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How to Upgrade to Rails 3.1.0

25 May 2011 {0 Comments}

The Rails 3.1.0 Release Candidate dropped a few days ago and thought I’d give it a try on an application I was busy upgrading already. Before starting you’ll probably want to check out the Release Notes or the railscasts overview video first.

1. Upgrade the Gemfile

source 'http://rubygems.org'

gem "rails", "3.1.0.rc1"
gem "mysql2", "0.3.2"
# Rails 3.1 - Asset Pipeline
gem 'json'
gem 'sass'
gem 'coffee-script'
gem 'uglifier'
# Rails 3.1 - JavaScript
gem 'jquery-rails'

# Rails 3.1 - Heroku
group :production do
  gem 'therubyracer-heroku', '0.8.1.pre3'
  gem 'pg'

Needed specifically the latest version of mysql2 as the earlier ones are incompatible. To get the asset pipeline working on heroku you’ll need therubyracer-heroku. Another issue with heroku, it appears you now need to be explicit about using postgres in production.

2. Config File Changes

Update config/boot.rb

require 'rubygems'

# Set up gems listed in the Gemfile.
ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile', __FILE__)

require 'bundler/setup' if File.exists?(ENV['BUNDLE_GEMFILE'])

Update application.rb

In config/application.rb add the following line.

# Enable the asset pipeline
config.assets.enabled = true

Update development.rb

I seemed to have to remove the following line from config/environments/development.rb

config.action_view.debug_rjs             = true

Update production.rb

Add the following lines to enable asset compression in config/environments/production.rb.

# Compress both stylesheets and JavaScripts
config.assets.js_compressor  = :uglifier
config.assets.css_compressor = :scss

3. Move Assets

Move the Folders

mkdir app/assets
git mv public/images app/assets/images
git mv public/javascripts app/assets/javascripts
git mv public/stylesheets app/assets/stylesheets

Fix Image References

Use your favourite find and replace, check judiciously.

find: /images/
replace: /assets/

Make CSS and JavaScript Manifest Files

I already had an app/assets/application.js file so I added this to the top of mine and moved the code in there out into separate files with app/assets/javascripts.

// This is a manifest file that'll be compiled into including all the files listed below.
// Add new JavaScript/Coffee code in separate files in this directory and they'll automatically
// be included in the compiled file accessible from http://example.com/assets/application.js
// It's not advisable to add code directly here, but if you do, it'll appear at the bottom of the
// the compiled file.
//= require jquery
//= require jquery_ujs
//= require_tree .

I did the same for app/assets/application.css

 * This is a manifest file that'll automatically include all the stylesheets available in this directory
 * and any sub-directories. You're free to add application-wide styles to this file and they'll appear at
 * the top of the compiled file, but it's generally better to create a new file per style scope.
 *= require_self
 *= require_tree . 

Fix the CSS and JavaScript references

Instead of requiring multiple files you’ll want to require the manifest files created above.

<%= stylesheet_link_tag    "application" %>
<%= javascript_include_tag "application" %>


On an app with good front end conventions established, already using a method of asset bundling, etc. this isn’t a big task.

However I do find that because Rails has set such good conventions it’s hard for people to go too wrong. Of all the applications where I’ve taken over from another developer over the years. Rescue missions, etc. It’s the prospect of looking in the public/ directory that scares the bajaysus out of me.

Thankfully with all this great new front end stuff I’m hoping that in the future, rescue missions into interface land will suffer less casualties.

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