UnhandledPromiseRejectionWarning: TypeError: place.toObject is not a function

Question

Here I am trying to fetch Users Created places using userId. Here are User model and places model and in Controller, I have writing logic to fetch places by userId. Unfortunately, I am getting error "UnhandledPromiseRejectionWarning: TypeError: place.toObject is not a function" during sending response in res.json({ }) method.

Place Model

const mongoose = require('mongoose');

const Schema = mongoose.Schema;


const placeSchema = new Schema({
    title: { type: String, required: true },
    description: { type: String, required: true },
    image: { type: String, required: true },
    address: { type: String, required: true },
    location: {
        lat: { type: Number, required: true },
        lng: { type: Number, required: true },
    },
    creator: { type: mongoose.Types.ObjectId, required: true, ref: 'User'}
});

module.exports = mongoose.model('placemodels', placeSchema);

User Model

const mongoose = require('mongoose');
const uniqueValidator = require('mongoose-unique-validator');

const Schema = mongoose.Schema;


const userSchema = new Schema({
    name: { type: String, required: true },
    email: { type: String, required: true, unique: true },
    password: { type: String, required: true, minlength: 6 },
    image: { type: String, required: true },
    places: [{ type: mongoose.Types.ObjectId, required: true, ref: 'Place'}]
});

userSchema.plugin(uniqueValidator);

module.exports = mongoose.model('usermodels', userSchema);

Controller

const getPlacesByUserId = async (req, res, next) => {
  const userId = req.params.uid;
  let userWithPlaces;
  try {
    userWithPlaces = await User.findById(userId).populate('placemodels');
  } catch (err) {
    console.log(err);
    const error = new HttpError(
      'Fetching places failed, please try again later',
      500
    );
    return next(error);
  }

  // if (!places || places.length === 0) {
  if (!userWithPlaces || userWithPlaces.places.length === 0) {
    return next(
      new HttpError('Could not find places for the provided user id.', 404)
    );
  }

  res.json({
    places: userWithPlaces.places.map(place =>
      place.toObject({ getters: true })
    )
  });
};

Answer 1

The references are really important in mongoose populate. In the schema, the refs refer to the mongoose name of the schema. Since the names are: 'placemodels' and 'usermodels'. The refs fields should use the exact name.

Reference: https://mongoosejs.com/docs/api.html#schematype_SchemaType-ref

The second important part is the parameters of the populate methods. The documentation specifies that the first argument of the populate function is a name path and is an object or a string. In the case above a string is used. It should refer to the name field to populate.

This means that the code should be the following because we want to populate the places field. The schema is responsible to know from where to get the information

...

userWithPlaces = await User.findById(userId).populate('places');

...

References: https://mongoosejs.com/docs/api.html#query_Query-populate