Ok, I have it like this now:
---------------------------------
class Comment(Object):
"""Allows commenting of any other entity in the server"""
__tablename__= 'comments'
uuid=Column(String(36),ForeignKey
('objects.uuid'),primary_key=True)
__mapper_args__ = {'polymorphic_identity': 'comment',
'inherit_condition':uuid==Object.uuid}
text=Column(String(),nullable=False)
author=Column(String(),nullable=False)
date=Column(AutoNowDateTime(),nullable=False)
subject_id=Column(String(36),ForeignKey('objects.uuid'))
def __repr__(self):
return u"<Comment('%s','%s','%s')>" % (self.author,str
(self.date),self.text[:20])
-------------------------
but I still get:
ArgumentError: Can't determine join between 'objects' and 'comments';
tables have more than one foreign key constraint relationship between
them. Please specify the 'onclause' of this join explicitly.
On Nov 12, 4:10 pm, Michael Bayer <[EMAIL PROTECTED]> wrote:
> On Nov 12, 2008, at 9:42 AM, tante wrote:
>
>
>
>
>
> > I'm working on a system that has a Base class called Object. Many
> > other classes inherit from this one class via joined table inheritance
> > and it's working great. But now there's a problem: The subclass
> > "Comment" does reference "Object" twice, once for the inheritance and
> > once as a ForeignKey to mark which object the comment is about.
>
> > Code example:
> > ----------------------------
> > Base = declarative_base()
> > class Object(Base):
> > "Base class for all our Entities"
>
> > __tablename__= 'objects'
>
> > uuid=Column(String(36),primary_key=True)
> > discriminator=Column(String(30), nullable=False)
>
> > __mapper_args__ = {'polymorphic_on': discriminator,
> > 'polymorphic_identity': 'object'}
>
> > def __init__(self,*args,**kwargs):
> > super(Object,self).__init__(*args,**kwargs)
> > if not self.uuid:
> > # create a random uuid
> > self.uuid=str(uuid4())
>
> > def __repr__(self):
> > return u"<Object('%s')>" % (self.uuid)
>
> > class Comment(Object):
> > """Allows commenting of any other entity in the server"""
> > __tablename__= 'comments'
> > __mapper_args__ = {'polymorphic_identity': 'comment'}
>
> > uuid=Column(String(36),ForeignKey
> > ('objects.uuid'),primary_key=True)
> > text=Column(String(),nullable=False)
> > author=Column(String(),nullable=False)
> > date=Column(AutoNowDateTime(),nullable=False)
> > subject_id=Column(String(36),ForeignKey('objects.uuid'))
>
> > def __repr__(self):
> > return u"<Comment('%s','%s','%s')>" % (self.author,str
> > (self.date),self.text[:20])
>
> > ------------------
> > This leads to this error:
> > #ArgumentError: Can't determine join between 'objects' and
> > 'comments';
> > #tables have more than one foreign key constraint relationship between
> > them.
> > #Please specify the 'onclause' of this join explicitly.
>
> > I tried to add __mapper_args__ to Comment like
> > "inherit_condition=Comment.c.uuid==Object.c.uuid"
> > but while I can get it to initialize, it won't let me query giving me
> > this error:
> > AttributeError: 'PropertyLoader' object has no attribute 'strategy'
>
> > How can I allow more than one reference between those Classes?
>
> strings aren't recognized for "inherit_condition", so do the dict lke
> __mapper_args__ = {'inherit_condition':uuid==Object.uuid}, and place
> __mapper_args__ in Comment after you define the "uuid" coumn.
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