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 underscore         to return  camel case string

User · Answer

The ruby core itself has no support to convert a string from (upper) camel case to (also known as pascal case) to underscore (also known as snake case).

So you need either to make your own implementation or use an existing gem.

There is a small ruby gem called lucky_case which allows you to convert a string from any of the 10+ supported cases to another case easily:

require 'lucky_case'

# convert to snake case string
LuckyCase.snake_case('CamelCaseString')      # => 'camel_case_string'
# or the opposite way
LuckyCase.pascal_case('camel_case_string')   # => 'CamelCaseString'

You can even monkey patch the String class if you want to:

require 'lucky_case/string'

'CamelCaseString'.snake_case  # => 'camel_case_string'
'CamelCaseString'.snake_case! # => 'camel_case_string' and overwriting original

Have a look at the offical repository for more examples and documentation:

https://github.com/magynhard/lucky_case

User · Answer

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

User · Answer

One-liner Ruby implementation   class String      ruby mutation methods have the expectation to return self if a mutation occurred  nil otherwise   see http   www ruby-doc org core-1 9 3 String html method-i-gsub-21     def to underscore       gsub        A-Z      1  2        downcase     end     def to underscore      dup tap    s  s to underscore       end end   So  SomeCamelCase  to underscore     gt  some camel case

User · Answer

I would like this   class String       n returns the capture group of  n  index   def snikize     self gsub                 gsub    a-z d    A-Z       1  2        downcase   end      or    def snikize     self gsub                 gsub    a-z d    A-Z     do           1     2       end      downcase   end  end   Monkey patch of String class  There are class that begin with two or more letters in uppercase

User · Answer

In case someone looking for case when he need to apply underscore to string with spaces and want to convert them to underscores as well you can use something like this    your String will be converted To underscore  parameterize underscore  your string will be converted to underscore   Or just use  parameterize      but keep in mind that this one is deprecated    your String will be converted To underscore  parameterize       your string will be converted to underscore

User · Answer

Receiver converted to snake case  http   rubydoc info gems extlib 0 9 15 String snake case-instance method  This is the Support library for DataMapper and Merb   http   rubygems org gems extlib   def snake case   return downcase if match   A A-Z   z     gsub    A-Z     A-Z  a-z       1  2      gsub    a-z    A-Z       1  2      downcase end   FooBar  snake case                foo bar   HeadlineCNNNews  snake case       headline cnn news   CNN  snake case                   cnn

User · Answer

There is a Rails inbuilt method called  underscore  that you can use for this purpose   CamelCaseString  underscore    gt   camel case string     The  underscore  method can typically be considered as inverse of  camelize

User · Answer

You can use    CamelCasedName  tableize singularize   Or just   CamelCasedName  underscore   Both options ways will yield  camel cased name   You can check more details it here

User · Answer

Check out snakecase from Ruby Facets  The following cases are handled  as seen below    SnakeCase  snakecase            gt   snake case   Snake-Case  snakecase           gt   snake case   Snake Case  snakecase           gt   snake case   Snake  -  Case  snakecase       gt   snake case    From  https   github com rubyworks facets blob master lib core facets string snakecase rb  class String      Underscore a string such that camelcase  dashes and spaces are     replaced by underscores  This is the reverse of   camelcase       albeit not an exact inverse             SnakeCase  snakecase            gt   snake case         Snake-Case  snakecase           gt   snake case         Snake Case  snakecase           gt   snake case         Snake  -  Case  snakecase       gt   snake case          Note  this method no longer converts      to      in that case     use the   pathize  method instead     def snakecase      gsub                 gsub    A-Z     A-Z  a-z      1  2        gsub    a-z d    A-Z      1  2        tr  -             gsub   s             gsub                  downcase   end        alias method  underscore   snakecase      TODO  Add  separators to  snakecase  like camelcase   end

User · Answer

Rails  ActiveSupport  adds underscore to the String using the following    class String   def underscore     self 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   gt   camel case

User · Answer

Short oneliner for CamelCases when you have spaces also included  doesn t work correctly if you have a word inbetween with small starting-letter    a    Test String  a gsub          underscore      gt   test string

[ruby-on-rails] Converting camel case to underscore case in ruby

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