You can create dependencies that have **sub-dependencies**.

They can be as **deep** as you need them to be.

**FastAPI** will take care of solving them.

## First dependency "dependable" { #first-dependency-dependable }

You could create a first dependency ("dependable") like:

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[8:9] *}

It declares an optional query parameter `q` as a `str`, and then it just returns it.

Let's see a very simple example. It will be so simple that it is not very useful, for now.

But this way we can focus on how the **Dependency Injection** system works.

### Create a dependency, or "dependable" { #create-a-dependency-or-dependable }

Let's first focus on the dependency.

It is just a function that can take all the same parameters that a *path operation function* can take:

* Cross-Origin Resource Sharing: Cross-Origin Resource Sharing (do not translate to "Compartilhamento de Recursos de Origem Cruzada")
* Deep Learning: Deep Learning (do not translate to "Aprendizado Profundo")
* dependable: dependable
* dependencies: dependências
* deprecated: descontinuado
* docs: documentação
* FastAPI app: aplicação FastAPI
* framework: framework (do not translate)
* feature: funcionalidade
* guides: tutoriais

* Release Notes: Release Notes (do not translate to "Notas de la Versión")
* Semantic Versioning: Semantic Versioning (do not translate to "Versionado Semántico")
* dependable: dependable (do not translate to "confiable" or "fiable")
* list (as in Python list): list
* context manager: context manager (do not translate to "gestor de contexto" or "administrador de contexto")
* a little bit: un poquito

# Security Tools

When you need to declare dependencies with OAuth2 scopes you use `Security()`.

But you still need to define what is the dependable, the callable that you pass as a parameter to `Depends()` or `Security()`.

There are multiple tools that you can use to create those dependables, and they get integrated into OpenAPI so they are shown in the automatic docs UI, they can be used by automatically generated clients and SDKs, etc.

## A `dict` from the previous example { #a-dict-from-the-previous-example }

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

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[9] *}

But then we get a `dict` in the parameter `commons` of the *path operation function*.

# 以類別作為相依性 { #classes-as-dependencies }

在更深入了解 **相依性注入（Dependency Injection）** 系統之前，我們先把前一個範例升級一下。

## 前一個範例中的 `dict` { #a-dict-from-the-previous-example }

在前一個範例中，我們從相依項（"dependable"）回傳了一個 `dict`：

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[9] *}

但接著我們在路徑操作函式（*path operation function*）的參數 `commons` 中取得的是一個 `dict`。

而我們知道，編輯器對 `dict` 無法提供太多輔助（例如自動完成），因為它無法預先知道其中的鍵與值的型別。

我們可以做得更好...

# 의존성으로서의 클래스 { #classes-as-dependencies }

**의존성 주입** 시스템에 대해 더 깊이 살펴보기 전에, 이전 예제를 업그레이드해 보겠습니다.

## 이전 예제의 `dict` { #a-dict-from-the-previous-example }

이전 예제에서는 의존성("dependable")에서 `dict`를 반환하고 있었습니다:

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[9] *}

하지만 그러면 *경로 처리 함수*의 매개변수 `commons`에서 `dict`를 받게 됩니다.

그리고 에디터는 `dict`의 키와 값 타입을 알 수 없기 때문에 `dict`에 대해서는 (완성 기능 같은) 많은 지원을 제공할 수 없다는 것을 알고 있습니다.

더 나은 방법이 있습니다...

これらすべてを、コードの繰り返しを最小限に抑えながら行います。

## 最初のステップ { #first-steps }

非常にシンプルな例を見てみましょう。あまりにもシンプルなので、今のところはあまり参考にならないでしょう。

しかし、この方法では **Dependency Injection** システムがどのように機能するかに焦点を当てることができます。

### 依存関係（「dependable」）の作成 { #create-a-dependency-or-dependable }

まずは依存関係に注目してみましょう。

以下のように、*path operation 関数*と同じパラメータを全て取ることができる関数にすぎません:

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[8:9] *}

これだけです。

**２行**。

- path: шлях
- query: запит
- cookie: кукі
- header: заголовок
- startup: запуск
- shutdown: вимкнення
- lifespan: тривалість життя
- authorization: авторизація
- forwarded header: направлений заголовок
- dependable: залежний
- dependent: залежний
- bound: межа
- concurrency: рівночасність
- parallelism: паралелізм
- multiprocessing: багатопроцесорність
- env var: змінна оточення
- dict: словник
- enum: перелік