Rails 4 Allow Users to Create and Attend Events

I found this mini-application on GIThub that allows users to create attend and cancel events here: http://ift.tt/1Xfqfz2 the only issue is that it was made for Rails 3. I'm trying to implement that app into my own practice application but using rails 4.2.4 so far i'm having issues with the attend events functionality.

I have three models that are connected using a rich join using has many through: user, event, and event_registration.

user.rb

class User < ActiveRecord::Base
has_many :event_registrations
has_many :events, through: :event_registrations 

.

event.rb
class Event < ActiveRecord::Base
has_many :event_registrations
has_many :users, through: :event_registrations

.

event_registration.rb
class EventRegistration < ActiveRecord::Base
belongs_to :event
belongs_to :user

The functionality that creates a new event is located within event_registrations_controller.rb

class EventRegistrationsController < ApplicationController

 def new
   EventRegistration.new(event_id: params[:event_id].to_i, user_id:
   current_user.id)
   redirect_to event_path(params[:event_id])
   flash[:notice] = "Thanks for attending this event!"
 end

 def destroy
   EventRegistration.where(event_id: params[:event_id].to_i, user_id:  
   current_user.id).first.destroy
   redirect_to event_path(params[:event_id])
 end


 private
 # Use callbacks to share common setup or constraints between actions.
 def set_event_registration
   @event_registration = EventRegistration.find(params[:id])
 end

 def event_registration_params
  params.require(:event_registration).permit(:user_id, :event_id)
 end
end

This is a snippet of my events\show.html.erb that creates the event.

<% if session[:user_id] %>
  <% if @event.attended_by(User.find(session[:user_id])) %>
    <%= link_to "Cancel attendance", event_registration_path(event_id:   
  @event.id), method: :delete, class: "btn
    btn-primary" %>
  <% else %>
    <%= link_to "Attend", new_event_registration_path(event_id: @event.id), 
    class: "btn btn-success" %>
  <% end %>
<% end %>

The problem is that I do get the "Thanks for attending this event!" message but no new record is made in the event_registrations table at all.

Thank you in advance for your help.