MongoDB Creating document and on success create another document - node.js

Question

I am working on application using Node.js and MongoDB. I have a particular use case wherein I create a new user and on success add the user's ObjectId into another collection called 'cities' by fetching the user's city if not existing or create a new one and append User's ObjectId to Subscriber's List field of the city document.
The Schemas look like below:
CitiesSchema:
var CitiesSchema = new Schema({
City:{
type: String
},
SubscribersList: [{type: Schema.ObjectId}]
});
User Schema:
var UsersSchema = new Schema({
emailId: {
type: String,
required: 'Mandatory field'
},
city: {
type: String
},
subscribedOn: {
type: Date,
default: Date.now
},
lastEmailSent: {
type: Date,
default: null
},
isActive: {
type: Boolean,
default: true
}
});
Please let me know how I can tackle this in the cleanest way possible or is there any design pattern I need to follow ?

Answer 1

You can use the then notation to continue processing after you have created your User. Like this
UserSchema.create({
emailId: 'email#exmaple.com',
city: 'Rome'
})
.then(user => {
// For example if you want to push to the city of the user
CityScema.update({
City: user.city
}, {
$push: {
SubscribersList: user._id
}
}).then(() => {
res.sendStatus(200);
}).catch(err => res.status(500).send(err));
}).catch(err => {
// Handle your errors here
console.error(err);
});
Make sure you check the Mongoose docs on Models for more information