Rails 5.2 changes in callbacks

In version 5.1 you may see deprecation warnings in after_save callbacks (related to changes in ActiveRecord::Dirty module).

But since 5.2 these changes were applied.

For examples, I will use Rails 4.2.11 and Rails 5.2.3 and model User with email attribute. Let's do:

u = User.new(email: 'old@domain.com')

u.save

u.email = 'new@domain.com'

u.save

and look at after_save callback in time of last save.

1. attribute_changed?

Rails 4

> email_changed?

=> true

Rails 5.2

> email_changed?

=> false

but you can use saved_changes?

> saved_change_to_email?

=> true

2. changed?

Rails 4

> changed?

=> true

Rails 5.2

> changed?

=> false

but you can use saved_changes?

> saved_changes?

=> true

3. changes

Rails 4

> changes

=> {"email"=>["old@domain.com", "new@domain.com"]}

Rails 5.2

> changes

=> {}

but you can use saved_changes

> saved_changes

=> {"email"=>["old@domain.com", "new@domain.com"]}

4. previous_changes

Rails 4

> previous_changes

=> {"email"=>[nil, "old@domain.com"]}

Rails 5.2

Now, this method returns the changes that were just saved (like saved_changes).

> previous_changes

=> {"email"=>["old@domain.com", "new@domain.com"]}

this method has no replacement.