<mxfile host="65bd71144e">
    <diagram id="jyERGzDynktFHFRGN0ph" name="Page-1">
        <mxGraphModel dx="2738" dy="2173" grid="1" gridSize="10" guides="1" tooltips="1" connect="1" arrows="1" fold="1" page="1" pageScale="1" pageWidth="1920" pageHeight="1200" math="0" shadow="0">
            <root>
                <mxCell id="0"/>
                <mxCell id="1" parent="0"/>

* `swagger_css_url`: the URL where the HTML for your Swagger UI docs can get the **CSS** file. This is the custom CDN URL.

And similarly for ReDoc...

```Python hl_lines="2-6  11-19  22-24  27-33"
{!../../../docs_src/custom_docs_ui/tutorial001.py!}
```

!!! tip
    The *path operation* for `swagger_ui_redirect` is a helper for when you use OAuth2.

* `swagger_css_url`: die URL, unter welcher der HTML-Code für Ihre Swagger-UI-Dokumentation die **CSS**-Datei abrufen kann. Dies ist die benutzerdefinierte CDN-URL.

Und genau so für ReDoc ...

```Python hl_lines="2-6  11-19  22-24  27-33"
{!../../../docs_src/custom_docs_ui/tutorial001.py!}
```

!!! tip "Tipp"
    Die *Pfadoperation* für `swagger_ui_redirect` ist ein Hilfsmittel bei der Verwendung von OAuth2.

    private static final Collection<String> TRANSLATED_PATH_EXPRESSIONS;

    static {
        Collection<String> translatedPrefixes = new HashSet<>();

        // MNG-1927, MNG-2124, MNG-3355:
        // If the build section is present and the project directory is non-null, we should make
        // sure interpolation of the directories below uses translated paths.

    <diagram id="zB4-QXJZ7ScUzHSLnJ1i" name="Page-1">
        <mxGraphModel dx="1154" dy="780" grid="1" gridSize="10" guides="1" tooltips="1" connect="1" arrows="1" fold="1" page="1" pageScale="1" pageWidth="1920" pageHeight="1200" math="0" shadow="0" extFonts="Roboto^https://fonts.googleapis.com/css?family=Roboto|Roboto Mono, mono^https://fonts.googleapis.com/css?family=Roboto+Mono%2C+mono">
            <root>
                <mxCell id="0"/>

И, в свою очередь, `dependency_b` нуждается в том, чтобы значение из `dependency_a` (здесь `dep_a`) было доступно для ее завершающего кода.

=== "Python 3.9+"

    ```Python hl_lines="18-19  26-27"
    {!> ../../../docs_src/dependencies/tutorial008_an_py39.py!}
    ```

=== "Python 3.6+"

    ```Python hl_lines="17-18  25-26"
    {!> ../../../docs_src/dependencies/tutorial008_an.py!}
    ```

```

### 创建回调*路径操作*

创建回调*路径操作*也使用之前创建的 `APIRouter`。

它看起来和常规 FastAPI *路径操作*差不多：

* 声明要接收的请求体，例如，`body: InvoiceEvent`
* 还要声明要返回的响应，例如，`response_model=InvoiceEventReceived`

```Python hl_lines="17-19  22-23  29-33"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

回调*路径操作*与常规*路径操作*有两点主要区别：

* 它不需要任何实际的代码，因为应用不会调用这段代码。它只是用于存档*外部 API*。因此，函数的内容只需要 `pass` 就可以了

  private static final long ONE_BYTE_ROUNDTRIPPABLE_CHARACTERS = 0x007f - 0x0000 + 1;

  // 128
  private static final long EXPECTED_ONE_BYTE_ROUNDTRIPPABLE_COUNT =
      ONE_BYTE_ROUNDTRIPPABLE_CHARACTERS;

  // 1920 [chars 0x0080 to 0x07FF]
  private static final long TWO_BYTE_ROUNDTRIPPABLE_CHARACTERS = 0x07FF - 0x0080 + 1;

  // 18,304
  private static final long EXPECTED_TWO_BYTE_ROUNDTRIPPABLE_COUNT =

func stack1916() { var buf [1916]byte; use(buf[:]); C.callGoStackCheck() }
func stack1920() { var buf [1920]byte; use(buf[:]); C.callGoStackCheck() }
func stack1924() { var buf [1924]byte; use(buf[:]); C.callGoStackCheck() }
func stack1928() { var buf [1928]byte; use(buf[:]); C.callGoStackCheck() }
func stack1932() { var buf [1932]byte; use(buf[:]); C.callGoStackCheck() }

所有这些依赖都可以使用`yield`。

在这种情况下，`dependency_c` 在执行其退出代码时需要`dependency_b`（此处称为 `dep_b`）的值仍然可用。

而`dependency_b` 反过来则需要`dependency_a`（此处称为 `dep_a`）的值在其退出代码中可用。

=== "Python 3.9+"

    ```Python hl_lines="18-19  26-27"
    {!> ../../../docs_src/dependencies/tutorial008_an_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="17-18  25-26"
    {!> ../../../docs_src/dependencies/tutorial008_an.py!}
    ```