Does your GET or POST hit the server but you see no response data come back?

I saw this because I was debugging this in a separate file (using Open File in my browser), outside my (Rails) project. WTF I thought

Turns out that even though I thought it hit the server, it was returning no data because of the cross-site scripting policy.

Solution? Learn JSONP

JSONP: what does that jQuery even look like?

I finally got this right: $.ajax({url: "http://localhost:3000/api/test.js", dataType: "jsonp", success: function(data) { $("#ajax_success").html("Success!"); }, });

Solution: Important parts here that I found: dataType: “jsonp” and the URL ending in a “.js”

Also note that the success function is what’s called, even with a JSONP request, when the AJAX call returns. Yes, it’s the same interface from a JSON call, and that’s cool.

(You can override this, but the success callback is a clean API. I like it)

RAILS, Y U NO FIND GET ROUTE FOR MY REQUEST?

JSONP only works via GET, because it works through the same mechanism that you would get an image from a web server - just a link. So, with that in mind, your actions need to respond to GETs too.

I had a line in my routes.rb file like resource :test, :only => [:create] To make that respond to both a GET and POST I had to do this ugly thing: resource :test, :only => [:create] do get :create post :create end

Solution: use this method. No, I couldn’t get :via => , to work

Ok, what does my action have to return?

So the JSONP support in Rails (3) is there, but it’s somewhat manual. I want to be able to return both JSON and JSONP, and I want to return my result in both cases.

My current solution is ugly as sin

Potential gotcha: in the format.js block, make sure the :callback key is outside the hash you want to return. This is hard to miss, and one of the reasons I made the hash as a separate object (the other is to try to make it DRYer)

If you see that your JSON response is coming out: {"success": true, "callback": "...."} you’d made the mistake above.

Solution: Use this pattern, and hope for a better future

I do have hope on Rack middleware, but I couldn’t figure out how to use the two rack middleware packages I found (Rack/Contrib nor Rack JSONP Middleware. I’m working with the latter author to get his solution into my app, because seriously? I want it DRY