MicroPosts

• Ruby: default gems

  Ruby's stdlib is composed of 3 different elements:

  • Standard libraries that are embedded in the language's source
  • Default gems that can be required, are maintained by the core team, and cannot be removed
  • Bundled gems that come installed with Ruby and can be removed

  Full list on stdgems.org.

• Ruby gem activation

  This is how you use a Ruby gem usually:

  require 'foo'
  Foo.bar
  

  For the require to work, the gem needs to be available on the LOAD_PATH:

  ruby -e 'puts $LOAD_PATH'
  

  The act of adding a gem to the LOAD_PATH is called "activating a gem".

  In a vanilla Ruby situation, you can add a directory to the LOAD_PATH with:

  ruby -I ./foo/lib -e "puts(require 'foo')"
  # true
  

  More often, you deal with a bundle that contains a Gemfile:

  gem 'foo'
  

  To activate the gems from the Gemfile (taking into account the versions from Gemfile.lock):

  require 'bundler/setup'
  require 'foo'
  

  or (equivalent):

  require 'bundler'
  Bundler.setup
  require 'foo'
  

  Notice that the setup step will first clear the LOAD_PATH and activate only the gems in the bundle.

  For example, Rails does it here and here.

  If you've ever wondered what the hell is up with bundle exec ..., the answer is simple: Bundler activates the gems in the bundle with something like

  RUBYOPT="-rbundler/setup" ruby ...
  

  Of course, things are more complex than that. But this should give you a starting point.

  Bundler: How to use Bundler with Ruby