title: Upgrade from Rails 3.2 to Rails 4
body: <p>I have an application in Rails 3.2 which is ready to deploy. I am wondering should I upgrade it to Rails 4 or not. I also not sure about which of the gems might give issues with while upgrading.</p>
  
  <p>Below is my Gemfile with several common gems.</p>
  
  <p>Gemfile.rb</p>
  
  <pre><code>source 'https://rubygems.org'
  
  gem 'rails', '3.2.8'
  gem 'pg', '0.12.2'
  
  gem 'bcrypt-ruby', '3.0.1'
  
  gem 'will_paginate', '3.0.3'
  gem 'bootstrap-will_paginate', '0.0.6'
  gem 'simple_form', '2.0'
  gem 'rails3-jquery-autocomplete', '1.0.10'
  gem 'show_for', '0.1'
  gem 'paperclip', '3.3.1'
  gem 'cocoon', '1.1.1'
  gem 'google_visualr', '2.1.0' 
  gem 'axlsx', '1.3.4'
  gem 'acts_as_xlsx', '1.0.6'
  gem 'devise' ,'2.1.2'
  gem 'cancan', '1.6.8'
  gem 'bootstrap-datepicker-rails', "0.6.32"
  gem 'country_select', '1.1.3'
  gem 'jquery-rails', '2.1.4'
  gem 'annotate', '2.5.0', group: :development
  gem 'ransack', '0.7.2'
  gem "audited-activerecord", "3.0.0"
  gem 'prawn', '1.0.0.rc2'
  gem 'exception_notification', '3.0.1'
  gem 'daemons', '1.1.9'
  gem 'delayed_job_active_record', '0.4.3'
  gem "delayed_job_web", '1.1.2'
  gem "less-rails"
  gem "therubyracer"
  gem 'twitter-bootstrap-rails', '~&gt;2.1.9'
  gem "spreadsheet", "~&gt; 0.8.8"
  
  # Gems used only for assets and not required
  # in production environments by default.
  group :assets do
    gem 'sass-rails',   '3.2.5'
    gem 'coffee-rails', '3.2.2'
  
    # See https://github.com/sstephenson/execjs#readme for more supported runtimes
    # gem 'therubyracer', :platforms =&gt; :ruby
  
    gem 'uglifier', '1.2.3'
  end
  
  # To use ActiveModel has_secure_password
  # gem 'bcrypt-ruby', '~&gt; 3.0.0'
  
  # To use Jbuilder templates for JSON
  # gem 'jbuilder'
  
  # Use unicorn as the app server
  # gem 'unicorn'
  
  # Deploy with Capistrano
  # gem 'capistrano'
  
  # To use debugger
  # gem 'debugger'
  
  group :development, :test do
    gem 'rspec-rails', '2.11.0'
  end
  
  group :test do
    gem 'capybara', '1.1.2'
    gem 'factory_girl_rails', '4.1.0'
    gem 'faker', '1.0.1'
  end
  </code></pre>
  
  <p>I started working on this application last year (Nov 2012) after reading this great book at
  <a href="http://ruby.railstutorial.org/">http://ruby.railstutorial.org/</a>. I have also checked out what's new in Rails 4 like strong parameters and it's all very tempting to try an upgrade.</p>
  
  <p>But I am concerned about compatibility of these gems and effort it may take.</p>
  
  <p>I need some advice from experienced guys in the community or someone who has tried upgrading before I move ahead.</p>