## 类作为依赖项 { #classes-as-dependencies_1 }

你可能会注意到，要创建一个 Python 类的实例，你可以使用相同的语法。

举个例子:

```Python
class Cat:
    def __init__(self, name: str):
        self.name = name


fluffy = Cat(name="Mr Fluffy")
```

在这个例子中, `fluffy` 是一个 `Cat` 类的实例。

为了创建 `fluffy`，你调用了 `Cat` 。

所以，Python 类也是 **可调用对象**。

因此，在 **FastAPI** 中，你可以使用一个 Python 类作为一个依赖项。

实际上 FastAPI 检查的是它是一个 "可调用对象"（函数，类或其他任何类型）以及定义的参数。

```console
// Go to the home directory
$ cd
// Create a directory for all your code projects
$ mkdir code
// Enter into that code directory
$ cd code
// Create a directory for this project
$ mkdir awesome-project
// Enter into that project directory
$ cd awesome-project
```

Result (German):

```console
// Gehe zum Home-Verzeichnis
$ cd

  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  public void testNullPointers() {
    /*
     * Don't bother testing: Preconditions defines a bunch of methods that accept a template (or
     * even entire message) that simultaneously:
     *
     * - _shouldn't_ be null, so we don't annotate it with @Nullable
     *
     * - _can_ be null without causing a runtime failure (because we don't want the interesting

  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  public void testNullPointers() {
    /*
     * Don't bother testing: Preconditions defines a bunch of methods that accept a template (or
     * even entire message) that simultaneously:
     *
     * - _shouldn't_ be null, so we don't annotate it with @Nullable
     *
     * - _can_ be null without causing a runtime failure (because we don't want the interesting

   * implementation of iterator() to define its contents, and methods like contains() are
   * implemented in terms of that method (though they will likely be overridden by subclasses for
   * performance reasons).) This means that a call to this method have can different behavior in GWT
   * and non-GWT environments UNLESS subclasses are careful to always override all methods

	// See #26462, #25907, #47276, #48398 for history.
}

// The readOp constants describe the last action performed on
// the buffer, so that UnreadRune and UnreadByte can check for
// invalid usage. opReadRuneX constants are chosen such that
// converted to int they correspond to the rune size that was read.
type readOp int8

// Don't use iota for these, as the values need to correspond with the

        out.println("</td></tr></table>");
        out.println("</BODY></HTML>");
        out.close();
    }

    private static String parseServerAndShare(final String pathInfo) {
        final char[] out = new char[256];
        char ch;
        int len, p, i;

        if (pathInfo == null) {
            return null;
        }
        len = pathInfo.length();

        p = i = 0;

type LRU[K comparable, V any] struct {
	size      int
	evictList *LruList[K, V]
	items     map[K]*Entry[K, V]
	onEvict   EvictCallback[K, V]

	// expirable options
	mu   sync.RWMutex
	ttl  time.Duration
	done chan struct{}

	// buckets for expiration
	buckets []bucket[K, V]
	// uint8 because it's number between 0 and numBuckets
	nextCleanupBucket uint8
}

// bucket is a container for holding entries to be expired

async def get_item() -> Item:
    return Item(name="Plumbus", description="All-purpose home device")
```

**Important**: Return types or response models are what filter data ensuring no sensitive information is exposed. And they are used to serialize data with Pydantic (in Rust), this is the main idea that can increase response performance.

The return type doesn't have to be a Pydantic model, it could be a different type, like a list of integers, or a dict, etc.

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//