POST to mongoose DB with Nested schema

Question

I have an inventory schema with item subschema as below:

const ItemSchema = new mongoose.Schema(
{
    name: { //Full name of product
        type: String,
    },
    type: { //Beer? Wine? Liquor? Cider?
        type: String,
    },
    unit: { //What is the minimum amount you can order? 
        type: Number,
    },
    volume: { //How much liquid is in it?(in mL)
        type: Number,
    },
    packaging: {
        type: String,
    },
    quantity: {
        type: Number,
    },
    price: {
        type: Number,
    },   
},
{
    timestamps: true,
}

const InventorySchema = new mongoose.Schema(
{
    user: { 
        type: mongoose.Schema.Types.ObjectId,
        required: [true, 'Need user ID'],
        ref: 'User'
    },
    items: {
        type: [ItemSchema],
        default: []
    }
},
{
    timestamps: true,
}

I am building an API to add subschema Item, but how do I do it?

const addItem = asyncHandler(async (req, res) => {
//req.user.id is given by authentication middleware
//req.body is the ItemSchema object
if (!req.user.id) {
    res.status(400);
    throw new Error('Cannot add without ID')
}
const newItem = {
    user: req.user.id,
    items: await ItemModel.create(req.body),
}

res.status(200).send(newItem)

This is what I have ATM, but I don't think I am doing it right. I get "Cannot read properties of undefined (reading 'create')" response.

Answer 1

First of all, When creating a schema, if you only have a regular type, just write the types, no need for all the overheads-

const ItemSchema = new mongoose.Schema({
 name: String,
 type: {type: String},
 unit: Number... etc..
}

also, arrays default value are empty arrays so you don't need to tell this to mongoose. so you can just do in your InventorySchema:

items:[ItemSchema]

regarding your question, First, you need to create Models out of your schemas. So for example:

const InventoryModel = new mongoose.model('Inventory', InventorySchema);

and also do it for the item schema

and then create a new item from it, and in your controller:

...
...
const newItem = new ItemModel({....});
const newInventory = new InventoryModel({user: req.user.id,});
newInventory.items.push(newItem);
newInventory.save(); 
...
...

Than the new inventory is saved in your DB and you can do whatever you want with it