How to implement voting in Rails without voting gem

Question

I have created a hacker news clone and I am trying to implement a voting system that ranks from most voted to least voted, based on the past 7 days. I know there are several gems to do this but I would like to do it once manually before using a gem.

First issue I am having, is with multiple votes. I want to have each user able to vote on as many links as they want but with a limit of one vote per link. I tried to make this happen in my votes_controller but it is only allowing the links themselves to have one vote total instead of the user having one vote per link. Here is my method in votes_controller :

 def create
    @vote = Vote.new(voter_params)
    if @vote.save
      redirect_to links_path, notice: "Thanks for voting!"
    else
      redirect_to links_path, notice: "Sorry, you can only vote on a link once."  
    end
  end

My schema.rb consists of users, links, and votes with a user_id attribute in both links and votes as listed here :

 create_table "links", force: true do |t|
    t.string   "description"
    t.string   "url"
    t.datetime "created_at"
    t.datetime "updated_at"
    t.integer  "user_id"
  end

  create_table "users", force: true do |t|
    t.string   "name"
    t.string   "email"
    t.string   "user_name"
    t.string   "password_digest"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  create_table "votes", force: true do |t|
    t.integer  "user_id"
    t.integer  "link_id"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

How can I refactor my current action to allow votes for any link but only one vote per user?

Ok, my second and last question is, once I have that voting issue squared away, how can I sort them from most voted, to least voted, based on the past 7 days, going through the postgres server approach of course. It just seems to me that going through the db is more efficient. I'd appreciate any insight I can get, I am totally stumped, thanks!!

Here is my link model to give a better idea :

class Link < ActiveRecord::Base
  validates :url, :presence => true, :url => true
  belongs_to :user
  has_many :votes
  has_many :comments, :as => :commentable

  def self.sort_by_votes
    sorted_votes = Link.all.sort_by { |link| link.votes.count }
    sorted_votes.reverse
  end
end

and here is my view :

<% if current_user %>
<p style="float:right; padding-right: 10px;"> Logged in as: <%= current_user.name %> </p>
<% end %>
<div class="container" id="content">
  <button class="btn btn-default btn-xs" style="float:right"><%= link_to "New Link", new_link_path %></button><br><br>
<table >
  <thead>
    <tr>
    </tr>
  </thead>
  <tbody class="stories">
    <% @links.sort_by_votes.each do |link| %>
          <%= form_for link.votes.new do |f| %>
                   <%= f.hidden_field :link_id %>
                   <%= f.submit '▲' %>
                   <% end %>
          <%= "#{link.votes.count} votes " %>
          <%= link_to link.description, link.url %>
          <small><%= "(#{link.url})" %></small>
          <span class="date"><%= link.created_at.to_time.strftime("%b %-d, %Y @ %-I:%M%P") %></span>
          <br>
          <button class="btn btn-default btn-xs">
            <%= link_to "Delete", link, :method => :delete, :data => { :confirm => "are you sure about that?" } %>
          </button>
          <button class="btn btn-default btn-xs">
            <%= link_to "Comment", link_path(link)%>
          </button><hr/>
      <% end %>
</tbody>

</div>

Answer 1

You should use validations for this:

class Vote
  #...
  validates :user_id, uniqueness: { scope: :link_id }

Relationship counters are rather complex depending on your db and also generally produce complex time consuming queries. I'd use the counter_cache option. There's a nice post about how to use those.

$ rails g migration add_votes_counter_to_link votes_count:integer
class AddVotesCounterToLinks < ActiveRecord::Migration
  def change
    add_column :links, :votes_count, :integer, default: 0
  end
end
$ rake db:migrate

class Vote
  belongs_to :link, counter_cache: true
end

class Link
  has_many :votes

  scope :most_voted, -> do
    where(created_at: (Time.now - 7.days)..Time.now ) # created 7 days ago
    .order('votes_count DESC')                        # ordered by votes_count
    .limit(100)                                       # first 100
  end

Then you can do things like:

Link.most_voted