🚥 👩‍💻 📨 `http://example.com/items/foo` ( `item_id` `"foo"`), 👈 👩‍💻 🔜 📨 🇺🇸🔍 👔 📟 2️⃣0️⃣0️⃣, & 🎻 📨:

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

✋️ 🚥 👩‍💻 📨 `http://example.com/items/bar` (🚫-🚫 `item_id` `"bar"`), 👈 👩‍💻 🔜 📨 🇺🇸🔍 👔 📟 4️⃣0️⃣4️⃣ ("🚫 🔎" ❌), & 🎻 📨:

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

/// tip

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

Aber wenn der Client `http://example.com/items/bar` anfragt (ein nicht-existierendes `item_id` `"bar"`), erhält er einen HTTP-Statuscode 404 (der „Not Found“-Fehler), und eine JSON-Response wie folgt:

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

/// tip | "Tipp"

  public void testControlsArraySize() {
    ImmutableSet.Builder<String> builder = new ImmutableSet.Builder<String>();
    for (int i = 0; i < 10; i++) {
      builder.add("foo");
    }
    builder.add("bar");
    RegularImmutableSet<String> set = (RegularImmutableSet<String>) builder.build();
    assertTrue(set.elements.length <= 2 * set.size());
  }

  @GwtIncompatible("internals")
  public void testReusedBuilder() {

     * <tr>
     * <td>{@literal foo}</td>
     * <td>{@literal foo}</td>
     * </tr>
     * <tr>
     * <td>{@literal foo_bar}</td>
     * <td>{@literal foo.bar}</td>
     * </tr>
     * <tr>
     * <td>{@literal foo_bar_baz}</td>
     * <td>{@literal foo.bar.baz}</td>
     * </tr>
     * </table>
     *
     * @param beanDelimiter
     *            JavaBeansのデリミタ
     * @return このインスタンス自身
     */

```

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