Getting started with Rails 3 using RVM

An article by Pedro Sampaio    3 Comments

In this post, I will show you how to get Rails 3 running with RVM.

Installing Rails

This a “chicken and egg” kind of problem. You’ll need to add Rails to your Gemfile, and use bundler. But until you install Rails, you won’t have access to the rails command. As of this writing, rails’ latest version is beta 4, so you will need to run the following command.

$ gem install rails --version "3.0.0.beta4"

Creating the application

Now that we have Rails installed, we can execute the rails new command.

$ rails new sample_app --skip-testunit --skip-prototype

This will create your Rails 3 application. As you can see from the command options, we skipped generating the test folder and the prototype files. The reason for this is that I use Rspec and jQuery, so there’s less cleanup to do. You can see other possible command options by executing this command:

$ rails --help

Using RVM

RVM has a really cool concept of gemsets. From the documentation:

RVM gives you compartmentalized independent ruby setups. This means that ruby, gems and irb are all separate and self-contained from system and from each other. You may even have separate named gem sets.

We will create a .rvmrc file in our application dir, and use an isolated gemset for our app, like so:

$ echo "rvm ruby-1.8.7@sample_app" > .rvmrc

Now we have a clean gemset to use with out application. You can change the ruby version to whatever you like, for instance, to 1.9.2 or head. To actually create the gemset, you can either do it manually

$ rvm gemset create "sample_app"

or export the following flag in .rvmrc:

$ rvm_gemset_create_on_use_flag=1

This way, when you change to the application directory, RVM will pick up the .rvmrc file and automagically switch to the sample_app gemset. All you need to do now is bundle install and you’re off to go.