I dont think i used
after_validation ever as
before_save(or similar callbacks like before_create or update) is the one which fits. Usually the flow is
before_save seems to be the last step in the process and by the time it reaches there the record is valid. Like you wanted it to happen every time when validation is successful.
after_validation is called irrespective of the validation failed or not. I cant think of a scenario where you want to use it.
We cannot substitute
before_save as we can not guarantee that the record is always going to be valid.