快递承诺链如何发送响应和结束承诺链流?

Question

使用下面的代码，我收到此错误：

Unhandled rejection Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client如果result === null.

'use strict'
const HttpStatus = require('http-status-codes')
const { handleErr } = require('ciitizen-express-helpers').utils
function updateOrganization(db, stats) {
return function (req, res) {
db.organization.findOne({
where: {
id: req.params.id
}
})
.then(result => {
if (result === null) {
return res.status(HttpStatus.NOT_FOUND).send() <-- IF RESULT IS NULL, I RETURN THIS 
}
console.log('original result = ', result)
// Update any fields that were passed in
if (req.body.name) {
result.name = req.body.name
}
if (req.body.address1) {
result.address1 = req.body.address1
}
if (req.body.address2) {
result.address2 = req.body.address2
}
if (req.body.city) {
result.city = req.body.city
}
if (req.body.state) {
result.state = req.body.state
}
if (req.body.zip) {
result.zip = req.body.zip
}
console.log('new result = ', result)
return result.save()
})
.then(result => {
console.log('final result = ', result)
return res.status(HttpStatus.CREATED).send(result) <-- BUT IT'S STILL TRYING TO CALL THIS, HENCE THE CAN'T SEND HEADERS ERROR
})
.catch(err => {
req.log.error(err)
return handleErr(res, HttpStatus.INTERNAL_SERVER_ERROR, err.message)
})
}
}
module.exports = updateOrganization

在不继续通过我的承诺链流程的情况下提前回复回复的最佳方法是什么？

Answer 1

这样的承诺链

你能做的是

A)return nullres.status(HttpStatus.NOT_FOUND)后(删除该代码之前的return)

B)then(result检查结果是否为空，如果是，请跳过res.status(...代码

例如

'use strict'
const HttpStatus = require('http-status-codes')
const { handleErr } = require('ciitizen-express-helpers').utils
function updateOrganization(db, stats) {
return function (req, res) {
db.organization.findOne({
where: {
id: req.params.id
}
})
.then(result => {
if (result === null) {
// change A
res.status(HttpStatus.NOT_FOUND).send();
return null;
}
// snip
return result.save()
})
.then(result => {
console.log('final result = ', result)
// change B
if (result !== null) {
return res.status(HttpStatus.CREATED).send(result)
}
})
.catch(err => {
req.log.error(err)
return handleErr(res, HttpStatus.INTERNAL_SERVER_ERROR, err.message)
})
}
}
module.exports = updateOrganization

或者，保留现有代码，直到

.then(result => {
// change C
if (!res.headersSent) {
console.log('final result = ', result)
return res.status(HttpStatus.CREATED).send(result)
}
})

老实说，这可能是一个"更干净"的修复

Answer 2

测试这个：

function updateOrganization(db, stats) {
return function (req, res) {
db.organization.findOne({
where: {
id: req.params.id
}
})
.then(result => {
if (!result) {
res.status(HttpStatus.NOT_FOUND).end();
return null;
}
console.log('original result = ', result)
// Update any fields that were passed in
if (req.body.name) {
result.name = req.body.name
}
if (req.body.address1) {
result.address1 = req.body.address1
}
if (req.body.address2) {
result.address2 = req.body.address2
}
if (req.body.city) {
result.city = req.body.city;
}
if (req.body.state) {
result.state = req.body.state;
}
if (req.body.zip) {
result.zip = req.body.zip;
}
console.log('new result = ', result);
return result.save();
})
.then(result => {
console.log('final result = ', result);
if(result) {
return res.status(HttpStatus.CREATED).json(result)
}
return null;
})
.catch(err => {
req.log.error(err);
return handleErr(res, HttpStatus.INTERNAL_SERVER_ERROR, err.message);
})
}
}