How to modify values of many to many relationship in the crud interface

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Hello everyone. I am having a really hard time updating a user with a many to many relationship. The models used are these.

class UserBase(BaseModel):
    email: Optional[EmailStr] = None
    is_active: Optional[bool] = True
    is_superuser: bool = False
    full_name: Optional[str] = None
    roles: List[Role] = []

class User(Base):
    id = Column(Integer, primary_key=True, index=True)
    full_name = Column(String, index=True)
    email = Column(String, unique=True, index=True, nullable=False)
    hashed_password = Column(String, nullable=False)
    is_active = Column(Boolean(), default=True)
    is_superuser = Column(Boolean(), default=False)
    items = relationship("Item", back_populates="owner")
    roles = relationship(
        'Role', secondary=user_role,
        backref=backref("users")
    )

All the models have Config orm=True

The usage is that I have an admin panel where I can add roles to a profile. So I get the json model to the Vue app, add new roles and then post it to the api. When this updated model tries to set the roles attribute it fails.

Now after the endpoint is called. I see the new roles in the pydantic model as expected. But when the crud update tries to apply the new roles in the list it fails.

But when it reaches this point

    def update(
        self,
        db: Session,
        *,
        db_obj: ModelType,
        obj_in: Union[UpdateSchemaType, Dict[str, Any]]
    ) -> ModelType:
        obj_data = jsonable_encoder(db_obj)
        if isinstance(obj_in, dict):
            update_data = obj_in
        else:
            update_data = obj_in.dict(exclude_unset=True)
        for field in obj_data:
            if field in update_data:
                setattr(db_obj, field, update_data[field]) <------- Fails here
        db.add(db_obj)
        db.commit()
        db.refresh(db_obj)
        return db_obj

When I try to update user profile and add more roles to the list. I get the following error. backend_1 | File “/usr/local/lib/python3.8/site-packages/sqlalchemy/orm/unitofwork.py”, line 45, in append backend_1 | item_state = attributes.instance_state(item) backend_1 | AttributeError: ‘dict’ object has no attribute ‘_sa_instance_state’

Any idea what I can be doing incorrectly ? Using fastapi = “^0.60.1” and Python 3.8 Thanks

[amirjani]

Hi,

after looking at SQLAlchemy I realized that for having many to many relations like user_role we should do something like below code:

"""
file: user.py
"""
class User(Base):
    __tablename__ = "user"

    id = Column(Integer, primary_key=True, index=True)
    full_name = Column(String, index=True)
    email = Column(String, unique=True, index=True, nullable=False)
    hashed_password = Column(String, nullable=False)
    is_active = Column(Boolean(), default=True)
    is_superuser = Column(Boolean(), default=False)

    items = relationship("Role", secondary=UserRole.__tablename__, back_populates="user")

"""
file: role.py
"""
class Role(Base):
    __tablename__ = 'role'

    id = Column(Integer, primary_key=True, index=True)
    name = Column(String, index=True)
    is_primary = Column(Boolean)

    items = relationship("User", secondary=UserRole.__tablename__, back_populates="role")

"""
file: user_role.py
"""
class UserRole(Base):
    __tablename__ = 'user_role'

    user_id = Column('user_id', ForeignKey('user.id'), primary_key=True)
    role_id = Column('role_id', ForeignKey('role.id'), primary_key=True)

don’t forget to import UserRole class in User and Role classes

[Silur]

the problem is that jsonable_encoder returns an empty object {} when called on a model that contains a many-to-many relationship, thus you cannot use inherited functions from crud/base.py