create a simple gem using jeweler

So, you’ve come up with some awesome re-usable utility in ruby, and you want to use it across your projects. And you don’t want to copy/paste the files across different projects, cause that’s a pain and keeping all your re-usable code across the projects up to date is not feasible.

It’s obvious at this point that what you want is a gem, which would make sharing of code across your projects a breeze, with the added benefits of seamless upgrades. Hopefully this blog post will teach you how to create a simple gem in a few steps.

Gem creation is very easy if you use the right tools. If you go to ruby-toolbox.com you can see that there is more than one tool for gem creation and management. The top-most on this list is Jeweler, It is an awesome gem with a lot of nifty features which makes gem management a breeze.

OK, Enough talk let’s fight. The first thing which you need to do is install jeweler with the command [sudo] gem install jeweler

Once you have jeweler installed just follow the steps below to create your own gem:

  • Run the command jeweler fixnum_extensions in the directory where you want to create your your gem (fixnum_extensions here is the name of the gem).
  • With the above command jeweler creates a bunch of files and directories for your gem. One of the files which it creates is the Rakefile which has a lot of predefined tasks which you can use to manager your gems.
  • The file where you need to put your ruby code is lib/fixnum_extensions.rb my file has the code below in it:
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#This is a contrived example but it's fine
class Fixnum
  def add(number)
    number + self
  end
  def sub(number)
    number - self
  end
  def mul(number)
    number * self
  end
  def div(number)
    number / self
  end
end

  • Now you need to open up the Rakefile and add a description and summary instead of the TODOs.
  • Note that it fills up the author name and email by looking at your git configuration files, it also creates a git repository with a nice .gitignore file and makes the initial commit.
  • The last thing you need to do before building your gem is create a VERSION file, to do this just run rake version:write. This command creates a VERSION file in your gem’s root folder which holds the version number of your gem.
  • Finally, to build our gem run rake build (ignore the warnings when you run this command). This will create a folder called pkg which holds your final gem file fixnum_extensions-0.0.0.gem.

Now, you can share this gemfile with anyone you want and they’ll get all your code in a nice gem package. To install it, just run the command gem install pkg/fixnum_extensions-0.0.0.gem

To test it out open an irb session and run the following commands

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require 'rubygems'
require 'fixnum_extensions'
1.add(2).mul(3)

Jeweler adds a lot of nifty tasks which are great, to check them out just run rake -T

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