Like button Ajax in Ruby on Rails

Question

I have a Ruby on Rails project with a model User and a model Content, among others. I wanted to make possible for a user to "like" a content, and I've done that with the acts_as_votable gem.

At the moment, the liking system is working but I'm refreshing the page every time the like button (link_to) is pressed.

I'd like to do this using Ajax, in order to update the button and the likes counter without the need to refresh the page.

In my Content -> Show view, this is what I have:

<% if user_signed_in? %>
  <% if current_user.liked? @content %>
      <%= link_to "Dislike", dislike_content_path(@content), class: 'vote', method: :put %>
  <% else %>
      <%= link_to "Like", like_content_path(@content), class: 'vote', method: :put %>
  <% end %>
  <span> · </span>
<% end %>

<%= @content.get_likes.size %> users like this
<br>

The Content controller does this to like/dislike:

def like
    @content = Content.find(params[:id])
    @content.liked_by current_user
    redirect_to @content
end

def dislike
    @content = Content.find(params[:id])
    @content.disliked_by current_user
    redirect_to @content
end

And in my routes.rb file, this is what I have:

resources :contents do
    member do
        put "like", to: "contents#like"
        put "dislike", to: "contents#dislike"
    end
end

As I said, the liking system is working fine, but does not update the likes counter nor the like button after a user presses it. Instead, to trick that, I call redirect_to @content in the controller action.

How could I implement this with a simple Ajax call? Is there another way to do it?

Answer 1

You can do so in various ways, the simple way goes like this:

Preparations

0. Include Rails UJS and jQuery in your application.js (if not already done so):

   //= require jquery
   //= require jquery_ujs
   

1. Add remote: true to your link_to helpers:

   <%= link_to "Like", '...', class: 'vote', method: :put, remote: true %>
   

2. Let the controller answer with a non-redirect on AJAX requests:

   def like
     @content = Content.find(params[:id])
     @content.liked_by current_user
   
     if request.xhr?
       head :ok
     else
       redirect_to @content
     end
   end
   

Advanced behaviour

You probably want to update the "n users liked this" display. To archieve that, follow these steps:

1. Add a handle to your counter value, so you can find it later with JS:

   <span class="votes-count" data-id="<%= @content.id %>">
     <%= @content.get_likes.size %>
   </span>
   users like this
   

   Please also note the use of data-id, not id. If this snippet gets used often, I'd refactor it into a helper method.

2. Let the controller answer with the count and not simply an "OK" (plus add some information to find the counter on the page; the keys are arbitrary):

   #…
   if request.xhr?
     render json: { count: @content.get_likes.size, id: params[:id] }
   else
   #…
   

3. Build a JS (I'd prefer CoffeeScript) to react on the AJAX request:

   # Rails creates this event, when the link_to(remote: true)
   # successfully executes
   $(document).on 'ajax:success', 'a.vote', (status,data,xhr)->
     # the `data` parameter is the decoded JSON object
     $(".votes-count[data-id=#{data.id}]").text data.count
     return
   

   Again, we're using the data-id attribute, to update only the affected counters.

Toggle between states

To dynamically change the link from "like" to "dislike" and vice versa, you need these modifications:

1. Modify your view:

   <% if current_user.liked? @content %>
     <%= link_to "Dislike", dislike_content_path(@content), class: 'vote', method: :put, remote: true, data: { toggle_text: 'Like', toggle_href: like_content_path(@content), id: @content.id } %>
   <% else %>
     <%= link_to "Like", like_content_path(@content), class: 'vote', method: :put, remote: true, data: { toggle_text: 'Dislike', toggle_href: dislike_content_path(@content), id: @content.id } %>
   <% end %>
   

   Again: This should go into a helper method (e.g. vote_link current_user, @content).

2. And your CoffeeScript:

   $(document).on 'ajax:success', 'a.vote', (status,data,xhr)->
     # update counter
     $(".votes-count[data-id=#{data.id}]").text data.count
   
     # toggle links
     $("a.vote[data-id=#{data.id}]").each ->
       $a = $(this)
       href = $a.attr 'href'
       text = $a.text()
       $a.text($a.data('toggle-text')).attr 'href', $a.data('toggle-href')
       $a.data('toggle-text', text).data 'toggle-href', href
       return
   
     return