How should I white label a Rails app?

whitelabeling.rb

class ApplicationController < ActionController::Base
  around_filter :set_white_label

  private

  def set_white_label
    subdomains = request.subdomains - RESERVED_SUBDOMAINS
    if subdomains.empty?
      yield
      return
    end

    # Obviously extract this out to work with any subdomain we want
    if subdomains.first == "mycompany"
      white_label_view_path = File.expand_path(File.join(RAILS_ROOT, 'app', 'white_labels', "mycompany"))
      prepend_view_path(white_label_view_path)
      yield
    end
  end
end

What do you think of this approach?
The work happens in line #16 with prepend_view_path which will ensure a specific view path for white labelled sites. This will allow me to have different layouts/partials etc

Of course, it might be a bit hard out. I might be able to just do it all in CSS and include a special CSS file for white labelled sites.

I like it. Does the prepend_view_path allow you to only override some view files or do you need to have a complete set in that directory structure?

Only the ones you want to override. The idea is that it looks for the file in the requested path, and if it can't find it, looks in the standard dir structure.