Answered: Simplest unpaginated page equivalent?

[gitpushdashf]

Hi everyone,

I have the rather odd problem of needing to get rid of pagination, perhaps temporarily, without breaking existing frontend. So we want to have items: list[Foo] instead of say list[Foo], for what was Page[Foo].

I can go through and write ListEndpointXResponse classes for each one, or I can make a generic to replace Page with.

from typing import Generic, TypeVar, Sequence
from pydantic.generics import GenericModel

T = TypeVar("T")


class UnpaginatedPage(GenericModel, Generic[T]):
    items: Sequence[T]

And this works great, except one issue. Let's say we're using SQLModel, and we have a different response model than the database object, itself. We want to convert to the Read version of that response.

This doesn't do that conversion. I've tried setting Config's orm_mode = True, but no dice. I've looked through the fastapi-pagination code and fastapi's code to figure out what makes the response_model setting tick, but I can't figure it out.

Curious if anyone knows the answer to this. I feel like it's a pretty short bit of code to make it work.

For now, I'm manually converting my database objects to their read variants.

Thanks!

[uriyyo]

Hi @gitpushdashf,

I hope the example below will help you:

from typing import Any, Generic, List, Optional, TypeVar

from fastapi import FastAPI
from pydantic import BaseModel
from pydantic.generics import GenericModel
from sqlalchemy import select
from sqlmodel import Field, Session, SQLModel, create_engine

engine = create_engine("sqlite:///database.db")


class User(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    name: str
    email: str


SQLModel.metadata.drop_all(engine)
SQLModel.metadata.create_all(engine)

app = FastAPI()


@app.on_event("startup")
async def on_startup() -> None:
    with Session(engine) as session:
        session.add(
            User(
                id=1,
                name="John Doe",
                email="user@example.com",
            ),
        )
        session.commit()


class UserOut(BaseModel):
    id: int
    name: str
    email: str

    class Config:
        orm_mode = True


T = TypeVar("T")


class GenericListSchema(GenericModel, Generic[T]):
    items: List[T]


@app.get("/users", response_model=GenericListSchema[UserOut])
async def get_users() -> Any:
    with Session(engine) as session:
        users = session.scalars(select(User)).all()

        return {"items": users}

[gitpushdashf]

This works great. Thank you!

The trick is definitely to return {"items": items} instead of return UnpaginatedPage(items=items).

[uriyyo]

Great, happy to hear that ✨

[uriyyo]

@gitpushdashf Could you please mark this discussion as answered?

[gitpushdashf]

I prefixed the title with Answered: -- is that a good way to do it? I didn't see any other means.

[uriyyo]

@gitpushdashf I converted it to Q&A discussion type and marked it as answered, thanks.