添加关系时，flaskSQLAlchemy:“NoneType”对象没有属性“filter\u by”错误

Question

我正在尝试为我的数据库创建以下结构：

我有一个父类UserModel，其中ChefModel和{}作为子类。在我尝试添加OrderModel和这两个类之间的关系之前，一切正常。对UserModel或ChefModel的所有调用都会出现以下错误。例如，当我想找厨师时：

    File "C:\Users\Moham\Documents\Food order\resources\chef.py", line 60, in get
    users = ChefModel.query.filter_by(active = True).all()
AttributeError: 'NoneType' object has no attribute 'filter_by'

这是我的支票模型：

^{pr2}$

客户型号：

class CustomerModel(UserModel):
    __tablename__ = 'customers'
    id = db.Column(db.Integer, db.ForeignKey('users.id'), primary_key = True)   
    __mapper_args__ = {'polymorphic_identity':'customers'}

和订单型号：

class OrderModel(db.Model):
    __tablename__ = 'orders'
    order_id = db.Column(db.Integer, primary_key = True)    
    updated_date = db.Column(db.DateTime, default=datetime.utcnow())
    description = db.Column(db.String(254)) 
    food_items = db.relationship("FoodItemModel", secondary = association_table)
    customer_id = db.relationship(db.Integer, db.ForeignKey('customers.id')) //if remove this line
    chef_id = db.relationship(db.Integer, db.ForeignKey('chefs.id')) //and this line, calls are normal

我做错什么了？在

Answer 1

我认为您错误地指定了OrderModel中的customer_id和chef_id列。尝试这样做：

class OrderModel(db.Model):
    __tablename__ = 'orders'
    order_id = db.Column(db.Integer, primary_key = True)
    updated_date = db.Column(db.DateTime, default=datetime.utcnow())
    description = db.Column(db.String(254)) 
    customer_id = db.Column(db.Integer, db.ForeignKey("customers.id"))
    chef_id = db.Column(db.Integer, db.ForeignKey("chefs.id"))