.collections import MappedCollection
>> from sqlalchemy.ext.declarative import declarative_base
>> from sqlalchemy.ext.associationproxy import association_proxy
>> import operator
>>
>> class Base(object):
>> id = Column(Integer, primary_key=True)
>>
>> Base = declarative_base(cls=Base)
>>
>> def _create_c_by_value(value):
>> return C(value)
>>
>> def _create_a_by_value(value):
>> return A(value)
>>
>> class A(Base):
>> __tablename__ = "a"
>> id = Column(Integer, primary_key=True)
>> value = Column(Unicode)
>> associations = relationship("B", cascade="all")
>> c_values = association_proxy("associations", "c_val",
>> creator=_create_c_by_value)
>>
>> def __init__(self, val):
>> self.value = val
>>
>> def __repr__(self):
>> return('<A>(%s)' % self.value)
>>
>> class B(Base):
>> __tablename__ = "b"
>> a_id = Column(Integer, ForeignKey("a.id"), nullable=False)
>> c_id = Column(Integer, ForeignKey("c.id"), nullable=False)
>> c_elements = relationship("C", cascade="all")
>> c_val = association_proxy("c_elements", "value")
>> a_elements = relationship("A", cascade="all")
>> a_val = association_proxy("a_elements", "value")
>>
>> class C(Base):
>> __tablename__ = "c"
>> id = Column(Integer, primary_key=True)
>> c_value = Column(Unicode)
>> associations = relationship("B", cascade="all")
>> a_values = association_proxy("associations", "a_val",
>> creator=_create_a_by_value)
>>
>> def __init__(self, val):
>> self.value = val
>>
>> def __repr__(self):
>> return('<C>(%s)' % self.value)
>>
>> if __name__ == "__main__":
>>
>> engine = create_engine('sqlite://', echo=True)
>> Base.metadata.create_all(engine)
>> session = Session(engine)
>>
>> Ok, running this sets up an example environment then you can
>> experiment. Try creating some As and relating them to some Cs. I'm
>> getting a bunch of different errors doing this. What am I doing wrong
>> or overlooking?
>>
>> The core of my inquiry is this: would this be the way to make two-way
>> relationships between two classes (two classes which have a many:many
>> relationship between them) work correctly when tunneled through an
>> associationproxy to hide the association object class between them?
>
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