Mongoose Relationship Populate Doesn't Return results - node.js

Question

var SecuritySchema = new Mongoose.Schema({
_bids: [{
type: Mongoose.Schema.Types.ObjectId,
ref: 'BuyOrder'
}],
_asks: [{
type: Mongoose.Schema.Types.ObjectId,
ref: 'SellOrder'
}]
});
var OrdersSchema = new Mongoose.Schema({
_security: {
type: Mongoose.Schema.Types.ObjectId,
ref: 'Security'
},
price: {
type: Number,
required: true
},
quantity: {
type: Number,
required: true
}
});
// declare seat covers here too
var models = {
Security: Mongoose.model('Security', SecuritySchema),
BuyOrder: Mongoose.model('BuyOrder', OrdersSchema),
SellOrder: Mongoose.model('SellOrder', OrdersSchema)
};
return models;
And than when I save a new BuyOrder for example:
// I put the 'id' of the security: order.__security = security._id on the client-side
var order = new models.BuyOrder(req.body.order);
order.save(function(err) {
if (err) return console.log(err);
});
And attempt to re-retrieve the associated security:
models.Security.findById(req.params.id).populate({
path: '_bids'
}).exec(function(err, security) {
// the '_bids' array is empty.
});
I think this is some sort of naming issue, but I'm not sure, I've seen examples here and on the moongoose website that use Number as the Id type: http://mongoosejs.com/docs/populate.html

Answer 1

The ref field should use the singular model name
Also, just do:
models.Security.findById(req.params.id).populate('_bids').exec(...
My main suspicion given your snippet at the moment is your req.body.order has _security as a string instead of an array containing a string.
Also, you don't need an id property. Mongodb itself will automatically do the _id as a real BSON ObjectId, and mongoose will add id as a string representation of the same value, so don't worry about that.

Answer 2

While I don't understand your schema (and the circular nature of it?), this code works:
var order = new models.BuyOrder({ price: 100, quantity: 5});
order.save(function(err, orderDoc) {
var security = new models.Security();
security._bids.push(orderDoc);
security.save(function(err, doc) {
models.Security.findById({ _id: doc._id })
.populate("_bids").exec(function(err, security) {
console.log(security);
});
});
});
It:
creates a BuyOrder
saves it
creates a Security
adds to the array of _bids the new orderDoc's _id
saves it
searches for the match and populates
Note that there's not an automatic method for adding the document to the array of _bids, so I've done that manually.
Results:
{ _id: 5224e73af7c90a2017000002,
__v: 0,
_asks: [],
_bids: [ { price: 100,
quantity: 5,
_id: 5224e72ef7c90a2017000001, __v: 0 } ] }