How to do a create endpoint with relationship with fastapi and sqlmodel?

Question

In models, have a User that can have many roles and Role that can have many users (many-to-many):

class UsersRoles(SQLModel, table=True):
    user_id: int = Field(foreign_key='users.id', primary_key=True)
    role_id: int = Field(foreign_key='roles.id', primary_key=True)


class User(SQLModel, table=True):
    id: int = Field(default=None, primary_key=True)
    name: str
    email: str = Field(unique=True, index=True)
    roles: list['Role'] = Relationship(back_populates='users', link_model=UsersRoles)


class Role(SQLModel, table=True):
    id: int = Field(default=None, primary_key=True)
    name: str = Field(unique=True)
    users: list['User'] = Relationship(back_populates='roles', link_model=UsersRoles)

In the api, declare the endpoint:

@router.post('/user')
def create_user(user: User) -> User:
    with get_session() as session:
        session.add(user)
        session.commit()
        session.refresh(user)
        return user

Then I want to create the User with roles and call the endpoint:

role = Role(name='admin')
user = User(name='Jane', email='test@xyz.com', roles=[role])

# payload = {
#   'name': 'Jane',
#   'email': 'test@xyz.com',
#   'roles': ['admin']
# }
payload = user.json()
response = requests.post('http://localhost:8000/user', json=payload)

Error: Get what looks like a SqlAlchemy error:

state = <sqlalchemy.orm.state.InstanceState object at 0x0000016B1F3B6BF0>
child = {'name': 'user'}
initiator = <sqlalchemy.orm.attributes.AttributeEvent object at 0x0000016B1F2FF780>

    def emit_backref_from_collection_append_event(state, child, initiator):
        if child is None:
            return
    
>       child_state, child_dict = instance_state(child), instance_dict(child)
E       AttributeError: 'dict' object has no attribute '_sa_instance_state'

How can I make this work?

The same thing happens whether the role already exists in the DB or not.
Works if the payload (user) doesn't have roles in it.
The error comes up before the controller code gets executed, ie, in api doesn't even reach the first line inside create_user(...).

How to do a create endpoint with relationship with fastapi and sqlmodel?

0 Answers0