but in fact it cannot be transformed in such object I think. At least I cannot replace it by TTree
I was not clear enough.
Where as you do something like
SomeClass object;
....
directory->Write(&object);
I recommend you do:
SomeClass object;
....
TTree *t = new TTree("holder","just one entry");
t->SetDirectory(directory);
t->Branch("object.",&object); // Defaults to maximum splitting.
t->Fill();
t->GetFile()->Write();
delete t; // or reuse.
Cheers,
Philippe.