# yieldを持つ依存関係

FastAPIは、いくつかの<abbr title='時々"exit"、"cleanup"、"teardown"、"close"、"context managers"、 ...のように呼ばれる'>終了後の追加のステップ</abbr>を行う依存関係をサポートしています。

これを行うには、`return`の代わりに`yield`を使い、その後に追加のステップを書きます。

!!! tip "豆知識"
    `yield`は必ず一度だけ使用するようにしてください。

!!! info "情報"
    これを動作させるには、**Python 3.7** 以上を使用するか、**Python 3.6** では"backports"をインストールする必要があります:

    ```
    pip install async-exit-stack async-generator
    ```

        echo "${'$'}REPO was polluted during the build"
        ${if (exitOnFailure) "exit 1" else ""}
    else
        echo "${'$'}REPO does not exist"
    fi

""".trimIndent()

fun checkCleanDirWindows(dir: String, exitOnFailure: Boolean = true) = """
    IF exist $dir (
        TREE $dir
        RMDIR /S /Q $dir
        ${if (exitOnFailure) "EXIT 1" else ""}
    )

""".trimIndent()

    1)
        # Don't do anything on upgrade, because the preun script in redhat gets executed after the postinst (madness!)
    ;;

    *)
        echo "pre remove script called with unknown argument \`$1'" >&2
        exit 1
    ;;
esac

# Stops the service
if [ "$STOP_REQUIRED" = "true" ]; then
    echo -n "Stopping fess service..."
    if command -v systemctl >/dev/null; then

        REMOVE_USER_AND_GROUP=true
    ;;
    1)
        # If $1=1 this is an upgrade
        IS_UPGRADE=true
    ;;

    *)
        echo "post remove script called with unknown argument \`$1'" >&2
        exit 1
    ;;
esac

# Sets the default values for fess variables used in this script
FESS_USER="${packaging.fess.user}"
FESS_GROUP="${packaging.fess.group}"
PID_DIR="${packaging.fess.pid.dir}"

                    -d "$FESS_USER_HOME"  \
                    "$FESS_USER"
            echo " OK"
        fi
    ;;

    *)
        echo "pre install script called with unknown argument \`$1'" >&2
        exit 1
    ;;
esac

        generator.setApplicationName("Gradle")
        generator.setOptsEnvironmentVar("GRADLE_OPTS")
        generator.setExitEnvironmentVar("GRADLE_EXIT_CONSOLE")
        generator.setMainClassName("org.gradle.launcher.GradleMain")
        generator.setScriptRelPath("bin/gradle")
        generator.setClasspath(listOf("lib/$launcherJarName"))

       But in .bazelrc, there is no "rbe_$TFCI_BAZEL_TARGET_SELECTING_CONFIG_PREFIX".
       That setting must exist for this script to function correctly.
EOF
  exit 1
fi
TFCI_BAZEL_COMMON_ARGS="$TFCI_BAZEL_COMMON_ARGS --config rbe_$TFCI_BAZEL_TARGET_SELECTING_CONFIG_PREFIX"

# These flags share the user's gcloud credentials with the container, so that bazel

* It can do something to that **response** or run any needed code.
* Then it returns the **response**.

!!! note "Technical Details"
    If you have dependencies with `yield`, the exit code will run *after* the middleware.

    If there were any background tasks (documented later), they will run *after* all the middleware.

## Create a middleware

* Sie kann etwas mit dieser **Response** tun oder beliebigen Code ausführen.
* Dann gibt sie die **Response** zurück.

!!! note "Technische Details"
    Wenn Sie Abhängigkeiten mit `yield` haben, wird der Exit-Code *nach* der Middleware ausgeführt.

    Wenn es Hintergrundaufgaben gab (später dokumentiert), werden sie *nach* allen Middlewares ausgeführt.

## Erstellung einer Middleware

        IS_UPGRADE=false
    ;;
    2)
        # If $1=1 this is an upgrade
        IS_UPGRADE=true
    ;;

    *)
        echo "post install script called with unknown argument \`$1'" >&2
        exit 1
    ;;
esac

if [ "x$IS_UPGRADE" != "xtrue" ]; then
    if command -v systemctl >/dev/null; then