RE: writing pointers to pointers to a file

>
> >
> > Dear rooters,
> >
> > would it be possible to write pointers to pointers into a file?
> The
> > problem arises from the need to write an instance of a class which
> > contains pointers to pointers data members into a file. In
particular,
> > the pointers to pointers are TH1F**, and the error message reads:
> >
> > Program received signal SIGSEGV, Segmentation fault.
> > [Switching to Thread -1433986848 (LWP 24923)]
> > 0x048e1245 in vtable for TAxis ()
> > from /home/zampolli/SOFT/ROOT/root/lib/libHist.so
> >
> > This, as I said, trying to write an instance of the class. Moreover,
> > trying to write directly on a file a pointer to pointer - such as
> with:
> >
> > TH1F **hSPD = new TH1F*[2];
> > char name[100];
> > for (Int_t i=0;i<2;i++){
> > sprintf(name,"hist_%i",i);
> > hSPD[i]=new TH1F(name,name,10*(i+1),10*i,10*(i+1));
> > }
> >
> > hSPD->Write();
> >
> > does not work either...
>
> I believe there is the straight forward ROOT ( and OO) solution for
that.
> You should create the ROOT container (for example TObjArray). Add all
> your obiect pointers there and write the container out.
>
> What about:
>
> TObjArray *h_array = new TObjArray;
>
> for (Int_t i=0;i<2;i++){
> sprintf(name,"hist_%i",i);
> h_array->Add(new TH1F(name,name,10*(i+1),10*i,10*(i+1)));
> }
>
> h_array->Write();
>
> Of course, you can create the nested container also, if you need.

Here you are the same solution as above. I have changed the variable names, and added the container size explicitly. (The container is to grow as needed with each Add method applied anyway) See: http://root.cern.ch/root/html/TObjArray.html  

      TObjArray * hSPD = new TObjArray(2);  

      for (Int_t i=0;i<2;i++){
          sprintf(name,"hist_%i",i);
          hSPD[i]  = new TH1F(name,name,10*(i+1),10*i,10*(i+1)));
      }
 
      hSPD->Write();



> Hope this helps,

>                               Valeri