# Abhängigkeiten mit `yield` { #dependencies-with-yield }

FastAPI unterstützt Abhängigkeiten, die nach Abschluss einige <abbr title="Manchmal auch genannt „Exit Code“, „Cleanup Code“, „Teardown Code“, „Closing Code“, „Kontextmanager Exit Code“, usw.">zusätzliche Schritte ausführen</abbr>.

Verwenden Sie dazu `yield` statt `return` und schreiben Sie die zusätzlichen Schritte / den zusätzlichen Code danach.

/// tip | Tipp

   *     for `hostname`.
   */
  @Throws(SSLPeerUnverifiedException::class)
  fun check(
    hostname: String,
    peerCertificates: List<Certificate>,
  ) = check(hostname) {
    (certificateChainCleaner?.clean(peerCertificates, hostname) ?: peerCertificates)
      .map { it as X509Certificate }
  }

  internal fun check(
    hostname: String,
    cleanedPeerCertificatesFn: () -> List<X509Certificate>,
  ) {

			}
		})
	}
}

func Test_pathNeedsClean(t *testing.T) {
	type pathTest struct {
		path, result string
	}

	cleantests := []pathTest{
		// Already clean
		{"", "."},
		{"abc", "abc"},
		{"abc/def", "abc/def"},
		{"a/b/c", "a/b/c"},
		{".", "."},
		{"..", ".."},
		{"../..", "../.."},
		{"../../abc", "../../abc"},
		{"/abc", "/abc"},

# 使用yield的依赖项

FastAPI支持在完成后执行一些<abbr title='有时也被称为"退出"("exit")，"清理"("cleanup")，"拆卸"("teardown")，"关闭"("close")，"上下文管理器"("context managers")。 ...'>额外步骤</abbr>的依赖项.

为此，你需要使用 `yield` 而不是 `return`，然后再编写这些额外的步骤（代码）。

/// tip | 提示

确保在每个依赖中只使用一次 `yield`。

///

/// note | 技术细节

任何一个可以与以下内容一起使用的函数：

		}

		// As this is path in the URL, we should use path package, not filepath package.
		// On MS Windows, filepath.Clean() converts into Windows path style ie `/foo` becomes `\foo`
		u.Path = path.Clean(u.Path)
		if isEmptyPath(u.Path) {
			return ep, fmt.Errorf("empty or root path is not supported in URL endpoint")
		}

Here, if you request `/unicorns/yolo`, the *path operation* will `raise` a `UnicornException`.

But it will be handled by the `unicorn_exception_handler`.

So, you will receive a clean error, with an HTTP status code of `418` and a JSON content of:

```JSON
{"message": "Oops! yolo did something. There goes a rainbow..."}
```

/// note | Technical Details

		t.Fatalf("lockUID len, got %d, want %d + %d", len(l.lockUID), len(rResources), len(wResources))
	}

	// Expire a minute ago.
	l.expireOldLocks(-time.Minute)
	if len(l.lockMap) != 0 {
		t.Fatalf("after cleanup should be empty, got %d", len(l.lockMap))
	}
	if len(l.lockUID) != 0 {
		t.Fatalf("lockUID len, got %d, want %d", len(l.lockUID), 0)
	}
}

func TestLocalLockerUnlock(t *testing.T) {
	const n = 1000

    exit 1
  fi
  if [ $wrapperSha256Result = false ]; then
    echo "Error: Failed to validate Maven wrapper SHA-256, your Maven wrapper might be compromised." >&2
    echo "Investigate or delete $wrapperJarPath to attempt a clean download." >&2
    echo "If you updated your Maven version, you need to update the specified wrapperSha256Sum property." >&2
    exit 1
  fi
fi

      // Note that if all the futures on the list are done prior to completing this loop, the last
      // call to addListener() will callback to setOneValue(), transitively call our cleanup
      // listener, and set this.futures to null.
      // This is not actually a problem, since the foreach only needs this.futures to be non-null
      // at the beginning of the loop.
      int i = 0;

# 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
```