Working with gems in Ruby

Apr 20, 2023 · 6 min read

programming

Ruby is a high-level, dynamic, and object-oriented programming language designed to be easy to read and write. Ruby is used for various applications, such as web development, scripting, and creating domain-specific languages.

If you are programming with Ruby, you will come across gems! Not the mineral or crystalline kind though. In Ruby, a "gem" is a package or a library that contains pre-written, reusable code to provide specific functionality or features. Gems are distributed and managed through RubyGems, a package management system specifically designed for Ruby. With RubyGems, developers can easily search, install, and update gems in their projects. RubyGems is included by default with Ruby installations from version 1.9 onwards.

The components of a Ruby gem

A Ruby gem consists of several components that work together to provide the desired functionality.

Here's an overview of the key components typically found in a gem:

Gemspec (.gemspec) file: This file contains metadata about the gem, such as its name, version, author, and a summary of its purpose. It also specifies dependencies on other gems, if applicable. The gemspec file is the core of the gem package and is required for building and distributing the gem.
lib/ directory: This is the main directory containing the Ruby source code files for the gem. The code is organized into modules and classes, providing the functionality that the gem offers.
bin/ directory (optional): This directory may contain executable files that can be run as standalone scripts or commands. These files are usually command-line interfaces for the gem or utilities related to the gem's functionality.
test/ or spec/ directory (optional): This directory contains the test suite for the gem, which is used to verify the correctness of the gem's code. Test suites are typically written using testing frameworks like RSpec or Minitest.
README file (optional): The README file provides documentation for the gem, including instructions for installation, usage, and configuration. It is often written in Markdown or plain text format.
Rakefile (optional): A Rakefile is used to define tasks related to the gem, such as building, testing, or deploying the gem. Rake is a Ruby-based build tool similar to Unix's make utility.
License file (optional): This file contains the gem's license information, specifying the terms under which the gem can be used, modified, or distributed.
Changelog file (optional): The changelog is a record of changes made to the gem over time, typically including bug fixes, new features, and improvements. This file helps users understand the differences between different versions of the gem.
These components work together to create a cohesive package that can be easily distributed, installed, and used in Ruby projects. By adhering to the standard gem structure, developers can ensure compatibility and ease of use for the Ruby community.

Popular gems in Ruby

Here is a list of some popular gems, along with their functionality.

Bundler: A dependency manager for Ruby that helps maintain a consistent environment for Ruby projects by tracking and installing the precise gems and versions required for each project.
JSON: A lightweight data-interchange format widely used for transmitting data between servers and web applications.
Devise: An authentication solution for Ruby on Rails that simplifies the process of managing user logins for websites.
Rails: A gem used to build robust, full-stack web apps.
Nokogiri: A gem that makes it easy to parse, build, and search HTML and XML documents.

How to use gems in Ruby applications

Working with gems in Ruby is straightforward. To use a gem in a Ruby application, you first need to install it using the gem command.

Use the following command to install any gem on your local machine.

gem install name_of_gem

Furthermore, run the following command to display previously installed gems.

gem list

Once the gem is installed, you can include it in your code using the ‘require’ statement. For example, to use the gem_name gem in your Ruby application, you would include the following line at the top of your file:

require 'gem_name'

How to create a Ruby gem

Follow these steps to create a simple Ruby gem.

The first step involves choosing a unique name for your gem. When naming your gem, ensure it's unique by checking with RubyGems to avoid naming conflicts.
After that, create a new directory that will hold your gem's files. You can create a new directory using the following command:
mkdir my_gem
Initialize a new gem project by running the bundle gem command followed by the name of your gem. For example, to create a new gem called my_gem, you can run the following command:
bundle gem my_gem
Edit the gemspec file to include information about your gem, including its name, version, and dependencies.
Create the necessary directories and files for your gem's functionality, such as a lib directory for your gem's code and a spec directory for tests.
Write the code for your gem's functionality, and add any necessary tests to the spec directory.
Once your code is complete, build your gem by running the gem build command followed by the name of your gemspec file. For instance, you may run the following command:
gem build my_gem.gemspec