Mongoose Refs to children - node.js

Question

I am struggling to find examples or documentation on mongoose children population.
http://mongoosejs.com/docs/populate.html
On the documentation they have:
var mongoose = require('mongoose')
, Schema = mongoose.Schema
var personSchema = Schema({
_id : Number,
name : String,
age : Number,
stories : [{ type: Schema.Types.ObjectId, ref: 'Story' }]
});
var storySchema = Schema({
_creator : { type: Number, ref: 'Person' },
title : String,
fans : [{ type: Number, ref: 'Person' }]
});
var Story = mongoose.model('Story', storySchema);
var Person = mongoose.model('Person', personSchema);
It makes sense, a Person can have many stories thus the 'parent' field 'stories' which has a list of all the stories in.
What I am struggling to understand is how do you push the the story into the person schema.
For example, i have an assignment schema:
var mongoose = require ( 'mongoose' ),
Schema = mongoose.Schema;
var assignmentSchema = new Schema (
{
_id: String,
assignName: String,
modInsID: [{ type: Schema.Types.Number, ref: 'ModuleInst' }],
studentAssigns: [{type: Schema.Types.ObjectId, ref: 'StudentAssign' }]
}
);
module.exports = mongoose.model ( 'Assignment', assignmentSchema );
The studentAssigns stores all the id's of the studentAssigns which then can be used with the .pre middleware for cascade deleting.
So now my StudentAssign schema:
var mongoose = require ( 'mongoose' ),
autoIncrement = require ( 'mongoose-auto-increment' ),
Schema = mongoose.Schema;
var connection = mongoose.createConnection("************");
autoIncrement.initialize(connection);
var studentAssignSchema = new Schema (
{
assID: [{ type: Schema.Types.String, ref: 'Assignment' }],
studentID: [{ type: Schema.Types.Number, ref: 'Student' }]
}
);
var StudentAssign = connection.model('StudentAssign', studentAssignSchema);
module.exports = mongoose.model ('StudentAssign', studentAssignSchema );
As you can see it already is referencing 'Assignment'
Here is my api code:
studentAssign POST:
router.route('/student-assignment').post( function(req, res) {
var studentAssign = new StudentAssign();
studentAssign.assID = req.body.assID;
studentAssign.studentID = req.body.studentID;
studentAssign.save(function(err, studentAssign) {
if(err) console.log(err);
res.status(200).json(studentAssign);
});
})
So that's the part I am confused at where would I push the 'studentAssign' into 'Assignment' schema's 'studentAssigns array ??
here is my current api json callback:
[
{
"_id": "As 1",
"assignName": "Software Implementation",
"__v": 0,
"studentAssigns": [],
"modInsID": [
{
"_id": 22,
"semester": "TRI 3",
"year": 2016,
"__v": 0,
"modID": [
111
]
}
]
}
]
The documentation just does not make it clear as they just show:
aaron.stories.push(story1);
aaron.save(callback);
With no explanation?
I have attempted:
var assignment = new Assignment();
assignment.studentAssigns.push(studentAssign); and nothing gets stored ??

Answer 1

Here is a working example based on the documentation docs
const mongoose = require('mongoose');
const { Schema } = mongoose;
const personSchema = Schema({
_id: Schema.Types.ObjectId,
name: String,
age: Number,
stories: [{ type: Schema.Types.ObjectId, ref: 'Story' }]
});
const storySchema = Schema({
author: { type: Schema.Types.ObjectId, ref: 'Person' },
title: String,
fans: [{ type: Schema.Types.ObjectId, ref: 'Person' }]
});
const Story = mongoose.model('Story', storySchema);
const Person = mongoose.model('Person', personSchema);
Person model has its stories field set to an array of ObjectId's
For saving Refs to children you may have first to save stories before pushing them to Person's stories field
const story1 = new Story({
title: 'Casino Royale',
author: author._id // assign the _id from the person
});
story1.save();
And before pushing story1 find the author id you want to push to
const author = await Person.findOne({_id: "624313f302e268b597b8df1f"})
if(Array.isArray(author.stories)) author.stories.push(story1);
author.save()

Answer 2

You model states :
assID: [{ type: Schema.Types.String, ref: 'Assignment' }],
studentID: [{ type: Schema.Types.Number, ref: 'Student' }]
I think from your code you don't want to store multiple assignments in assID and multiple Students in studentID. Modify your model to
assID: { type: Schema.Types.String, ref: 'Assignment' },
studentID: { type: Schema.Types.Number, ref: 'Student' }
Your save code can stay the same.
If you do want to store for example multiple assignments, you need to push them into the assID array ;-)

Answer 3

router.get('/author', (req, res, next) => {
Person.
find().
exec( (err, person) => {
if (err) return handleError(err)
Story.find({author: person[0]._id}).
exec( (err, story) => {
if (err) return handleError(err)
person[0].stories.push(story[0])
res.json( { person: person })
})
})
})