You might have seen some deprecation warnings when updating to Rails 5.1+:
DEPRECATION WARNING: The behavior of `attribute_changed?` inside of
after callbacks will be changing in the next version of Rails.
The new return value will reflect the behavior of calling the method
after `save` returned (e.g. the opposite of what it returns now).
To maintain the current behavior, use `saved_change_to_attribute?` instead.
I was getting these warnings inside a before_save callback, so the message was a bit misleading. (saved_change_to_attribute? should be used in a after_save callback, but not in a before_save callback.)
This blog post was really helpful for figuring out what to do with after_save callbacks: Underrated and enhanced dirty attributes changes in Rails 5.1.
However, I couldn’t seem to find anything about before_save callbacks. I read the source code to figure out the new methods, so I decided to put together some tables to show you how you can update your before_save and after_save callbacks for Rails 5.1+. The following examples are for a status attribute:
before_save callbacks
| Rails 5.0 | Rails 5.1+ |
|---|---|
status_changed? | will_save_change_to_status? |
status_was | status_in_database |
changes['status'] | status_change_to_be_saved |
after_save callbacks
| Rails 5.0 | Rails 5.1+ |
|---|---|
status_changed? | saved_change_to_status? |
status_was | status_before_last_save |
changed? | saved_changes? |
changed_attributes | saved_changes.transform_values(&:first) |