from fastapi import Depends, FastAPI, Header, status
from fastapi.testclient import TestClient

app = FastAPI()


def get_header(*, someheader: str = Header()):
    return someheader


def get_something_else(*, someheader: str = Depends(get_header)):
    return f"{someheader}123"


@app.get("/")
def get_deps(dep1: str = Depends(get_header), dep2: str = Depends(get_something_else)):
    return {"dep1": dep1, "dep2": dep2}

    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:

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_for_access_token(
    form_data: Annotated[OAuth2PasswordRequestForm, Depends()],
) -> Token:

from fastapi import Depends


async def dependency_a():
    dep_a = generate_dep_a()
    try:
        yield dep_a
    finally:
        dep_a.close()


async def dependency_b(dep_a: Annotated[DepA, Depends(dependency_a)]):
    dep_b = generate_dep_b()
    try:
        yield dep_b
    finally:
        dep_b.close(dep_a)


async def dependency_c(dep_b: Annotated[DepB, Depends(dependency_b)]):

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 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(

    ## 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")

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)],

**FastAPI**는 `CommonQueryParams` 클래스를 호출합니다. 이것은 해당 클래스의 "인스턴스"를 생성하고 그 인스턴스는 함수의 매개변수 `commons`로 전달됩니다.

## 타입 힌팅 vs `Depends`

위 코드에서 `CommonQueryParams`를 두 번 작성한 방식에 주목하십시오:

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

마지막 `CommonQueryParams` 변수를 보면:

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

... **FastAPI**가 실제로 어떤 것이 의존성인지 알기 위해서 사용하는 방법입니다.

# Dependencies - `Depends()` and `Security()`

## `Depends()`

Dependencies are handled mainly with the special function `Depends()` that takes a callable.

Here is the reference for it and its parameters.

You can import it directly from `fastapi`:

```python
from fastapi import Depends
```

::: fastapi.Depends

## `Security()`