CODEWITHSUNDEEP
pythonflaskflask-sqlalchemy
Mohamed_AbdAllah
Mohamed_AbdAllah

Reputation: 5322

flask-SQLAlchemy: 'NoneType' object has no attribute 'filter_by' error when adding relations

I am trying to create the following Structure for my DB:

I have a Parent class UserModel with ChefModel and CustomerModel as children. Everything is working fine until I try adding relations between an OrderModel and both classes. I get the following error on all calls to UserModel or ChefModel. For example, when I try to find a Chef:

    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'

Here is my ChefModel:

class ChefModel(UserModel):
    __tablename__ = 'chefs'
    id = db.Column(db.Integer, db.ForeignKey('users.id'), primary_key = True)
    food_items = db.relationship("FoodItemModel", backref="chef", lazy=True)
    __mapper_args__ = {'polymorphic_identity':'chefs'}

CustomerModel:

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

And OrderModel:

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

What am I doing wrong?

Upvotes: 1

Views: 2357

Answers (1)

bow
bow

Reputation: 2563

I think you've incorrectly specified the customer_id and chef_id columns in OrderModel. Try doing something like this:

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"))

Upvotes: 1

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