# Headers de Response { #response-headers }

## Usa un parámetro `Response` { #use-a-response-parameter }

Puedes declarar un parámetro de tipo `Response` en tu *path operation function* (como puedes hacer para cookies).

Y luego puedes establecer headers en ese objeto de response *temporal*.

{* ../../docs_src/response_headers/tutorial002_py39.py hl[1, 7:8] *}

 *       typically because the type forbids nullable type arguments: For example, {@code
 *       ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
 *       {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)
 *   <li>methods whose return type is a type variable but which can return {@code null} regardless
 *       of the type argument supplied by the user of the class: For example, {@code

 *       typically because the type forbids nullable type arguments: For example, {@code
 *       ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
 *       {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)
 *   <li>methods whose return type is a type variable but which can return {@code null} regardless
 *       of the type argument supplied by the user of the class: For example, {@code

 *       typically because the type forbids nullable type arguments: For example, {@code
 *       ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
 *       {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)
 *   <li>methods whose return type is a type variable but which can return {@code null} regardless
 *       of the type argument supplied by the user of the class: For example, {@code

Pero todavía quieres poder filtrar y convertir los datos que devuelves con un `response_model`.

Para esos casos, puedes usar un parámetro `Response`.

## Usa un parámetro `Response` { #use-a-response-parameter }

Puedes declarar un parámetro de tipo `Response` en tu *path operation function* (como puedes hacer para cookies y headers).

Y luego puedes establecer el `status_code` en ese objeto de response *temporal*.

"""
Regression test, Error 422 if Form is declared before File
See https://github.com/tiangolo/fastapi/discussions/9116
"""

from pathlib import Path
from typing import Annotated

import pytest
from fastapi import FastAPI, File, Form
from fastapi.testclient import TestClient

app = FastAPI()


@app.post("/file_before_form")
def file_before_form(
    file: bytes = File(),
    city: str = Form(),
):

import org.junit.jupiter.params.provider.ValueSource;
import org.mockito.Mock;
import org.mockito.junit.jupiter.MockitoExtension;

/**
 * Tests for the {@link AllocInfo} interface.
 * Since {@code AllocInfo} only declares getters, the tests focus on
 * verifying that implementations honour the contract.
 */
@ExtendWith(MockitoExtension.class)
public class AllocInfoTest {

    @Mock
    AllocInfo mockAllocInfo;

    /**

        assertTrue(c.isInterface(), "SpnegoConstants must be an interface");
        assertEquals(4, c.getDeclaredFields().length, "Unexpected number of fields");
        assertEquals(0, c.getDeclaredMethods().length, "No declared methods expected");
        assertEquals(0, c.getDeclaredConstructors().length, "Interfaces have no constructors");
    }

    @Test
    @DisplayName("Fields are public static final Strings with expected values")

   * Throwable}. But we <i>can</i> write {@code sneakyThrow(t);}.
   *
   * <p>We sometimes also use {@code sneakyThrow} for testing how our code responds to
   * sneaky checked exception.
   *
   * @return never; this method declares a return type of {@link Error} only so that callers can
   *     write {@code throw sneakyThrow(t);} to convince the compiler that the statement will always
   *     throw.
   */
  @CanIgnoreReturnValue

Para eso necesitas acceder al request directamente.

{* ../../docs_src/using_request_directly/tutorial001_py39.py hl[1,7:8] *}

Al declarar un parámetro de *path operation function* con el tipo siendo `Request`, **FastAPI** sabrá pasar el `Request` en ese parámetro.

/// tip | Consejo