But **FastAPI** will know that it has to solve `query_extractor` first, to pass the results of that to `query_or_cookie_extractor` while calling it.

///

```mermaid
graph TB

query_extractor(["query_extractor"])
query_or_cookie_extractor(["query_or_cookie_extractor"])

read_query["/items/"]

/// info

👀 👈 👥 🕴 📣 1️⃣ 🔗 *➡ 🛠️ 🔢*, `query_or_cookie_extractor`.

✋️ **FastAPI** 🔜 💭 👈 ⚫️ ✔️ ❎ `query_extractor` 🥇, 🚶‍♀️ 🏁 👈 `query_or_cookie_extractor` ⏪ 🤙 ⚫️.

///

```mermaid
graph TB

query_extractor(["query_extractor"])
query_or_cookie_extractor(["query_or_cookie_extractor"])

read_query["/items/"]

query_extractor --> query_or_cookie_extractor --> read_query
```

## ⚙️ 🎏 🔗 💗 🕰

Aber **FastAPI** wird wissen, dass es zuerst `query_extractor` auflösen muss, um dessen Resultat `query_or_cookie_extractor` zu übergeben, wenn dieses aufgerufen wird.

///

```mermaid
graph TB

query_extractor(["query_extractor"])
query_or_cookie_extractor(["query_or_cookie_extractor"])

read_query["/items/"]

    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(
    query_or_default: Annotated[str, Depends(query_or_cookie_extractor)],
):

    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(
    query_or_default: Annotated[str, Depends(query_or_cookie_extractor)],
):

Но **FastAPI** будет знать, что сначала он должен выполнить `query_extractor`, чтобы передать результаты этого в `query_or_cookie_extractor` при его вызове.

///

```mermaid
graph TB

query_extractor(["query_extractor"])
query_or_cookie_extractor(["query_or_cookie_extractor"])

read_query["/items/"]

Mas o **FastAPI** saberá que precisa solucionar `query_extractor` primeiro, para passar o resultado para `query_or_cookie_extractor` enquanto chama a função.

///

```mermaid
graph TB

query_extractor(["query_extractor"])
query_or_cookie_extractor(["query_or_cookie_extractor"])

read_query["/items/"]

*path operation関数*の中で宣言している依存関係は`query_or_cookie_extractor`の１つだけであることに注意してください。

しかし、**FastAPI** は`query_extractor`を最初に解決し、その結果を`query_or_cookie_extractor`を呼び出す時に渡す必要があることを知っています。

///

```mermaid
graph TB

query_extractor(["query_extractor"])
query_or_cookie_extractor(["query_or_cookie_extractor"])

read_query["/items/"]

query_extractor --> query_or_cookie_extractor --> read_query
```

## 同じ依存関係の複数回の使用

/// info | "信息"

注意，这里在*路径操作函数*中只声明了一个依赖项，即 `query_or_cookie_extractor` 。

但 **FastAPI** 必须先处理 `query_extractor`，以便在调用 `query_or_cookie_extractor` 时使用 `query_extractor` 返回的结果。

///

```mermaid
graph TB

query_extractor(["query_extractor"])
query_or_cookie_extractor(["query_or_cookie_extractor"])

read_query["/items/"]

query_extractor --> query_or_cookie_extractor --> read_query
```

## 多次使用同一个依赖项

def query_extractor(q: str | None = None):
    return q


def query_or_cookie_extractor(
    q: str = Depends(query_extractor), last_query: str | None = Cookie(default=None)
):
    if not q:
        return last_query
    return q


@app.get("/items/")
async def read_query(query_or_default: str = Depends(query_or_cookie_extractor)):