Beginner’s Guide: Creating Your First Ruby Project

Getting started with Ruby is quick if you follow a few simple steps. In this guide, you’ll install Ruby, scaffold a new gem project, write a tiny program, run tests, and produce a gem build.

I’ll keep it minimal and practical so you can get productive fast.

1) Install Ruby

• Using RVM (Ruby Version Manager, macOS/Linux):

curl -sSL https://get.rvm.io | bash -s stable
source ~/.rvm/scripts/rvm

• Install Ruby:

rvm install ruby --latest
rvm use ruby --default

• Verify:

ruby --version
gem --version
bundler --version

2) Create a new project

Ruby uses bundler for dependency management and project scaffolding.

• Gem library:

bundle gem my_gem
cd my_gem

This creates a basic structure:

my_gem/
├─ Gemfile
├─ lib/
│   └─ my_gem.rb
├─ my_gem.gemspec
└─ spec/
    └─ my_gem_spec.rb

3) Write your first program

Open lib/my_gem.rb and define a simple module:

module MyGem
  def self.greet(name = "Ruby")
    "Hello, #{name}!"
  end
end

Run it:

ruby -e "require_relative 'lib/my_gem.rb'; puts MyGem.greet"

4) Manage dependencies

If you add dependencies to Gemfile, install them:

bundle install

You generally won’t need this for the very first “hello world,” but it’s essential once you pull in libraries like HTTP clients or web frameworks.

5) Format your code

Install and use RuboCop:

gem install rubocop

• Lint:

rubocop

• Auto-fix:

rubocop -a

6) Add a simple test (RSpec)

Edit spec/my_gem_spec.rb:

require "my_gem"

RSpec.describe MyGem do
  it "greets with default name" do
    expect(MyGem.greet).to eq "Hello, Ruby!"
  end

  it "greets a custom name" do
    expect(MyGem.greet("World")).to eq "Hello, World!"
  end
end

Run tests:

bundle exec rspec
# or verbose:
bundle exec rspec -v

7) Build a gem

Build your gem:

gem build my_gem.gemspec

Test install:

gem install ./my_gem-0.1.0.gem

8) Check dependencies graph (nice debugging tool)

bundle viz

9) Optional: Lint with RuboCop

As mentioned, for more config:

rubocop --auto-gen-config

Visual overview

Here’s a simple flow of your first project:

 flowchart LR
  A[Install Ruby] --> B[bundle gem my_gem]
  B --> C[Edit lib/my_gem.rb]
  C --> D[ruby run]
  D --> E[bundle exec rspec]
  E --> F[rubocop]
  F --> G[gem build]
  G --> H[gem install]

What’s next?

• Explore popular gems:
  • Web frameworks: Sinatra, Rails
  • Testing: RSpec
  • HTTP client: Faraday
• Build a gem, a CLI tool, or a Rails app and publish it on RubyGems.

You’ve just created, tested, and built your first Ruby gem. Keep it small, iterate quickly, and enjoy the flexibility of Ruby.