Question

我在Node.js中使用Typescript。使用Express中间件时，通常会转换Request对象。但是，使用Typescript，我们无法跟踪Request对象的转换方式。如果你知道之前通过的中间件，有没有办法从中找出请求的类型？如果在快递中不可能，我想找到另一个可行的框架。是否可以在Nest（https://github.com/kamilmysliwiec/nest）？

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类中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;
}

由于它们是回调，因此将收到默认Request，其签名中没有user。

因此，您有2个选项，进行类型断言或编写自定义声明。如果正确执行，两者都很好。

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();
  }
}

自定义声明

但是我们需要了解用户并非总是存在于请求中，我们应该将其标记为可选。

interface User {
  id: string;
}

declare module 'express' {
  export interface Request {
    user?: User; // adding our custom declaration.
  }
}

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

如何使用express中间件来处理类型？

1 个答案: