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[英]{NodeJS} "Cannot set headers after they are sent to the client NodeJS"
[英]NodeJS - Cannot set Headers after they are sent to the client
因此,我進行了搜索,發現要解決上述問題,我必須在發送響應后返回。 但是我的問題是,即使我回來了,我仍然會遇到錯誤。
const dbEditCourse = (req, res, db, logger) => {
let {
origCourse, code, description, type
} = req.body;
if (!code || !description || !type) {
res.json({
haveEmpty: true
});
return;
}
db.transaction((trx) => {
db.select('*').from('course_strand').where('code', '=', code)
.then(data => {
if (data[0]) {
//error happens in this block of code
res.json({
isSuccess: false
});
return;
//i also tried return res.json({ isSuccess: false });
}
//wrapping this in 'else' also does not work
return db('course_strand')
.returning('*')
.where('code', '=', origCourse)
.update({ code, description, type })
})
.then(course => {
return db('activity_logs')
.returning('*')
.insert({
date: new Date(),
employee_id: req.session.emp_id,
module: "COURSE / STRAND",
activity: "EDIT"
})
})
.then(activity => {
if (activity[0]) {
res.json({
isSuccess: true
});
return;
} else {
res.json({
isSuccess: false
});
return;
}
})
.then(trx.commit)
.catch(err => {
logger.error(err);
trx.rollback;
res.render('pages/error-500');
});
})
.catch(err => logger.error(err));
}
module.exports = {
dbEditCourse
}
我要產生錯誤的原因是,如果記錄存在,它將進入上面的代碼塊。 除了該特定的代碼塊之外,我在其他地方均未遇到該錯誤。 即使我遇到錯誤,代碼也可以正常工作。
你不能違背諾言鏈return關鍵字,所有.then
語句將被執行(排除你在拋出一個錯誤.then
),該res.json
已經被多次調用。
在catch塊中處理所有錯誤(包括您的錯誤和系統錯誤)。
在catch塊中,檢查您是否拋出了錯誤以返回響應。
const dbEditCourse = (req, res, db, logger) => {
let {
origCourse, code, description, type
} = req.body;
if (!code || !description || !type) {
res.json({
haveEmpty: true
});
return;
}
// util throw a error
const breakWithMyError = () => {
throw new Error("MY_ERROR");
}
db.transaction((trx) => {
db.select('*').from('course_strand').where('code', '=', code)
.then(data => {
if (data[0]) {
//error happens in this block of code
breakWithMyError();
//i also tried return res.json({ isSuccess: false });
}
//wrapping this in 'else' also does not work
return db('course_strand')
.returning('*')
.where('code', '=', origCourse)
.update({ code, description, type })
})
.then(course => {
return db('activity_logs')
.returning('*')
.insert({
date: new Date(),
employee_id: req.session.emp_id,
module: "COURSE / STRAND",
activity: "EDIT"
})
})
.then(activity => {
// revert logic, we check for error case first
if (!activity[0]) {
breakWithMyError();
}
})
.then(trx.commit)
.then(() => {
// finally you can run to here without any error
res.json({
isSuccess: true
});
})
.catch(err => {
// If you any error, the error comes form `breakWithMyError` or any things.
if (err.message === "MY_ERROR") {
// the error throw by `breakWithMyError`
return res.json({
isSuccess: false
});
}
logger.error(err);
trx.rollback;
// Why you return a html page in failed case? `res.status(500).json({message: "Internal server!"});`
res.render('pages/error-500');
});
})
.catch(err => logger.error(err));
}
module.exports = {
dbEditCourse
}
const dbEditCourse = (req, res, db, logger) => {
let {
origCourse, code, description, type
} = req.body;
if (!(code && description && type)) {
res.json({
haveEmpty: true
});
return;
} else { // Please Try this.
db.transaction((trx) => {
db.select('*').from('course_strand').where('code', '=', code)
.then(data => {
if (data[0]) {
//error happens in this block of code
res.json({
isSuccess: false
});
return;
//i also tried return res.json({ isSuccess: false });
}
//wrapping this in 'else' also does not work
return db('course_strand')
.returning('*')
.where('code', '=', origCourse)
.update({ code, description, type });
})
.then(course => {
return db('activity_logs')
.returning('*')
.insert({
date: new Date(),
employee_id: req.session.emp_id,
module: "COURSE / STRAND",
activity: "EDIT"
});
})
.then(activity => {
if (activity[0]) {
res.json({
isSuccess: true
});
return;
} else {
res.json({
isSuccess: false
});
return;
}
})
.then(trx.commit)
.catch(err => {
logger.error(err);
trx.rollback;
res.render('pages/error-500');
});
})
.catch(err => logger.error(err));
}
};
module.exports = {
dbEditCourse
};
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