Re: [Boost-users] Serialization newbie needs help

From: Nat Goodspeed (nat.goodspeed_at_[hidden])
Date: 2007-08-25 11:32:27

At 06:51 PM 8/18/2007, Dominick Layfield wrote:

>if you could provide me an example of when pointer serialization shines,
>then I would say "Aha! Now I understand why Robert went to so much trouble to
>make this work.", and I could be at peace with the world again!  :-)

   (Apologies if someone else has already said this more succinctly; 
I'm still catching up with list traffic from a recent vacation.)
   Suppose your application has classes A and B. Class A contains a 
B* pointer. It doesn't directly contain a B instance; it points to a 
distinct B instance.
   To me, the most compelling argument for object tracking is when 
you have two instances of A, a1 and a2, each of which points to the 
SAME B instance b1.

a1 ---> b1 <--- a2

You serialize that data structure. When a subsequent run of the app 
reloads it, let's say that you now have A instance a3 pointing to B 
instance b3, and A instance a4 pointing to a distinct B instance b4.

a3 ---> b3      a4 ---> b4

Is that acceptable? Probably not, else why would the original session 
have linked the data that way?
   Object tracking is the way the serialization library recognizes 
the shared B instance and reconstitutes two new A instances which, 
again, contain pointers to the SAME B instance.

a3 ---> b3 <--- a4