The code following the `yield` statement is executed after the response:

{* ../../docs_src/dependencies/tutorial007_py39.py hl[5:6] *}

/// tip

You can use `async` or regular functions.

**FastAPI** will do the right thing with each, the same as with normal dependencies.

///

## A dependency with `yield` and `try` { #a-dependency-with-yield-and-try }

	csvDstPool   bpool.Pool[[][]string] // pool of [][]string used for output
	close        chan struct{}          // used for shutting down the splitter before end of stream
	readerWg     sync.WaitGroup         // used to keep track of async reader.
}

// queueItem is an item in the queue.
type queueItem struct {
	input []byte          // raw input sent to the worker
	dst   chan [][]string // result of block decode

// Code generated by github.com/tinylib/msgp DO NOT EDIT.

package dsync

import (
	"github.com/tinylib/msgp/msgp"
)

// DecodeMsg implements msgp.Decodable
func (z *LockArgs) DecodeMsg(dc *msgp.Reader) (err error) {
	var field []byte
	_ = field
	var zb0001 uint32
	zb0001, err = dc.ReadMapHeader()
	if err != nil {
		err = msgp.WrapError(err)
		return
	}
	for zb0001 > 0 {
		zb0001--
		field, err = dc.ReadMapKeyPtr()

| `minio_notify_current_send_in_progress`        | Number of concurrent async Send calls active to all targets (deprecated, please use `minio_notify_target_current_send_in_progress` instead) |

	close       chan struct{}             // used for shutting down the splitter before end of stream
	readerWg    sync.WaitGroup            // used to keep track of async reader.
}

// queueItem is an item in the queue.
type queueItem struct {
	input []byte             // raw input sent to the worker
	dst   chan []jstream.KVS // result of block decode

如果您有类似文件的对象（例如，由 `open()` 返回的对象），则可以在 `StreamingResponse` 中将其返回。

包括许多与云存储，视频处理等交互的库。

{* ../../docs_src/custom_response/tutorial008.py hl[2,10:12,14] *}

/// tip | 小贴士

注意在这里，因为我们使用的是不支持 `async` 和 `await` 的标准 `open()`，我们使用普通的 `def` 声明了路径操作。

///

### `FileResponse`

异步传输文件作为响应。

与其他响应类型相比，接受不同的参数集进行实例化：

* `path` - 要流式传输的文件的文件路径。
* `headers` - 任何自定义响应头，传入字典类型。

        public void process(Consumer<TransferEvent> consumer) {
            consumer.accept(event);
        }

        public void waitForProcessed() throws InterruptedException {
            // nothing, is async
        }
    }

    private static class BlockingExchange extends Exchange {
        private final CountDownLatch latch = new CountDownLatch(1);

        private BlockingExchange(TransferEvent event) {

			name = trimLeadingSlash(path.Clean(name))
		default:
			// ignore symlink'ed
			continue
		}
		if o.prefixAll != "" {
			name = pathJoin(o.prefixAll, name)
		}

		// Do small files async
		n++
		if header.Size <= xioutil.MediumBlock {
			asyncWriters <- struct{}{}
			bufp := xioutil.ODirectPoolMedium.Get()
			b := (*bufp)[:header.Size]
			if _, err := io.ReadFull(tarReader, b); err != nil {

高度なシナリオでは、「キャッシュされた」値を使うのではなく、同じリクエストの各ステップ（おそらく複数回）で依存関係を呼び出す必要があることがわかっている場合、`Depens`を使用する際に、`use_cache=False`というパラメータを設定することができます。

```Python hl_lines="1"
async def needy_dependency(fresh_value: str = Depends(get_value, use_cache=False)):
    return {"fresh_value": fresh_value}
```

## まとめ

ここで使われている派手な言葉は別にして、**依存性注入** システムは非常にシンプルです。

*path operation関数*と同じように見えるただの関数です。

                ```python
                from fastapi import FastAPI

                app = FastAPI(redirect_slashes=True)  # the default

                @app.get("/items/")
                async def read_items():
                    return [{"item_id": "Foo"}]
                ```

                With this app, if a client goes to `/items` (without a trailing slash),