依赖项 - `Depends()` 和 `Security()`¶

`Depends()`¶

依赖项主要通过特殊的函数 Depends() 来处理，该函数接受一个可调用对象。

以下是它的参考及其参数。

你可以直接从 fastapi 导入它：

from fastapi import Depends

fastapi.Depends ¶

Depends(dependency=None, *, use_cache=True)

Declare a FastAPI dependency.

It takes a single "dependable" callable (like a function).

Don't call it directly, FastAPI will call it for you.

Read more about it in the FastAPI docs for Dependencies.

Example

from typing import Annotated

from fastapi import Depends, FastAPI

app = FastAPI()


async def common_parameters(q: str | None = None, skip: int = 0, limit: int = 100):
    return {"q": q, "skip": skip, "limit": limit}


@app.get("/items/")
async def read_items(commons: Annotated[dict, Depends(common_parameters)]):
    return commons

PARAMETER DESCRIPTION

dependency

A "dependable" callable (like a function).

Don't call it directly, FastAPI will call it for you, just pass the object directly.

TYPE: Optional[Callable[..., Any]] DEFAULT: None

use_cache

By default, after a dependency is called the first time in a request, if the dependency is declared again for the rest of the request (for example if the dependency is needed by several dependencies), the value will be re-used for the rest of the request.

Set use_cache to False to disable this behavior and ensure the dependency is called again (if declared more than once) in the same request.

TYPE: bool DEFAULT: True

Source code in fastapi/param_functions.py

def Depends(  # noqa: N802
    dependency: Annotated[
        Optional[Callable[..., Any]],
        Doc(
            """
            A "dependable" callable (like a function).

            Don't call it directly, FastAPI will call it for you, just pass the object
            directly.
            """
        ),
    ] = None,
    *,
    use_cache: Annotated[
        bool,
        Doc(
            """
            By default, after a dependency is called the first time in a request, if
            the dependency is declared again for the rest of the request (for example
            if the dependency is needed by several dependencies), the value will be
            re-used for the rest of the request.

            Set `use_cache` to `False` to disable this behavior and ensure the
            dependency is called again (if declared more than once) in the same request.
            """
        ),
    ] = True,
) -> Any:
    """
    Declare a FastAPI dependency.

    It takes a single "dependable" callable (like a function).

    Don't call it directly, FastAPI will call it for you.

    Read more about it in the
    [FastAPI docs for Dependencies](https://fastapi.tiangolo.com/tutorial/dependencies/).

    **Example**

    ```python
    from typing import Annotated

    from fastapi import Depends, FastAPI

    app = FastAPI()


    async def common_parameters(q: str | None = None, skip: int = 0, limit: int = 100):
        return {"q": q, "skip": skip, "limit": limit}


    @app.get("/items/")
    async def read_items(commons: Annotated[dict, Depends(common_parameters)]):
        return commons
    ```
    """
    return params.Depends(dependency=dependency, use_cache=use_cache)

`Security()`¶

在许多场景中，你可以使用依赖项来处理安全性（授权、认证等），使用 Depends()。

但当你想要同时声明 OAuth2 范围时，你可以使用 Security() 而不是 Depends()。

你可以直接从 fastapi 导入 Security()：

from fastapi import Security

fastapi.Security ¶

Security(dependency=None, *, scopes=None, use_cache=True)

Declare a FastAPI Security dependency.

The only difference with a regular dependency is that it can declare OAuth2 scopes that will be integrated with OpenAPI and the automatic UI docs (by default at /docs).

It takes a single "dependable" callable (like a function).

Don't call it directly, FastAPI will call it for you.

Read more about it in the FastAPI docs for Security and in the FastAPI docs for OAuth2 scopes.