[QUESTION] Is it possible to have multiple body schemas?

Description

In a Response, according to the documentation, I can have a Union of multiple pydantic models as the response of an endpoint operation. That works fine. However, it seems that there is no way to use a similar approach when receiving input in a a body. My problem: I have an endpoint, and this endpoint could receive any of 4 different models as valid input in the body. I tried to define a Union, and it breaks the fastapi schema generation; I tried to use Any, from pydantic, and fastapi treats the input as a query operation instead of a body operation (the same happens if I don’t use any model at all)

Consider Foobar, Model1 and Model2 as pydantic classes.

The following breaks schema generation:

@router.post("/{foobar}")
def post_foobar(foobar: Foobar, bar: Union[Model1, Model2], response: Response):

The following makes fastapi understand bar as a query:

@router.post("/{foobar}")
def post_foobar(foobar: Foobar, bar: Any, response: Response):

The following makes fastapi understand bar as a query either:

@router.post("/{foobar}")
def post_foobar(foobar: Foobar, bar, response: Response):

Is there a way to fix this behavior? Or simply force fastapi to understand “bar” as body and NOT a query parameter?

[ritikjain51]

I have tried the approach. Dynamic schema detection is not happening here.

The current approach is working with basic datatypes like int, float and all but user-defined structures or pydantic models not working. It is considering the object in basic datatype like dict or list.

Thanks in advance

[inikolaev]

As I understand it depends on pydantic and I found the following ticket there: https://github.com/samuelcolvin/pydantic/issues/619