One to one with populate mongoose not working - mongodb

Question

I'm new to mongoose and mongodb.
I have two collection (cart and produk)
1 cart have 1 produk, and I get the cart and populate the product but is not show the data relations.
Here the code:
routing
router.route('/relations/:app_id')
.get(cartController.relation);
model (cartModel)
var mongoose = require('mongoose');
var cartSchema = mongoose.Schema({
app_id: {
type: String,
required: true
},
product_id: {
type: mongoose.Schema.Types.ObjectId,
ref: 'Produk'
},
qty: Number
});
var collectionName = 'cart';
var Cart = module.exports = mongoose.model('Cart', cartSchema, collectionName);
module.exports.get = function (callback, limit) {
Cart.find(callback).limit(limit);
}
model (produkModel)
var mongoose = require('mongoose');
// Setup schema
var produkSchema = new Schema({
name: {
type: String,
required: true
},
stok: Number
});
// Export Cart model
var collectionName = 'produk';
var Produk = module.exports = mongoose.model('Produk', produkSchema, collectionName);
module.exports.get = function (callback, limit) {
Produk.find(callback).limit(limit);
}
controller (cartController)
Cart = require('../model/cartModel');
exports.relation = function (req, res) {
const showCart = async function() {
const carto = await Cart.find().select('app_id product_id qty').populate("produk");
return carto;
};
showCart()
.then(cs => {
return apiResponse.successResponseWithData(res, "Operation success", cs);
})
.catch(err => console.log(err));
};
// Result
{
"status": 1,
"message": "Operation success",
"data": [
{
"_id": "60af72022d57d542a41ffa5a",
"app_id": "CvR4dTTjC7qgr7gA2yoUnIJnjRXaYokD6uc2pkrp",
"qty": 1,
"product_id": "60112f3a25e6ba2369424ea3"
},
{
"_id": "60b020536ccea245b410fb38",
"app_id": "CvR4dTTjC7qgr7gA2yoUnIJnjRXaYokD6uc2pkrp",
"product_id": "603f5aff9437e12fe71e6d41",
"qty": 1
}
]
}
expecting result
{
"status": 1,
"message": "Operation success",
"data": [
{
"_id": "60af72022d57d542a41ffa5a",
"app_id": "CvR4dTTjC7qgr7gA2yoUnIJnjRXaYokD6uc2pkrp",
"qty": 1,
"product_id": {
"_id": "60112f3a25e6ba2369424ea3",
"name": "snack"
}
},
{
"_id": "60b020536ccea245b410fb38",
"app_id": "CvR4dTTjC7qgr7gA2yoUnIJnjRXaYokD6uc2pkrp",
"product_id": {
"_id": "603f5aff9437e12fe71e6d41",
"name": "snack"
}
"qty": 1
}
]
}
what I miss ???
Thanks for your help

Answer 1

You need to pass the path to populate or an object specifying parameters to .populate(). So in this case, Your code should be:
const carto = await Cart.find().select('app_id product_id qty').populate("product_id");