Question

I have a Post, Comment and Vote model

Each time an instance of Vote model is created (either with :polarity +1 or -1) it updates the total_votes column of the post it belongs to:

vote.rb:

class Vote < ActiveRecord::Base
  belongs_to :votable, :polymorphic => true
  belongs_to :user

  before_create :update_total

  protected

  def update_total
    total_average = self.votable.total_votes
    self.votable.update_attribute(:total_votes, total_average + self.polarity)
  end
end

This is how I call it in the show.html.erb view:

  <div class="post-<%= @post.id %>">
   <h3><span class="vote-count"><%= @post.total_votes %></span> votes</h3><br />

example of votes_controller.rb:

 def vote_up
    @post = Post.find(params[:id])

    if @post.votes.exists?(:user_id => current_user.id)
      @notice = 'You already voted'
    else
      @vote = @post.votes.create(:user_id => current_user.id, :polarity => 1)
    end

    respond_to do |format|
      format.js
    end
  end

routes.rb:

 get 'votes/:id/vote_up' => 'votes#vote_up', as: 'vote_up'

For some reason @post.total_votes gives 0, the default of the column (whether its actual value is -1 or 1) if it is attached to show.html.erb via Ajax from this file:

vote_up.js.erb:

<% unless @notice.blank? %>
  alert("<%= @notice %>");
<% end %>

<% unless @vote.blank? %>
  $('.post-<%=@post.id%> span.vote-count').html('<%= @post.total_votes %>');
  $('.post-<%=@post.id%> div.voted-user').html('<% @post.votes.each do |vote| %><%= link_to vote.user.username, vote.user %><% end %>');
<% end %>

Any suggestion to fix this?

Answer 1

You’re loading the @post object, then changing it in your Vote model’s callbacks, but the @post object doesn’t know about this change and continues to use its cached results from the database. You can force it to reload by putting a @post.reload right after your @post.votes.create line.