1 files changed, 8 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/core_ext/hash/diff.rb b/activesupport/lib/active_support/core_ext/hash/diff.rb
index deace40a29..6abd678822 100644
--- a/activesupport/lib/active_support/core_ext/hash/diff.rb
+++ b/activesupport/lib/active_support/core_ext/hash/diff.rb
@@ -2,6 +2,14 @@ module ActiveSupport #:nodoc:
   module CoreExtensions #:nodoc:
     module Hash #:nodoc:
       module Diff
+        # Returns a hash that represents the difference between two hashes.
+        #
+        # Examples:
+        #
+        #   {1 => 2}.diff(1 => 2)         # => {}
+        #   {1 => 2}.diff(1 => 3)         # => {1 => 2}
+        #   {}.diff(1 => 2)               # => {1 => 2}
+        #   {1 => 2, 3 => 4}.diff(1 => 2) # => {3 => 4}
         def diff(h2)
           self.dup.delete_if { |k, v| h2[k] == v }.merge(h2.dup.delete_if { |k, v| self.has_key?(k) })
         end