Mongoose increment nested array by id

Question

This is my model:

const mongoose = require("mongoose");
const shortid = require("shortid");
const { v4: uuidv4 } = require("uuid");

const PollSchema = new mongoose.Schema({
  id: {
    type: String,
    default: shortid.generate
  },
  question: {
    type: String
  },
  options: [
    {
      option: {
        type: String
      },
      votes: {
        type: Number,
        default: 0
      },
      uid: {
        type: String,
        default: uuidv4
      }
    }
  ],
  created: {
    type: Date,
    default: Date.now
  }
});

module.exports = Poll = mongoose.model("poll", PollSchema);

I need to search for the poll by uid and increment the votes number by 1. This is what I've tried and it doesnt work:

Poll.findOneAndUpdate(
  { options: { $elemMatch: { uid: optionId } } },
  { $inc: { "options.$.votes": 1 } },
  { new: true }
);

nothing updates in the database I'm not sure why. The var of the search uid that I supply is optionId.

You could try this out Poll.findOneAndUpdate({ "options.uid": optionId }, { $inc: { "options.$.votes": 1 }, { new: true } }) — Ilijanovic
– Ilijanovic, Commented Jun 10, 2020 at 5:51

Ilijanovic · Accepted Answer · 2020-06-10 05:55:36Z

2

For 1 Level nesting its not necessary to use arrayFilters so this should work:

Poll.findOneAndUpdate({ _id: yourId, "options.uid": optionId }, { $inc: { "options.$.votes": 1 }, { new: true } })

answered Jun 10, 2020 at 5:55

Ilijanovic

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3 Comments

chrus54321 Over a year ago

This also worked and had to perform less computation.

Jakub A Suplicki Over a year ago

That is true. I believe that arrayFilters are great when it comes to arrays in general as you can very easily modify the code in order to write a reusable function that will take dynamic values, instead of predefined ones. For example, he could now just replace votes with ${req.body.votes} and options with ${req.body.field}. I understand it is beyond the scope of the question, I just thought it is worth mentioning.

Ilijanovic Over a year ago

arrayFilters is good if you search in a array, that is in an another array that means more then 1 level of nesting. Yes you could go with arrayFilters but id like to keep it simple

Jakub A Suplicki · Accepted Answer · 2020-06-22 19:44:22Z

1

Can you please try this code:

Poll.findOneAndUpdate(
  { _id: id }, //that is poll id
  {
    $inc: { [`options.$[outer].votes`]: 1 }
  },
  {
    arrayFilters: [{ "outer.uid": optionId }],
    new: true
  },
  function(err, poll) {
    if (!err) {
      console.log(poll);
    }
  }
);

edited Jun 22, 2020 at 19:44

answered Jun 10, 2020 at 5:37

Jakub A Suplicki

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3 Comments

chrus54321 Over a year ago

I tried it and it logs the poll but it still doesnt increment the votes. Also, what is outer?

Jakub A Suplicki Over a year ago

"outer" is just a reference for arrayFilters. You could name it any other way really. Edited the answer. Can you try it now, please?

Jakub A Suplicki Over a year ago

Glad to hear. Had a typo initially, sorry for that.

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