#include <iostream>
#include "TTree.h"
#include "TFile.h"


class Test : public TObject
{
public:
   Double_t testVar;
   ClassDef(Test, 1)
   
};
ClassImp(Test);

Test *CreateTest(TTree *tr)
{
   Test *module = new Test();
   tr->SetBranchAddress("testClass", &module);
   return module;
}

void writeTree()
{
   TFile *f = new TFile("test.root", "RECREATE");
   TTree *tr = new TTree("test", "test");
   Test *t = new Test();
   tr->Branch("testClass", t);

   for(int i = 0; i < 10; ++i)
   {
      t->testVar = i;
      tr->Fill();
   }
   tr->Write();
   f->Close();
}

void readTreeWorks()
{
   TFile *f = new TFile("test.root");
   TTree *tr = (TTree*)f->Get("test");

   Test *t = new Test();
   tr->SetBranchAddress("testClass", &t);
   
   for( auto i = 0; i < 10; ++i)
   {
      tr->GetEntry(i);
      std::cout << t->testVar << std::endl;
   }
   
}

void readTreeFails()
{
   TFile *f = new TFile("test.root");
   TTree *tr = (TTree*)f->Get("test");

   Test *t = CreateTest(tr);
   
   for( auto i = 0; i < 10; ++i)
   {
      tr->GetEntry(i);
      std::cout << t->testVar << std::endl;
   }

}