Question

我尝试使用SQLAlchemy工具箱的关联代理。这是两个相关的模型，映射为一对多关系：

class User(object):
    query = db_session.query_property()
    def __init__(self, id):
        self.id = id
    def __repr__(self):
        return '{\"id: \"%i}' % (self.id)

class Context(object):
    query = db_session.query_property()
    def __init__(self, name, user, description=None, private=False):
        self.name = name
        self.description = description
        self.private = private
        self.user_id = user
    def __repr__(self):
        return '{\"id\": %i,\"name\":\"%s\", \"description\":\"%s\", \"private\":\"%r\" }' \
        % (self.id, self.name, self.description, self.private)

users = Table('users', metadata, 
    Column('id',Integer, primary_key=True))   
    mapper(User, users, properties={
'contexts' : relationship(Context, backref='user', lazy='dynamic')
})

contexts = Table('contexts', metadata, 
    Column('id', Integer, primary_key=True), 
    Column('name', String(50), nullable=True), 
    Column('description', String(255)), 
    Column('private', Boolean, default=True), 
    Column('user_id', Integer, ForeignKey('users.id'), nullable=False),
    UniqueConstraint('name', 'user_id','private')) 
mapper(Context, contexts)})

对于查询，我使用以下内容：

user = User.query.filter(User.id==id)
for context in user.contexts:
   context.do_stuff()

但出现以下错误：

AttributeError: 'Query' object has no attribute 'contexts'

Answer 1

问题的原因是您的关系中的lazy='dynamic'，它返回一个Query对象（以便执行其他操作，如过滤/排序等）。要解决此问题，请致电all()：

user = User.query.filter(User.id==id)
for context in user.contexts.all():
   context.do_stuff()

SQLAlchemy中关联代理的属性错误

1 个答案: