Just some quick thoughts...

gistfile1.rb

class FoosController < ApplicationController
  before_filter :foobar
 
  class Bar
    before_filter :find_bar
 
    def new
      ...
    end
 
    def create
      ...
    end
 
    private
 
    def find_bar
      ...
    end
  end
 
  def show
    ...
  end
 
  private
 
  def foobar
    ...
  end
end

Pro

• Support for both - "simple" methods and nested classes
• Should be easy to route
• Auto reloading this should be easy
• ...

Cons

• Magic!!
• Tons of nested classes - really?!
• ...

Questions

• Would this be a good solution after all?
• How much magic should be involved? (e.g. calling outer methods "just works", filter chains)
• ...