How to convert a Ruby classname ("NewUserBatch") to string with underscores ("new_user_batch")

Question

I need a generic way to convert classnames to lowercase with underscores. For example, I wish to convert the classname NewUserBatch to new_user_batch. How to do this?

Answer 1

Underscore.

>> 'NewUserBatch'.underscore
=> "new_user_batch"

It is included in Rails so if you don't use it, you can refer to its source code.

def underscore(camel_cased_word)
  word = camel_cased_word.to_s.dup
  word.gsub!(%r::/, '/')
  word.gsub!(%r(?:([A-Za-z\d])|^)(#{inflections.acronym_regex})(?=\b|[^a-z])/) { "#{$1}#{$1 && '_'}#{$2.downcase}" }
  word.gsub!(%r([A-Z\d]+)([A-Z][a-z])/,'\1_\2')
  word.gsub!(%r([a-z\d])([A-Z])/,'\1_\2')
  word.tr!("-", "_")
  word.downcase!
  word
end