camelize and underscore are sort of inverse of each other, but not in a mathematical sense [#5174 state:resolved]

1 files changed, 11 insertions, 1 deletions

diff --git a/activesupport/lib/active_support/inflector/methods.rb b/activesupport/lib/active_support/inflector/methods.rb
index b3dc5b2f3a..de49750083 100644
--- a/activesupport/lib/active_support/inflector/methods.rb
+++ b/activesupport/lib/active_support/inflector/methods.rb
@@ -20,6 +20,11 @@ module ActiveSupport
     #   "active_record".camelize(:lower)        # => "activeRecord"
     #   "active_record/errors".camelize         # => "ActiveRecord::Errors"
     #   "active_record/errors".camelize(:lower) # => "activeRecord::Errors"
+    #
+    # As a rule of thumb you can think of +camelize+ as the inverse of +underscore+,
+    # though there are cases where that does not hold:
+    #
+    #   "SSLError".underscore.camelize # => "SslError"
     def camelize(lower_case_and_underscored_word, first_letter_in_uppercase = true)
       if first_letter_in_uppercase
         lower_case_and_underscored_word.to_s.gsub(/\/(.?)/) { "::#{$1.upcase}" }.gsub(/(?:^|_)(.)/) { $1.upcase }
@@ -28,13 +33,18 @@ module ActiveSupport
       end
     end
 
-    # The reverse of +camelize+. Makes an underscored, lowercase form from the expression in the string.
+    # Makes an underscored, lowercase form from the expression in the string.
     #
     # Changes '::' to '/' to convert namespaces to paths.
     #
     # Examples:
     #   "ActiveRecord".underscore         # => "active_record"
     #   "ActiveRecord::Errors".underscore # => active_record/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:
+    #
+    #   "SSLError".underscore.camelize # => "SslError"
     def underscore(camel_cased_word)
       word = camel_cased_word.to_s.dup
       word.gsub!(/::/, '/')