ActiveRecord allows you to view saved changes

Say you have an Activerecord object that you are making changes to.

user = User.last
user.update(first_name: "Joe", last_name: "Hashrocket")

With ActiveModel's Dirty module, you can view the changes made to the model even after it has been saved using the saved_changes method

user.saved_changes
# {"first_name"=>[nil, "Joe"], "last_name"=>[nil, "Hashrocket"]]}