gistfile1.rb

class SlideshowsController < ApplicationController
  before_filter :authenticate, :authorize

  def show
    if file_exists?(file)
      render :file => file
    else
      render :nothing => true, :status => 404 and return false
    end
  end

  protected

  def file
    File.join(directory, "#{params[:id]}.html")
  end

  def directory
    File.join(RAILS_ROOT, "app", "views", "slideshows")
  end

  def file_exists?(path)
    File.file?(path)
  end
end