Dis-functioning Relationship - or - how do you work with relationships?

[drorata]

First Check

• I added a very descriptive title here.
• I used the GitHub search to find a similar question and didn't find it.
• I searched the SQLModel documentation, with the integrated search.
• I already searched in Google "How to X in SQLModel" and didn't find any information.
• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to SQLModel but to Pydantic.
• I already checked if it is not related to SQLModel but to SQLAlchemy.

Commit to Help

• I commit to help with one of those options 👆

Example Code

# models.py
from typing import List, Optional

from sqlmodel import Column, Field, Relationship, SQLModel, String

from foo_hardware import constants


class UserBase(SQLModel):
    username: str = Field(sa_column=Column("username", String, unique=True))
    password: str
    email: str = Field(sa_column=Column("email", String, unique=True))
    items: List["HardwareItem"] = Relationship(back_populates="owner")


class User(UserBase, table=True):
    id: int = Field(default=None, primary_key=True)


class UserCreate(UserBase):
    pass


class UserRead(UserBase):
    id: int


class HardwareItemBase(SQLModel):
    kind: constants.HARDWARE_KINDS = Field(
        default=...,
        title="Type of hardware",
        description=(
            "Possible kinds are:"
            f" {[(e.name, e.value) for e in constants.HARDWARE_KINDS]}"
        ),
    )
    owner_id: int = Field(foreign_key="user.id")
    owner: User = Relationship(back_populates="items")
    comment: Optional[str]


class HardwareItem(HardwareItemBase, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)


class HardwareItemCreate(HardwareItemBase):
    class Config:
        pass


class HardwareItemRead(HardwareItemBase):
    id: int


#########################
# backend.py
from typing import List

from fastapi import FastAPI, HTTPException, status
from sqlmodel import Session, SQLModel, create_engine, select

from foo_hardware import models

sqlite_file_name = "../data/foo_hardware.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

connect_args = {"check_same_thread": False}
engine = create_engine(sqlite_url, echo=True, connect_args=connect_args)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


app = FastAPI()


@app.on_event("startup")
def on_startup():
    create_db_and_tables()


@app.post("/user/", response_model=models.UserRead)
def create_user(user: models.UserCreate):
    with Session(engine) as session:
        db_user = models.User.from_orm(user)
        session.add(db_user)
        session.commit()
        session.refresh(db_user)
        return db_user


@app.get("/user/", response_model=List[models.UserRead])
def read_users():
    with Session(engine) as session:
        users = session.exec(select(models.User)).all()
        return users


@app.post("/hardware/", response_model=models.HardwareItemRead)
def create_hardware_item(hardware_item: models.HardwareItemCreate):
    with Session(engine) as session:
        owner = session.exec(
            select(models.User).where(models.User.id == hardware_item.owner_id)
        ).fetchall()
        if len(owner) != 1:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND, detail="Owner not found"
            )
        owner = owner[0]
        db_hardware_item = models.HardwareItem.from_orm(hardware_item)
        # db_hardware_item.owner = owner
        session.exec
        session.add(db_hardware_item)
        session.commit()
        session.refresh(db_hardware_item)
        return db_hardware_item


@app.get("/hardware/", response_model=List[models.HardwareItemRead])
def read_hardware_items():
    with Session(engine) as session:
        hardware_items = session.exec(select(models.HardwareItem)).all()
        return hardware_items

Description

The code above can also be found in models.py and backend.py.

It all works pretty much as expected, except this part:

        db_hardware_item = models.HardwareItem.from_orm(hardware_item)
        # db_hardware_item.owner = owner
        session.exec

As soon as I uncomment the middle line, I cannot add new hardware items. The error I get is something like:

ValueError: "HardwareItem" object has no field "owner"

which I find odd, because in here:

owner: User = Relationship(back_populates="items")

it can be seen that owner is a member of HardwareItemBase which is the base class of HardwareItem.

I'm afraid I don't know how to solve this. I compared it a lot to the section relationship-attributes in the docs, but the example there doesn't use the concept of ItemBase, Item, ItemRead and ItemCreate (which are discussed in here for example).

Operating System

macOS

Operating System Details

No response

SQLModel Version

0.0.8

Python Version

3.11.2

Additional Context

No response