Rails plugin that allows RESTful controllers to work with JSONP
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This is a Rails plugin (Railtie) that allows your existing RESTful controllers to work over JSONP.


REST is designed around the four HTTP request methods (GET, POST, PUT, and DELETE), but JSONP requests are always GETs. To get around this restriction, this Railtie lets you specify the desired method in a special _method parameter.

For example, to make a PUT request to /users/1.json, you would make a JSONP (GET) request to /users/1.json?_method=PUT.


The plugin also adds a custom Responder for JSONP that automatically adds special behaviour to respond_with (via a custom display method).

For JSONP requests handled with respond_with:

  1. :callback => param[:callback] will be automatically added to the render options
  2. Error :status codes (e.g. :unprocessable_entity) will be changed to :accepted, since error responses cannot be handled by JSONP. To detect errors in JSONP responses check for an error attribute in the returned data.


First, install the gem:

gem install restful_jsonp

Then add this to your Rails app's Gemfile:

`gem 'restful_jsonp'

Note that this only works for Rails 3. In principle you could try to swap in the RestfulJSONP::MethodOverride middleware into a Rails 2.3+ app, but this has not been tested.

To enable the custom JSONP Responder, add this to your ApplicationController (or any controller that you want to enable the responder for):

self.responder = RestfulJSONP::JSONPResponder

How it Works

The _method functionality is built in to Rails (via Rack), but is normally only available for POST requests. This Railtie replaces the default Rack::MethodOverride middleware with a slightly altered version that checks for the _method parameter regardless of whether it's in a POST or GET request.

Note that this functionality is enabled for all requests, regardless of whether they are done via JSONP or otherwise.


  • Fixed error response processing in JSONPResponder
  • Initial release