# Classes as Dependencies

Before diving deeper into the **Dependency Injection** system, let's upgrade the previous example.

## A `dict` from the previous example

In the previous example, we were returning a `dict` from our dependency ("dependable"):

=== "Python 3.10+"

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

=== "Python 3.9+"

    ```Python hl_lines="11"

    In diesem Fall müssen Sie sich darüber keine Sorgen machen. 🤷

### Beispiele für Strategien für Vorab-Schritte

Es hängt **stark** davon ab, wie Sie **Ihr System bereitstellen**, und hängt wahrscheinlich mit der Art und Weise zusammen, wie Sie Programme starten, Neustarts durchführen, usw.

Hier sind einige mögliche Ideen:

that you can more easily get a good answer, or even solve the problem yourself even before asking. And in GitHub I can make sure I always answer everything, even if it takes some time. I can't personally do that with the chat systems. 😅

Conversations in the chat systems are also not as easily searchable as in GitHub, so questions and answers might get lost in the conversation. And only the ones in GitHub count to become a [FastAPI Expert](fastapi-people.md#fastapi-experts){.internal-link...

Here's a little bit of that history.

## Alternatives

I have been creating APIs with complex requirements for several years (Machine Learning, distributed systems, asynchronous jobs, NoSQL databases, etc), leading several teams of developers.

As part of that, I needed to investigate, test and use many alternatives.

### 单独的程序

为了实现这一点，您通常会有一个**单独的程序**来确保您的应用程序在启动时运行。 在许多情况下，它还可以确保其他组件或应用程序也运行，例如数据库。

### 启动时运行的示例工具

可以完成这项工作的工具的一些示例是：

* Docker
* Kubernetes
* Docker Compose
* Docker in Swarm Mode
* Systemd
* Supervisor
* 作为其服务的一部分由云提供商内部处理
* 其他的...

我将在接下来的章节中为您提供更具体的示例。


## 重新启动

与确保应用程序在启动时运行类似，您可能还想确保它在挂掉后**重新启动**。

### 我们会犯错误

作为人类，我们总是会犯**错误**。 软件几乎*总是*在不同的地方隐藏着**bug**。 🐛

Tudo construído como ferramentas e componentes reutilizáveis que são fáceis de integrar com seus sistemas, armazenamento de dados, banco de dados relacionais e não-relacionais etc.

### Injeção de dependência

FastAPI inclui um sistema de <abbr title='também conhecido como "components", "resources", "services", "providers"'><strong>injeção de dependência</strong></abbr> extremamente fácil de usar, mas extremamente poderoso.

### Typen und Validierung

Diese Umgebungsvariablen können nur Text-Zeichenketten verarbeiten, da sie außerhalb von Python liegen und mit anderen Programmen und dem Rest des Systems (und sogar mit verschiedenen Betriebssystemen wie Linux, Windows, macOS) kompatibel sein müssen.

* Como configurar **Limitações de Validação** como `maximum_length` ou `regex`.
* Um poderoso e fácil de usar sistema de **<abbr title="também conhecido como componentes, recursos, fornecedores, serviços, injetáveis">Injeção de Dependência</abbr>**.

<img src="/img/tutorial/query-params-str-validations/image01.png">

## Exclude from OpenAPI

To exclude a query parameter from the generated OpenAPI schema (and thus, from the automatic documentation systems), set the parameter `include_in_schema` of `Query` to `False`:

=== "Python 3.10+"

    ```Python hl_lines="10"
    {!> ../../../docs_src/query_params_str_validations/tutorial014_an_py310.py!}
    ```

* Çox güclü və istifadəsi asan **<abbr title="components, resources, providers, services, injectables olaraq da bilinir">Dependency Injection</abbr>** sistemi.
* Təhlükəsizlik və autentifikasiya, **JWT tokenləri** ilə **OAuth2** dəstəyi və **HTTP Basic** autentifikasiyası.