RubyGems, Bundler and Dependency Management

38.1 RubyGems

gem install nokogiri
gem install rails -v 8.0.0
gem list; gem outdated; gem update; gem uninstall nokogiri
gem search faraday --remote
gem info faraday; gem contents faraday; gem env

38.2 Bundler

Version constraints: "= 1.2", ">= 1.2", "~> 1.2" (≥1.2, <2.0), "~> 1.2.3" (≥1.2.3, <1.3).

Gemfile.lock: commit it for applications. For gems, don't rely on it (constraints go in the gemspec).

# Gemfile
source "https://rubygems.org"
ruby "3.4.1"

gem "sinatra", "~> 4.0"          # pessimistic constraint: >= 4.0, < 5.0
gem "puma", ">= 6.4"
gem "pg", require: false
gem "my_lib", path: "../my_lib"
gem "rack", github: "rack/rack", branch: "main"

group :development, :test do
  gem "rspec", "~> 3.13"
  gem "rubocop", require: false
  gem "debug"
end

bundle init                 # create a Gemfile
bundle install              # install + write Gemfile.lock (commit it for apps)
bundle exec rspec           # run with the bundle's gem versions
bundle add faraday          # add a dependency
bundle update rack          # update one gem (conservative)
bundle outdated
bundle config set --local path vendor/bundle
bundle lock --add-platform x86_64-linux
bundle exec ruby app.rb

require "bundler/setup"     # in scripts: use the Gemfile's versions
require "bundler/inline"    # single-file scripts with dependencies
gemfile do
  source "https://rubygems.org"
  gem "colorize"
end