hello_meleu

A useless gem created for the sole purpose to show people how to create a Ruby Gem and publish it to https://RubyGems.org.

In this README I describe 3 simple steps to create a Ruby Gem.

IMPORTANT: if you want to follow along and create your own gem you'll need to use a different name than hello_meleu!

• Step 1: very minimum files you need for a gem
• Step 2: add metadata with useful links
• Step 3: add documentation
• Final Words

The very minimum you need to create a Ruby Gem and publish it to RubyGems.org is a file structure like this:

hello_meleu/
├── hello_meleu.gemspec
└── lib
    └── hello_meleu.rb

The lib/hello_meleu.rb is as simple as this:

class HelloMeleu
  def self.hello
    'Hello meleu!'
  end
end

The very minimum you need for your .gemspec is something like this:

Gem::Specification.new do |s|
  s.name = 'hello_meleu'
  s.authors = ['meleu']
  s.files = ['lib/hello_meleu.rb']
  s.summary = 'Greeting meleu'
  s.version = '0.0.1'
end

The most important field here is the s.files, as this is an array with the name of the source file(s) we want to distribute in our gem. In our case here it's just one file, then we have an array with only one string: ["lib/hello_meleu.rb"].

In the official documenation you can see the details of all these fields. Another reading that I found enlightening was this article by Piotr Murach.

These two files (the .rb code and the gemspec) are enough to build and publish our gem!

# building your gem
gem build hello_meleu.gemspec
# this creates the hello_meleu-0.0.1.gem file

# publish your gem to RubyGems.org
gem push hello_meleu-0.0.1.gem
# in the first run it'll give you instructions
# to create a RubyGems.org account

🎉 Yay! We published our gem at https://rubygems.org/gems/hello_meleu.

Now you can even install it:

gem install hello_meleu

# now launch irb, require 'hello_meleu'
# and execute `HelloMeleu.hello`

• Link to the commit.
  • NOTE: in this first commit I also created a .gitignore file (it's not needed for a Ruby Gem, but useful when working with git repositories). The file was created via https://gitignore.io.

We want our gem to be open source, right! We want to share the code to the world and hopefully receive contributions from the community.

A cool thing to do is to add a link to the project's repo in our gem's page at RubyGems.org.

So, let's enrich our hello_meleu.gemspec with the following content:

Gem::Specification.new do |s|
  # ...
  s.version = '0.0.2'

  s.homepage = 'https://github.com/meleu/hello_meleu'
  s.metadata = {
    'bug_tracker_uri' => "#{s.homepage}/issues",
    'changelog_uri' => "#{s.homepage}/releases",
    'wiki_uri' => "#{s.homepage}/wiki",
    'source_code_uri' => s.homepage,
  }
end

You can see that I specified the homepage of the gem as the github repository, and then added some other useful links to report bugs, check release notes, wiki, etc.

Have you noticed that I bumped the version to 0.0.2? Although we didn't change anything in our gem's logic, we need to bump the version. This is needed because once we publish a specific version, we cannot change it anymore!

Once we added those links to our gemspec, let's publish our gem again:

# build the gem
gem build hello_meleu.gemspec

# publish a new version
gem push hello_meleu-0.0.2.gem

Now go the gem's page and check those links the right sidebar! That's cool, isn't it? :)

• Link to the commit

A nice practice developers have is to document their libraries so other developers can know how to use them. Here we are going to document our code adding top-level documentation comments. Like this:

# Class used to greet meleu with "hello".
class HelloMeleu
  # Greets meleu with "hello".
  #
  # @return [String] "Hello meleu!"
  def self.hello
    'Hello meleu!'
  end
end

You may be thinking: will other developers using my gem really open each source file and read these comments?!

Yeah... probably not...

But there's a cool thing that RubyGems.org does for us...

Let's add the documentation_uri to our gem's metadata:

Gem::Specification.new do |s|
  # ...
  s.version = '0.0.3'

  s.metadata = {
    # ...
    'documentation_uri' => 'https://www.rubydoc.info/gems/hello_meleu'
  }
end

The link in documentation_uri is a cool service provided by RubGems.org, where it automatically create a documentation site for our gem. And yeah! The service read the top-level documentation comments in our code and our gem will have a neat documentation website!

Let's publish a new version and check it:

# build the gem
gem build hello_meleu.gemspec

# publish a new version
gem push hello_meleu-0.0.3.gem

Now go the gem's page and look for the Documentation link in that right sidebar. Click on it and you'll see the documentation website you have for your gem. Note that your comments are there, documenting your class and method.

• Link to the commit

Of course there are more to say about maintaining a Ruby Gem, but I hope you now can see that it's really easy to get started! :)

Happy coding!