How to update object inside array inside object? - arrays

Question

I have the following Mongooose schema:
{
_id: {
type: String,
required: true
},
semesters: [
{
_id: {
type: String,
required: true
},
grades: [
{
subject: String,
literalGrade: String,
grade: Number,
credits: Number
}
]
}
]
}
I want to be able to update one grade that is inside semester's grades object using its id. I tried using MongoDb new multiple positional operator to no avail.
This is my current snippet:
User.findOneAndUpdate(
{
_id: req.params.user_id,
"semesters._id": req.params.semester_id
},
{
$set: {
"semesters.$[x].grades.$[y].subject": req.body.grades.subject,
"semesters.$[x].grades.$[y].literalGrade": req.body.grades.literalGrade,
"semesters.$[x].grades.$[y].grade": req.body.grades.grade,
"semesters.$[x].grades.$[y].credits": req.body.grades.credits
}
},
{
arrayFilters: [
{ "x._id": req.params.semester_id },
{ "y._id": req.params.grade_id }
]
},
(err, user) => {
if (err) return res.json(err);
res.send({
message: "Updated grade",
data: user
});
}
);

Answer 1

Couldn't get any results with the MongoDb positional operator, but found a way to programmatically do it with the help of Naing Lin Aung's answer. Here is the solution:
User.findOne(
{
_id: req.params.user_id,
"semesters.grades._id": req.params.grade_id
},
{ "semesters.$.grades": 1 },
(err, user) => {
if (err) return res.json(err);
let grades = user.semesters[0].grades;
let index = null;
for (let t in grades) {
if (grades[t]._id == req.params.grade_id) {
index = t;
break;
}
}
let grade = grades[index];
grade.subject = req.body.grades.subject;
grade.literalGrade = req.body.grades.literalGrade;
grade.grade = req.body.grades.grade;
grade.credits = req.body.grades.credits;
user.save(function(err) {
if (err) return res.json(err);
res.json({
message: "Updated grade",
data: user
});
});
}
);

Answer 2

You can take advantage of $[] syntax with arrayFilters
refer this link : https://docs.mongodb.com/manual/reference/operator/update/positional-all
db.col.update(
{ _id: req.params.user_id },
{ $set: { "semesters.$[cond1].grades.$[cond2].subject": req.body.grades.subject } },
{ arrayFilters: [ { "cond1._id": req.params.semester_id }, { "cond2._id": req.params.grade_id } ] })
You can similarly update other fields in $set