JSONP with Rails

Question

I'm trying to retrieve JSON data from a remote site with Rails/Prototype.

I've found that there's a branch of Prototype that has an Ajax.JSONRequest() function. I can't get this to work.

jQuery has a $.getJSON() function, but I'm using some Prototype functions and I'd rather not switch to jQuery or use no conflict mode.

What am I missing? It seems like this would be easily done with Rails or Prototype.

Answer 1

Do you need to use Rails helpers to make the client request JSON? It's easy with Prototype

new Ajax.Request('/some_url', { method:'get', onSuccess: function(transport){ var json = transport.responseText.evalJSON(); } });

You just need to make sure that /some_url responds with JSON to an XHTTPRequest (preferably using respond_to?, but you can also check request.xhr?), using Rails' Object#to_json method.

Answer 2

You can also use the JSONP rack middlware that's available in rack-contrib. This gives you the ability to just append &callback=method to your query string and have the response from rails wrapped in your callback method.

Just add this to your application.rb:

require "rack/contrib/jsonp"

class Application < Rails::Application
  config.middleware.use Rack::JSONP
end

Answer 3

nothing built into rails specifically for jsonp, but there's a couple things that you could do if you wanted your rails app to play nice with jsonp.

• create a jsonp mime-type in config/initializers/mime_types.rb
• extend object with a to_jsonp method that will wrap calls to json in your passed callback. something like:

def to_jsonp(callback, options={}) "#{callback}(#{self.to_json(options)})" end

• follow this guys article.

http://blogs.sitepoint.com/2006/10/05/json-p-output-with-rails/