Version Ranges

gem 'foo'
gem 'bar', '>= 1.2.3'
gem 'baz', '~> 4.5.6'

• default range is "any version"
• >= means "greater or equal"
• ~> means "approximately"
  • "~> 1.2.3" matches 1.2.4 but not 1.3.0

Bundler Workflow

Gemfile vs. Gemfile.lock

• you always check in both Gemfile and Gemfile.lock
  • same Gemfile.lock => same gems and versions
  • assures consistency between all developers and servers

bundle install vs. bundle update

• you usually run bundle install
• you occasionally run bundle update

bundle update

• queries the gem repository (usually rubygems.org)
• tries to find the most recent versions of all gems
• figures out the best versions of all gems
  • best = most compatible x most recent
• rewrites Gemfile.lock
• runs bundle install

bundle install

• if there is no Gemfile.lock, does a bundle update
• if there is Gemfile.lock, then:
  • looks for the specific version of each gem inside Gemfile.lock
  • if not found, tries to download and install it

bundle exec

bundle exec command

• sets up the environment so that all and only the gems inside Gemfile.lock are available
• then runs command

groups

group :test do
  gem "wrong"
end

• Groups define optional subsets of gems
• groups usually map to environments

more help

• bundle help
• http://gembundler.com
• http://gembundler.com/gemfile.html