Converting camel case to underscore case in ruby

Question

Is there any ready function which converts camel case Strings into underscore separated string? I want something like this

"CamelCaseString".to_undescore

to return "camel_case_string"

Answer 1

Rails' ActiveSupport adds underscore to the String using the following:

class String
   def underscore(camel_cased_word)
     camel_cased_word.to_s.gsub(/::/, '/').
       gsub(/([A-Z]+)([A-Z][a-z])/,'\1_\2').
       gsub(/([a-z\d])([A-Z])/,'\1_\2').
       tr("-", "_").
       downcase
   end
end

Then you can do fun stuff:

"CamelCase".underscore

Answer 2

Here's how Rails does it:

   def underscore(camel_cased_word)
     camel_cased_word.to_s.gsub(/::/, '/').
       gsub(/([A-Z]+)([A-Z][a-z])/,'\1_\2').
       gsub(/([a-z\d])([A-Z])/,'\1_\2').
       tr("-", "_").
       downcase
   end

Answer 3

One-liner Ruby implementation:

class String
   def to_underscore!
     self.gsub!(/(.)([A-Z])/,'\1_\2').downcase!
   end
   def to_underscore
     self = self.clone.to_underscore!
   end
end

So "SomeCamelCase".to_underscore # =>"some_camel_case"