SailsJS how to correct this promise issue? - promise

Question

I use sails.js to update stock data from difference variable. When I do, console.log(product.stock), the value is 4. But it seems product.save() function below is not executed because attribute stock still not changed to 4. I guess the problem is at promise. Anybody know how to fix this?
exports.updateProductStock = function (details) {
details.forEach(function( detail ) {
var findPrevDetailRule = {
invoice: detail.invoice,
product: detail.product.id
};
var createPrevDetailRule = {
invoice: detail.invoice,
product: detail.product.id,
quantity: detail.quantity
};
var requirementBeforeUpdateStock = [
PreviousDetail.findOne(findPrevDetailRule).sort('createdAt desc').then(),
PreviousDetail.create(createPrevDetailRule).then()
];
Q.all(requirementBeforeUpdateStock)
.spread(function( prevDetail, newPrevDetail ) {
var difference = detail.quantity - prevDetail.quantity;
return {
prevDetail: prevDetail,
difference: difference
};
})
.then(function( results ) {
Product.findOne(results.prevDetail.product).then(function(product) {
product.stock += results.difference;
// maybe this below is not execute
product.save();
console.log(product.stock);
});
})
});
Note: I use sails 0.10-rc8. Have tested with sails-mysql, sails-mongo, sails-postgres, but still same.

Answer 1

.save() accepts a callback with which you can report success/failure.
For example, you can repost back to the client (from the sails documentation) :
product.save(function (err) {
if (err) return res.send(err, 500);
res.json(product);
});
Depending on scope, you may need to pass res into your function
Alternatively, monitor success/failure in the console, eg ,
product.save(function (err) {
if (err) console.log('save error: ' + err);//assuming err to be a string
console.log('save success');
});
Should at least give you a clue as to what's going wrong.