# Usando Dataclasses

FastAPI está construido sobre **Pydantic**, y te he estado mostrando cómo usar modelos de Pydantic para declarar requests y responses.

Pero FastAPI también soporta el uso de <a href="https://docs.python.org/3/library/dataclasses.html" class="external-link" target="_blank">`dataclasses`</a> de la misma manera:

{* ../../docs_src/dataclasses/tutorial001.py hl[1,7:12,19:20] *}

## 0.29.0

* Add support for declaring a `Response` parameter:
    * This allows declaring:
        * [Response Cookies](https://fastapi.tiangolo.com/advanced/response-cookies/).
        * [Response Headers](https://fastapi.tiangolo.com/advanced/response-headers/).
        * An HTTP Status Code different than the default: [Response - Change Status Code](https://fastapi.tiangolo.com/advanced/response-change-status-code/).

        request.url(), chain.connection(), request.headers()));

    Response response = chain.proceed(request);

    long t2 = System.nanoTime();
    logger.info(String.format("Received response for %s in %.1fms%n%s",
        response.request().url(), (t2 - t1) / 1e6d, response.headers()));

    return response;
  }
}
```

		if rec.Code != testCase.expectedRespStatus {
			t.Errorf("Test %d: %s: Expected the response status to be `%d`, but instead found `%d`", i+1, instanceType, testCase.expectedRespStatus, rec.Code)
		}

		// Verify response the V2 signed HTTP request.
		// initialize HTTP NewRecorder, this records any mutations to response writer inside the handler.
		recV2 := httptest.NewRecorder()

	apiErr, ok := e[errCode]
	if !ok {
		return e[ErrSTSInternalError]
	}
	return apiErr
}

// error code to STSError structure, these fields carry respective
// descriptions for all the error responses.
var stsErrCodes = stsErrorCodeMap{
	ErrSTSAccessDenied: {
		Code:           "AccessDenied",
		Description:    "Generating temporary credentials not allowed for this request.",
		HTTPStatusCode: http.StatusForbidden,

Il inclut les `tags`, `parameters`, `requestBody`, `responses`, etc.

Ce schéma OpenAPI spécifique aux *operations* est normalement généré automatiquement par **FastAPI**, mais vous pouvez également l'étendre.

/// tip | Astuce

Si vous avez seulement besoin de déclarer des réponses supplémentaires, un moyen plus pratique de le faire est d'utiliser les [réponses supplémentaires dans OpenAPI](additional-responses.md){.internal-link target=_blank}.

///

            throw new SmbException("Response buffer is null");
        }

        if (buffer.length < expectedSize) {
            failedValidations.incrementAndGet();
            bufferOverflowsPrevented.incrementAndGet();
            log.warn("Response buffer too small: {} < {}", buffer.length, expectedSize);
            throw new SmbException("Response buffer too small: " + buffer.length + " < " + expectedSize);
        }

{* ../../docs_src/request_files/tutorial002.py hl[10,15] *}

👆 🔜 📨, 📣, `list` `bytes` ⚖️ `UploadFile`Ⓜ.

/// note | 📡 ℹ

👆 💪 ⚙️ `from starlette.responses import HTMLResponse`.

**FastAPI** 🚚 🎏 `starlette.responses` `fastapi.responses` 🏪 👆, 👩‍💻. ✋️ 🌅 💪 📨 👟 🔗 ⚪️➡️ 💃.

///

### 💗 📁 📂 ⏮️ 🌖 🗃

& 🎏 🌌 ⏭, 👆 💪 ⚙️ `File()` ⚒ 🌖 🔢, `UploadFile`:

/**
 * This class represents the base response structure for API results.
 * It encapsulates the API response and provides methods to build different types of API responses.
 */
public class ApiResult {

    /**
     * The API response object.
     */
    protected ApiResponse response = null;

    /**
     * Constructs an ApiResult with the specified ApiResponse.
     * @param response The API response object.
     */

    ```

 *  New: Make the content-type header optional for request bodies.
 *  New: `Response.isSuccessful()` is a convenient API to check response codes.
 *  New: The response body can now be read outside of the callback. Response
    bodies must always be closed, otherwise they will leak connections!
 *  New: APIs to create multipart request bodies (`MultipartBuilder`) and form