1  module ActiveSupport #:nodoc:
   2    module CoreExtensions #:nodoc:
   3      module Hash #:nodoc:
   4        module Diff
   5          # Returns a hash that represents the difference between two hashes.
   6          #
   7          # Examples:
   8          #
   9          #   {1 => 2}.diff(1 => 2)         # => {}
  10          #   {1 => 2}.diff(1 => 3)         # => {1 => 2}
  11          #   {}.diff(1 => 2)               # => {1 => 2}
  12          #   {1 => 2, 3 => 4}.diff(1 => 2) # => {3 => 4}
  13          def diff(h2)
  14            self.dup.delete_if { |k, v| h2[k] == v }.merge(h2.dup.delete_if { |k, v| self.has_key?(k) })
  15          end
  16        end
  17      end
  18    end
  19  end