Christoph Obexer <******@****.***> 1749718797 +0200

## Type annotation vs `Depends` { #type-annotation-vs-depends }

Notice how we write `CommonQueryParams` twice in the above code:

//// tab | Python 3.9+

```Python
commons: Annotated[CommonQueryParams, Depends(CommonQueryParams)]
```

////

        self.q = q
        self.skip = skip
        self.limit = limit


@app.get("/items/")
async def read_items(commons=Depends(CommonQueryParams)):
    response = {}
    if commons.q:
        response.update({"q": commons.q})
    items = fake_items_db[commons.skip : commons.skip + commons.limit]
    response.update({"items": items})

## Anotações de Tipo vs `Depends` { #type-annotation-vs-depends }

Perceba como escrevemos `CommonQueryParams` duas vezes no código abaixo:

//// tab | Python 3.9+

```Python
commons: Annotated[CommonQueryParams, Depends(CommonQueryParams)]
```

////

import java.util.ArrayList;
import java.util.List;

import org.apache.commons.jxpath.ri.Compiler;
import org.apache.commons.jxpath.ri.compiler.NodeNameTest;
import org.apache.commons.jxpath.ri.compiler.NodeTest;
import org.apache.commons.jxpath.ri.compiler.NodeTypeTest;
import org.apache.commons.jxpath.ri.model.NodeIterator;
import org.apache.commons.jxpath.ri.model.NodePointer;
import org.apache.maven.api.xml.XmlNode;

):
    return {"q": q, "skip": skip, "limit": limit}


@app.get("/items/")
async def read_items(commons: dict = Depends(common_parameters)):
    return {"message": "Hello Items!", "params": commons}


@app.get("/users/")
async def read_users(commons: dict = Depends(common_parameters)):
    return {"message": "Hello Users!", "params": commons}


client = TestClient(app)


async def override_dependency(q: Union[str, None] = None):

在本例中，第一个 `CommonQueryParams` ：

```Python
commons: CommonQueryParams ...
```

...对于 **FastAPI** 没有任何特殊的意义。FastAPI 不会使用它进行数据转换、验证等 (因为对于这，它使用 `= Depends(CommonQueryParams)`)。

你实际上可以只这样编写:

```Python
commons = Depends(CommonQueryParams)
```

..就像:

{* ../../docs_src/dependencies/tutorial003_py310.py hl[17] *}

但是声明类型是被鼓励的，因为那样你的编辑器就会知道将传递什么作为参数 `commons` ，然后它可以帮助你完成代码，类型检查，等等：

import java.util.function.Consumer;
import java.util.function.UnaryOperator;

import org.apache.commons.cli.CommandLine;
import org.apache.commons.cli.DefaultParser;
import org.apache.commons.cli.DeprecatedAttributes;
import org.apache.commons.cli.HelpFormatter;
import org.apache.commons.cli.Option;
import org.apache.commons.cli.ParseException;
import org.apache.maven.api.cli.Options;
import org.apache.maven.api.cli.ParserRequest;

{* ../../docs_src/dependencies/tutorial002.py hl[19] *}

**FastAPI**는 `CommonQueryParams` 클래스를 호출합니다. 이것은 해당 클래스의 "인스턴스"를 생성하고 그 인스턴스는 함수의 매개변수 `commons`로 전달됩니다.

## 타입 힌팅 vs `Depends`

위 코드에서 `CommonQueryParams`를 두 번 작성한 방식에 주목하십시오:

```Python
commons: CommonQueryParams = Depends(CommonQueryParams)
```

마지막 `CommonQueryParams` 변수를 보면:

```Python
... = Depends(CommonQueryParams)
```

## Typannotation vs. `Depends` { #type-annotation-vs-depends }

Beachten Sie, wie wir `CommonQueryParams` im obigen Code zweimal schreiben:

//// tab | Python 3.9+

```Python
commons: Annotated[CommonQueryParams, Depends(CommonQueryParams)]
```

////