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Guides - Migrating from MRI to Rubinius

This guide will assist you to migrate your Ruby or Rails application from MRI (Matz's Ruby Implementation) to Rubinius. This guide assumes that you are familiar with Ruby or Ruby or Rails, RubyGems, and Bundler. It also assumes that you can use the command line shell.

1. Installing Rubinius

The first step in migrating to Rubinius is to install Rubinius. Since you will likely need to switch back and forth between MRI and Rubinius while migrating, the easiest approach is to use a Ruby switcher utility.

The chruby command line tool for switching between Ruby implementations is recommended for use with Rubinius. All examples in the guides will use chruby.

Installing chruby and ruby-install

If you are using OS X, the easiest way to install chruby and ruby-install is to use the Homebrew package manager as follows:

$ brew update
$ brew install chruby ruby-install

If you are not using Homebrew or are using a different operating system than OS X, please see the the following:

  1. chruby install instructions
  2. ruby-install install instructions

Enabling chruby

To enable chruby, add the following to the ~/.bashrc or ~/.zshrc file:

source /usr/local/opt/chruby/share/chruby/chruby.sh

See the documentation for more configuration instructions.

Using ruby-install

Once you have installed the ruby-install utility, installing Rubinius is straightforward:

$ ruby-install rbx 2.2.6

For instructions for installing other Ruby implementations, please see the ruby-install installation synopsis.

Using chruby

Now that Rubinius is installed, you can make it active with the following command:

$ chruby rbx

2. Gems

Most gems that run on MRI should run on Rubinius, with the exceptions noted below. Additionally, Rubinius makes many components of the system available as gems. These include the Rubinius tools for parsing and compiling Ruby code, the Ruby debugger and profiler, and the Ruby standard library. All these gems are pre-installed when you install Rubinius.

C-extension Gems

Many gems that use C-extensions run fine on Rubinius. The exceptions are ones that rely on MRI internal data structures. These gems cannot be supported on Rubinius and include gems like ruby-debug and ruby-prof. Rubinius provides its own Ruby source debugger and profiler, as well as other tools. See the tools documentation for more details.

3. Gemfiles

Your Gemfile should work fine with Rubinius but you should run bundle update to force the gem dependencies to be recomputed for Rubinius. Also, if you are using gems that are incompatible with Rubinius, you can put them in a platforms block until completing the migration to Rubinius as follows:

# Example platforms block for MRI-specific gems
platforms :mri do
  gem 'ruby-prof'
  gem 'ruby-debug'
end

4. Compatibility Issues

Rubinius created the RubySpec project, and continually enhances it, to describe the behavior of Ruby and monitor compatibility with MRI.

With few exceptions, Rubinius is expected to be compatible with MRI 2.1. Some features, like keyword arguments, are not yet implemented. Other features may not be implemented because they are unknown and no RubySpecs exist for the feature yet. Several standard library components, including Continuation, Ripper, TracePoint, and Tracer, are not yet implemented but may be in the future.

If you encounter an incompatible behavior in Rubinius compared to MRI, it's most likely a bug. Please open an issue for it.

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