我想实现一些映射类型，many to many例如. 例如，“apple”是“juicy fruits”的子代，同时，“apple”是许多“特定种类的苹果”的父代，而“juicy fruits”当然有很多父代喜欢“吃的东西” ”。简而言之就是关系。而且，它们都是关键字 class( ) 的实例。我将其定义如下，self referentialkeyword netmany to manyself referential
kw2kw_table=Table('kw2kw_table',Base.metadata,
Column('child_id',Integer,ForeignKey('kw_table.id'),primary_key=True),
Column('parent_id',Integer,ForeignKey('kw_table.id'),primary_key=True),
)
class KW(Base):
__tablename__='kw_table'
id=Column(Integer,primary_key=True)
name=Column(Unicode(28),unique=True)
parents=relationship('KW',
secondary=kw2kw_table,
primaryjoin=id==kw2kw_table.c.child_id,
secondaryjoin=id==kw2kw_table.c.parent_id,
backref='children',
)
def __init__(self,name,parent=None):
self.name=name
self.children=[]
if parent==None: #default to a root keyword
self.parents.append(self)
else:
self.parents.append(parent)
在我的视图文件中：
...
keywordName = request.params['keyword']
parentName = request.params.get('parent',u'')
if parentName:
parent=DBSession.query(KW).filter(KW.name==parentName)
if parent: #if parent exists
new_kw=KW(keywordName,parent)
else:
parent=KW(parentName)
new_kw=KW(keywordName,parent)
else: #if the parent was not provided
new_kw=KW(keywordName)
DBSession.add(new_kw)
...
但是，当使用 提交视图时(keyword,parent)，出现错误：
File "build/bdist.macosx-10.6-intel/egg/sqlalchemy/orm/attributes.py", line 910, in fire_append_event
value = fn(state, value, initiator or self)
File "build/bdist.macosx-10.6-intel/egg/sqlalchemy/orm/attributes.py", line 1138, in emit_backref_from_collection_append_event
child_state, child_dict = instance_state(child), \
AttributeError: 'Query' object has no attribute '_sa_instance_state'
我用谷歌搜索了它，但无法弄清楚。请帮忙。