Mongoose - CastError Cast to string failed for value "Object"

Question

I have Mongoose CastError issue. I made a nodeJs API. At the specific route, it returns data appended with some other data. I saw many fixes available here but my scenario is different.

Here is my model and the problem occurs at fields property.

 const deviceSchema = new Schema({
  device_id: { type: String, required: true },
  user_id: { type: Schema.Types.ObjectId, ref: 'User', require: true },
  location_latitude: { type: String, default: '0' },
  location_longitude: { type: String, default: '0' },
  fields: [{ type: String }],
  field_id: { type: Schema.Types.ObjectId, ref: 'Field', required: true },
  timestamp: {
    type: Date,
    default: Date.now,
  },
});

and my controller is

exports.getAllDevices = async (req, res) => {
  try {
    let devices = await Device.find({})
      .sort({
        timestamp: 'desc',
      })
      .populate('user_id', ['name']);

    // Let us get the last value of each field
    for (let i = 0; i < devices.length; i++) {
      for (let j = 0; j < devices[i].fields.length; j++) {
        if (devices[i].fields[j] !== null && devices[i].fields[j] !== '') {
          await influx
            .query(
              `select last(${devices[i].fields[j]}), ${devices[i].fields[j]} from mqtt_consumer where topic = '${devices[i].device_id}'`
            )
            .then((results) => {
             ************** Problem occurs here ************** 
              if (results.length > 0) {
                devices[i].fields[j] = {
                  name: devices[i].fields[j],
                  last: results[0].last,
                };
              } else {
                devices[i].fields[j] = {
                  name: devices[i].fields[j],
                  last: 0,
                };
              }
            ************** Problem occurs here **************  
            });
        }
      }
    }

    // Return the results
    res.status(200).json({
      status: 'Success',
      length: devices.length,
      data: devices,
    });
  } catch (err) {
    console.log(err);
    res.status(500).json({
      error: err,
    });
  }
};

It actually gets data from InfluxDB and appends it to fields property which was fetched from MongoDB as mentioned in my model. But it refused to append and CastError occurs.

After addition, it will look like this

I can't resolve this error after trying so many fixes. I don't know where I'm wrong. Please suggest to me some solution for this.

can you please provide console.log(devices ) and console.log(results) for some keys only ? — Brijesh Dave
– Brijesh Dave, Commented Nov 9, 2021 at 11:40
I edited my question and added screenshots of the final data. — Ahsan Danish
– Ahsan Danish, Commented Nov 9, 2021 at 12:27

Arif Khan · Accepted Answer · 2021-11-09 13:04:52Z

1

I can see you are not using devices variable as Mongoose Document. devices is an array of Documents.

I would like to suggest you to use lean() function to convert from Document to plain JavaScript object like

let devices = await Device.find({})
      .sort({
        timestamp: 'desc',
      })
      .populate('user_id', ['name'])
      .lean();

answered Nov 9, 2021 at 13:04

Arif Khan

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1 Comment

Ahsan Danish Over a year ago

Your solution helps me to solve the problem Thanks for that, but I have a question to clear my concept about it. "devices variable as Mongoose Document". What does that mean Should I get a single document in order to append data in it? I try with a single document without lean() also, but query behavior is same one I was facing before.

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