The simplicity of the dependency injection system makes **FastAPI** compatible with:

* all the relational databases
* NoSQL databases
* external packages
* external APIs
* authentication and authorization systems
* API usage monitoring systems
* response data injection systems
* etc.

## Simple and Powerful

Dies ist nicht einmal Python, NestJS ist ein von Angular inspiriertes JavaScript (TypeScript) NodeJS Framework.

Es erreicht etwas Ähnliches wie Flask-apispec.

Es verfügt über ein integriertes Dependency Injection System, welches von Angular 2 inspiriert ist. Erfordert ein Vorab-Registrieren der „Injectables“ (wie alle anderen Dependency Injection Systeme, welche ich kenne), sodass der Code ausschweifender wird und es mehr Codeverdoppelung gibt.

And it will save the returned value in a <abbr title="A utility/system to store computed/generated values, to re-use them instead of computing them again.">"cache"</abbr> and pass it to all the "dependants" that need it in that specific request, instead of calling the dependency multiple times for the same request.

Das bedeutet, dass anstelle des normalen Prozesses, bei dem Benutzer Requests an Ihre API senden, **Ihre API** (oder Ihre Anwendung) **Requests an deren System** (an deren API, deren Anwendung) senden könnte.

Das wird normalerweise als **Webhook** bezeichnet.

## Webhooks-Schritte

This means that instead of the normal process of your users sending requests to your API, it's **your API** (or your app) that could **send requests to their system** (to their API, their app).

This is normally called a **webhook**.

## Webhooks steps

The process normally is that **you define** in your code what is the message that you will send, the **body of the request**.

async def read_own_items(
    current_user: User = Security(get_current_active_user, scopes=["items"]),
):
    return [{"item_id": "Foo", "owner": current_user.username}]


@app.get("/status/")
async def read_system_status(current_user: User = Depends(get_current_user)):

    current_user: Annotated[User, Security(get_current_active_user, scopes=["items"])],
):
    return [{"item_id": "Foo", "owner": current_user.username}]


@app.get("/status/")
async def read_system_status(current_user: Annotated[User, Depends(get_current_user)]):

First you need to install `WebSockets`:

<div class="termy">

```console
$ pip install websockets

---> 100%
```

</div>

## WebSockets client

### In production

In your production system, you probably have a frontend created with a modern framework like React, Vue.js or Angular.

And to communicate using WebSockets with your backend you would probably use your frontend's utilities.

### Dependency Injection

FastAPI includes an extremely easy to use, but extremely powerful <abbr title='also known as "components", "resources", "services", "providers"'><strong>Dependency Injection</strong></abbr> system.

* Even dependencies can have dependencies, creating a hierarchy or **"graph" of dependencies**.
* All **automatically handled** by the framework.

# Klassen als Abhängigkeiten

Bevor wir tiefer in das **Dependency Injection** System eintauchen, lassen Sie uns das vorherige Beispiel verbessern.

## Ein `dict` aus dem vorherigen Beispiel

Im vorherigen Beispiel haben wir ein `dict` von unserer Abhängigkeit („Dependable“) zurückgegeben:

=== "Python 3.10+"

    ```Python hl_lines="9"
    {!> ../../../docs_src/dependencies/tutorial001_an_py310.py!}
    ```

=== "Python 3.9+"