This post refers to exercise 46 in the book Learn Ruby the Hard Way. Here is the work flow for building a simple Ruby gem:

• Build a project skeleton. Example of a simple project skeleton:

Rakefile	data		ext		hello.gemspec	tests
bin		doc		hello-1.0.gem	lib

./bin:
hello

./data:

./doc:

./ext:

./lib:
hello.rb

./tests:
test_hello.rb

• Write some code to the /lib directory. I just wrote a simple Ruby function.

• Put a script in the /bin directory. I wrote one line of Ruby code.

• Get the script running. This part required adding execute permissions to the file. I went one step further and moved the script file to /usr/local/bin/ directory and created an alias for the $PATH. This mean’t I could I could just type the filename (in this case hello) to invoke the Ruby script.

• Make sure the details in the gemspec file are correct.

• Build the gem.

wickinot:ex46-scriptexercise wickinot$ gem build hello.gemspec
  Successfully built RubyGem
  Name: hello
  Version: 1.0
  File: hello-1.0.gem

• Install the gem.

wickinot:ex46-scriptexercise wickinot$ gem install ./hello-1.0.gem
Successfully installed hello-1.0
Parsing documentation for hello-1.0
Installing ri documentation for hello-1.0
Done installing documentation for hello after 0 seconds
1 gem installed

• Check if everything works by ‘requiring’ the newly created gem and using it in the Ruby console.

wickinot:ex46-scriptexercise wickinot$ irb
2.5.1 :001 > require 'hello'
 => true 
2.5.1 :002 > Hello.hi
Hello, World!
 => nil 
2.5.1 :003 > 

References I found helpful for this exercise are: https://commandercoriander.net/blog/2013/02/16/making-a-ruby-script-executable/ https://guides.rubygems.org/make-your-own-gem/

What are the .gemspec and gemfiles?

Gemfile

When developing an app it is important to declare which version of a gem to use and to declare the dependency of the app on that particular gem - This is specified in the gemfile (for example in a Rails app) so the bundler tool knows exactly where to look for the gem.

.gemspec file

The .gemspec file contains all the necessary information for a Gem. It contains a list of dependencies including information about where to find them.

A break down of what each of these .gemspec attributes is as follows:

• spec.name: This is the gem’s name.
• spec.version: The gem’s version.
• spec.authors: The developer(s) name.
• spec.email: The developer(s) email.
• spec.summary: A short description of the gem.
• spec.description: A longer description of the gem.
• spec.homepage: The domain name of the gem.
• spec.license: The license for the gem.

There are further gemspec attributes you can use which can be found RubyGems.org. Another resource I found helpful in getting my head around this was Yehuda Katz’s blog post on this topic found here.