Rapid Prototyping with Rails: Lesson 3, part 4

28 Oct 2014

1. Create vote controller action

class PostsController < ApplicationController
  def vote
    binding.pry
  end
 end

Entering params in rails console, will show us that we passing an id parameter but not the boolean to indicate true/false, whether the post is up or down.

2. Add boolean parameter to views to create link

Add boolean parameter to views to create link /posts/2/vote?vote=true&param2=2

#posts/index.html.erb
 <div class='row'>
    <div class='span0 well text-center'>
      <%= link_to vote_post_path(post, vote: true), method: 'post' do %>

3. Now that we have our thing we are voting on and our vote, we can create our vote action

class PostsController < ApplicationController
  before_action :set_post, only: [:show, edit, :update, :vote]

def vote
  #post = Post.find(params[:id]) or use @post(created in the before_action)
  @vote = Vote.create(voteable: @post, creator: current_user, vote: params[:vote])

  if @vote.valid?
    flash[:notice] = "Your vote was recorded"
  else
    flash[:error] = "Your vote was not recorded"
  end
    redirect_to :back (to go back to the original page viewed)
  end
end

4. Wire up the same for the down vote in the views/posts/index

<div class='row'>
  <div class='span0 well text-center'>
    <%= link_to vote_post_path(post, vote: false), method: 'post' do %>

5. What if I want to display the number of votes

<%post.votes.size%>

6. What if I want the number of votes to decrease when pressing the down button.

Although this may seem like a presentational concern that would require a helper method - however storing the number of votes is a data concern and not a presentational one. Method regarding business logic belong in the model itself.

class Post < ActiveRecord::Base
   def total_votes
    up_votes - down_votes
   end

   def up_votes
    self.votes.where(vote: true).size
   end

   def down_votes
    self.votes.where(vote: false).size
   end
 end

So now in the presentation layer, we can call total_votes:

<% post.total_votes %>

7. What if we wanted to sort

class PostsController < ApplicationController

  def index
    @posts = Post.all(|x| x.total_votes).reverse
  end
end

8. How can we make sure that each user only votes once for post:

There are many ways to accomplish this but the best way would be to add the uniqueness validation to the model:

class  Vote < ActiveRecord::Base
  validates_uniqueness_of :creator, scope: :voteable
end

9. Using html_safe

Rails by default escapes everything so user input html, js or script tags are escaped to prevent malicious intent. In order to write html in any place besides the html.erb files, you must append html_safe at the end of your statement

def vote
  #post = Post.find(params[:id]) or use @post(created in the before_action)
  @vote = Vote.create(voteable: @post, creator: current_user, vote: params[:vote])
    ** We do not need to use strong_params because we are not using the key value
    pairs for mass assignment, instead we are hard coding in the keys.
  if @vote.valid?
    flash[:notice] = "Your vote was recorded"
  else
    flash[:error] = "Your vote was <strong>not</strong> recorded".html_safe
  end
    redirect_to :back #(to go back to the original page viewed)
end

This will cause the rails to not escape those tags and apply the html. You generally do not want to add html_safe on user input elements.

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