Thanks for your answer Karl Actually yes, i want to do some versioning on model instance, but the problem is that the state of the model instance in pre_save is same as at the post_save.
On Sat, May 12, 2012 at 2:32 PM, Karl Sutt <k...@sutt.ee> wrote: > Regarding pre_save signal, it is useful for doing something with the "old" > instance. Consider a use case where you might want to "archive" all changes > to, say, the user's profile. Every time a user makes a change to their > profile, you want to save the current state of the profile to another > table, or another database, and then save the new model (which overwrites > the current state and becomes the new current state). This sort of > mechanism is useful for versioning your model instances. The pre_save > signal allows you to create a hook that does precisely that. That is just > one of the use cases, but I'm sure you can think of others. > > Karl Sutt > > > > On Sat, May 12, 2012 at 10:46 AM, Alireza Savand <alireza.sav...@gmail.com > > wrote: > >> Hi >> >> What is the different between pre_save signal and post_save singal. >> I know post_save will emited after model instance saved, and pre_save is >> before the saving the instance[?] >> but what it the point of pre_save when we cannot access the object data >> before the data changes. >> I mean user try to change the model content, like body of a post in a >> blog. using pre_save signal would be reasonable if i can access the post's >> body before the changes or in other word before the actual save() happens. >> If i can't access to data before save() happends, So what is the point of >> pre_save ? >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Django users" group. >> To view this discussion on the web visit >> https://groups.google.com/d/msg/django-users/-/NLEgGtpvQ4cJ. >> To post to this group, send email to django-users@googlegroups.com. >> To unsubscribe from this group, send email to >> django-users+unsubscr...@googlegroups.com. >> For more options, visit this group at >> http://groups.google.com/group/django-users?hl=en. >> > > -- > You received this message because you are subscribed to the Google Groups > "Django users" group. > To post to this group, send email to django-users@googlegroups.com. > To unsubscribe from this group, send email to > django-users+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/django-users?hl=en. > -- + <https://github.com/Alir3z4/>+ <https://sourceforge.net/users/alir3z4>+<https://sourceforge.net/projects/yodownet/> + <https://www.transifex.net/accounts/profile/Alir3z4/>+<https://gist.github.com/Alir3z4> + <http://pastebin.com/u/Alir3z4>+ <https://www.ohloh.net/accounts/Alir3z4> -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
