class User < ActiveRecord::Base
  include DeltaChanges::Extension
  delta_changes columns: [:name], attributes: [:full_name]
end

user.name = "bar"
user.delta_changes # => {"name" => [nil, "bar"]}

user.full_name_will_change!
user.delta_changes # => {"name" => [nil, "bar"], "full_name" => [nil, "Mr. Bar"]}

user.save!
user.delta_changes # => {"name" => [nil, "bar"], "full_name" => [nil, "Mr. Bar"]}

user.reset_delta_changes!
user.delta_changes # => {}