@noop_wrap_async
    def __call__(self):
        return True


class_instance_wrapped_async_dep = ClassInstanceWrappedAsyncDep()


class ClassInstanceWrappedGenDep:
    @noop_wrap
    def __call__(self):
        yield True


class_instance_wrapped_gen_dep = ClassInstanceWrappedGenDep()


class ClassInstanceWrappedAsyncGenDep:
    @noop_wrap_async
    def __call__(self):
        yield True

但也可以为依赖项设置参数，避免声明多个不同的函数或类。

假设要创建校验查询参数 `q` 是否包含固定内容的依赖项。

但此处要把待检验的固定内容定义为参数。

## **可调用**实例

Python 可以把类实例变为**可调用项**。

这里说的不是类本身（类本就是可调用项），而是类实例。

为此，需要声明 `__call__` 方法：

{* ../../docs_src/dependencies/tutorial011.py hl[10] *}

本例中，**FastAPI**  使用 `__call__` 检查附加参数及子依赖项，稍后，还要调用它向*路径操作函数*传递值。

## 参数化实例

接下来，使用 `__init__` 声明用于**参数化**依赖项的实例参数：

{* ../../docs_src/dependencies/tutorial011.py hl[7] *}

class CallableDependency:
    def __call__(self, value: str) -> str:
        return value


class CallableGenDependency:
    def __call__(self, value: str) -> Generator[str, None, None]:
        yield value


class AsyncCallableDependency:
    async def __call__(self, value: str) -> str:
        return value


class AsyncCallableGenDependency:
    async def __call__(self, value: str) -> AsyncGenerator[str, None]:

        dunder_call = getattr(_impartial(self.call), "__call__", None)  # noqa: B004
        if dunder_call is None:
            return False  # pragma: no cover
        if inspect.isgeneratorfunction(
            _impartial(dunder_call)
        ) or inspect.isgeneratorfunction(_unwrapped_call(dunder_call)):
            return True
        dunder_unwrapped_call = getattr(_unwrapped_call(self.call), "__call__", None)  # noqa: B004

class CallableDependency:
    def __call__(self, value: str) -> str:
        return value


class CallableGenDependency:
    def __call__(self, value: str) -> Generator[str, None, None]:
        yield value


class AsyncCallableDependency:
    async def __call__(self, value: str) -> str:
        return value


class AsyncCallableGenDependency:
    async def __call__(self, value: str) -> AsyncGenerator[str, None]:

from fastapi import Depends, FastAPI

app = FastAPI()


class FixedContentQueryChecker:
    def __init__(self, fixed_content: str):
        self.fixed_content = fixed_content

    def __call__(self, q: str = ""):
        if q:
            return self.fixed_content in q
        return False


checker = FixedContentQueryChecker("bar")


@app.get("/query-checker/")

            location=APIKeyIn.query,
            name=name,
            scheme_name=scheme_name,
            description=description,
            auto_error=auto_error,
        )

    async def __call__(self, request: Request) -> Optional[str]:
        api_key = request.query_params.get(self.model.name)
        return self.check_api_key(api_key)


class APIKeyHeader(APIKeyBase):
    """

from typing import Annotated

from fastapi import Depends, FastAPI

app = FastAPI()


class FixedContentQueryChecker:
    def __init__(self, fixed_content: str):
        self.fixed_content = fixed_content

    def __call__(self, q: str = ""):
        if q:
            return self.fixed_content in q
        return False


checker = FixedContentQueryChecker("bar")


@app.get("/query-checker/")

        return HTTPException(
            status_code=HTTP_401_UNAUTHORIZED,
            detail="Not authenticated",
            headers=self.make_authenticate_headers(),
        )

    async def __call__(
        self, request: Request
    ) -> Optional[HTTPAuthorizationCredentials]:
        authorization = request.headers.get("Authorization")
        scheme, credentials = get_authorization_scheme_param(authorization)

from __future__ import annotations

from typing import Annotated

from fastapi import Depends, FastAPI, Request
from fastapi.testclient import TestClient

from .utils import needs_py310


class Dep:
    def __call__(self, request: Request):
        return "test"


@needs_py310
def test_stringified_annotations():
    app = FastAPI()

    client = TestClient(app)

    @app.get("/test/")