The structure of a Gem:

 The Bin folder:

    your_gem/
   |-- bin/

• The bin directory: Holds any binaries that we want
  to distribute with our gem. Usually an 'executable' file;
  which loads the user’s PATH when the gem is installed.
    
• An 'Executable' is an operating system command, 
  like the 'bundler' command in the shell.

The structure of a Gem:

 The Bin folder

• Calling them ‘binaries’ is not quite right, since most
  of the time, they are just Ruby scripts, starting off
  with a ‘shebang line' --which initiates the executable:
  
  

  #!/usr/bin/env ruby
    begin
      require 'your_gem'
    rescue LoadError
      require 'rubygems'
      require 'your_gem'
    end
    #more code goes here

The structure of a Gem:

What are  'binaries'?

• 'Binaries' are executable files from machine
  code that have been compiled. That's the kind of
  thing that happens with programs like C or C+. 
  
  
• Ruby is a different animal. We never compile the
  code in Ruby --it's dynamic. So the bin folder holds
  executable ruby scripts; that will be loaded by the
  Ruby interpreter. 

The structure of a Gem:

 The lib folder:

  your_gem/
  |-- bin/
  |-- lib/|
  |   |-- your_gem.rb
  |   |-- your_gem/
 

• The lib directory: All the code for the gem
  is under the lib/ directory.
• This directory gets added to your  $LOAD_PATH and
  contains two things:
    • A ruby file with the name of the gem ( your_gem.rb ) 
  

    • A directory of the gem’s name  ( your_gem/ ). 

The structure of a Gem:

 The lib folder:

  your_gem/
  |-- bin/
  |-- lib/
  |   |-- your_gem.rb
  |   |-- your_gem/
  |   |   |-- source1.rb
  |   |   |-- source2.rb
 

• If there were more files in lib/your_gem,
  they’d be required here, too.
  
  
• Why?  So that you can break up the project 
  into as many files as you want, name them 
  whatever you want and nobody gets hurt.
  

The structure of a Gem

The Rakefile:

  your_gem/
  |-- bin/
  |-- lib/
  |   |-- your_gem.rb
  |   |-- your_gem/
  |   |   |-- source1.rb
  |   |   |-- source2.rb
  |-- | spec/
  |-- README
  |-- Rakefile
 

• The Rakefile: Most gems have a Rakefile,
  which the rake program uses to automate tests,
   generate code, and perform other tasks.
  ‘rake’ is just Ruby’s ‘make’ program.

The structure of a Gem

 
To download and install ‘rake’

  gem install rake

• Rakefile is extremely useful. 
  It can hold various tasks to help build,
  test and debugg your gem.

The structure of a Gem

The gemspec:

  your_gem/
  |-- bin/
  |-- lib/
  |   |-- your_gem.rb
  |   |-- your_gem/
  |   |   |-- source1.rb
  |   |   |-- source2.rb
  |-- | spec/
  |-- README
  |-- Rakefile
  |-- your_gem.gemspec
 

• The gemspec: As the name implies
  —contains all the gem’s specification by defining
  several attributes. It’s got the gem’s files, name,
  version, summary, author info and email, and homepage.

The structure of a Gem

The Specification class contains the info for a Gem:

 Gem::Specification.new do |s|
  s.name              = ‘your_gem’
  s.version           = ‘0.1.0’
  s.platform          = Gem::Platform::RUBY
  s.summary           = "Sample gem"
  s.description       = "The big takeaway about the gem!"
  s.authors           = ["Girl Coder"]
  s.email             = ["girl_coder@gmail.com"]
  s.homepage          = "http://github.com/girl_coder/your_gem"    
  s.required_rubygems_version = ">= 1.9.3"

  # If you have runtime dependencies, add them here
  s.add_runtime_dependency ‘launchy’, ‘~> 1.2"

  # If you have development dependencies, add them here
  s.add_development_dependency "rspec", "-> 2.5.0"
  
  # The list of files to be contained in the gem
  s.files         = `git ls-files`.split("\n")
  s.executables   = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) }
  # s.extensions    = `git ls-files ext/extconf.rb`.split("\n")
  s.require_path = 'lib'

end