Creating your own Gem

1. Run this command in your Terminal. This creates and names all the files you need for your gem. We are going to create a Lorem Ipsum Generator; you can call it whatever you want but seeing as we are creating a Lorem Ipsum generator we'll call it lorem. Read about gem naming conventions.

    $ bundle gem lorem
   

   Notice that this command also initialized a git repository for you on your local machine and gives you the path name for it.

2. cd into lorem. Make your lorem.gemspec file look like this. Add your name and your email. Read more about the gemspec file.

    \# coding: utf-8
    lib = File.expand_path('../lib', __FILE__)
    $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
    require 'lorem/version'
   
    Gem::Specification.new do |spec|
        spec.name          = "lorem"
        spec.version       = Lorem::VERSION
        spec.platform      = Gem::Platform::RUBY
        spec.authors       = ["your name"]
        spec.email         = ["your@email.com"]
        spec.homepage      = ""
        spec.summary       = %q{Jenipsum generator}
        spec.description   = %q{Generates jenipsum text}
        spec.license       = "MIT"
   
        spec.add_development_dependency "bundler", "~> 1.3"
        spec.add_development_dependency "rake"
   
        spec.files         = `git ls-files`.split($/)
        spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
        spec.executables   = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
        spec.require_paths = ["lib"]
   
    end
   

   If you neglect to change these areas you will get this error when you go to run $ gem build lipsum.gemspec

    ERROR:  While executing gem ... (Gem::InvalidSpecificationException) "FIXME" or "TODO" is not a description
   

3. Open your file lib/lipsum.rb Make it look like this. This is the file that is loaded when people require your gem. You can customize it with the behavior you want it to have.

    require "lipsum/version"
       
    module Lipsum
        def self.ipsum
            "Lorem ipsum bespoke flexitarian bitters, non next level consequat stumptown  
            pork belly selfies sartorial. Laborum vegan excepteur ad, hashtag id non.  
            Eiusmod Tonx squid intelligentsia biodiesel art party YOLO bicycle rights  
            fashion axe, +1 roof party non quis do. Trust fund nesciunt odio, mustache  
            Terry Richardson Odd Future vinyl thundercats kogi placeat cliche put a bird  
            on it aliquip lo-fi. Pickled hashtag bitters american apparel fanny pack tempor.  
            Accusamus pork belly do Williamsburg nihil, salvia eiusmod tattooed excepteur  
            in street art. Meggings Tonx forage occaecat magna tote bag."
        end
    end
   

4. Run this command.

    $ gem build lipsum.gemspec
   

Congratulations, you have created a gem.

Now you can add Thor.

Here are some good resources if you have questions.
Video tutorial that will explain all the files and file structure.
This is Bundler's Tutorial
RubyGems Guides