### Create an `Enum` class

Import `Enum` and create a sub-class that inherits from `str` and from `Enum`.

By inheriting from `str` the API docs will be able to know that the values must be of type `string` and will be able to render correctly.

* Được sử dụng cho các ứng dụng sản phẩm.

## Tính năng của Starlette

`FastAPI` is thực sự là một sub-class của `Starlette`. Do đó, nếu bạn đã biết hoặc đã sử dụng Starlette, đa số các chức năng sẽ làm việc giống như vậy.

Với **FastAPI**, bạn có được tất cả những tính năng của **Starlette**:

```Python hl_lines="3  6-8"
{!../../../docs_src/sub_applications/tutorial001.py!}
```

### Sub-application

Then, create your sub-application, and its *path operations*.

This sub-application is just another standard FastAPI application, but this is the one that will be "mounted":

```Python hl_lines="11  14-16"
{!../../../docs_src/sub_applications/tutorial001.py!}
```

### Mount the sub-application

```Python hl_lines="3  6-8"
{!../../../docs_src/sub_applications/tutorial001.py!}
```

### 子应用

接下来，创建子应用及其*路径操作*。

子应用只是另一个标准 FastAPI 应用，但这个应用是被**挂载**的应用：

```Python hl_lines="11  14-16"
{!../../../docs_src/sub_applications/tutorial001.py!}
```

### 挂载子应用

在顶层应用 `app` 中，挂载子应用 `subapi`。

本例的子应用挂载在 `/subapi` 路径下：

```Python hl_lines="11  19"
{!../../../docs_src/sub_applications/tutorial001.py!}
```

### 🔝-🎚 🈸

🥇, ✍ 👑, 🔝-🎚, **FastAPI** 🈸, & 🚮 *➡ 🛠️*:

```Python hl_lines="3  6-8"
{!../../../docs_src/sub_applications/tutorial001.py!}
```

### 🎧-🈸

⤴️, ✍ 👆 🎧-🈸, & 🚮 *➡ 🛠️*.

👉 🎧-🈸 ➕1️⃣ 🐩 FastAPI 🈸, ✋️ 👉 1️⃣ 👈 🔜 "🗻":

```Python hl_lines="11  14-16"
{!../../../docs_src/sub_applications/tutorial001.py!}
```

### 🗻 🎧-🈸

👆 🔝-🎚 🈸, `app`, 🗻 🎧-🈸, `subapi`.

client = TestClient(app)


async def overrider_dependency_simple(q: Optional[str] = None):
    return {"q": q, "skip": 5, "limit": 10}


async def overrider_sub_dependency(k: str):
    return {"k": k}


async def overrider_dependency_with_sub(msg: dict = Depends(overrider_sub_dependency)):
    return msg


def test_main_depends():
    response = client.get("/main-depends/")
    assert response.status_code == 422

        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_data = TokenData(username=username)
    except JWTError:
        raise credentials_exception

So, to avoid ID collisions, when creating the JWT token for the user, you could prefix the value of the `sub` key, e.g. with `username:`. So, in this example, the value of `sub` could have been: `username:johndoe`.

The important thing to keep in mind is that the `sub` key should have a unique identifier across the entire application, and it should be a string.

## Check it

        headers={"WWW-Authenticate": authenticate_value},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_scopes = payload.get("scopes", [])
        token_data = TokenData(scopes=token_scopes, username=username)

    Incluindo como manipular estado do lifespan que pode ser usado em outras áreas do seu código.

## Sub Aplicações