Save array of ObjectId in Schema - node.js

Question

I have a model called Shop whos schema looks like this:
'use strict';
var mongoose = require('mongoose'),
Schema = mongoose.Schema;
var ShopSchema = new Schema({
name: { type: String, required: true },
address: { type: String, required: true },
description: String,
stock: { type: Number, default: 100 },
latitude: { type: Number, required: true },
longitude: { type: Number, required: true },
image: String,
link: String,
tags: [{ type: Schema.ObjectId, ref: 'Tag' }],
createdAt: { type: Date, default: Date.now },
updatedAt: { type: Date, default: Date.now }
});
module.exports = mongoose.model('Shop', ShopSchema);
I want to use the array tags to reference to another model via ObjectId obviously. This set up works fine when I add ids into the property via db.shops.update({...}, {$set: {tags: ...}}) and the ids get set properly. But when I try to do it via the Express.js controller assigned to the model, nothing gets updated and there even is no error message. Here is update function in the controller:
// Updates an existing shop in the DB.
exports.update = function(req, res) {
if(req.body._id) { delete req.body._id; }
Shop.findById(req.params.id, function (err, shop) {
if (err) { return handleError(res, err); }
if(!shop) { return res.send(404); }
var updated = _.merge(shop, req.body);
shop.updatedAt = new Date();
updated.save(function (err) {
if (err) { return handleError(res, err); }
return res.json(200, shop);
});
});
};
This works perfect for any other properties of the Shop model but just not for the tags. I also tried to set the type of the tags to string, but that didn't help.
I guess I am missing something about saving arrays in Mongoose?

Answer 1

It looks like the issue is _.merge() cannot handle merging arrays properly, which is the tags array in your case. A workaround would be adding explicit assignment of tags array after the merge, if it is ok to overwrite the existing tags.
var updated = _.merge(shop, req.body);
if (req.body.tags) {
updated.tags = req.body.tags;
}
Hope this helps.. If the workaround is not sufficient you may visit lodash forums.