How can I access a changed values before and after update?
Suppose, I have Person1.
Person1.friends = [P2, P3, P4]
and then I update it so it becomes:
Person1.friends = [P2, P3]
how can I access the previous
Person1.friends, so I could know that only
P4 is removed from
I tried to compare
after_update, but they both yield the same results.