1 files changed, 16 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb b/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb
index feef5d2d57..4e35b1b488 100644
--- a/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb
+++ b/activesupport/lib/active_support/core_ext/class/attribute_accessors.rb
@@ -3,11 +3,27 @@ require 'active_support/core_ext/array/extract_options'
 # Extends the class object with class and instance accessors for class attributes,
 # just like the native attr* accessors for instance attributes.
 #
+# Note that unlike +class_attribute+, if a subclass changes the value then that would
+# also change the value for parent class. Similarly if parent class changes the value
+# then that would change the value of subclasses too.
+#
 #  class Person
 #    cattr_accessor :hair_colors
 #  end
 #
 #  Person.hair_colors = [:brown, :black, :blonde, :red]
+#  Person.hair_colors     #=> [:brown, :black, :blonde, :red]
+#  Person.new.hair_colors #=> [:brown, :black, :blonde, :red]
+#
+# To opt out of the instance writer method, pass :instance_writer => false.
+# To opt out of the instance reader method, pass :instance_reader => false.
+#
+#   class Person
+#     cattr_accessor :hair_colors, :instance_writer => false, :instance_reader => false
+#   end
+#
+#   Person.new.hair_colors = [:brown]  # => NoMethodError
+#   Person.new.hair_colors             # => NoMethodError
 class Class
   def cattr_reader(*syms)
     options = syms.extract_options!