active_record_self_diff.rb

# class User < ActiveRecord::Base
#   include ActiveRecordSelfDiff
# end
#
# u = User.create(name: "toqoz")
# u.name = "toqoz-2"
# u.self_diff
# => {"name" => #<struct Struct::Diff old="toqoz", now="toqoz-2">}

module ActiveRecordSelfDiff
  DIFF = Struct.new("Diff", :old, :now)

  def self_diff
    attributes.keys.
      select { |attr| send("#{attr}_changed?") }.
      reduce({}) { |diff, attr|
        diff[attr] = DIFF.new(send("#{attr}_was"), send(attr))
        diff
      }
  end
end