Flask sqlalchemy PUT请求，如何从关系表中查询两个动态外键ID

Question

I'm trying to update data in the front end using React/Redux from a PUT request in a flask/sqlalchemy/postgres backend. My problem is that my endpoint is only able to be updated by the id, which is useless to the frontend. The reason this is, is because the data being updated is from a relationship class that only exists to join two other classes. What I need to do is figure out how to query and return by user_id and country_id rather than id. By the way, I'm testing locally with Postman. The models for the join class(table) are as follows

class users_countries_join(db.Model):
    id = db.Column(Integer, autoincrement=True, primary_key=True)
    user_id = db.Column(Integer, ForeignKey(users.id), nullable=False)
    country_id = db.Column(Integer, ForeignKey(countries.id), nullable=False)
    status = db.Column(Integer, nullable=False)
    notes = db.Column(TEXT, nullable=True)
    user = db.relationship('users', backref='user_countries')
    country = db.relationship('countries', backref='travelers')

    def __init__(self, user_id, country_id, status, notes):
        self.user_id = user_id
        self.country_id = country_id
        self.status = status
        self.notes = notes

    def __repr__(self):
        return '<{}>' % self.__name__

The code for the endpoint is:

@app.route('/api/mapview/<int:user_id>/<int:country_id>/<int:id>', methods=['PUT'])
def update_mapView_data(user_id, country_id, id):
   user_country = users_countries_join.query.get(id)
   user_country.user_id = request.json[‘user_id’]
   user_country.country_id = request.json[‘country_id’]
   user_country.status = request.json[‘status’]
   user_country.notes = request.json[‘notes’]
    db.session.commit()
    return user_country_schema.jsonify(user_country)

I've tried to change the endpoint to the code, below, but that doesn't work. In theory, that's the sort of update i need though. One that updated by accessing the data via the user_id and country_id rather than the id of the class. I'm beginning to think that id is unnecessary to begin with.

@app.route('/api/mapview/<int:user_id>/<int:country_id>', methods=['PUT'])
def update_mapView_data(user_id, country_id):
   user_country = users_countries_join.query.get(user_id, country_id)
   user_country.user_id = request.json[‘user_id’]
   user_country.country_id = request.json[‘country_id’]
   user_country.status = request.json[‘status’]
   user_country.notes = request.json[‘notes’]
    db.session.commit()
    return user_country_schema.jsonify(user_country)

Can someone point me in the right direction in how to do this? I'm hoping I'm just making this more difficult than it has to be.

Answer 1

You can use filter_by() method to filter rows. For example, if you want to get first user_country using user_id and country_id you can use following query:

user_country = users_countries_join.query.filter_by(user_id=user_id, country_id=country_id).first()

If you have more than one database row with same user_id or country_id:

user_country = users_countries_join.query.filter_by(user_id=user_id, country_id=country_id).all()

In your example I guess that you want to get the only one unique row so you can use the first query. Also, after you change model properties values you have to add that change to the db.session:

db.session.add(user_country)

and commit change to the database:

db.session.commit()

I want also to note that you should use camel case when you declaring python class name like UserCountry or only Cuntry and for joining two models(tables) you shouldn't define same attributes that you have in User class or Country class. In my opinion that way of joining two tables is redundant.