load_hst.C

void load_hst(TString cstr = "hst/default.hst.root") {
  // Read histogramms from the file
  TFile* fHist = TFile::Open(cstr, "READ");
  TIter next(fHist->GetListOfKeys());

  gROOT->cd();
  gDirectory->pwd();

  TObject* obj;
  TKey* key;
  TClass* cls;
  while ((key = (TKey*) next())) {
    cls = TClass::GetClass(key->GetClassName());
    if (cls->InheritsFrom(TH1::Class())) {
      obj = fHist->Get(key->GetName());
      dynamic_cast<TH1*>(obj)->SetDirectory(gROOT);
    } else if (cls->InheritsFrom(TEfficiency::Class())) {
      obj = fHist->Get(key->GetName());
      dynamic_cast<TEfficiency*>(obj)->SetDirectory(gROOT);
    }
  }

  fHist->Close();
}