问题:

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".

...

回答1:

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 => "camel_case"

回答2:

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.

回答3:

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 # =>"some_camel_case"

回答4:

There is a Rails inbuilt method called 'underscore' that you can use for this purpose

"CamelCaseString".underscore #=> "camel_case_string"

The 'underscore' method can typically be considered as inverse of 'camelize'

回答5:

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

回答6:

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"

回答7:

Check out snakecase from Ruby Facets

The following cases are handled, as seen below:

"SnakeCase".snakecase         #=> "snake_case" "Snake-Case".snakecase        #=> "snake_case" "Snake Case".snakecase        #=> "snake_case" "Snake  -  Case".snakecase    #=> "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         #=> "snake_case"   #   "Snake-Case".snakecase        #=> "snake_case"   #   "Snake Case".snakecase        #=> "snake_case"   #   "Snake  -  Case".snakecase    #=> "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

回答8:

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    => "test_string"

回答9:

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.

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