一种方法是提出这样的目录结构:

One approach would be to come up with directory structure like this:

(root dir)
├── a
│   ├── first.rb
│   ├── second.rb
│   └── third.rb
└── a.rb

文件内容:

# a.rb
require_relative './a/first.rb'
require_relative './a/second.rb'
require_relative './a/third.rb'

module A
end


# a/first.rb
module A
  class First
    # ...
  end
end


# a/second.rb
module A
  class Second
    # ...
  end
end


# a/third.rb
module A
  class Third
    # ...
  end
end