!!! info
    Keep in mind that dataclasses can't do everything Pydantic models can do.

    So, you might still need to use Pydantic models.

    But if you have a bunch of dataclasses laying around, this is a nice trick to use them to power a web API using FastAPI. 🤓

## Dataclasses in `response_model`

You can also use `dataclasses` in the `response_model` parameter:

```Python hl_lines="1  7-13  19"

## Data validation

But if you go to the browser at <a href="http://127.0.0.1:8000/items/foo" class="external-link" target="_blank">http://127.0.0.1:8000/items/foo</a>, you will see a nice HTTP error of:

```JSON
{
  "detail": [
    {
      "type": "int_parsing",
      "loc": [
        "path",
        "item_id"
      ],

* 📝 Add External Link: 10 Tips for adding SQLAlchemy to FastAPI. PR [#11036](https://github.com/tiangolo/fastapi/pull/11036) by [@Donnype](https://github.com/Donnype).
* 📝 Add External Link: Tips on migrating from Flask to FastAPI and vice-versa. PR [#11029](https://github.com/tiangolo/fastapi/pull/11029) by [@jtemporal](https://github.com/jtemporal).

```
/files/{file_path:path}
```

En este caso el nombre del parámetro es `file_path` y la última parte, `:path`, le dice que el parámetro debería coincidir con cualquier path.

Entonces lo puedes usar con:

```Python hl_lines="6"
{!../../../docs_src/path_params/tutorial004.py!}
```

!!! tip "Consejo"

  - author: Jessica Temporal
    author_link: https://jtemporal.com/socials
    link: https://jtemporal.com/tips-on-migrating-from-flask-to-fastapi-and-vice-versa/
    title: Tips on migrating from Flask to FastAPI and vice-versa
  - author: Ankit Anchlia
    author_link: https://linkedin.com/in/aanchlia21
    link: https://hackernoon.com/explore-how-to-effectively-use-jwt-with-fastapi

<img src="/img/async/concurrent-burgers/concurrent-burgers-06.png" class="illustration">

You and your crush eat the burgers and have a nice time. ✨

<img src="/img/async/concurrent-burgers/concurrent-burgers-07.png" class="illustration">

!!! info

    * `app`: el objeto creado dentro de `main.py` con la línea `app = FastAPI()`.
    * `--reload`: hace que el servidor se reinicie cada vez que cambia el código. Úsalo únicamente para desarrollo.

En el output, hay una línea que dice más o menos:

```hl_lines="4"
INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
```

Esa línea muestra la URL dónde se está sirviendo tu app en tu maquina local.

### Revísalo

Llega tu turno, haces tu pedido de 2 hamburguesas impresionantes para esa persona 😍 y para ti.

<img src="https://fastapi.tiangolo.com/img/async/concurrent-burgers/concurrent-burgers-02.png" alt="illustration">

El cajero 💁 le dice algo al chico de la cocina 👨‍🍳 para que sepa que tiene que preparar tus hamburguesas 🍔 (a pesar de que actualmente está preparando las de los clientes anteriores).

With just that Python type declaration, **FastAPI** will:

* Read the body of the request as JSON.
* Convert the corresponding types (if needed).
* Validate the data.
    * If the data is invalid, it will return a nice and clear error, indicating exactly where and what was the incorrect data.
* Give you the received data in the parameter `item`.