///

## Type hints in **FastAPI**

**FastAPI** maakt gebruik van type hints om verschillende dingen te doen.

Met **FastAPI** declareer je parameters met type hints en krijg je:

* **Editor ondersteuning**.
* **Type checks**.

...en **FastAPI** gebruikt dezelfde declaraties om:

from typing import Union

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer
from pydantic import BaseModel

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


class User(BaseModel):
    username: str
    email: Union[str, None] = None
    full_name: Union[str, None] = None
    disabled: Union[bool, None] = None


def fake_decode_token(token):
    return User(

from typing import Dict, List, Optional

from fastapi import FastAPI
from pydantic import BaseModel, Field
from starlette.testclient import TestClient

app = FastAPI()


class Item(BaseModel):
    name: str = Field(alias="aliased_name")
    price: Optional[float] = None
    owner_ids: Optional[List[int]] = None


@app.get("/items/valid", response_model=Item)
def get_valid():
    return Item(aliased_name="valid", price=1.0)

from typing import Union

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer
from pydantic import BaseModel
from typing_extensions import Annotated

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


class User(BaseModel):
    username: str
    email: Union[str, None] = None
    full_name: Union[str, None] = None
    disabled: Union[bool, None] = None

import secrets
from typing import Annotated

from fastapi import Depends, FastAPI, HTTPException, status
from fastapi.security import HTTPBasic, HTTPBasicCredentials

app = FastAPI()

security = HTTPBasic()


def get_current_username(
    credentials: Annotated[HTTPBasicCredentials, Depends(security)],
):
    current_username_bytes = credentials.username.encode("utf8")
    correct_username_bytes = b"stanleyjobson"

# 高级用户指南

## 额外特性

主要的教程 [教程 - 用户指南](../tutorial/index.md){.internal-link target=_blank} 应该足以让你了解 **FastAPI** 的所有主要特性。

你会在接下来的章节中了解到其他的选项、配置以及额外的特性。

/// tip

接下来的章节**并不一定是**「高级的」。

而且对于你的使用场景来说，解决方案很可能就在其中。

///

## 先阅读教程

你可能仍会用到 **FastAPI** 主教程 [教程 - 用户指南](../tutorial/index.md){.internal-link target=_blank} 中的大多数特性。

from fastapi.testclient import TestClient

from docs_src.query_params_str_validations.tutorial014_an import app

client = TestClient(app)


def test_hidden_query():
    response = client.get("/items?hidden_query=somevalue")
    assert response.status_code == 200, response.text
    assert response.json() == {"hidden_query": "somevalue"}


def test_no_hidden_query():
    response = client.get("/items")

`OAuth2PasswordBearer` makes **FastAPI** know that it is a security scheme. So it is added that way to OpenAPI.

But `OAuth2PasswordRequestForm` is just a class dependency that you could have written yourself, or you could have declared `Form` parameters directly.

But as it's a common use case, it is provided by **FastAPI** directly, just to make it easier.

///

# 子依赖项

FastAPI 支持创建含**子依赖项**的依赖项。

并且，可以按需声明任意**深度**的子依赖项嵌套层级。

**FastAPI** 负责处理解析不同深度的子依赖项。

### 第一层依赖项

下列代码创建了第一层依赖项：

```Python hl_lines="8-9"
{!../../docs_src/dependencies/tutorial005.py!}
```

这段代码声明了类型为 `str` 的可选查询参数 `q`，然后返回这个查询参数。

这个函数很简单（不过也没什么用），但却有助于让我们专注于了解子依赖项的工作方式。

### 第二层依赖项

接下来，创建另一个依赖项函数，并同时用该依赖项自身再声明一个依赖项（所以这也是一个「依赖项」）：

```Python hl_lines="13"

////

Esse código de status será usado na resposta e será adicionado ao esquema OpenAPI.

/// note | "Detalhes Técnicos"

Você também poderia usar `from starlette import status`.

**FastAPI** fornece o mesmo `starlette.status` como `fastapi.status` apenas como uma conveniência para você, o desenvolvedor. Mas vem diretamente do Starlette.

///

## Tags