from fastapi import Depends, FastAPI

from .dependencies import get_query_token, get_token_header
from .internal import admin
from .routers import items, users

app = FastAPI(dependencies=[Depends(get_query_token)])


app.include_router(users.router)
app.include_router(items.router)
app.include_router(
    admin.router,
    prefix="/admin",
    tags=["admin"],
    dependencies=[Depends(get_token_header)],

from fastapi import Depends, FastAPI

app = FastAPI()


async def common_parameters(
    q: Union[str, None] = None, skip: int = 0, limit: int = 100
):
    return {"q": q, "skip": skip, "limit": limit}


@app.get("/items/")
async def read_items(commons: dict = Depends(common_parameters)):
    return commons


@app.get("/users/")
async def read_users(commons: dict = Depends(common_parameters)):

from typing import Annotated, Union

from fastapi import Cookie, Depends, FastAPI

app = FastAPI()


def query_extractor(q: Union[str, None] = None):
    return q


def query_or_cookie_extractor(
    q: Annotated[str, Depends(query_extractor)],
    last_query: Annotated[Union[str, None], Cookie()] = None,
):
    if not q:
        return last_query
    return q


@app.get("/items/")
async def read_query(

**FastAPI** 调用 `CommonQueryParams` 类。这将创建该类的一个 "实例"，该实例将作为参数 `commons` 被传递给你的函数。

## 类型注解 vs `Depends`

注意，我们在上面的代码中编写了两次`CommonQueryParams`：

```Python
commons: CommonQueryParams = Depends(CommonQueryParams)
```

最后的 `CommonQueryParams`:

```Python
... = Depends(CommonQueryParams)
```

...实际上是 **Fastapi** 用来知道依赖项是什么的。

FastAPI 将从依赖项中提取声明的参数，这才是 FastAPI 实际调用的。

def on_startup():
    create_db_and_tables()


@app.post("/heroes/")
def create_hero(hero: Hero, session: Session = Depends(get_session)) -> Hero:
    session.add(hero)
    session.commit()
    session.refresh(hero)
    return hero


@app.get("/heroes/")
def read_heroes(
    session: Session = Depends(get_session),
    offset: int = 0,
    limit: int = Query(default=100, le=100),
) -> list[Hero]:

    return user


async def get_current_active_user(
    current_user: Annotated[User, Depends(get_current_user)],
):
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user


@app.post("/token")
async def login(form_data: Annotated[OAuth2PasswordRequestForm, Depends()]):
    user_dict = fake_users_db.get(form_data.username)
    if not user_dict:

Ainda que `Depends` seja utilizado nos parâmetros da função da mesma forma que `Body`, `Query`, etc, `Depends` funciona de uma forma um pouco diferente.

Você fornece um único parâmetro para `Depends`.

Esse parâmetro deve ser algo como uma função.

Você **não chama a função** diretamente (não adicione os parênteses no final), apenas a passe como parâmetro de `Depends()`.

## Typannotation vs. `Depends` { #type-annotation-vs-depends }

Beachten Sie, wie wir `CommonQueryParams` im obigen Code zweimal schreiben:

//// tab | Python 3.9+

```Python
commons: Annotated[CommonQueryParams, Depends(CommonQueryParams)]
```

////

//// tab | Python 3.9+ nicht annotiert

/// tip | Tipp

    ## Usage

    Create an instance object and use that object as the dependency in `Depends()`.

    The dependency result will be a string containing the key value.

    ## Example

    ```python
    from fastapi import Depends, FastAPI
    from fastapi.security import APIKeyQuery

    app = FastAPI()

    query_scheme = APIKeyQuery(name="api_key")

    )


async def get_current_user(token: str = Depends(oauth2_scheme)):
    user = fake_decode_token(token)
    return user


@app.get("/users/me")
async def read_users_me(current_user: User = Depends(get_current_user)):