FastAPI-TortoiseORM: Problem regarding ForeignKeyField

I use FastAPI with TortoiseORM to create a simple todo app. The problem happened when i tried to connect the todo models to the user using ForeignKeyField. Here’s the code. main.py

from typing import List
import os

from fastapi import FastAPI, Depends, HTTPException, status

from models import User, Todo, User_pydantic, UserIn_pydantic, Todo_pydantic, TodoIn_pydantic
from tortoise.contrib.fastapi import register_tortoise, HTTPNotFoundError

app = FastAPI()

@app.post("/users/", response_model=User_pydantic)
async def create_user(user: UserIn_pydantic):
    user_obj = await User.create(**user.dict(exclude_unset=True))
    return await User_pydantic.from_tortoise_orm(user_obj)


@app.get("/users/", response_model=List[User_pydantic])
async def read_all_users():
    return await User_pydantic.from_queryset(User.all())

models.py

from tortoise.models import Model
from tortoise import fields
from tortoise.contrib.pydantic import pydantic_model_creator


class Todo(Model):
    id = fields.IntField(pk=True)
    title = fields.CharField(500)
    description = fields.TextField(null=True)

Todo_pydantic = pydantic_model_creator(Todo, name="Todo")
TodoIn_pydantic = pydantic_model_creator(Todo, name="TodoIn", exclude_readonly=True)

class User(Model):
    id = fields.IntField(pk=True)
    username = fields.CharField(500, unique=True)
    email = fields.CharField(100, unique=True)
    password = fields.CharField(100)
    is_active = fields.BooleanField(default=True)
    todo: fields.ForeignKeyNullableRelation[Todo] = fields.ForeignKeyField("models.Todo", related_name="todo", null=True)

    class PydanticMeta:
        exclude = ["is_active", "todo"]

User_pydantic = pydantic_model_creator(User, name="User")
UserIn_pydantic = pydantic_model_creator(User, name="UserIn", exclude_readonly=True)

My expected result when creating a user Input

{
  "username":"string",
  "email":"string",
  "password:"string"
}

Output

{
  "id":1,
  "username":"string",
  "password":"string",
  "is_active":True,
  "todo":[]
}

The real result Input

{
  "username":"string",
  "email":"string",
  "password":"string"
}

Output

{
  "id":1,
  "username":"string",
  "password":"string",
  "is_active":True,
}

Error message in Swagger UI

{
  "detail": [
    {
      "loc": [],
      "msg": "null value in column \"todo_id\" of relation \"user\" violates not-null constraint\nDETAIL:  Failing row contains (6, bob, [e-mail], bob123, t, null).",
      "type": "IntegrityError"
    }
  ]
}

Notice that there is no todo column in the output when creating a user

[metakot]

You need to clearly understand what you doing. In the function create_todo_list you take the user_id but are not using it anywhere =) And the docs for FastAPI is rare state-of-the-art, spoon-feeding almost anything what you need to know.

[BryanEgbert]

Thanks @metakot, the code removed the error when creating a user, but there is an internal server error when creating the todo for specific user. Due to the lack of tutorial for FastAPI w/ Tortoise ORM in relational models, i don’t know how to solve this. Here’s the code in main.py that relate to the problem i’m having.

@app.post("/users/{user_id}/todo/", response_model=Todo_pydantic)
async def create_todo_list(user_id: int, todo: TodoIn_pydantic):
    todo_obj = await Todo.create(**Todo.dict(exclude_unset=True))
    return await Todo_pydantic.from_tortoise_orm(todo_obj)


@app.get("/items/", response_model=List[Todo_pydantic])
async def read_todo():
    return await Todo_pydantic.from_queryset(Todo.all())

The updated models

class User(Model):
    id = fields.IntField(pk=True)
    username = fields.CharField(500, unique=True)
    email = fields.CharField(100, unique=True)
    password = fields.CharField(100)
    is_active = fields.BooleanField(default=True)

User_pydantic = pydantic_model_creator(User, name="User")
UserIn_pydantic = pydantic_model_creator(User, name="UserIn", exclude_readonly=True)

class Todo(Model):
    id = fields.IntField(pk=True)
    title = fields.CharField(500)
    description = fields.TextField(null=True)
    user = fields.ForeignKeyField("models.User", related_name="user", null=True)

Todo_pydantic = pydantic_model_creator(Todo, name="Todo")
TodoIn_pydantic = pydantic_model_creator(Todo, name="TodoIn", exclude_readonly=True)