Flask-sqlalchemy-Marshmallow nesting Schema not working - flask

Question

Basically what i want to do is, join 2 tables 'users' & 'company' and get the users with their relevant company details .
this is the user model:
class User(db.Model):
__tablename__ = 'user'
id = db.Column(db.Integer, primary_key=True, autoincrement=True)
firstname = db.Column(db.String(10), nullable=False)
lastname = db.Column(db.String(25), nullable=False)
username = db.Column(db.String(250), nullable=False)
email = db.Column(db.String(100), nullable=False)
password = db.Column(db.String(250), nullable=False)
isPasswordReset = db.Column(db.Boolean, nullable=False)
companyId = db.Column(db.Integer, db.ForeignKey(
'company.id'), nullable=True)
and this is the schema
class UserSchema(ma.Schema):
id = fields.Integer()
firstname = fields.String(required=True)
lastname = fields.String(required=True)
username = fields.String(required=True)
email = fields.String(required=True)
password = fields.String(required=True)
isPasswordReset = fields.Boolean(required=True)
companyId = fields.Integer()
company_name = fields.Nested(CompanySchema)
This is the company model:
class Company(db.Model):
__tablename__ = 'company'
id = db.Column(db.Integer, primary_key=True, autoincrement=True)
companyName = db.Column(db.String(100), nullable=True)
companyCode = db.Column(db.String(20), nullable=True)
companyTheme = db.Column(db.String(300), nullable=True)
this is the company schema:
class CompanySchema(ma.Schema):
id = fields.Integer()
companyName = fields.String(required=True)
companyCode = fields.String(required=True)
companyTheme = fields.String(required=True)
and this is the resource-user.py :
users_schema = UserSchema(many=True)
user_schema = UserSchema()
class UsersResource(Resource):
def get(self):
users = db.session.query(User.firstname, Company.companyName).join(
Company, User.companyId == Company.id).all()
if users:
results = users_schema.dump(users).data
return {'status': 'success', 'message': json.dumps(results, default=str)}, 200
and this is output i get :
{
"status": "success",
"message": "[{\"firstname\": \"abc\"}, {\"firstname\": \"xyz\"}]"
}
only user table are shown, not from company table.i have followed a lot of tutorial and stuff for hours. but still couldn't fix it.i'm new to flask and sqlalchemy. please does anyone knows how to correct this?

Answer 1

At first you need to declare relationship object in your sqlalchemy model:
class User(db.Model):
__tablename__ = 'user'
id = db.Column(db.Integer, primary_key=True, autoincrement=True)
firstname = db.Column(db.String(10), nullable=False)
lastname = db.Column(db.String(25), nullable=False)
username = db.Column(db.String(250), nullable=False)
email = db.Column(db.String(100), nullable=False)
password = db.Column(db.String(250), nullable=False)
isPasswordReset = db.Column(db.Boolean, nullable=False)
companyId = db.Column(db.Integer, db.ForeignKey(
'company.id'), nullable=True)
company = db.relationship("Company", backref="parents") # <--
Then in the user schema declare field that represents that object:
class UserSchema(ma.Schema):
id = fields.Integer()
firstname = fields.String(required=True)
lastname = fields.String(required=True)
username = fields.String(required=True)
email = fields.String(required=True)
password = fields.String(required=True)
isPasswordReset = fields.Boolean(required=True)
companyId = fields.Integer()
company = fields.Nested(CompanySchema) # <--
Please notice, that field names must be the same (or you can use attribute argument).
While querying you could simply do:
user_schema = UserSchema()
users = User.query.all()
results = users_schema.dump(users).data
return {'status': 'success', 'message': json.dumps(results, default=str)}, 200
(or return users_schema.dump(users) for testing purposes)
After all you should get output like this:
{
id: 'something',
firstname: 'something',
lastname: 'something',
username: 'something',
email: 'something',
password: 'something',
isPasswordReset: 'something',
company : {
id: 'something',
companyName: 'something',
companyCode: 'something',
companyTheme: 'something',
}
}
Does this cover your needs?