例如，我正在开发一个gem，而在我开发的时候，我使用pry了IRB，而不是debugger用于调试。但是，我不希望可能的贡献者必须安装它们（因为他们可能不需要它们）。我的第一个想法是将它们放在一个 Bundler 组中：
source :rubygems
gemspec
group :extras do
gem "pry"
gem "debugger"
end
然后人们可以使用：
$ bundle install --without extras
但我希望它是未安装的默认值。完美的是它们不在my 中Gemfile，但我仍然可以要求它们（如果它们存在于计算机上）。这个解决方案可以，因为我不在乎他们被锁定在哪个版本。可以做到吗？
您可以添加任意加载路径，然后从它们中获取 gem。查看全局变量$:
puts $:.inspect
# ["/var/myproject/releases/20200918191637/lib", "/var/myproject/releases/20200918191637/vendor", "/var/myproject/releases/20200918191637/app/assets", "/var/myproject/releases/20200918191637/app/controllers", "/var/myproject/releases/20200918191637/app/helpers", "/var/myproject/releases/20200918191637/app/mailers", "/var/myproject/releases/20200918191637/app/models", "/home/deploy/.rvm/gems/ruby-2.3.0/gems/bundler-2.0.2/lib", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/gems/2.3.0/gems/json-1.8.3/lib", "/home/deploy/.rvm/gems/ruby-2.3.0/gems/bundler-2.0.2/lib/gems/bundler-2.0.2/lib", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/site_ruby/2.3.0", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/site_ruby/2.3.0/x86_64-linux", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/site_ruby", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/vendor_ruby/2.3.0", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/vendor_ruby/2.3.0/x86_64-linux", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/vendor_ruby", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/x86_64-linux"]
现在让我们追加$:并要求一个宝石
require 'method_source'
# LoadError: cannot load such file -- method_source
$: << '/home/deploy/.rvm/gems/ruby-2.2.4@myset/gems/method_source-1.0.0/lib'
# ["/var/myproject/releases/20200918191637/lib", "/var/myproject/releases/20200918191637/vendor", "/var/myproject/releases/20200918191637/app/assets", "/var/myproject/releases/20200918191637/app/controllers", "/var/myproject/releases/20200918191637/app/helpers", "/var/myproject/releases/20200918191637/app/mailers", "/var/myproject/releases/20200918191637/app/models", "/home/deploy/.rvm/gems/ruby-2.3.0/gems/bundler-2.0.2/lib", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/gems/2.3.0/gems/json-1.8.3/lib", "/home/deploy/.rvm/gems/ruby-2.3.0/gems/bundler-2.0.2/lib/gems/bundler-2.0.2/lib", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/site_ruby/2.3.0", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/site_ruby/2.3.0/x86_64-linux", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/site_ruby", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/vendor_ruby/2.3.0", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/vendor_ruby/2.3.0/x86_64-linux", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/vendor_ruby", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0", "/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/x86_64-linux", "/home/deploy/.rvm/gems/ruby-2.2.4@myset/gems/method_source-1.0.0/lib"]
require 'method_source'
# true
但是，如果您有很多依赖项，那可能会很乏味，因此您可以尝试以下方法：
Dir['/home/deploy/.rvm/gems/ruby-2.2.4@myset/gems/*'].each do |gem_path|
$: << File.join(gem_path, 'lib')
end
bundle install是“选择退出”——除非您指定--without some_group，否则它会安装所有内容。
如果你绝对不想在你的 Gemfile 中有一个给定的 gem，你可以在你的包之外只是gem install那个流氓 gem。然后它会在下面irb直接对你可见（但如果你在运行的代码中ruby尝试它，显然你会得到错误）。requirebundle exec
您可以将基于环境变量的条件添加到 Gemfile。例子：
source :rubygems
gemspec
if ENV['WITH_EXTRAS'] == '1'
gem "pry"
gem "debugger"
end
'1'如果您将环境变量设置为eg ，则仅安装/加载 gems WITH_EXTRAS=1 bundle install。
现在你可以使用“可选”参数，它会按照你的要求做：它不会安装额外的，除非人们bundle --with extras
group :extras, optional:true do
...
end