Archiving objects with multiple references

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2 total messages Started by Brian Glaeske Wed, 04 Nov 1992 06:16

#135

Author: Brian Glaeske
Date: Wed, 04 Nov 1992 06:16

26 lines
1405 bytes

Ok, here is what I got.

First of all I have a main controlling view.  In this view are some subviews
and other objects that need to keep pointers to each other in order to send
messages.

Pictorially, I have:

	Obj1 ---> Obj2 ---> Obj3  and visa versa  Obj3 ---> Obj2 --1

Obj2 only has pointers to Obj1 and Obj3, ut Obj3 and Obj1 are basically
instances of the same class.  This class can have many such relationships at
the same time.  In other words Class1 (Obj1 and Obj2) use a List to hold
multiple Obj2 instances.

Now, how do I archive this and restore this mess?  I haven't seen any source
code that does anything like this (I might have missed something).

Thanks,

-- 
Brian Glaeske
 -  /|                        glaeske@plains.NoDak.edu  [Internet] 
  o.O`   --Ooop ACK!!         ..!uunet!plains!gehenna!brian [NeXT UUCP]
=(___)=                      
   U    "Bloom County Forever!!"

Re: Archiving objects with multiple references

#1387

Author: Andreas Ploeger
Date: Fri, 06 Nov 1992 15:32

37 lines
1445 bytes

In article <Bx6HEs.F1v@ns1.nodak.edu> glaeske@plains.NoDak.edu (Brian Glaeske)  
writes:
> 
> Pictorially, I have:
> 
> 	Obj1 ---> Obj2 ---> Obj3  and visa versa  Obj3 ---> Obj2 --1
> (...)
> Now, how do I archive this and restore this mess?  I haven't seen any source
> code that does anything like this (I might have missed something).
> 

I would do it this way:

    - read:(NXTypedStream*)stream
    {
      myTarget = NXReadObject(stream);
      return self;
    }
    
    - write:(NXTypedStream*)stream
    {
      NXWriteObject(stream, myTarget);
      return self;
    }

Look up NXWriteObject in Digital Librarian:
  "...These functions also ensure that objects are written only once."

So, even when multiple Objects (Obj1, Obj3) have references to a given object  
(Obj2) which are written this way, the target (obj2) is only written once.

Hope this helps,

Andreas

-- 
Andreas Ploeger, Kiel, Germany

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