Hi!
I try to clean up my code, and read in google group about possibility
create relation to self when class is not defined yet. I write
example,
but got an error (see below).
My code is:
================ cut ====================
engine = create_engine('sqlite:///:memory:', echo=True)
Base = declarative_base(bind=engine)
class Node(Base):
__tablename__ = 'node'
id = Column(Integer, primary_key=True)
title = Column(String(64))
node_id = Column(Integer, ForeignKey('node.id'))
children = relation('Node', \
backref=backref('parent', remote_side='Node.id'))
Base.metadata.create_all()
Session = scoped_session( \
sessionmaker(autocommit=False, \
autoflush=False, bind=engine))
session = Session()
root = Node(title='root')
node = Node(title='node')
root.children.append(node)
session.save(root)
session.commit()
================ cut ====================
Workaround worked correctly:
class Node(Base):
# define attrs without `children'
# ...
Node.__mapper__.add_property('children', relation(Node, \
backref=backref('parent', remote_side=Node.id)))
Last traceback lines (formated):
...
File "...orm/properties.py", line 578, in do_init
self._determine_local_remote_pairs()
File "...orm/properties.py", line 820, in
_determine_local_remote_pairs
self.local_side, self.remote_side = \
[util.OrderedSet(x) for x in zip(*list(self.local_remote_pairs))]
ValueError: need more than 0 values to unpack
(self.local_remote_pairs is `[]' here)
Can I define relation inside non-defined class, or I must use some
workarounds?
Thank you.
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