return err
		}
	case !f.Tag.IsEmpty():
		if err := e.EncodeElement(f.Tag, xml.StartElement{Name: xml.Name{Local: "Tag"}}); err != nil {
			return err
		}
	default:
		// Always print Prefix field when both And & Tag are empty
		if err := e.EncodeElement(f.Prefix, xml.StartElement{Name: xml.Name{Local: "Prefix"}}); err != nil {
			return err
		}

		if f.ObjectSizeLessThan > 0 {

```JSON
{
    "detail": [
        {
            "loc": [
                "query",
                "needy"
            ],
            "msg": "field required",
            "type": "value_error.missing"
        }
    ]
}
```

La présence de `needy` étant nécessaire, vous auriez besoin de l'insérer dans l'URL :

```

```JSON
{
  "detail": [
    {
      "type": "missing",
      "loc": [
        "query",
        "needy"
      ],
      "msg": "Field required",
      "input": null
    }
  ]
}
```

Da `needy` ein erforderlicher Parameter ist, müssen Sie ihn in der URL setzen:

```
http://127.0.0.1:8000/items/foo-item?needy=sooooneedy
```

本例把标准的 `dataclasses` 直接替换为 `pydantic.dataclasses`：

```{ .python .annotate hl_lines="1  5  8-11  14-17  23-25  28" }
{!../../docs_src/dataclasses_/tutorial003.py!}
```

1. 本例依然要从标准的 `dataclasses` 中导入 `field`；

2. 使用 `pydantic.dataclasses` 直接替换 `dataclasses`；

3. `Author` 数据类包含 `Item` 数据类列表；

4. `Author` 数据类用于 `response_model` 参数；

5. 其它带有数据类的标准类型注解也可以作为请求体；

    本例使用的是 `Item` 数据类列表；

///

## Anotaciones de tipos con metadata { #type-hints-with-metadata-annotations }

     * normal property on the renderer instance and just set the location of the API file in it.
     *
     * Instead, we'll encode the path to the file in the description data field, as a link.  This is
     * useful regardless of this renderer's needs, since now there will be a link embedded in the report
     * to quickly open the changes file.  By then we can also regex that path out of the description

    mod.sqlite_url = "sqlite://"
    mod.engine = create_engine(
        mod.sqlite_url, connect_args={"check_same_thread": False}, poolclass=StaticPool
    )

    with TestClient(mod.app) as c:
        yield c
    # Clean up connection explicitly to avoid resource warning
    mod.engine.dispose()


def test_crud_app(client: TestClient):
    # TODO: this warns that SQLModel.from_orm is deprecated in Pydantic v1, refactor

Sie können dies mit <a href="https://docs.pydantic.dev/latest/concepts/validators/#field-after-validator" class="external-link" target="_blank">Pydantic's `AfterValidator`</a> innerhalb von `Annotated` erreichen.

/// tip | Tipp

Pydantic unterstützt auch <a href="https://docs.pydantic.dev/latest/concepts/validators/#field-before-validator" class="external-link" target="_blank">`BeforeValidator`</a> und andere. 🤓

///

Você pode fazer isso usando o <a href="https://docs.pydantic.dev/latest/concepts/validators/#field-after-validator" class="external-link" target="_blank">`AfterValidator` do Pydantic</a> dentro de `Annotated`.

/// tip | Dica

O Pydantic também tem <a href="https://docs.pydantic.dev/latest/concepts/validators/#field-before-validator" class="external-link" target="_blank">`BeforeValidator`</a> e outros. 🤓

///

func (endpoint *Endpoint) SetDiskIndex(i int) {
	endpoint.DiskIdx = i
}

func isValidURLEndpoint(u *url.URL) bool {
	// URL style of endpoint.
	// Valid URL style endpoint is
	// - Scheme field must contain "http" or "https"
	// - All field should be empty except Host and Path.
	isURLOk := (u.Scheme == "http" || u.Scheme == "https") &&
		u.User == nil && u.Opaque == "" && !u.ForceQuery &&
		u.RawQuery == "" && u.Fragment == ""