gem install record_history
rails g record_history:install

# activate history logging for model
class Item < ActiveRecord::Base
  has_record_history
end

# activate history logging for model (only for "name" field)
class Item < ActiveRecord::Base
  has_record_history :only => [:name]
end

# activate history logging for model (except 'name' field)
class Item < ActiveRecord::Base
  has_record_history :ignore => [:name]
end

# activate history logging for model (on update)
class Item < ActiveRecord::Base
  has_record_history :on => [:update]
end

# get history for object
item = Item.first
history = item.first.record_history
history.first.old_value
hostory.first.new_value


# declare that User is author for some record_history items
class User < ActiveRecord::Base
  is_record_history_author
end

# get record_history items created by user
User.first.written_history