Mongoose populate returning empty array

Question

I am trying to use mongoose populate function but in response I am getting empty array, I have seen multiple posts regarding this

var MerchantSchema = new mongo         


        

Answer 1

Can you try by removing second parameter from the findBbyId:

Merchant
.findById( req.params.id)
.populate('packages')
.exec(function (err, merchant) {
    if (err)
        next(err);
    else
        res.status(200).json(merchant);
});

Answer 2

Well because your packages field on your Schema is an array you should populate it as an array as well.

Try

.populate([
    {path:'packages', model:Package}
])

wher Package is the instance of your Package Model.

Answer 3

Use type insted of $type in MerchantSchema.

var MerchantSchema = new mongoose.Schema({
  packages: [{ type: mongoose.Schema.Types.ObjectId, ref: 'Package'}]
},
{
    typeKey: '$type',
    timestamps: { createdAt: 'created_at', updatedAt: 'updated_at'}
});

module.exports = mongoose.model('Merchant', MerchantSchema);

Verify there is an array of ObjectId against packages in your Merchant document.

Answer 4

Make sure that packages array in Merchant schema contains ObjectIds of type string, (not number). You can ensure this with something like:

merchant.packages.map(r => { r._id = r._id + ''; });