sample of how to use acts_as_follower with rails3 and ajax

_follow_user.html.erb

<% unless user == current_user %>
  <% if current_user.following?(user) %>
    <%= button_to("Un-Follow #{user.nickname}", user_follow_path(user.to_param, current_user.get_follow(user).id), :method => :delete, :remote => true) %>
  <% else %>
    <%= button_to("Follow #{user.nickname}", user_follows_path(user.to_param), :remote => true) %>
  <% end %>
<% end %>

create.js.erb

$('#follow_user').html('<%= escape_javascript(render :partial => "shared/follow_user", :locals => {:user => @user}) %>');

#jQuery

destroy.js.erb

$('#follow_user').html('<%= escape_javascript(render :partial => "shared/follow_user", :locals => {:user => @user}) %>');

#jQuery

FollowsController.rb

class FollowsController < ApplicationController

  def create
    @user = User.find(params[:user_id])
    current_user.follow(@user)
  end

  def destroy
    @user = User.find(params[:user_id])
    current_user.stop_following(@user)
  end

end

routes.rb

...

resources :users, :only => [:index, :show] do
  resources :follows, :only => [:create, :destroy]
end

...

show.html.erb

<% if user_signed_in? %>
  <div id="follow_user">
    <%= render :partial => "shared/follow_user", :locals => {:user => @user} %>
  </div>
<% end %>

user.rb

class User < ActiveRecord::Base
  
  ...

  acts_as_follower
  acts_as_followable
  
  ...  
  
end

If we want implement it with mongodb then How can we do it ?

Can you update this solution for Rails 4 please?

Does it work with MongoDB?