Rails 4.0 development has started a while back. It was merged into Rails’ master branch on Github in 2011. As the writing of this blog entry, the stable version of Rails is 3.2.8. Release candidate is at 3.2.9.rc1. Because 4.0 is not yet official available, you have to jump through hoops to get a Rails 4 application up and running.
Create this Gemfile:
source 'http://rubygems.org' gem 'rails', :git => 'git://github.com/rails/rails.git' gem 'uglifier', '>= 1.0.30' gem 'activerecord-deprecated_finders', :git => 'git://github.com/rails/activerecord-deprecated_finders.git' gem 'journey', :git => 'git://github.com/rails/journey.git'
In the same directory of the Gemfile, issue
bundle install. This should install Rails 4.0.0.beta.
gem list rails won’t show 4.0 being installed. So do this instead:
zlu@zlu-mba:~/projects/test$ bundle show rails /Users/zlu/.rvm/gems/ruby-1.9.3-p0/bundler/gems/rails-4e23c0ef341c
The Rails executable is at:
`bundle show rails`/railties/bin/rails
`bundle show rails`/railties/bin/rails -v should show: Rails 4.0.0.beta
Now you can use this version of rails to generate an app named foo.
`bundle show rails`/railties/bin/rails new foo
This command creates a typical rails app called foo and output an error about not being able to find Rails 4 gem, which should not be a surprise.
You will edit foo/Gemfile to make
bundle install work.
Add the two gems Rails depends on:
gem 'journey', github: 'rails/journey' gem 'activerecord-deprecated_finders', github: 'rails/activerecord-deprecated_finders'
Change the source definition for the following gems:
gem 'rails', '4.0.0.beta' gem 'sass-rails', '~> 4.0.0.beta' gem 'coffee-rails', '~> 4.0.0.beta'
gem 'rails', github: 'rails/rails' gem 'sass-rails', github: 'rails/sass-rails' gem 'coffee-rails', github: 'rails/coffee-rails'
Now you should be
bundle install, sit back and enjoy your new Rails 4.0 app.