def __call__(self, q: str = ""):
        if q:
            return self.fixed_content in q
        return False


checker = FixedContentQueryChecker("bar")


@app.get("/query-checker/")
async def read_query_check(fixed_content_included: bool = Depends(checker)):

```Python hl_lines="7"
{!../../../docs_src/path_params/tutorial002.py!}
```

In this case, `item_id` is declared to be an `int`.

!!! check
    This will give you editor support inside of your function, with error checks, completion, etc.

## Data <abbr title="also known as: serialization, parsing, marshalling">conversion</abbr>

```Python hl_lines="16"
{!../../../docs_src/dependencies/tutorial011.py!}
```

这样就可以**参数化**依赖项，它包含 `checker.fixed_content` 的属性 - `"bar"`。

## 把实例作为依赖项

然后，不要再在 `Depends(checker)` 中使用 `Depends(FixedContentQueryChecker)`， 而是要使用 `checker`，因为依赖项是类实例 - `checker`，不是类。

处理依赖项时，**FastAPI** 以如下方式调用 `checker`：

```Python
checker(q="somequery")
```

……并用*路径操作函数*的参数 `fixed_content_included` 返回依赖项的值：

```Python hl_lines="20"

{!../../../docs_src/dependencies/tutorial011.py!}
```

& 👈 🌌 👥 💪 "🔗" 👆 🔗, 👈 🔜 ✔️ `"bar"` 🔘 ⚫️, 🔢 `checker.fixed_content`.

## ⚙️ 👐 🔗

⤴️, 👥 💪 ⚙️ 👉 `checker` `Depends(checker)`, ↩️ `Depends(FixedContentQueryChecker)`, ↩️ 🔗 👐, `checker`, 🚫 🎓 ⚫️.

& 🕐❔ ❎ 🔗, **FastAPI** 🔜 🤙 👉 `checker` 💖:

```Python
checker(q="somequery")
```

...& 🚶‍♀️ ⚫️❔ 👈 📨 💲 🔗 👆 *➡ 🛠️ 🔢* 🔢 `fixed_content_included`:

This will help us inside of the function with all the completion and type checks.

!!! tip
    You might remember that request bodies are also declared with Pydantic models.

    Here **FastAPI** won't get confused because you are using `Depends`.

!!! check

#!/usr/bin/env bash

set -e
set -x

mypy fastapi
ruff check fastapi tests docs_src scripts

Check the in-code annotation tips above to see more specific details.

## Learn More

You can also combine `dataclasses` with other Pydantic models, inherit from them, include them in your own models, etc.

## Available versions

You can see the available versions (e.g. to check what is the current latest) in the [Release Notes](../release-notes.md){.internal-link target=_blank}.

## About versions

{!../../../docs_src/path_params/tutorial002.py!}
```

本例把 `item_id` 的类型声明为 `int`。

!!! check "检查"

    类型声明将为函数提供错误检查、代码补全等编辑器支持。

## 数据<abbr title="也称为：序列化、解析">转换</abbr>

运行示例并访问 <a href="http://127.0.0.1:8000/items/3" class="external-link" target="_blank">http://127.0.0.1:8000/items/3</a>，返回的响应如下：

```JSON
{"item_id":3}
```

!!! check "检查"

    注意，函数接收并返回的值是 `3`（ `int`），不是 `"3"`（`str`）。

SQLALCHEMY_DATABASE_URL = "sqlite:///./sql_app.db"
# SQLALCHEMY_DATABASE_URL = "postgresql://user:password@postgresserver/db"

engine = create_engine(
    SQLALCHEMY_DATABASE_URL, connect_args={"check_same_thread": False}
)
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)