Hi Luigi,
Setting a flag in memory does not modify the data base.
Whay you can do is something like
TFile f1("oldfile.root");
TTree *oldTree = (TTree*)f1.Get("treename");
MyClass *a = 0;
oldTree->SetBranchAddress("branchname",&a);
TFile *f2 = new TFile("newfile.root","recreate");
TTree *newTree = oldTree->CloneTree(0);
Int_t nentries = oldTree->GetEntries();
for (Int_t i=0;i<nentries;i++) {
oldTree->GetEntry(i);
if event is not OK continue;
SetFlag(...)
newTree->Fill();
}
newTree->Write();
f2->Close();
Rene Brun
Luigi Bardelli wrote:
>
> Dear ROOTers,
>
> (Probably a beginner question...)
> This is my problem: after creating an unsplit TTree made of MyEvent
> objects with inside some Signal objects and rereading it from disk,
> I'd like to scan all the events, make some selections, and upgrade
> some flag INSIDE the Signal Object (I'd like also to upgrade the file on
> disk). I have provided the following methods:
>
> void Signal::SetFlag(int value)
> Signal* MyEvent::GetSignal()
> // to retrieve a pointer to the
> // Signal Object
>
> I've tried with TTree::MakeSelector("SetFlag"), with these modifications:
> ....
> => void SetFlag::ProcessFill(Int_t entry)
> => {
> => // function called for selected entries only
> => // entry is the entry number in the current Tree
> => // read branches not processed in ProcessCut and fill histograms
> => // to read complete event, call fChain->GetTree()->GetEntry(entry)
> => fChain->GetTree()->GetEntry(entry);
> => int i,newFlag;
> => Signal *s;
> => s=MyBranch->GetSignal();
> => /*-- here I compute newFlag --*/
> => ...
> => /*----------------------------*/
> => s->SetFlag(newFlag);
> => }
>
> and
>
> => void SetFlag::Terminate()
> => {
> => // function called at the end of the event loop
> => f->Write();
> => }
>
> where f (global at the moment) is the file containg the TTree.
> Every event is processed in the right way, but
> nor the file on disk, neither the TTree here in memory change.
>
> Someone can help me?
>
> Thank you very much
> Luigi Bardelli
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