Before diving deeper into the **Dependency Injection** system, let's upgrade the previous example.

## A `dict` from the previous example { #a-dict-from-the-previous-example }

In the previous example, we were returning a `dict` from our dependency ("dependable"):

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[9] *}

But then we get a `dict` in the parameter `commons` of the *path operation function*.

            boolean defaultsToEmpty);

    /**
     * Creates a composite function from a collection of functions.
     *
     * @param functions A collection of functions, each taking a String as input and returning a String.
     * @return A function that applies each function in the collection in order until a non-null result is found.
     *         If all functions return null, the composite function returns null.
     *

// for each op.
// TODO(srbs): We need to define `ZerosLike` here to keep the compiler happy.
// Figure out a way to avoid this.
// TODO(srbs): Should ZerosLike check-fail instead of returning nullptr?
class TapeTensor {
 public:
  explicit TapeTensor(AbstractTensorHandle* handle);
  TapeTensor(const TapeTensor& other);
  ~TapeTensor();

  int64_t GetID() const;

    return (E[]) new Object[capacity];
  }

  /**
   * Inserts the specified element at the tail of this queue if it is possible to do so immediately
   * without exceeding the queue's capacity, returning {@code true} upon success and throwing an
   * {@code IllegalStateException} if this queue is full.
   *
   * @param e the element to add
   * @return {@code true} (as specified by {@link Collection#add})

`from starlette.responses import JSONResponse`를 사용할 수도 있습니다.

**FastAPI**는 개발자의 편의를 위해 `starlette.responses`를 `fastapi.responses`로 제공합니다. 하지만 대부분의 사용 가능한 응답은 Starlette에서 직접 제공합니다.

///

## 사용자 정의 `Response` 반환하기 { #returning-a-custom-response }

위 예제는 필요한 모든 부분을 보여주지만, 아직은 그다지 유용하지 않습니다. `item`을 그냥 직접 반환했어도 **FastAPI**가 기본으로 이를 `JSONResponse`에 넣고 `dict`로 변환하는 등의 작업을 모두 수행해 주었을 것이기 때문입니다.

이제, 이를 사용해 사용자 정의 응답을 반환하는 방법을 알아보겠습니다.

/// note | 技术细节

你也可以使用 `from starlette.responses import JSONResponse`。

出于方便，**FastAPI** 会提供与 `starlette.responses` 相同的 `fastapi.responses` 给开发者。但是大多数可用的响应都直接来自 Starlette。

///

## 返回自定义 `Response` { #returning-a-custom-response }

上面的例子展示了需要的所有部分，但还不够实用，因为你本可以只是直接返回 `item`，而 **FastAPI** 默认帮你把这个 `item` 放到 `JSONResponse` 中，又默认将其转换成了 `dict` 等等。

现在，让我们看看你如何才能返回一个自定义的响应。

假设你想要返回一个 [XML](https://en.wikipedia.org/wiki/XML) 响应。

			return
		case <-t.C:
			m.lastHandout = time.Now()

			if m2, err := rpc.UpdateMetacacheListing(ctx, m); err == nil {
				if m2.status != scanStateStarted {
					if serverDebugLog {
						console.Debugln("returning", m.id, "due to scan state", m2.status, time.Now().Format(time.RFC3339))
					}
					return
				}
				m = m2
				if serverDebugLog {
					console.Debugln("refreshed", m.id, time.Now().Format(time.RFC3339))

  // session has been run (this is detected in RecordMutation function). If the
  // string is empty, no mutation has occurred. Otherwise the string is a
  // description of the mutation suitable for returning to the user.
  //
  // Sessions are added to this map in TF_NewSession, and removed in
  // TF_DeleteSession.
  // TF_Graph may only / must be deleted when
  //   sessions.size() == 0 && delete_requested == true
  //

    }

    /**
     * Retrieves the character mapping file for the specified dictionary ID.
     * <p>
     * This method looks up the dictionary file and ensures it is a character mapping file
     * before returning it wrapped in an OptionalEntity.
     * </p>
     *
     * @param dictId the dictionary ID to retrieve the character mapping file for

# Background Tasks { #background-tasks }

You can define background tasks to be run *after* returning a response.

This is useful for operations that need to happen after a request, but that the client doesn't really have to be waiting for the operation to complete before receiving the response.

This includes, for example:

* Email notifications sent after performing an action: