Method: ActiveSupport::Inflector#underscore

Defined in:
activesupport/lib/active_support/inflector/methods.rb

#underscore(camel_cased_word) ⇒ Object

Makes an underscored, lowercase form from the expression in the string.

Changes ‘::’ to ‘/’ to convert namespaces to paths.

underscore('ActiveModel')         # => "active_model"
underscore('ActiveModel::Errors') # => "active_model/errors"

As a rule of thumb you can think of underscore as the inverse of #camelize, though there are cases where that does not hold:

camelize(underscore('SSLError'))  # => "SslError"
[View source]

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# File 'activesupport/lib/active_support/inflector/methods.rb', line 97

def underscore(camel_cased_word)
  return camel_cased_word.to_s.dup unless /[A-Z-]|::/.match?(camel_cased_word)
  word = camel_cased_word.to_s.gsub("::", "/")
  word.gsub!(inflections.acronyms_underscore_regex) { "#{$1 && '_' }#{$2.downcase}" }
  word.gsub!(/([A-Z])(?=[A-Z][a-z])|([a-z\d])(?=[A-Z])/) { ($1 || $2) << "_" }
  word.tr!("-", "_")
  word.downcase!
  word
end