How can I implement advanced relationships in Flask-SQLAlchemy?

How can I implement advanced relationships in Flask-SQLAlchemy?

You can implement advanced relationships using techniques like backref, association tables, and hybrid properties. What specific relationship are you looking to create?

I want to create a many-to-many relationship between users and roles.

You can achieve this by creating an association table. Define a User model, a Role model, and an association table to link them. Would you like a code example?

Yes, please provide a code example for that.

Sure! Here's a simple example:

from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

user_roles = db.Table('user_roles',
    db.Column('user_id', db.Integer, db.ForeignKey('user.id')),
    db.Column('role_id', db.Integer, db.ForeignKey('role.id'))
)

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    roles = db.relationship('Role', secondary=user_roles, backref='users')

class Role(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(50))

That looks great! How do I add a user and assign roles to them?

You can create a user and assign roles like this:

new_user = User()
role1 = Role.query.get(1)
role2 = Role.query.get(2)
new_user.roles.append(role1)
new_user.roles.append(role2)
db.session.add(new_user)
db.session.commit()