* Dependency ("dependable") fonksiyonunuzu doğru parametrelerle çağırır.
* Fonksiyonunuzun sonucunu alır.
* Bu sonucu *path operation function*'ınızdaki parametreye atar.

```mermaid
graph TB

common_parameters(["common_parameters"])
read_items["/items/"]
read_users["/users/"]

common_parameters --> read_items
common_parameters --> read_users
```

Послідовність виконання приблизно така, як на цій діаграмі. Час тече зверху вниз. І кожна колонка - це одна з частин, що взаємодіють або виконують код.

```mermaid
sequenceDiagram

participant client as Client
participant handler as Exception handler
participant dep as Dep with yield
participant operation as Path Operation
participant tasks as Background tasks

Но **FastAPI** будет знать, что сначала он должен выполнить `query_extractor`, чтобы передать результаты этого в `query_or_cookie_extractor` при его вызове.

///

```mermaid
graph TB

query_extractor(["query_extractor"])
query_or_cookie_extractor(["query_or_cookie_extractor"])

read_query["/items/"]

query_extractor --> query_or_cookie_extractor --> read_query
```

```mermaid
flowchart LR
    stone(philosophers-stone) -->|requires| harry-1[harry v1]
```

Então, em algum momento depois, você cria outro projeto chamado `prisoner-of-azkaban`, e esse projeto também depende de `harry`, mas esse projeto precisa do **`harry` versão `3`**.

```mermaid
flowchart LR
    azkaban(prisoner-of-azkaban) --> |requires| harry-3[harry v3]

* Chamar sua dependência ("dependable") com os parâmetros corretos.
* Obter o resultado da função.
* Atribuir esse resultado para o parâmetro em sua *função de operação de rota*.

```mermaid
graph TB

common_parameters(["common_parameters"])
read_items["/items/"]
read_users["/users/"]

common_parameters --> read_items
common_parameters --> read_users
```

该函数接收的参数与*路径操作函数*的参数相同。

/// tip | 提示

下一章会介绍除了函数之外，还有哪些“东西”可以用作依赖项。

///

接收到新的请求时，**FastAPI** 会负责：

* 用正确的参数调用你的依赖项（“dependable”）函数
* 获取函数返回的结果
* 将该结果赋值给你的*路径操作函数*中的参数

```mermaid
graph TB

common_parameters(["common_parameters"])
read_items["/items/"]
read_users["/users/"]

common_parameters --> read_items
common_parameters --> read_users
```

而該函式的參數宣告方式與「路徑操作函式」相同。

/// tip | 提示

除了函式之外，還有其他「東西」也能當作依賴，會在下一章介紹。

///

當有新的請求到達時，**FastAPI** 會負責：

* 以正確的參數呼叫你的依賴（dependable）函式。
* 取得該函式的回傳結果。
* 將結果指定給你的「路徑操作函式」中的對應參數。

```mermaid
graph TB

common_parameters(["common_parameters"])
read_items["/items/"]
read_users["/users/"]

common_parameters --> read_items
common_parameters --> read_users
```

Mais **FastAPI** saura qu'il doit d'abord résoudre `query_extractor`, pour passer ses résultats à `query_or_cookie_extractor` lors de son appel.

///

```mermaid
graph TB

query_extractor(["query_extractor"])
query_or_cookie_extractor(["query_or_cookie_extractor"])

read_query["/items/"]

query_extractor --> query_or_cookie_extractor --> read_query
```

Mas o **FastAPI** saberá que precisa solucionar `query_extractor` primeiro, para passar o resultado para `query_or_cookie_extractor` enquanto chama a função.

///

```mermaid
graph TB

query_extractor(["query_extractor"])
query_or_cookie_extractor(["query_or_cookie_extractor"])

read_query["/items/"]

query_extractor --> query_or_cookie_extractor --> read_query
```

Yani ilk öğeyi gönderirsiniz, istemci onu alıp işlemeye başlar, bu sırada siz bir sonraki öğeyi üretmeye devam edebilirsiniz.

```mermaid
sequenceDiagram
    participant App
    participant Client

    App->>App: Produce Item 1
    App->>Client: Send Item 1
    App->>App: Produce Item 2
    Client->>Client: Process Item 1