mongoose save internal documents creating a document that contains a document - node.js

Question

Im learning mongoose and i have a question how to save several documents:
// Product.js
const categorySchema = mongoose.Schema(
{ name: String },
{ collection: "categories" }
);
const productSchema = mongoose.Schema(
{ name: String, category: categorySchema },
{ collection: "products" }
);
modules.exports = mongoose.model("Product", productSchema);
The idea is that when I create a product this way
const Product = require("./Product.js")
const product = new Product({name: 'Soccer Ball', category: {name: "Sports"})
await product.save()
i want to get a document in the collection products and also a document in the collection categories
how can it be possible
thanks in advance
PD : Im getting this but category is not save in the collection
{
"msg": "Product created succesfully",
"ok": true,
"product": {
"name": "Soccer ball",
"category": {
"name": "Sports",
"_id": "6275df4c8149967bea21e7c0"
},
"_id": "6275df4c8149967bea21e7bf",
"__v": 0
}
}

Answer 1

You should define your Product's category as a ref attribute:
// Product.js
const categorySchema = mongoose.Schema(
{ name: String },
{ collection: 'categories' }
);
const productSchema = mongoose.Schema(
{
name: String,
category: { type: mongoose.Schema.Types.ObjectId, ref: 'categories' },
},
{ collection: 'products' }
);
modules.exports = {
Category: mongoose.model('Category', categorySchema),
Product: mongoose.model('Product', productSchema),
}
Doing this you will need to assign the _id of the category to the new Product:
const { Category } = require("./Product.js")
const { Product } = require("./Product.js")
// Create category (supposing it is not present)
const category = new Category({ name: "Sports" })
await category.save()
// Add category _id to product
const product = new Product({name: 'Soccer Ball', category: category._id})
await product.save()
Finally, you will be able to retrieve the product by using populate:
const product = await Product.findById(<product_id>).populate('categories').exec()
This query should give the same result than before, but the Category data will be loaded from the reference in the Category collection.