)


async def get_current_user(token: Annotated[str, Depends(oauth2_scheme)]):
    user = fake_decode_token(token)
    return user


@app.get("/users/me")
async def read_users_me(current_user: Annotated[User, Depends(get_current_user)]):

from fastapi import Depends, FastAPI

app = FastAPI()


fake_items_db = [{"item_name": "Foo"}, {"item_name": "Bar"}, {"item_name": "Baz"}]


class CommonQueryParams:
    def __init__(self, q: str | None = None, skip: int = 0, limit: int = 100):
        self.q = q
        self.skip = skip
        self.limit = limit


@app.get("/items/")
async def read_items(commons: Annotated[Any, Depends(CommonQueryParams)]):

from datetime import datetime, timedelta, timezone
from typing import Annotated

import jwt
from fastapi import Depends, FastAPI, HTTPException, Security, status
from fastapi.security import (
    OAuth2PasswordBearer,
    OAuth2PasswordRequestForm,
    SecurityScopes,
)
from jwt.exceptions import InvalidTokenError
from pwdlib import PasswordHash
from pydantic import BaseModel, ValidationError

# to get a string like this run:

from datetime import datetime, timedelta, timezone
from typing import Annotated, Union

import jwt
from fastapi import Depends, FastAPI, HTTPException, Security, status
from fastapi.security import (
    OAuth2PasswordBearer,
    OAuth2PasswordRequestForm,
    SecurityScopes,
)
from jwt.exceptions import InvalidTokenError
from pwdlib import PasswordHash
from pydantic import BaseModel, ValidationError

# to get a string like this run:

Let's focus on the parameters declared:

* Even though this function is a dependency ("dependable") itself, it also declares another dependency (it "depends" on something else).
    * It depends on the `query_extractor`, and assigns the value returned by it to the parameter `q`.
* It also declares an optional `last_query` cookie, as a `str`.

from fastapi import Depends, FastAPI, Security
from fastapi.security import SecurityScopes
from fastapi.testclient import TestClient

app = FastAPI()


def get_user(required_scopes: SecurityScopes):
    return "john", required_scopes.scopes


def get_user_override(required_scopes: SecurityScopes):
    return "alice", required_scopes.scopes


def get_data():
    return [1, 2, 3]


def get_data_override():

from fastapi import APIRouter, Depends, HTTPException

from ..dependencies import get_token_header

router = APIRouter(
    prefix="/items",
    tags=["items"],
    dependencies=[Depends(get_token_header)],
    responses={404: {"description": "Not found"}},
)


fake_items_db = {"plumbus": {"name": "Plumbus"}, "gun": {"name": "Portal Gun"}}


@router.get("/")
async def read_items():
    return fake_items_db

**FastAPI** 调用 `CommonQueryParams` 类。这将创建该类的一个 "实例"，该实例将作为参数 `commons` 被传递给你的函数。

## 类型注解 vs `Depends`

注意，我们在上面的代码中编写了两次`CommonQueryParams`：

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

最后的 `CommonQueryParams`:

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

...实际上是 **Fastapi** 用来知道依赖项是什么的。

FastAPI 将从依赖项中提取声明的参数，这才是 FastAPI 实际调用的。

from typing import Annotated, Union

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

app = FastAPI()


async def common_parameters(
    q: Union[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 {"message": "Hello Items!", "params": commons}

    return user


async def get_current_active_user(
    current_user: Annotated[User, Depends(get_current_user)],
):
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user


@app.post("/token")
async def login(form_data: Annotated[OAuth2PasswordRequestForm, Depends()]):
    user_dict = fake_users_db.get(form_data.username)
    if not user_dict: