* The interactive API documentation will be automatically updated, including the new body:

![Swagger UI](https://fastapi.tiangolo.com/img/index/index-03-swagger-02.png)

* Click on the button "Try it out", it allows you to fill the parameters and directly interact with the API:

Now create Pydantic *models* (schemas) that will be used when reading data, when returning it from the API.

For example, before creating an item, we don't know what will be the ID assigned to it, but when reading it (when returning it from the API) we will already know its ID.

The same way, when reading a user, we can now declare that `items` will contain the items that belong to this user.

    ```Python hl_lines="13-14"
    {!> ../../../docs_src/dependencies/tutorial008c.py!}
    ```

In this case, the client will see an *HTTP 500 Internal Server Error* response as it should, given that we are not raising an `HTTPException` or similar, but the server will **not have any logs** or any other indication of what was the error. 😱

### Always `raise` in Dependencies with `yield` and `except`

    ```

Those parameters are what **FastAPI** will use to "solve" the dependency.

In both cases, it will have:

* An optional `q` query parameter that is a `str`.
* A `skip` query parameter that is an `int`, with a default of `0`.
* A `limit` query parameter that is an `int`, with a default of `100`.

In both cases the data will be converted, validated, documented on the OpenAPI schema, etc.

## Use it

Next it will convert and validate the data. So, when you use that `settings` object, you will have data of the types you declared (e.g. `items_per_user` will be an `int`).

### Use the `settings`

    *, route: routing.APIRoute, method: str
) -> str:  # pragma: nocover
    warnings.warn(
        "fastapi.openapi.utils.generate_operation_id() was deprecated, "
        "it is not used internally, and will be removed soon",
        DeprecationWarning,
        stacklevel=2,
    )
    if route.operation_id:
        return route.operation_id
    path: str = route.path_format

Typer CLIをインストールする場合、次のコマンドで補完をインストールできます:

<div class="termy">

```console
$ typer --install-completion

zsh completion installed in /home/user/.bashrc.
Completion will take effect once you restart the terminal.
```

</div>

### アプリとドキュメントを同時に

以下の様にサンプルを実行すると:

<div class="termy">

```console
$ uvicorn tutorial001:app --reload

**Note**: You can mix `def` and `async def` in your *path operation functions* as much as you need and define each one using the best option for you. FastAPI will do the right thing with them.

Anyway, in any of the cases above, FastAPI will still work asynchronously and be extremely fast.

But by following the steps above, it will be able to do some performance optimizations.

## Technical Details

* The interactive API documentation will be automatically updated, including the new body:

![Swagger UI](https://fastapi.tiangolo.com/img/index/index-03-swagger-02.png)

* Click on the button "Try it out", it allows you to fill the parameters and directly interact with the API:

```Python hl_lines="2  7"
{!../../../docs_src/custom_response/tutorial001b.py!}
```

!!! info
    The parameter `response_class` will also be used to define the "media type" of the response.

    In this case, the HTTP header `Content-Type` will be set to `application/json`.

    And it will be documented as such in OpenAPI.

!!! tip
    The `ORJSONResponse` is currently only available in FastAPI, not in Starlette.