Ruby Bundler

Key Bundler Features

gem 'sinatra'

sinatra (3.0.5)

bundle install

bundle update

🔹 Creating a Gemfile

The Gemfile lists all gems your project needs. Create it in your project root directory and specify gem names with optional version constraints for better dependency control.

# Gemfile
source 'https://rubygems.org'

# Specify exact version
gem 'rails', '7.0.4'

# Allow minor updates
gem 'puma', '~> 6.0'

# Any version
gem 'rake'

# Development only
group :development do
  gem 'pry'
end

🔹 Installing Dependencies

Use bundle install to download and install all gems listed in your Gemfile. Bundler creates a Gemfile.lock file that records exact versions for consistent installations across environments.

# Install all gems
bundle install

# Short version
bundle

# Install to specific path
bundle install --path vendor/bundle

# Skip production gems
bundle install --without production

🔹 Using Bundler in Code

Add Bundler setup to your Ruby files to load all gems from your Gemfile. This ensures your application uses the correct gem versions specified in Gemfile.lock.

# app.rb
require 'bundler/setup'
Bundler.require(:default)

# Now all gems from Gemfile are loaded
require 'sinatra'

get '/' do
  'Hello from Sinatra with Bundler!'
end

🔹 Common Bundler Commands

Bundler provides several commands to manage your project dependencies effectively. These commands help you install, update, check, and troubleshoot gems in your Ruby applications.

# Run rake with bundled gems
bundle exec rake db:migrate

# Show where a gem is installed
bundle show rails

# Check for outdated gems
bundle outdated

🔹 Version Constraints

Bundler supports various version constraint operators to control which gem versions can be installed. This helps maintain compatibility while allowing safe updates to your dependencies.

# Gemfile version constraints

# Exact version
gem 'rails', '7.0.4'

# Greater than or equal
gem 'rake', '>= 13.0'

# Pessimistic operator (recommended)
gem 'puma', '~> 6.0'  # >= 6.0 and < 7.0

# Multiple constraints
gem 'nokogiri', '>= 1.13', '< 1.15'

# Latest version
gem 'httparty'

🔹 Gem Groups

Organize gems into groups for different environments like development, test, and production. This allows you to install only the gems needed for specific environments, reducing overhead.

# Gemfile with groups
source 'https://rubygems.org'

gem 'rails'

group :development do
  gem 'pry'
  gem 'spring'
end

group :test do
  gem 'rspec'
  gem 'factory_bot'
end

group :production do
  gem 'pg'
end