Rerouting to AWS hosted assets from a Heroku Rails app - ruby-on-rails

Question

I have a Heroku hosted Rails app that has reached the 300MB limit for the slug size and can no push to Heroku. To fix this issue, I've setup an AWS S3 account and want to redirect the assets being requested from my Rails app to the new S3 location. The Rails app is basically just serving JSON files that point to the static assets using a relative URL. An iOS app using the Rails JSON then has a hardcoded domain URL, and appends the path to the resources to that domain and requests assets it needs.
I want to update my Heroku app and change my asset locations without requiring an update to the iOS app in order to change the asset domain. So, I need to redirect static asset requests from the Rails app to the AWS server.
In my git repo, I've ignored the assets in the public folder that I've moved to the AWS server. The asset files are present on my local machine, but are not part of the git repo when uploaded to Heroku.
So far I've tried changing the config.action_controller.asset_host which does not seem to work since these are static assets and are being returned by the web server before Rails gets it.
I tried using routes rules to redirect to a different domain, but these routes never seem to be captured. The static files appear to be returned before the Rails app has a chance to handle the request.
I've tried using the rack-rewrite gem to try and redirect my assets to a different domain with the following in `initializers/rack_rewrite.rb:
require 'rack/rewrite'
AppNamespace::Application.config.middleware.insert_before(Rack::Lock, Rack::Rewrite) do
r301 %r{/images(.*)}, 'http://my-subdomain.amazonaws.com/images$1'
end
This doesn't seem to work either and it always just returns the static files.
So far I've been trying for hours to figure out the proper way to handle this situation. I'm not a Rails developer by trade, I build iOS apps, so please let me know if I'm going about this the wrong way or completely missed the "right" way of doing this.

Answer 1

I solved this using routes and the 'rails_serve_static_assets'. I had to move the local images out of the public folder in order to avoid Nginx from returning the images before hitting the Rails app. The route ended up like so:
match '/images/(*path)', :to => redirect { |params, request|
"#{Rails.configuration.assets.aws_url}#{request.path}"
}