Rene,
thanks for the help, for anyone else with this problem I finally found out that this works too (hope that this is not wrong and just works by accident):
pBase=(TJObject*)(TMyDerivedClass*)File.Get("MyDerivedClass);
Joe
>
> JoeDerived *MyDerivedClass = new JoeDerived;
> TJObject* pBase = (TJObject*)&MyDerivedClass;
>
> is perfectly legal.
>
> BUT, not the following operation
> pBase=(TJObject*)File.Get("MyDerivedClass");
>
> File.Get returns a TObject*. You cannot cast it to TJObject*
> One has to do:
>
> pBase=(MyDerivedClass*)((void*)File.Get("MyDerivedClass"));
>
> see: http://root.cern.ch/root/htmldoc/TDirectory.html#TDirectory:Get
>
> Rene
>
> joer00@bellsouth.net wrote:
> >
> > Rene and others,
> >
> > well I STILL go mad with this problem. Your example works but my setup does NOT.
> >
> > The virtual function call fails when I use the GET method !!!
> >
> > class TJObject
> > {
> > TJObject(){};
> > virtual function Visualize(){printf("class TJObject called\n");};
> > }
> >
> > class JoeDerived:public TVectorD,public TJObject
> > {
> > JoeDerived(){};
> > virtual function Visualize(){printf("class JoeDerivedcalled\n");};
> > }
> >
> > Now in main:
> >
> > TJObject* pBase;
> > JoeDerived MyDerivedClass;
> > TFile File("f:\\Shittemp\\rotz.root","RECREATE");
> > MyDerivedClass.Write("MyDerivedClass");
> > pBase=(TJObject*)&MyDerivedClass;
> > pBase->Visualize(); -->WORKS CORRECT
> > pBase=(MyDerivedClass*)File.Get("MyDerivedClass");
> > pBase->Visualize(); -->WORKS CORRECT
> > pBase=(TJObject*)File.Get("MyDerivedClass");
> > pBase->Visualize(); -->Does NOT WORK !!! (sometimes just prints nothing, sometimes crashes)
> >
> > Now I tried to do:
> >
> > class TJObject:public TObject
> > { etc.
> >
> > But now I get tons of ambitious errors in TJoeDerived ...
> >
> > So I am still happy for any help how to create this correct !
> >
> > Joe
> >
> > >
> > > From: Rene Brun <Rene.Brun@cern.ch>
> > > Date: Wed, 23 Jan 2002 17:05:44 +0000
> > > To: joer00@bellsouth.net
> > > CC: roottalk@pcroot.cern.ch
> > > Subject: Re: [ROOT] Multiple inheritance from TObject problem/ old cutoms class read/write problem
> > >
> > > I think that giving a simple example is better:
> > >
> > > //-------file joe.cxx
> > > #include "TObject.h"
> > >
> > > //-------------------------
> > > class A {
> > >
> > > private:
> > > int fA1;
> > > int fA2;
> > >
> > > public:
> > > A() {fA1=1;fA2=2;}
> > > ClassDef(A,0)
> > > };
> > >
> > > //-------------------------
> > > //class B : public A, public TObject { //<===wrong order
> > > class B : public TObject, public A {
> > >
> > > private:
> > > int fB1;
> > > int fB2;
> > >
> > > public:
> > > B() {fB1=11;fB2=12;}
> > >
> > > ClassDef(B,1)
> > > };
> > >
> > > ClassImp(A)
> > > ClassImp(B)
> > > //------------end of jeoe.cxx
> > >
> > > In interactive root, do
> > > root > .L joe.cxx++
> > > root > TFile f("junk.root","recreate");
> > > root > B b;
> > > root > b.Write("b");
> > >
> > > ClassDef is mandatory for all classes involved in I/O.
> > > Specify ClassDef(A,0) if you do not want to write the members
> > >
> > > Rene Brun
> > >
> > >
> > > joer00@bellsouth.net wrote:
> > > >
> > > > Rene,
> > > >
> > > > just to be 100 % sure now, from you posts this should work: (if yes just asnwer yes to save time, if no please explain because it than cotradicts with your provious posts !)
> > > >
> > > > Class A does NOT deriver from TObject, does NOT define the ClassDef macros and has NO streamer. It HAS datamemebers which I do NOT want/need to write to disk.
> > > >
> > > > Class B:public A,TObject
> > > >
> > > > DOES deriver from TObject, DOES implement ClassDef, HAS a dictionary file,HAS data members which need to be written to disk.
> > > >
> > > > BObject->Write("NAME"); and
> > > > BObject=(B*)SomeFile->Get("Name");
> > > >
> > > > WILL work although base class does NOT deriver from TObject and has no streamer !
> > > >
> > > > Joe
> > >
>
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