gistfile1.rb

class ThingsController < ApplicationController
  respond_to :html, :json

  before_filter { @thing = {one: 1, two: 2} }

  # /things/a       -> renders template at things/a.html.erb
  # /things/a.json  -> renders @thing.to_json
  def a
    respond_with @thing
  end

  # /things/b       -> renders the template at b.html.erb
  def b
    do_some_stuff_with @thing
    do_some_other_stuff
  end

  private

  def do_some_stuff_with(something)
    something[:three] = 3
  end

  def do_some_other_stuff
    # whatever...
  end
end