Serialization Question

Kalyan -- chakri@sunserv.cmc.stph.net
Monday, October 14, 1996

Environment : Win95, VC++ 4.2

Hi all,
   I have two classes like this :

   class CBase : public CObject
   {
   protected:
     int a;

   public :
     virtual void Serialize(CArchive& ar);
     int getA();
   };

   class CDerived : protected CBase
   {
   public :
     void SetA(int);
     virtual void Serialize(CArchive& ar);
   };

   I an application say App1, I use the class CDerived to declare 
   objects and use the setA function to set the attribute 'a' and then
   serialize them to an archive (file). And in other application say App2 I
   declare objects of CBase so that those object's attribute can only 
   be read using getA function and these objects are serialized(read) from the
   same archive(file) as that of App1; Will this approach workout?


   Any suggestions would be appreciated.

Thanx in advance,
Kalyan.V

---

ganeshs@nationwide.com
Tuesday, October 15, 1996

[Mini-digest: 4 responses]

Environment : Win95, VC++ 4.2

> Hi all,
>    I have two classes like this :
>
>    class CBase : public CObject
>    {
>    protected:
>      int a;
>
>    public :
>      virtual void Serialize(CArchive& ar);
>      int getA();
>    };
>
>    class CDerived : protected CBase
>    {
>    public :
>      void SetA(int);
>      virtual void Serialize(CArchive& ar);
>    };
>
>    I an application say App1, I use the class CDerived to declare
>    objects and use the setA function to set the attribute 'a' and then
>    serialize them to an archive (file). And in other application say App2 I
>    declare objects of CBase so that those object's attribute can only
>    be read using getA function and these objects are serialized(read) from
>    the
>    same archive(file) as that of App1; Will this approach workout?
>
>
>    Any suggestions would be appreciated.
>
> Thanx in advance,
> Kalyan.V

    As  long  as CBase  and  CDerived  are serializable  (Basically  the
CRuntimeClass  information needs  to  be in  the  class registry,  which
happens even if you use the DYNCREATE macros. To do something like

    ar << pDerived

in  App1 of  course, you  would need  to have  the SERIALIZE  macros for
CDerived as well ...), there's no reason why something like

    ar >> pBase;

shouldn't work in App2...

/ ___|    / ___| __ _ _ __   ___  ___| |    I do not speak for
\___ \   | |  _ / _` | '_ \ / _ \/ __| '_ \ Tata   Unisys   or
 ___) |  | |_| | (_| | | | |  __/\__ \ | | |Nationwide    Ins.
|____(_)  \____|\__,_|_| |_|\___||___/_| |_|------------------
-----From: rkumar@mail.cswl.com

It all depends on how u implement the serilization routines.
I guess the derived class dose not hava any persistant attributes
in that case there is no need for a serialise function in the derived 
class U can use the serialization routine of the base class for both
classes.

                                                Ratan
                                                Rkumar@cswl.com

-----From: CraigTT@ccmail01.PE-Nelson.COM

     Kalyan,
     
     Since you're not adding any variables, it should work IF you serialize 
     via a direct call to Serialize.
     
     If you serialize via pointers through the insert and extract 
     operators, hit the problem of the runtime class information being 
     written and it won't match between the two instances.  You can 
     probably get around this if the writing app casts the CDerived 
     pointers to CBase before using the insert operator.  If the writing 
     app also needs to read the archive it would have to use a temporary 
     variable of CBase* to read each item from the archive and then use a 
     downcast to assign it to a CDerived pointer.
     
     Tim Craig

-----From: Mike Kurtinitis 

Hi Kalyan,

I would suggest trying it out on two test apps. You can use App Wizard to
bang out two generic apps, then put the interesting code in OnNewDocument().
I would bet that it'll would work, but there's nothing like real-world testing!

Good luck,

-Mike

---

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