How to change name of items field of the Page model?

[lelecanfora]

Is there an elegant way to change the name of the field "items" of the Page model that is outputted by fast api pagination?

For example instead of this output:

{
  "items": [
    {
      "id": "3fa85f64-5717-4562-b3fc-2c963f66afa6"
    }
  ],
  "total": 0,
  "page": 0,
  "size": 0,
  "pages": 0
}

I would like to have this output

{
  "objects": [
    {
      "id": "3fa85f64-5717-4562-b3fc-2c963f66afa6"
    }
  ],
  "total": 0,
  "page": 0,
  "size": 0,
  "pages": 0
}

In Pydantic unfortunately you have to redeclare the Field in full if you want to override on a child class.

[uriyyo]

Hi @lelecanfora,

Sorry for a long response.

I hope answers bellow will help you:

For pydantic v1:

from typing import Generic, TypeVar

from fastapi import FastAPI
from pydantic import Field

from fastapi_pagination import Page, add_pagination, paginate

T = TypeVar("T")


class ObjectsPage(Page[T], Generic[T]):
    items: list[T] = Field(..., alias="objects")

    class Config:
        allow_population_by_field_name = True


app = FastAPI()


@app.get("/items")
def get_items() -> ObjectsPage[int]:
    return paginate([*range(1_000)])
    

add_pagination(app)

For pydantic v2:

from typing import Generic, TypeVar

from fastapi import FastAPI
from pydantic import Field

from fastapi_pagination import Page, add_pagination, paginate

T = TypeVar("T")


class ObjectsPage(Page[T], Generic[T]):
    items: list[T] = Field(..., alias="objects")

    model_config = {
        "populate_by_name": True,
    }



app = FastAPI()


@app.get("/items")
def get_items() -> ObjectsPage[int]:
    return paginate([*range(1_000)])


add_pagination(app)

[lelecanfora]

Yes, that seems easy enough, I ended up creating a class generator and it works as intended:

from typing import Generic, TypeVar, Sequence
from pydantic import Field, ConfigDict
from fastapi_pagination import Page

T = TypeVar("T")

def create_custom_page(items_alias: str):
    class CustomPage(Page[T], Generic[T]):
        items: Sequence[T] = Field(alias=items_alias)
        model_config = ConfigDict(
            **Page.model_config,
            populate_by_name=True
        )
    return CustomPage