Nested Model in request body producing only default values

[david-saeger]

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Example Code

from pydantic import BaseModel, Field
from typing import List, Optional
router = APIRouter()
from fastapi import APIRouter, Depends

class Contract(BaseModel):
    contract_uuid: str = Field(
        None,
        alias="CONTRACT_UUID",
,
    )
    contract_id: Optional[str] = Field(
        None,
        alias="CONTRACT_ID",

    )
    contract_name: Optional[str] = Field(
        None,
        alias="CONTRACT_NAME",
        title="Project/Contract Name",

    )
   
    full_part_time: Optional[EmploymentType] = Field(
        None,
        alias="FULL_PART_TIME",
        title="Employment Type",
 
    )


class UpdateContracts(BaseModel):
    contract_array: List[Contract] = Field(
        [], description="A list of contracts submitted by the employer"
    )
    case_id: str = Field(
        None,
        title="Case ID",
      
    )
    company_id: str = Field(
        None,
        title="Company Identifier",

    )


@router.put("/contracts/")
async def put_contracts(data: UpdateContracts):
    """ Update contracts for one applicant """
    print(data.json())

Description

I am building an API that returns a nested model UpdateContracts which contains some fields and a list of contracts. The fields show up fine but in the nested list of Contracts I can only produce the default null values specified in the Contract model. I can validate that the appropriately shaped data is being sent, here is the payload (it contains some extrainious fields but that should not matter):

from fastapi import APIRouter, Body, Depends
{"company_id":"pae","nvc_siv_case_id":"Ip0XkAZc","contract_array":[{"contract_id":"flomo","contract_name":"asdf","badge_id":"12345","job_location":null,"full_part_time":"FULLTIME","reason_for_separation":"currently_employed","employment_details":null,"employment_details_other":null,"contract_uuid":"909a1d12-43fe-42d9-ba0d-56c74aa167d2"}]}

Operating System

macOS

Operating System Details

No response

FastAPI Version

fastapi==0.61.1

Python Version

3.8

Additional Context

No response

[harunyasar]

I have to say I felt like I was lost in the first place. But I believe you should use aliases instead of the field definitions. What I mean by saying that you can see as follows.

import inspect
inspect.signature(Contract)
# <Signature (*, CONTRACT_UUID: str = None, CONTRACT_ID: str = None, CONTRACT_NAME: str = None) -> None>

Which means your Contract object's signature should have been like above one. So,

update_contract = UpdateContracts(
    case_id="1230",
    company_id="3210",
    contract_array=[
        Contract(
            CONTRACT_UUID="c4469310-b22e-4305-a530-3b8b8dc15b6f",
            CONTRACT_ID="9876",
            CONTRACT_NAME="Example contract name"
        )
    ]
)

# Output
# UpdateContracts(
#     contract_array=[
#         Contract(
#             contract_uuid='c4469310-b22e-4305-a530-3b8b8dc15b6f',
#             contract_id='9876',
#             contract_name='Example contract name'
#         )
#     ], 
#     case_id='1230', 
#     company_id='3210'
# )

I hope that it can help.

[david-saeger]

that is helpful, is there a way for me to specify to use field definitions and not aliases?

[harunyasar]

that is helpful, is there a way for me to specify to use field definitions and not aliases?

If you don’t want to use the aliases at all you could remove them from the field definitions.

[david-saeger]

thank you @harunyasar