Mongoose nested document update failing? - node.js

Question

If I have a nested document, how can I update a field in that nested document in Mongoose?
I carefully researched this problem using everything available I could find, and even changed my test code to match a similar answered question about this here on Stackoverflow, but I am still unable to figure this out. Here are is my Schema and Models, the code, and the Mongoose debug output. I am unable to understand what I am doing wrong, here.
var mongoose = require('mongoose')
, db = mongoose.createConnection('localhost', 'test')
, assert = require("node-assert-extras");
var Schema = mongoose.Schema;
var ObjectId = Schema.ObjectId;
db.once('open', function () {
// yay!
});
mongoose.set('debug', true);
var PDFSchema = new Schema({
title : { type: String, required: true, trim: true }
})
var docsSchema = new Schema({
PDFs : [PDFSchema]
});
var A = db.model('pdf', PDFSchema);
var B = db.model('docs', docsSchema);
function reset(cb) {
B.find().remove();
// create some data with a nested document A
var newA = new A( { title : "my title" })
var newB = new B( { PDFs: newA});
newB.save();
cb();
}
function test1( ) {
reset(function() {
B.findOne({}, 'PDFs', function(e,o)
{
console.log(o);
pdf_id = o.PDFs[0]._id;
console.log("ID " + pdf_id);
B.update(
{ 'pdfs.pdf_id': pdf_id },
{ $set: {
'pdfs.$.title': 'new title'
}}, function (err, numAffected) {
if(err) throw err;
assert.equal(numAffected,1); //KA Boom!
}
);
});
});
}
test1();
/*
$ node test2.js
Mongoose: docs.remove({}) {}
Mongoose: docs.findOne({}) { fields: { PDFs: 1 }, safe: true }
Mongoose: docs.insert({ __v: 0, PDFs: [ { _id: ObjectId("50930e3d0a39ad162b000002"), title: 'my title' } ], _id: ObjectId("50930e3d0a39ad162b000003") }) { safe: true }
{ _id: 50930e3d0a39ad162b000003,
PDFs: [ { _id: 50930e3d0a39ad162b000002, title: 'my title' } ] }
ID 50930e3d0a39ad162b000002
assert.js:102
throw new assert.AssertionError({
^
AssertionError: 0 == 1
*/

Answer 1

You're not using the correct field names in your B.update call. It should be this instead:
B.update(
{ 'PDFs._id': pdf_id }, // <== here
{ $set: {
'PDFs.$.title': 'new title' // <== and here
}}, function (err, numAffected) {
if(err) throw err;
assert.equal(numAffected,1);
}
);
You should also fix your reset function to not call its callback until the save completes:
function reset(cb) {
B.find().remove();
// create some data with a nested document A
var newA = new A( { title : "my title" })
var newB = new B( { PDFs: newA});
newB.save(cb); // <== call cb when the document is saved
}