[FIXED] Implement Login system in python using flask_login with different user types

Issue

I am trying to create a college system using flask but I have a problem with log in system basically I have two classes Teacher class and Student class the problem is that I cant figure a way to make the login manager handle the two classes login at the same time only one can log in and when the other class try to log in it log me as the class what I mean is when I setup the login manager to accept student it works with the student but when I try to login as a teacher it searches in the student table instead of teacher table I don't know if I explained it right but i hope code snippet help

this is models

attend = db.Table('attend',
    db.Column('teacher_id',db.Integer,db.ForeignKey('teacher.id')),
    db.Column('student_id', db.Integer, db.ForeignKey('student.id'))
)

class Teacher(db.Model,UserMixin):
    id = db.Column(db.Integer, primary_key=True)
    name=db.Column(db.String(60),nullable=False)
    email=db.Column(db.String(100),nullable=False,unique=True)
    password=db.Column(db.String(60),nullable=False)
    department=db.Column(db.String(50),nullable=False)
    students=db.relationship('Student',secondary=attend,backref='students',lazy='dynamic')


    def type_auth(self):
        return True

    def __repr__(self) -> str:
        return f'name:{self.name} email:{self.email} department:{self.department}'


class Student(db.Model,UserMixin):
    id = db.Column(db.Integer, primary_key=True)
    name=db.Column(db.String(60),nullable=False)
    email = db.Column(db.String(100), nullable=False, unique=True)
    password = db.Column(db.String(60), nullable=False)
    year=db.Column(db.Integer,nullable=False)
    grades = db.relationship('Grades', backref='Rates', lazy='dynamic')

    def type_auth(self):
        return False
    
    def __repr__(self) -> str:
        return f'name:{self.name} email:{self.email} year:{self.year}'

this login manager

def create_app():
    app=Flask(__name__)
    app.config['SQLALCHEMY_DATABASE_URI']=f'sqlite:///{DB_NAME}'
    app.config['SECERT_KEY'] = '1853d2c8983cff3b'
    app.config['FLASK_ADMIN_SWITCH']='Cyborg'
    db.init_app(app)

    from .auth import auth
    from .routes import routes

    app.register_blueprint(auth,prefix_url='/')
    app.register_blueprint(routes,prefix_url='/')

    login_manger=LoginManager()
    login_manger.login_view='auth.login'
    login_manger.login_message_category='info'
    login_manger.init_app(app)

    @login_manger.user_loader
    def user_loader(id):
        #i need help here

    return app

Solution

The user_loader callback received an id as an argument and from that information is expected to return an instance of whatever you have defined as your "User" class. You have effectively defined two "User" classes, and in the current configuration there is no way for the user loader, if passed "1", to determine whether it should return the Teacher with id 1 or the Student with id 1.

A better design might be to move email and password into a new User class, and create one-to-one relationships between User and Student and Teacher. You can add some validation to ensure that a User cannot relate to both a Student and a Teacher.

Answered By - snakecharmerb