如何使用 express 中间件处理类型？

Question

我在 Node.js 中使用 Typescript。当您使用 Express 中间件时，您经常会转换 Request 对象。但是，使用 Typescript，我们无法跟踪 Request 对象是如何转换的。如果知道之前通过的中间件，有没有办法从中找出请求的类型？如果在 express 中不可能，我想找到另一个可能的框架。在 Nest ( https://github.com/kamilmysliwiec/nest ) 中可以吗？

示例代码

import { Request, Response, NextFunction } from 'express';

function userMiddleware(req: Request & User, res: Response, next: NextFunction) {
    req.user = {
        id: 'user_id',
    };
    next();
}

interface User {
    user: {
        id: string;
    }
}

interface Middleware {
    <T>(req: Request & T, res: Response, next: NextFunction): void;
}

class Controller {
    middleware = [userMiddleware];

    get = new GetMethod(this.middleware);

    post = (req: Request /* I don't know exact req type */, res: Response, next: NextFunction) => {
        console.log(req.user) // Error!
    }
}

class GetMethod {
    constructor(middleware: Middleware[]) {
        // How to deduce type of req from Middleware array?
    }
}

const controller = new Controller();

express.use('/', controller.middleware, controller.post);

我想从 Controller 类的中间件列表中提取类型信息。

Answer 1

首先我认为正确的界面是

interface User {
  id: string;
}

因为它们是回调，所以它们将收到其签名中Request没有的默认值。user

因此，您有两个选择：执行类型断言或编写自定义声明。如果你做得正确的话，两者都会被罚款。

类型断言：

interface User {
  id: string;
}

const isObject = (value: unknown): value is {[key: string]: unknown} => {
  return value && typeof value === 'object';
};

const isReqWithUser = (req: Request): req is Request & {user: User} => {
  return isObject(req) && !!req.user;
}

class Controller {
  post = (req: Request, res: Response, next: NextFunction) => {
    if (isReqWithUser(req)) {
      console.log(req.user) // now it works
    }
    next();
  }
}

报关：

但我们需要了解用户并不总是存在于请求中，我们应该将其标记为可选。

interface User {
  id: string;
}

const isObject = (value: unknown): value is {[key: string]: unknown} => {
  return value && typeof value === 'object';
};

const isReqWithUser = (req: Request): req is Request & {user: User} => {
  return isObject(req) && !!req.user;
}

class Controller {
  post = (req: Request, res: Response, next: NextFunction) => {
    if (isReqWithUser(req)) {
      console.log(req.user) // now it works
    }
    next();
  }
}