Mongodb Increment value inside nested array not working - mongodb

Question

I'm building a app where you can vote on user submitted polls. Here's the schema for my polls:
const pollSchema = new Schema({
userID: String,
pollQuestion: String,
pollOptions: [
{
name: String,
quantity: Number
}
]
})
This is the express route that handles incrementing the quantity of a poll option:
app.put('/vote', (req, res) => {
Poll.update(
{
id: req.body.id,
'pollOptions.name': req.body.selection
},
{ $inc: { 'pollOptions.$.quantity': 1 } }
).then(updatedPoll => {
console.log('poll', updatedPoll)
res.send(updatedPoll)
})
})
here req.body.selection is the option that the user has chosen to vote for.
I basically want the quantity of the user's chosen option to increment by one. This way of updating the database I derived from the answer to this question
When I send a request to this route I get some very unexpected behaviour. For one thing, the database doesn't get updated or changed in any way. The second thing is the updatedPoll is a really bizarre object. Here's what i get from the console.log:
poll { n: 0,
nModified: 0,
opTime:
{ ts: Timestamp { _bsontype: 'Timestamp', low_: 1, high_: 1510783687 },
t: 1 },
electionId: 7fffffff0000000000000001,
ok: 1 }
The one thing I've tried is include { new: true } as a third parameter after the object with the $inc operator. I doesn't change anything. Can someone please help with this issue?

Answer 1

Thanks to Neil Lunn in the comments, changing my route to the following worked for me:
poll.put('/vote', (req, res) => {
Poll.findOneAndUpdate(
{
_id: req.body.id,
pollOptions: {
$elemMatch: { name: req.body.selection }
}
},
{ $inc: { 'pollOptions.$.quantity': 1 } },
{ new: true }
).then(poll => {
res.send(poll)
})
})