Por ejemplo, podemos definir un modelo `Image`:

{* ../../docs_src/body_nested_models/tutorial004_py310.py hl[7:9] *}

### Usar el submodelo como tipo { #use-the-submodel-as-a-type }

Y luego podemos usarlo como el tipo de un atributo:

{* ../../docs_src/body_nested_models/tutorial004_py310.py hl[18] *}

Esto significaría que **FastAPI** esperaría un cuerpo similar a:

```JSON
{
    "name": "Foo",

## Optionale Parameter { #optional-parameters }

Auf die gleiche Weise können Sie optionale Query-Parameter deklarieren, indem Sie deren Defaultwert auf `None` setzen:

{* ../../docs_src/query_params/tutorial002_py310.py hl[7] *}

In diesem Fall wird der Funktionsparameter `q` optional und standardmäßig `None` sein.

/// check | Testen

{* ../../docs_src/body_nested_models/tutorial002_py310.py hl[12] *}

## Set types { #set-types }

But then we think about it, and realize that tags shouldn't repeat, they would probably be unique strings.

And Python has a special data type for sets of unique items, the `set`.

Then we can declare `tags` as a set of strings:

{* ../../docs_src/body_nested_models/tutorial003_py310.py hl[12] *}

Например, мы можем определить модель `Image`:

{* ../../docs_src/body_nested_models/tutorial004_py310.py hl[7:9] *}

### Использование подмодели как типа { #use-the-submodel-as-a-type }

Также мы можем использовать эту модель как тип атрибута:

{* ../../docs_src/body_nested_models/tutorial004_py310.py hl[18] *}

Это означает, что **FastAPI** будет ожидать тело запроса, аналогичное этому:

```JSON
{

{* ../../docs_src/path_operation_configuration/tutorial004_py310.py hl[17:25] *}

Será usado en la documentación interactiva:

<img src="/img/tutorial/path-operation-configuration/image02.png">

## Descripción del Response { #response-description }

Puedes especificar la descripción del response con el parámetro `response_description`:

{* ../../docs_src/path_operation_configuration/tutorial005_py310.py hl[19] *}

/// info | Información

{* ../../docs_src/path_operation_configuration/tutorial004_py310.py hl[17:25] *}

Ela será usada nas documentações interativas:

<img src="/img/tutorial/path-operation-configuration/image02.png">

## Descrição da resposta { #response-description }

Você pode especificar a descrição da resposta com o parâmetro `response_description`:

{* ../../docs_src/path_operation_configuration/tutorial005_py310.py hl[19] *}

/// info | Informação

* `limit=10`: çünkü varsayılan değer buydu.

## İsteğe Bağlı Parametreler

Aynı şekilde, varsayılan değerlerini `None` olarak atayarak isteğe bağlı parametreler tanımlayabilirsiniz:

{* ../../docs_src/query_params/tutorial002_py310.py hl[7] *}

Bu durumda, `q` fonksiyon parametresi isteğe bağlı olacak ve varsayılan değer olarak `None` alacaktır.

/// check | Ek bilgi

但如果访问：

```
http://127.0.0.1:8000/items/?skip=20
```

查询参数的值就是：

* `skip=20`：在 URL 中设定的值
* `limit=10`：使用默认值

## 可选参数

同理，把默认值设为 `None` 即可声明**可选的**查询参数：

{* ../../docs_src/query_params/tutorial002_py310.py hl[7] *}

本例中，查询参数 `q` 是可选的，默认值为 `None`。

/// check | 检查

注意，**FastAPI** 可以识别出 `item_id` 是路径参数，`q` 不是路径参数，而是查询参数。

///

/// note | 笔记

因为默认值为 `= None`，FastAPI 把 `q` 识别为可选参数。

from fastapi.testclient import TestClient
from inline_snapshot import snapshot

from tests.utils import needs_py310


@pytest.fixture(
    name="client",
    params=[
        pytest.param("tutorial002_py39"),
        pytest.param("tutorial002_py310", marks=needs_py310),
    ],
)
def get_client(request: pytest.FixtureRequest):
    mod = importlib.import_module(f"docs_src.dataclasses_.{request.param}")

    client = TestClient(mod.app)

///

## Dataclasses em `response_model` { #dataclasses-in-response-model }

Você também pode usar `dataclasses` no parâmetro `response_model`:

{* ../../docs_src/dataclasses_/tutorial002_py310.py hl[1,6:12,18] *}

A dataclass será automaticamente convertida para uma dataclass Pydantic.

Dessa forma, seu esquema aparecerá na interface de documentação da API: