#include <iostream>
#include <iomanip>
#include "TGraph2DErrors.h"
#include "TFile.h"
#include "TString.h"

void PrintGraphInfo(TGraph2DErrors* gr)
{
    std::cout << std::hex << std::showbase
                << "\ngr @ " << gr
                << "\ngr->GetX()=" << gr->GetX()
                << "\ngr->GetY()=" << gr->GetY()
                << "\ngr->GetZ()=" << gr->GetZ()
                << std::endl;
                
    std::cout << std::dec << std::noshowbase;
}

// Open the file,
// --> get the graph, 
//   --> copy it, 
//     --> close the file, 
//       --> return the copy
TGraph2DErrors* GetGraph(TString filename)
{
    TGraph2DErrors* gr = NULL;

    TFile *f = new TFile(filename.Data(),"UPDATE");
    if (f==NULL) 
        return gr;
    else if (!f->IsOpen()) 
        return gr;
   
    TString my_graph_name = "mygraph";
    gr = dynamic_cast<TGraph2DErrors*>( f->Get(my_graph_name.Data()) );

   
   if (gr!=NULL)
   {
        std::cout << "\n\nInformation about TGraph2DErrors"  
                << "\nB/4 Clone...";     
        PrintGraphInfo(gr);
        // ... copy the graph
        TString name(gr->GetName());
        TGraph2DErrors* temp_gr = static_cast<TGraph2DErrors*>(gr->Clone("temp_gr"));
        
        gr = temp_gr;
        gr->SetName(name.Data());    
   }

   std::cout << "\n\n...AFTER Copy";   
   PrintGraphInfo(gr);   
   f->Close();
   
   std::cout << "\n\n...AFTER File Closed";   
   PrintGraphInfo(gr);   
   
   return gr;
}


Int_t Main()
{
//    TString root_fname;
//    std::cout << "Enter location of graph : ";
//    root_fname.ReadLine(std::cin);

    TGraph2DErrors *gr = GetGraph("myfile.root");
    
    /*
        do something with the graph
    */
  
// ** the TFILE thinks it owns the graph ** //
//    delete gr;    
    return 0;
}

#ifndef __CINT__
Int_t main()
{
    return Main();
}
#endif