Follow-up to Extra Credit Challenge for Chicago 2013 RailsBridge for Code4Lib-ers

index.html.erb

<!-- Found in /app/views/topics/index.html.erb -->
<h1>Listing topics</h1>

<table>
  <tr>
    <th></th>
    <th></th>
    <th></th>
    <th></th>
  </tr>

  <% @topics.each do |topic| %>
    <tr>
      <td><%= link_to topic.title, topic %></td>
      <!-- replaced topic.votes.length with topics.votes_count -->
      <td><%= pluralize(topic.votes_count, "vote") %></td>
      <td><%= button_to '+1', votes_path(topic_id: topic.id), method: :post %></td>
      <td><%= link_to 'Delete', topic, confirm: 'Are you sure?', method: :delete %></td>
    </tr>
  <% end %>
</table>

<br />

<%= link_to 'New Topic', new_topic_path %>

topic.rb

# Found in ./app/models/topic.rb
class Topic < ActiveRecord::Base
  attr_accessible :title, :body
  has_many :votes

  def self.sorted
    # There are ways to do this with database agnostic syntax, but the resulting
    # Ruby/Rails code is rather overwhelming
    find_by_sql(
      "SELECT topics.*,
      (SELECT count(votes.topic_id) FROM votes WHERE votes.topic_id = topics.id)
        AS votes_count
      FROM topics
      ORDER BY votes_count"
    )
  end

  def votes_count
    # In the above SQL there is the line that counts the votes and creates the
    # selected query column "votes_count", which means that each Topic has a
    # "votes_count" attribute.
    #
    # If we have the attribute, use it, otherwise compute the attribute. For
    # this to truly be effective, in the index page, replace "topic.votes.count"
    # with "topic.vote_count"
    attributes['votes_count'] || votes.count
  end
end

topics_controller.rb

# Found in ./app/controllers/topics_controller.rb
class TopicsController < ApplicationController
  # GET /topics
  # GET /topics.json
  def index
    # @topics = Topic.all
    @topics = Topic.sorted

    respond_to do |format|
      format.html # index.html.erb
      format.json { render json: @topics }
    end
  end
  # ... Removed for brevity ...
end

vote.rb

# Found in ./app/models/vote.rb
class Votes < ActiveRecord::Base
  attr_accessible :topic_id
  belongs_to :topic
end