_id not being generated for subdocs when It's supposed to - node.js

Question

Here are my two schemas
var reviews = new Schema({
scenarioId: { type: Schema.Types.ObjectId, required: true},
authorId: { type: Schema.Types.ObjectId , required:true },
reviewNote: String,
subReviews: [subReviewSchema],
active: {type: Boolean, default: true},
display: {type: Boolean, default: true},
date : {type: Date, default: Date.now()}
});
and the subscheA for subreviews
var subReviews = new Schema({
authorId: { type: Schema.Types.ObjectId, required:true },
subReviewNote: String,
date: {type: Date, default: Date.now()},
active: {type: Boolean, default: true},
display: {type: Boolean, default: true}
});
and here is my code that updates the document
exports.addSubReview = function (req, res) {
var id = req.params.id;
var update = req.body;//scenario Id
Review.findById(id, function (err, obj) {
if (err || !obj) { return res.send(404, { error: err.message }); }
obj.subReviews.push(update);
obj.save(function (err) {
if (err) { return res.send(404, { error: err.message }); }
return res.send(200, obj);
});
});
};
For some reason though whenever I send an http post to this code the results only adds what i send in the post request not _id _v or any other things that I would expect mongoose/mongodb to add as boilerplate. Here is an example document in my database
{
"__v": 2,
"_id": "531e3214a30f5f8427830a97",
"authorId": "52fd0e6df8352c184b000004",
"reviewNote": "aaaaaaaaaaaaaaaaa",
"scenarioId": "531a5b80af15cffc051cea67",
"date": "2014-03-10T21:37:05.230Z",
"display": true,
"active": true,
"subReviews": [
{
"subReviewNote": "This is a subReview",
"authorId": "52fd0e6df8352c184b000004"
},
{
"subReviewNote": "This is a subReview",
"authorId": "52fd0e6df8352c184b000004"
}
]
}
Any ideas on why _id is not being added to my subDocs in subReviews?.

Answer 1

My guess is that the problem is in the parent doc where you say:
subReviews: [subReviewSchema]
But you named the child schema variable
subReviews
Not subReviewSchema. But that's a guess, from what you've posted. I'd have to see the code together to get a better picture, unless this is it.
But this would explain it, since subReviews: is just expecting an Object because of this naming issue - and an object is exactly what it gets when you POST,so it just pushes it into the array as it expects.
EDIT
I poked around in the mongoose code on github and I am less confident in my answer above, although I guess it could still be possible. However, I did stumble upon this comment, when declaring schemas:
When nesting schemas, (children in the example above), always declare the child schema first before passing it into is parent.
I have less confidence in my original answer, because it looks like if you named the variable incorrectly, mongoose is going to throw a TypeError