Voting API for comments with backbonejs - backbone.js

Question

I have just started experimenting with backbone.js and have hit a roadblock while designing my very first front-end module with it. Here's what I have:
I followed the basic todos tutorial and created a commenting system upon my custom REST API. All good there.
I have a vote up or vote down button for each comment, just like SO. I want to call the REST API which is at
POST /api/comments/vote/:id
A parameter "direction" (up or down) is also passed.
In my comments view I have a function that calls another function it the comments model like this:
vote_up: function() {
this.model.voteUp();
return false;
}
the function in model:
voteUp: function() {
var up_votes = this.get('up_votes') - 0;
up_votes++;
this.save({up_votes: up_votes});
}
I am pretty sure I don't need this.save here which actually calls the comments API and the sends all the parameters as POST.
I am not sure how to do this in a backbonejs-way (I am looking for something standard).

Answer 1

You should do a manual $.ajax call to /api/comments/vote/:id and tell it if you have an upvote or downvote. Then /api/comments/vote/:id would send an atomic increment or decrement into the database, read out the new value, and send that back. Then the success handler for your $.ajax can do a set to update the client-side value.
Your voteUp implementation is subject to some obvious timing problems: what happens if you have 6 upvotes in your JavaScript, then 11 other people upvote, and your voteUp tries to tell the server that a new upvote has occurred so there should be 7 upvotes? You shouldn't try to maintain counters like this, not even in server-side code.
I guess I'm trying to say that there isn't really a Backboney way to do this, there is a correct way and all sorts of incorrect ways. Do it the correct way and declare, by fiat, that that is the Backboney way.

Answer 2

I think the standard way would be to take advantage of Backbone's urlRoot property.
var Vote = Backbone.Model.extend({urlRoot : '/api/comments/vote'});
// ....in comments view:
vote_up: function() {
// send HTTP Post '/api/comments/vote/' -- server will create ID
new Vote({direction: 1}).save()
return false;
}
If you need the Id right away, or to otherwise react to the successful insert, you can pass a success callback to save.
See: http://backbonejs.org/#Model-save