Mongoose Sub-documents on separate files, how to embed them - node.js

Question

I'm defining my application models and i have separate files for each model that i'm defining, my question is, i need to create a model that use a sub-document, but that's on another file, how can i use that Schema on my model ? what i mean is that all examples i've seen declare the Child model and the Parent on the same file, example:
var childSchema = new Schema({ name: 'string' });
var parentSchema = new Schema({
children: [childSchema]
});
I have one file called user.js that defines the user model :
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var userSchema = new Schema({
_id : Schema.Types.ObjectId,
username : String,
});
module.exports = mongoose.model( 'User', userSchema );
And on another file called sport.js i have the other model definition for the sports:
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var sportSchema = new Schema({
_id : Schema.Types.ObjectId,
name : String
});
module.exports = mongoose.model( 'Sport', sportSchema );
So on my user model I need to define a field for the sports that the user will follow, but i do not know how to define that sub-document since the sports definition is on another file, I tried this:
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var SportsModel = require('sport');
var userSchema = new Schema({
_id : Schema.Types.ObjectId,
username : String,
sports : [SportsModel]
});
module.exports = mongoose.model( 'User', userSchema );
But i'm not sure if that's the correct way since what i'm exporting is the model, not the Schema.
Thanks in advance, i want to define each model on separate files to maintain order.

Answer 1

You can access a Model's schema via its schema property. So this should work:
var userSchema = new Schema({
_id : Schema.Types.ObjectId,
username : String,
sports : [SportsModel.schema]
});

Answer 2

Use ref
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var userSchema = new Schema({
_id : Schema.Types.ObjectId,
username: String,
sports : [{ type: Schema.Types.ObjectId, ref: 'Sport' }]
});
module.exports = mongoose.model('User', userSchema);
Incidentally, with ref, you can use .populate('sports') when you query, and mongoose will expand those types for you.