Populate in Mongoose not working - node.js

Question

I am trying to perform associations by referencing method. There are 2 models:
1. User
2. Product
I have established one-to-one relationship of 1 user can have multiple products. User creation is successful
Product creation is successful
Code Inputs
var mongoose = require("mongoose");
mongoose.connect("mongodb://localhost/product_demo_x9");
Product Schema
var productSchema = new mongoose.Schema({
category : String,
Brand: String
});
var Product = mongoose.model("product", productSchema);
User Schema
var userSchema = new mongoose.Schema({
email: String,
name: String,
products: [
{
type: mongoose.Schema.Types.ObjectId,
ref: "Product"
}
]
});`
var User = mongoose.model("user", userSchema);
User Creation
User.create({
email: "madhur#google.com",
name: "Maddy"
},function(err,newUser){
if(err){
console.log(err);
}
else {
console.log(newUser);
}
});
Product Creation
Product.create({
category: "Smartwatches",
Brand: "Samsung and Google"
},
function(err,product){
console.log(product);
User.findOne({name : "Maddy"},function(err,foundUser){
if(err) {
console.log(err);
}
else {
foundUser.products.push(product);
foundUser.save(function(err,updatedUser){
if(err){
console.log(err);
}
else {
console.log(updatedUser);
}
});
}
});
});
Display of associated Data on the console
User.find({email: "madhur#google.com"}).
populate("products").
exec(function(err,user){
if(err){
console.log(err);
}
else {
console.log(user);
}
});
Code Outputs
User Creation (Success)
[{
products: [],
_id: 5a47acb0317d4e3c2081b8ce,
email: 'madhur#google.com',
name: 'Maddy',
__v: 0
}]
Product Creation and associating (Success)
{
_id: 5a47acd53c771123b4018ff1,
category: 'Smartwatches_2',
Brand: 'Samsung and Google',
__v: 0
}
{
products: [ 5a47acd53c771123b4018ff1 ],
_id: 5a47acb0317d4e3c2081b8ce,
email: 'madhur#google.com',
name: 'Maddy',
__v: 1
}
Display of embedded data using populate - Failure!!
{ MissingSchemaError: Schema hasn't been registered for model "products".
Use mongoose.model(name, schema)
at new MissingSchemaError
Can anyone please explain me how to do it correctly?
Thanks in Advance

Answer 1

Model Name is Case-sensitive
'Product' is not equal to 'product'
and when u create a model as 'product' (singular) it converts it into plural, i.e. 'products', this is default mongoose behavior, can be overridden.
so change the following:
var userSchema = new mongoose.Schema({
email: String,
name: String,
products: [
{
type: mongoose.Schema.Types.ObjectId,
ref: "products" //<---- changed 'Product' to 'products'
}
]
});`
var User = mongoose.model("user", userSchema);

Answer 2

Try this
var mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/product_demo_x9');
var productSchema = new mongoose.Schema({
category: String,
Brand: String
});
var Product = mongoose.model('Product', productSchema);
var userSchema = new mongoose.Schema({
email: String,
name: String,
products: [
{
type: mongoose.Schema.Types.ObjectId,
ref: 'Product'
}
]
});
var User = mongoose.model('User', userSchema);
User.create({
email: 'madhur#google.com',
name: 'Maddy'
}, function(err, newUser) {
if (err) {
console.log(err);
} else {
console.log(newUser);
}
});
Product.create({
category: 'Smartwatches',
Brand: 'Samsung and Google'
},
function(err, product) {
console.log(product);
User.findOne({name: 'Maddy'}, function(err, foundUser) {
if (err) {
console.log(err);
} else {
foundUser.products.push(product);
foundUser.save(function(err, updatedUser) {
if (err) {
console.log(err);
} else {
console.log(updatedUser);
}
});
}
});
});
User.find({email: 'madhur#google.com'})
.populate('products')
.exec(function(err, user) {
if (err) {
console.log(err);
} else {
console.log(user);
}
});

Answer 3

Solved
Did the following
Downgraded my Mongoose version from 5.00x to 4.10.8 using the following command npm remove mongoose then npm install mongoose#4.10.8 --save
Made the following change in app.js file
var userSchema = new mongoose.Schema({
email: String,
name: String,
products: [
{
type: mongoose.Schema.Types.ObjectId,
ref: "product" //<---- changed 'Product' to 'product'
}
]
});`
var User = mongoose.model("user", userSchema);
Thanks to the Stack community for giving a try!