RackMotion provides a Rack-like interface for middleware that can intercept and alter HTTP requests and responses in RubyMotion. It's built on top of NSURLProtocol, which makes it, to borrow a line from Mattt Thompson, an Apple-sanctioned man-in-the-middle attack.

For example, here's how easy it is to enable cross-origin resource sharing for most Javascript XMLHttpRequests:

class EnableCORS
  def initialize(app)
    @app = app
  end

  def call(request)
    status, headers, data = @app.call(request)

    if request.allHTTPHeaderFields['Origin']
      headers['Access-Control-Allow-Origin'] = request.allHTTPHeaderFields['Origin']
    end

    return status, headers, data
  end
end

And then, in your AppDelegate:

RackMotion.use EnableCORS

Installation

Add this line to your application's Gemfile:

gem 'RackMotion'

And then execute:

$ bundle

Or install it yourself as:

$ gem install RackMotion