How to reference another schema in my Mongoose schema?

Question

I'm building a Mongoose schema for a dating app.

I want each person document to contain a reference to all the events they've been to, where events is another schema with its own models in the system. How can I describe this in the schema?

var personSchema = mongoose.Schema({     firstname: String,     lastname: String,     email: String,     gender: {type: String, enum: ["Male", "Female"]}     dob: Date,     city: String,     interests: [interestsSchema],     eventsAttended: ??? }); 

Answer 1

You can describe it by using Population

Population is the process of automatically replacing the specified paths in the document with document(s) from other collection(s). We may populate a single document, multiple documents, plain object, multiple plain objects, or all objects returned from a query.

Suppose your Event Schema is defined as follows:

var mongoose = require('mongoose')   , Schema = mongoose.Schema  var eventSchema = Schema({     title     : String,     location  : String,     startDate : Date,     endDate   : Date });  var personSchema = Schema({     firstname: String,     lastname: String,     email: String,     gender: {type: String, enum: ["Male", "Female"]}     dob: Date,     city: String,     interests: [interestsSchema],     eventsAttended: [{ type: Schema.Types.ObjectId, ref: 'Event' }] });  var Event  = mongoose.model('Event', eventSchema); var Person = mongoose.model('Person', personSchema); 

To show how populate is used, first create a person object, aaron = new Person({firstname: 'Aaron'}) and an event object, event1 = new Event({title: 'Hackathon', location: 'foo'}):

aaron.eventsAttended.push(event1); aaron.save(callback);  

Then, when you make your query, you can populate references like this:

Person .findOne({ firstname: 'Aaron' }) .populate('eventsAttended') // only works if we pushed refs to person.eventsAttended .exec(function(err, person) {     if (err) return handleError(err);     console.log(person); });