Create a Rails 4.0 beta application
Rails 4.0 is not a stable version yet and there is not official gem available so you must set it to get it from the master branch.
Rails 4.0 require ruby 1.9.3
git clone https://github.com/rails/rails.git
Now let's install Rails dependencies
cd rails bundle
You will probably get
Bundler could not find compatible versions for gem "bundler": In Gemfile: rails (>= 0) ruby depends on bundler (< 2.0, >= 1.2.2) ruby Current Bundler version: bundler (1.1.4) This Gemfile requires a different version of Bundler. Perhaps you need to update Bundler by running `gem install bundler`?
If you do, you would must run
gem install bundler --pre bundle
Now we are ready to create a rails 4 application
Must specify --edge (master branch)
railties/bin/rails new NEW_APP_PATH --edge
Now you have your Rails 4.0 beta app ready