我有以下代码来注册用户。我首先验证用户输入的位置。其次,我检查用户是否已经存在,如果是,则应返回响应400。否则请转到步骤3并添加新用户。最后,在步骤4中返回新创建的条目。从逻辑上讲,它可以正常工作并将数据正确添加到数据库,但是,即使是新用户,也总是在邮递员上回复'User already exists'
(来自第2步),即使该用户已将用户正确添加到数据库中。这使我认为在发送步骤2中的响应之前已经完成了第三步,这意味着我没有正确地链接诺言。另外,新用户永远不会作为响应发送回去,这是因为我没有正确地将Promise.then()与user.save()一起使用。我还收到以下错误(在代码之后发布),我理解这意味着我在尝试发送第一个响应之后尝试发送第二个响应。我可以通过异步和等待解决此问题,但想学习如何以这种方式进行。谢谢,感谢您的帮助。
const { User,validateUser } = require('../models/userModel');
const mongoose = require('mongoose');
const express = require('express');
const router = express.Router();
router.post('/',(req,res) => {
return Promise.resolve()
.then(() => {
//Step 1: validae the user input and if there is an error,send 400 res and error message
console.log('My user post body req::',req.body);
const { error } = validateUser(req.body); //this is using Joi.validate() which has a error property if errors are found
if (error) {
return res.status(400).send(error.details[0].message);
}
})
.then(() => {
//step 2: check if user already exists,if yes send res 400
let user = User.findOne({ email: req.body.email });
if (user) {
return res.status(400).send('User already exists');
}
})
.then(() => {
//Step 3: enter new user into the database
user = new User({
name: req.body.name,email: req.body.email,password: req.body.password
});
return user.save();
})
.then((result) => {
//step 4: return the newly added user
return res.status(200).send(result);
})
.catch((error) => {
console.log('Error Adding new User',error);
});
});
module.exports = router;
我从捕获中得到以下错误消息。即使我是我的每一次回应都返回
Error Adding new User Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
at ServerResponse.setHeader (_http_outgoing.js:494:11)
at ServerResponse.header (/home/ssaquif/WebDevProjects/movie-reviews-backend/node_modules/express/lib/response.js:771:10)
at ServerResponse.send (/home/ssaquif/WebDevProjects/movie-reviews-backend/node_modules/express/lib/response.js:170:12)
at ServerResponse.json (/home/ssaquif/WebDevProjects/movie-reviews-backend/node_modules/express/lib/response.js:267:15)
at ServerResponse.send (/home/ssaquif/WebDevProjects/movie-reviews-backend/node_modules/express/lib/response.js:158:21)
at /home/ssaquif/WebDevProjects/movie-reviews-backend/routes/users.js:35:27
at processTicksAndRejections (internal/process/task_queues.js:93:5) {
code: 'ERR_HTTP_HEADERS_SENT'