application_helper.rb

module ApplicationHelper

  def sortlist (column, title = nil, filter, css_class)
    title ||= column.titleize
    css_id = column == :sort_column ? "hilite" : "#{column}_header"
    direction = column == :sort_column && :sort_direction == "asc" ? "desc" : "asc"
    link_to title, {:sort => column, :direction => direction, :ratings => filter}, {:id => css_id}
  end
  def th_class (column)
    css_class = column == params[:sort] ? "hilite" : nil
  end
end

controller.rb

 helper_method :sort_column, :sort_direction

  def index
    @movies = Movie.order(sort_column + " " + sort_direction).filter(filter_selection)
    @all_ratings = Movie.all_ratings
    @selected_ratings = (params[:ratings].present? ? params[:ratings] : [])
  end
end

....

  def filter_selection
    params[:ratings] == nil ? Movie.all_ratings : params[:ratings]
  end
  
  def sort_column
    Movie.column_names.include?(params[:sort]) ? params[:sort] : "id"
  end
  
  def sort_direction
    %w[asc desc].include?(params[:direction]) ? params[:direction] : "asc"
  end

index.rb

-# This file is app/views/movies/index.html.haml
%h1 All Movies

= form_tag movies_path, :method => :get do
  Include:
  - @all_ratings.each do |rating|
    = rating
    = check_box_tag( "ratings[#{rating}]", " ", @selected_ratings.include?(rating), :id => "ratings_#{rating}")
  = submit_tag 'Refresh', :id => "ratings_submit"
%table#movies
  %thead
    %tr
      %th{:class => th_class("title")}= sortlist "title", "Movie Title", @selected_ratings, "title_header"
      %th Rating
      %th{:class => th_class("release_date")}= sortlist "release_date", "Release Date", @selected_ratings, "release_date_header"
      %th More Info
  %tbody
    - @movies.each do |movie|
      %tr
        %td= movie.title
        %td= movie.rating
        %td= movie.release_date
        %td= link_to "More about #{movie.title}", movie_path(movie)

= link_to 'Add new movie', new_movie_path   

movie.rb

class Movie < ActiveRecord::Base

  def self.all_ratings
    self.select(:rating).map(&:rating).uniq
  end
  
  def self.filter(selection)
    begin
      self.where(:rating => selection.keys)
    rescue
      self.where(:rating => selection)
    end
  end
end   

url.txt

http://secret-beach-3782.herokuapp.com/movies