Generate boiler plate code for writing my own gem

Writing-Own-Gem

Thanks to Fabiano (original author and CTO @ magnetis)..This is just a copy of his work in medium and all the credits are to his work out there...
I'm just trying to make it available through github....!! TO see a complete simple CLI tool please visit gitub.com/DevAuto/Learn-Tech
------------------------------------------------------------------------------------------------------------------------------
In this article we will write a simple example inspired by one of the best Breaking Bad scenes. But apart of its simplicity, it is the same process to create a CLI for really anything you want.

Creating a new gem
Let’s get started by creating a new gem, that will make it easier to distribute our software, in this case the executable file.

To create a new gem, bundler has a handy command (bundler itself is crafted with Thor):

$ bundle gem --exe walter
This will generate a skeleton as follows:

 create walter/Gemfile
 create walter/lib/walter.rb
 create walter/lib/walter/version.rb
 create walter/walter.gemspec
 create walter/Rakefile
 create walter/README.md
 create walter/bin/console
 create walter/bin/setup
 create walter/.gitignore
 create walter/.travis.yml
 create walter/.rspec
 create walter/spec/spec_helper.rb
 create walter/spec/walter_spec.rb
 create walter/LICENSE.txt
 create walter/exe/walter
Now we need to add the Thor as a dependency to our project, open up walter.gemspec and add:

spec.add_dependency "thor", "~> 0.20"
We will also need to remove the TODO items in the gemspec file, so go ahead and edit the values for summary, description and homepage. Run the bundle install command and it is all setup to write some Thor lines.

Enter Thor
Open up lib/walter.rb and let’s add some code, first thing you need to require and inherit from Thor.

require 'walter'
require 'thor'
module Walter
 class CLI < Thor
   # ...
 end
end
Now, let’s add a simple hello world

class CLI < Thor
  desc "hello world", "my first cli yay"
  def hello
    puts "Hello world"
  end
end

Come on, hello world in 2017? Let’s make it a Hello Heisenberg!

class CLI < Thor
  desc "hello [name]", "say my name"
  def hello(name)
    if name == "Heisenberg"
      puts "you are goddman right"
    else
      puts "say my name"
    end
  end
end
We are almost there, last thing is to call our lib from the binary file.

The binary
The exe directive we used to create the gem, generated a walter binary at our project. First thing you need to do is to change the permissions so we can actually execute the file:

chmod +x exe/walter
Now, we are able to call it:

$ bundle exec exe/walter
This will give no output, but don’t worry. This is expected. Open up exe/walter in your favorite editor and let’s append this:

Walter::CLI.start(ARGV)
We are calling the CLI we just created, and passing the arguments received. Now let’s call it again:

$ bundle exec exe/walter
  walter hello [name]    # say hello
  walter help [COMMAND]  # Describe available commands or one specific command
Thor list all the commands this CLI has available, so sweet.

If you try to call our hello command without the name:

$ bundle exec exe/walter hello
ERROR: “walter hello” was called with no arguments
Usage: “walter hello [name]”
Yeah, it tell us how to use it. Making this in shell script would require some conditionals, but Thor has this built-in.

$ bundle exec exe/walter hello Heisenberg
you are goddman right.
Installing and publishing
To install the gem to your system, this way you can it it from anywhere:

$ rake install 
Call it:

$ walter hello Jesse
say my name
If you want to release it to rubygems, just run

$ rake release
The Ruby ecosystem is beautiful, isn’t it?

Conclusion
Thor makes daily scripts much more expressive and meaningful. It is a nice addition to a team that is already using Ruby as an official language, since all the team members can contribute to make your commands even better.

In our case, it was used to create commands to bring up kubernetes clusters and to deploy our app for the staging environment. You can use to automate some internal process or workflow you have in your company!

To finish this up, some final tips:

whenever possible try to use command methods that are common to other CLIs: init, status, new, create, update.
try to expose as CLI the least amount of methods possible, so you can encapsulate things that are only needed inside the code.
if you need to write some config file use $HOME/.<yourcli>