One to Many Relationship MongoDb Using Mongoose - node.js

Question

I am creating a relationship between a User and Address. User can have multiple Address. Here is my schema:
userSchema.js
const mongoose = require('mongoose')
const Schema = mongoose.Schema
const Address = require('./addressSchema')
let userSchema = mongoose.Schema({
name :String,
age : Number,
cohort :String,
addresses : [{type : Schema.Types.ObjectId, ref : 'Address'}]
})
let User = mongoose.model('User',userSchema)
module.exports = User
addressSchema.js
const mongoose = require('mongoose')
let addressSchema = mongoose.Schema({
city : String,
state :String
})
let Address = mongoose.model('Address',addressSchema)
module.exports = Address
Adding New User and Address (app.js)
let user = new User({name : 'Mary', age : 36, cohort : 2019})
let address = new Address({ city : 'Houston', state : 'TX'})
user.addresses.push(address)
user.save(function(error,newUser){
console.log(newUser)
})
Fetching the users and their addresses
// fetch all users
User.find(function(error,users){
users.forEach((user) => {
console.log('addresses')
user.addresses.forEach((address) => {
console.log(address.city) // prints undefined
})
})
})
Any ideas what I am doing wrong?

Answer 1

It depends on what you are trying to accomplish: storing the addresses as embedded documents in user OR storing references to address documents in user. The example code above has blended both approaches which, as you have noticed, does not work.
Embedded:
Combine the schemas:
const mongoose = require('mongoose')
const Schema = mongoose.Schema
const addressSchema = Schema({
city : String,
state :String
})
const userSchema = Schema({
name :String,
age : Number,
cohort :String,
addresses : [addressSchema]
});
const User = mongoose.model('User',userSchema);
And the rest of the code can remain the same.
References:
The existing schema and model declarations remain the same.
Then when the data is stored, the address also needs to be stored:
const user = new User({name : 'Mary', age : 36, cohort : 2019})
const address = new Address({ city : 'Houston', state : 'TX'})
user.addresses.push(address)
Promise.all([
user.save(),
address.save()
]).then(([newUser, newAddress]) => {
console.log({newUser, newAddress});
});
And finally when fetching the document, if the address is meant to be included then it needs to be populated:
User.find().populate('addresses').exec().then((users) => {
users.forEach((user) => {
user.addresses.forEach((address) => {
console.log({user, address});
});
});
});