Make your own gem

From start to finish, show you how to package your Ruby code in a gem
First we’re going to create a simple gem called hello that generates a hello world

$ bundle gem hello
     create  hello/Gemfile
      create  hello/Rakefile
      create  hello/.gitignore
      create  hello/hello.gemspec
      create  hello/lib/hello.rb
      create  hello/lib/hello/version.rb
Initializating git repo in /Users/mert/....

we’ll walk you through some of the generated files, starting with the hello.gemspec file.

# -*- encoding: utf-8 -*-  
$:.push File.expand_path("../lib", __FILE__)  
require "hello/version"  

Gem::Specification.new do |s|  
  s.name        = "hello"  
  s.version     = Hello::VERSION  
  s.platform    = Gem::Platform::RUBY  
  s.authors     = ["TODO: Write your name"]  
  s.email       = ["TODO: Write your email address"]  
  s.homepage    = ""  
  s.summary     = %q{TODO: Write a gem summary}  
  s.description = %q{TODO: Write a gem description}  

  s.rubyforge_project = "hello"  

  s.files         = `git ls-files`.split("\n")  
  s.test_files    = `git ls-files -- {test,spec,features}/*`.split("\n")  
  s.executables   = `git ls-files -- bin/*`.split("\n").map{|f| File.basename(f) }  
  s.require_paths = ["lib"]  
end 

We can see straight away by looking at the TODO items that this file is designed to be edited directly. Once we complete these items we’ll have a working Gemspec file.

Now we are going to modify our hello file.

require "hello/version"
require 'hello/translator'

module Hello
  def self.hi(language = "english")
    translator = Translator.new(language)
    translator.hi       
  end
end

The Translator is now in lib/hello, which can easily be picked up with a require statement from lib/hello.rb. The code for the Translator:

class Hello::Translator
    def initialize(language)
        @language = language
    end

    def hi
        case @language
        when "spanish"
            "hola mundo"
        else
            "hello world"
        end
    end
end

Now you can build a gem from it. Then you can install the generated gem locally to test it out.

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

$ gem install ./hello-0.0.0.gem
    Successfully installed hello-0.0.1
    1 gem installed

Of course, the smoke test isn’t over yet: the final step is to require the gem and use it:

$ irb
    >>require 'hello'
    => true
    >>Hello.hi
    =>Hello world!
    >>Hello.hi("spanish")
    =>hola mundo

Bundler is a great solution for creating and managing gems.

https://github.com/yuzdeyuzmert/hello-gem