I've been an advocate of open source for a long time. First via software that I used, like Mozilla's Firefox, and later though consuming open source code and contributing back to it. I've used open source code on a number of platforms over the years including PHP, Java, .NET, and Ruby on Rails.

Out of the platforms that I have used, I believe Rails has the most accesible open source ecosystem because it enables consumption and contribution better than most other platforms.

This post will be my attempt at describing a developer's work flow when using open source with Ruby on Rails.


The first step to consuming open source to use on a Rails project is discover existing open source libraries, called gems in Ruby, to solve a problem that you encounter while building your application.

There are number of screencast sites, podcasts, and mailing lists out there that highlight useful gems and how to use them.
Here's a few that I use:

Most gems are hosted via This site also maintains a search index with links to source and documentation for any gems
hosted there.

GitHub is also a good place to discover gems via search.

Some key criteria that I look for in a gem that I'm considering for use in a production
application are the following:

  • Publically Hosted on GitHub
  • Recent commits within the last 3 months
  • A high number of Forks/Watchers
  • A low number of currently open Pull Requests.

These are just my personal guidelines, so feel free to relax them as you see fit. For side projects to hack on,
you can (and should) be a lot more willing to try more experimental gems.

Installing Gems with Bundler

Once you've identified a few gems that you'd like to use, the standard
recommendation is to use Bundler to manage your external gems.

Bunder is a dependency management gem that uses a manifest file called a GemFile that lists out the gems in the root of your project.

To add a dependency in the simplest way, edit your Gemfile and add a line similar the following line to add the Carrier Wave gem.

gem 'carrierwave'  

Once you've updated your Gemfile, run 'bundle install' to have Bundler pull down your gems and install them for use in your app.

Adjusting your versions

In the course of using your gem, you may find that you need to use a different version than the current version published on

To go back to an older published version of the gem, you can adjust your Gemfile like below.

gem 'carrierwave', '0.5.4'  

After updating your GemFile, run 'bundle update ' to force Bundler to reinstall the gem using the correct version.

If you're feeling more adventurous, or simply want to test the most current code for the gem with your app, you can point directly to its public git repository by putting this in your GemFile.

gem 'carrierwave', :git => 'git://'  

Finally, if you've cloned the gem's source code locally, you can point to a local directory for the gem here.

gem 'carrierwave', :path => "~/Projects/carrierwave/"  

Forking to fix

If you find that the gem you are using contains a bug, and the gem's code is on GitHub, it's very easy to attempt a bug fix and test it locally in your application.

The first step is to fork the gem's repository using your GitHub account.

Then clone your fork locally.

cd ~/Projects  
git clone  

Next, point your application to your locally cloned Git repository for your fork of the gem which contains the bug.

gem 'carrierwave', :path => "~/Projects/carrierwave/"  

Now you're all set to edit your local clone of the gem and fix it.

If you're using your application to test your fix, you'll need to run 'bundle update ' to rebundle the gem into your application whenever you make changes.

Because this can sometimes be a slow process, I advise writing tests within the gem's source code first before bundling into your app for integration testing.

Once you've fixed the gem, you can commit your fix, and push to your fork on GitHub.

git commit -am 'Fixing this gnarly bug'  
git push origin master  

Then you can modify your application's GemFile and point to your GitHub
fork of the gem:

gem 'carrierwave', :git => 'git://'  

From here, you could continue to maintain your fork and keep it up to date with the latest changes from the original gem's repository. While you can certainly choose to go this route, I would recommend contributing back the fix with the eventual goal of deleting your fork.

Contributing back

So now that you've fixed the code in the gem, you're back to cruising along on your app. Why not make the fix available for anyone else using the gem? GitHub makes this process easy.

Browse to your fork on GitHub and click the Pull Request button.

Fill in some details about the fix you've made. Submit the pull request and wait for feedback from the project maintainers. If they accept your pull request then your fix
will make it into the master repository instantly.

If your fix is accepted and later incorporated in the next published version of the gem, I recommend moving your application back to the published gem and deleting your fork on GitHub.

While you can leave your fork out there, if you're not actively maintaining it, you're likely to confuse anyone else looking for the source code of the gem. Unmaintained forks are just unnecessary noise on GitHub, and I don't suggest keeping them around.


I hope this post gave you a good start on how to contribute to open source while building applications in Ruby on Rails.

You don't have to be an expert to start contributing to open source. All you need is the right tools and a little bit of knowledge on how to get started. It's a great feeling to watch your first pull requests get accepted into your favorite open source project and realize that you've just given back.

I've used a lot of open source in the past, but only recently have I felt confident enough to start contributing back. I'm glad I did, as it's great feeling to give back in some small way to projects that have saved me countless hours while building applications. I hope that I've inspired you to do the same.

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