for instance if I want to fetch a url if the url attribute has changed.
I know that I can use before_save and do:
def get_url get_url if url_changed? end
However, this is not really correct. If that call is using delayed job or some other technique since the object is not yet saved in the before_save callback, for instance.
def get_url Queue.add(:fetch_url, id) end
might end up getting the old URL if it is executed before the update completes. The prior technique would also end up using the new URL if the update fails. This is the sort of thing that should be done after the object is updated.
I'd like to do something like:
after_save :get_url, :if => url_changed?
but this won't work because the url is no longer "dirty" after the save.
Settings flags in the before_save and executing after_save gets ugly real fast, and has potential for infinite loops, requiring hackery.
Is there a clean way to do this?
