How Do I Create And Publish My First Ruby Gem?

What’s a Ruby Gem?

To solve various problems with Ruby, you might develop your own libraries. Also, you might want to open-source your libraries to get help from the Ruby community and have many developers working on the same.

A gem is a packaged Ruby application or library. RubyGems is the standard way to distribute Ruby applications and libraries and is available to you after you have downloaded and installed Ruby 1.9+.

Let us create a simple Ruby library

Let’s first create a simple library that extends the String class and store this in a file called my_string_extend.rb¹ in the folder my_string_extend/lib. The lib folder will contain the Ruby code related to the library:

# my_string_extend.rb
class String
  def writesize
    self.size
  end
end

The library opens up the String class and adds a method writesize (which returns the size of the string).

For open-source applications, the gem server to use for your applications is the one provided at https://rubygems.org/. This is where users will look, and is where gem will also look by default when you issue a gem install command. Please make sure that the name of your gem isn’t in use already. Type:

$ gem list -r my_string_extend

*** REMOTE GEMS ***

Observe that no gem of the name my_string_extend exists. We are safe! Now let us now turn our library into a gem, so that one can use it anywhere.

Steps for publishing our gem

1. Update to the latest RubyGem – In the folder my_string_extend open a command window and type:

$ gem update --system

2. Create an account on RubyGems.org – http://rubygems.org/sign_up and confirm your email. Later on, you’ll need to provide your login credentials the first time you push a gem to the server.

3. Create a Gem Specification – In the folder my_string_extend copy the following file my_string_extend.gemspec and edit it as per your needs:

Gem::Specification.new do |s|
  s.name        = 'my_string_extend'
  s.version     = '0.0.1'
  s.date        = '2011-10-27'
  s.summary     = "String Extend"
  s.description = "The library opens up the String class and adds a method writesize, which returns the size of the string."
  s.authors     = ["Satish Talim"]
  s.email       = ["satish@rubylearning.org"]
  s.homepage    = "http://rubylearning.org/"
  s.files       = ["lib/my_string_extend.rb"]
end

The gemspec defines what’s in the gem, who made it, and the version of the gem. The gemspec is a chunk of Ruby code that the gem command will read and execute to understand our app, such as its name, files, and dependencies. It’s also our interface to RubyGems.org, all the information you see on a gem page comes from the gemspec.

4. Once we have our gemspec, we have to build a gem from it. In the folder my_string_extend type:

$ gem build my_string_extend.gemspec
  Successfully built RubyGem
  Name: my_string_extend
  Version: 0.0.1
  File: my_string_extend-0.0.1.gem

We can then install it locally to test it out:

$ gem install ./my_string_extend-0.0.1.gem
Successfully installed my_string_extend-0.0.1
1 gem installed
Installing ri documentation for my_string_extend-0.0.1...
Installing RDoc documentation for my_string_extend-0.0.1...

Lets require our gem and use it:

$ irb --simple-prompt
>> require 'my_string_extend'
=> true
>> puts "Hello".writesize
5
=> nil
>> quit

5. Now publish our gem out to RubyGems.org. In the folder my_string_extend type:

$ gem push my_string_extend-0.0.1.gem
Enter your RubyGems.org credentials.
Don't have an account yet? Create one at http://rubygems.org/sign_up
   Email:   satish@rubylearning.org
Password:

Pushing gem to https://rubygems.org...
Signed in.
Pushing gem to https://rubygems.org...
Successfully registered gem: my_string_extend (0.0.1)

In just a few moments (usually a minute), your gem will be available for installation by anyone:

$ gem list -r my_string_extend

*** REMOTE GEMS ***

my_string_extend (0.0.1)

Here’s our Ruby gem on the RubyGems.org site

That’s it.

Credits: This article has been adopted from Nick Quaranto’s article on RubyLearning – Gem Sawyer, Modern Day Ruby Warrior. RubyGems further adopted this article – Make your own gem.