I have a Mongoose model like this:

const centerSchema = mongoose.Schema({
  centerName: {
    type: String,
    required: true,
  },
  candidates: [
    {
      candidateName: String,
      voteReceived: {
        type: Number,
        default: 0,
      },
      candidateQR: {
        type: String,
        default: null,
      },
    },
  ],
  totalVote: {
    type: Number,
    default: 0,
  },
  centerQR: String,
});

I have a Node.JS controller function like this:

exports.createCenter = async (req, res, next) => {
  const newCenter = await Center.create(req.body);

  newCenter.candidates.forEach(async (candidate, i) => {
    const candidateQRGen = await promisify(qrCode.toDataURL)(
      candidate._id.toString()
    );
    candidate.candidateQR = candidateQRGen;

    // ** Tried these: **
    // newCenter.markModified("candidates."   i);
    // candidate.markModified("candidateQR");
  });

  // * Also tried this *
  // newCenter.markModified("candidates");
  const upDatedCenter = await newCenter.save();
  res.status(201).json(upDatedCenter);
};

Simply, I want to modify the candidateQR field on the subdocument. The result should be like this:

{
    "centerName": "Omuk Center",
    "candidates": [
        {
            "candidateName": "A",
            "voteReceived": 0,
            "candidateQR": "some random qr code text",
            "_id": "624433fc5bd40f70a4fda276"
        },
        {
            "candidateName": "B",
            "voteReceived": 0,
            "candidateQR": "some random qr code text",
            "_id": "624433fc5bd40f70a4fda277"
        },
        {
            "candidateName": "C",
            "voteReceived": 0,
            "candidateQR": "some random qr code text",
            "_id": "624433fc5bd40f70a4fda278"
        }
    ],
    "totalVote": 0,
    "_id": "624433fc5bd40f70a4fda275",
    "__v": 1,
}

But I am getting the candidateQR still as null in the Database. I tried markModified() method. But that didn't help (showed in the comment section in the code above). I didn't get any error message. In response I get the expected result. But that result is not being saved on the database. I just want candidateQR field to be changed. But couldn't figure out how.

CodePudding user response：

As far as I understand, you are just looping through the candidates array but you are not storing the updated array. You need to store the updated data in a variable as well. Please give it a try with the solution below using map.

exports.createCenter = async (req, res, next) => {
  const newCenter = await Center.create(req.body);

  let candidates = newCenter.candidates;
  
  candidates = candidates.map(candidate => {
      const candidateQRGen = await promisify(qrCode.toDataURL)(
          candidate._id.toString()
      );

      return {
          ...candidate,
          candidateQR: candidateQRGen  
      }
  });

  newCenter.candidates = candidates;

  const upDatedCenter = await newCenter.save();

  res.status(201).json(upDatedCenter);
};

CodePudding user response：

You can use this before save()

newCenter.markModified('candidates');