saved_change_to_attribute? always returns false when called inside method

user_69349 0
Viewed 1755

So I have an after_update callback in an ActiveRecord model to notify an external service. This should only be called if a couple of attributes are being updated. So I encapsulated the saved_change_to_attribute? calls in a method that is then used in the callback filter:

after_update :tell_service!, if: :update_for_service?

def update_for_service?
  saved_change_to_name? ||
  saved_change_to_city? 
end

Now update_for_service? always returns false and I don't understand why.

In the console:

> p = Person.last
> p.name = 'Tom'
> p.save
true
> p.saved_change_to_name?
true
> p.update_for_service?
false

What is going on here?

ruby-on-rails-5 activerecord ruby-on-rails
1 Answers

This is due to when after_update runs in the callback lifecycle. This answer by pan.goth explains:

after_save, after_create, after_update are called within the transaction block, so they will be executed before executing the SQL statement.

If you want to do something when the statement execution is completed, you should use after_commit callback.

user_2031300
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