```

本例中，**FastAPI** 不使用 `__init__`，我们要直接在代码中使用。

## 创建实例

使用以下代码创建类实例：

```Python hl_lines="16"
{!../../docs_src/dependencies/tutorial011.py!}
```

这样就可以**参数化**依赖项，它包含 `checker.fixed_content` 的属性 - `"bar"`。

## 把实例作为依赖项

然后，不要再在 `Depends(checker)` 中使用 `Depends(FixedContentQueryChecker)`， 而是要使用 `checker`，因为依赖项是类实例 - `checker`，不是类。

处理依赖项时，**FastAPI** 以如下方式调用 `checker`：

```Python
checker(q="somequery")
```

import com.google.caliper.BeforeExperiment;
import com.google.caliper.Benchmark;
import com.google.caliper.Param;
import java.util.Random;

/**
 * Benchmarks for various ways of writing the expression {@code foo + ((bar < baz) ? 1 : 0)}.
 *
 * @author Louis Wasserman
 */
public class LessThanBenchmark {
  static final int SAMPLE_SIZE = 0x1000;
  static final int SAMPLE_MASK = 0x0FFF;

  @Param("1234")
  int randomSeed;

## Create an instance

We could create an instance of this class with:

{* ../../docs_src/dependencies/tutorial011_an_py39.py hl[18] *}

And that way we are able to "parameterize" our dependency, that now has `"bar"` inside of it, as the attribute `checker.fixed_content`.

## Use the instance as a dependency

    mockWebServer: MockWebServer,
  ) {
    setUp(protocol, mockWebServer)
    val pushPromise =
      PushPromise(
        "GET",
        "/foo/bar",
        headersOf("foo", "bar"),
        MockResponse(body = "bar"),
      )
    server.enqueue(
      MockResponse.Builder()
        .body("ABCDE")
        .addPush(pushPromise)
        .build(),
    )

Это означает, что **FastAPI** будет ожидать тело запроса, аналогичное этому:

```JSON
{
    "name": "Foo",
    "description": "The pretender",
    "price": 42.0,
    "tax": 3.2,
    "tags": ["rock", "metal", "bar"],
    "image": {
        "url": "http://example.com/baz.jpg",
        "name": "The Foo live"
    }
}
```

Ещё раз: сделав такое объявление, с помощью **FastAPI** вы получите:

```

이는 **FastAPI**가 다음과 유사한 본문을 기대한다는 것을 의미합니다:

```JSON
{
    "name": "Foo",
    "description": "The pretender",
    "price": 42.0,
    "tax": 3.2,
    "tags": ["rock", "metal", "bar"],
    "image": {
        "url": "http://example.com/baz.jpg",
        "name": "The Foo live"
    }
}
```

다시 한번, **FastAPI**를 사용하여 해당 선언을 함으로써 얻는 것은:

* 중첩 모델도 편집기 지원(자동완성 등)
* 데이터 변환

This would mean that **FastAPI** would expect a body similar to:

```JSON
{
    "name": "Foo",
    "description": "The pretender",
    "price": 42.0,
    "tax": 3.2,
    "tags": ["rock", "metal", "bar"],
    "image": {
        "url": "http://example.com/baz.jpg",
        "name": "The Foo live"
    }
}
```

Again, doing just that declaration, with **FastAPI** you get:

	"istio.io/istio/pkg/test/util/assert"
)

func TestWithProcFs(t *testing.T) {
	n := NewPodNetnsProcFinder(fakeFs())
	pod := &corev1.Pod{ObjectMeta: metav1.ObjectMeta{
		Name:      "foo",
		Namespace: "bar",
		UID:       types.UID("863b91d4-4b68-4efa-917f-4b560e3e86aa"),
	}}
	podUIDNetns, err := n.FindNetnsForPods(map[types.UID]*corev1.Pod{
		pod.UID: pod,
	})
	if err != nil {
		panic(err)
	}

///

```Python hl_lines="16"
{!> ../../docs_src/dependencies/tutorial011.py!}
```

////

E deste modo nós podemos "parametrizar" a nossa dependência, que agora possui `"bar"` dentro dele, como o atributo `checker.fixed_content`.

## Utilize a instância como dependência

### 响应结果

请求为 `http://example.com/items/foo`（`item_id` 为 `「foo」`）时，客户端会接收到 HTTP 状态码 - 200 及如下 JSON 响应结果：

```JSON
{
  "item": "The Foo Wrestlers"
}

```

但如果客户端请求 `http://example.com/items/bar`（`item_id` `「bar」` 不存在时），则会接收到 HTTP 状态码 - 404（「未找到」错误）及如下 JSON 响应结果：

```JSON
{
  "detail": "Item not found"
}

```

/// tip | "提示"

触发 `HTTPException` 时，可以用参数 `detail` 传递任何能转换为 JSON 的值，不仅限于 `str`。