FastAPI pydantic response_model - fastapi

Question

FastAPI with uvicorn. So far i have everything working fine, now wanted to add extra validation with pydantic and response_model validation. My challange is, the response is a nested object, example:
{
"name": "always the same",
"value": ["ACL1", "ACL2", "ACL3"]
}
I have tried to:
class ACL(BaseModel):
name: str
#app.post(
"get/acls",
response_model=List[ACL]
)
def get_acls(credentials: HTTPBasicCredentials = Depends(security)):
But obviously it will fail. How to define correctly the response model so that it's correctly validated ? (and also visible in openapi documentation page ?)
Thanks,

Answer 1

You can use nested models in Pydantic and by by extension also in FastAPI. Like so:
class ACL(BaseModel):
name: str
class YourResponseModel(BaseModel):
name: str
value: list[ACL]
#app.post("/get/acls", response_model=YourResponseModel)
def get_acl():
return {"name": "always the same", "value": [{"name":"ACL1"}, {"name":"ACL2"}, {"name":"ACL3"}]}
If you don't want nested objects in your value list, then you have to build some logic to parse it. Below is an example of this:
class ACL(BaseModel):
name: str
class AnotherResponseModel(BaseModel):
name: str
value: list[str]
#app.post("/get/acls2", response_model=AnotherResponseModel)
def get_acl():
acls = [ACL(name="ACL1"), ACL(name="ACL2"), ACL(name="ACL3")]
return {"name": "always the same", "value": [acl.name for acl in acls] }
Please note, it is bad practice to mix up POST and GET requests (you are defining a POST endpoint, that will 'get' some ACLs for the end user). That is however unrelated to this question.