I wonder how to write CRUD operations as callbacks so that the Seperation of Concerns is respected.
As an example, I coded the operation that can return all users:
UserService.js
function getUsers(callback) {
User.find(function(err, users) {
if (err) {
console.log("Fehler bei Suche: " + err)
return callback(err, null)
}
console.log("Alles gut gelaufen.");
return callback(null, users);
})
}
UserRoute.js
router.get('/publicUser', function(req, res, next) {
userService.getUsers(function(err, result) {
console.log("Resultat: " + result)
if (result) {
res.send(Object.values(result))
} else {
res.send("Es gab Probleme.")
}
})
})
A corresponding CRUD function, with no callback, that returns exactly one user looks like this to me.
Userservice.js
function getByUserId(req, res, next) {
let userIDD = req.body.userID;
User.findOne({
userID: userIDD
}, function(err, result) {
if (err) {
console.log("Fehler bei Suche: " + err)
} else {
console.log("Alles gut gelaufen.");
res.send(result)
}
})
}
UserRoute.js
router.post('/publicUser/getByUserID', userService.getByUserId)
Now what exactly does the same function look like with callback ?
Generally arrow functions are used for callback so that the Seperation of Concerns is respected.
Example: In UserRoute.js
router.get('/publicUser', (req, res, next) => {
userService.getUsers( (err, result) => {
console.log("Resultat: " + result)
if (result) {
res.send(Object.values(result))
} else {
res.send("Es gab Probleme.")
}
})
})
Here you can see there is no need for writing function for every callback and arrow function also helps in seperation
This is my first time answering any questions on stackoverflow , i hope solution understood you :)