[英]Express promise chain how to send response and end promise chain flow?
與下面的代碼,我得到這個錯誤:
Unhandled rejection Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
如果result === null
則Unhandled rejection Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
。
'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
在不繼續履行承諾鏈流程的情況下,盡早返回響應的最佳方法是什么?
這樣的承諾鏈
你能做的是
A)在res.status(HttpStatus.NOT_FOUND)
)之后return null
(刪除該代碼之前的return
)
B) then(result
在then(result
檢查結果是否為null,如果是,則跳過res.status(...
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,保留現有代碼,直到
.then(result => {
// change C
if (!res.headersSent) {
console.log('final result = ', result)
return res.status(HttpStatus.CREATED).send(result)
}
})
老實說,這可能是“更清潔”的解決方案
測試一下:
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);
})
}
}
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