Two queries in FindOneAndUpdate don't work with arrays - node.js

Question

I have this schema in Mongoose:
var CoinAmountSchema = new Schema(
{
user: [{ type: Schema.ObjectId, ref: 'User' }],
coinAmounts: [{
_id: false,
coinID: { type: Number, ref: 'Coin' },
amount: Number
}]
})
I am writing this query, that checks the userID and coinID and should update the amount of only that coinID's amount.
exports.coin_amount_update = [
(req, res, next) => {
CoinAmount.update({
"user": req.params.userId,
"coinAmounts.coinID": req.params.coinId
},
{
'$set': {
'coinAmounts.$.amount': req.body.amount
}
},
function (err, model) {
if (err) {
console.log(err)
return res.send(err)
}
return res.json(model)
})
}]
But like this, it only updates the first coin's in the array amount. BUT, if I delete the line "user": req.params.userId, it would find and update the right coin. I need to check for a user as well though, so how can I make it work?
Is there something wrong with the query or the way the data is structured?
EDIT: I send a request in React-native:
fetch(`${apiBaseURL}/users/${getState().user._id}/coins/${id}/update`, {
method: 'PUT',
headers: {
'Content-Type': 'application/json',
},
body: JSON.stringify({
amount: getState().coins[id].amount
}),
})
If the request is /users/:userID/coins/0/update (with amount: 1)
then the result will be
{ _id: 5a579d0d44e7390ba3029327,
__v: 0,
coinAmounts:
[ { coinID: 0, amount: 1 },
{ coinID: 1, amount: 0 },
{ coinID: 2, amount: 0 },
{ coinID: 3, amount: 0 },
{ coinID: 4, amount: 0 } ],
user: [ 5a579d0d44e7390ba3029326 ] }
The same result if the request is /users/:userID/coins/1/update with the same amount.
But if as mentioned before, I remove the check for userID, the request /users/:userID/coins/1/update would produce this:
{ _id: 5a579d0d44e7390ba3029327,
__v: 0,
coinAmounts:
[ { coinID: 0, amount: 0 },
{ coinID: 1, amount: 1 },
{ coinID: 2, amount: 0 },
{ coinID: 3, amount: 0 },
{ coinID: 4, amount: 0 } ],
user: [ 5a579d0d44e7390ba3029326 ] }
Hope I was clear.

Answer 1

It looks like a bug when using two arrays in find with $ positional update, it gets matching index of user for $ positional update
tried below workarounds, both updates correct coinID
workaround-1, using arrayFilters
db.coins.update(
{ "user" : "5a579d0d44e7390ba3029326" }, //user
{
$set: { "coinAmounts.$[elem].amount" : 1 } //update
},
{
multi: false,
arrayFilters: [
{ "elem.coinID": 2 } //coinID
]
}
)
workaround-2, using elemMatch for user array
db.coins.update(
{
"coinAmounts.coinID" : 1, //coinID
"user" : { $elemMatch : { $eq : "5a579d0d44e7390ba3029326" } } //user
},
{ $set : { "coinAmounts.$.amount" : 1 } } //update
)