Re: writing a TObjArray

Chiara,

Your question is really unclear. Are you still working on the same problem for which you posted
a few mails some months ago and where I recommended you twice to use a TTree for this job?

Rene Brun

Chiara Zampolli wrote:
> Dear rooters,
>
> I would like to write a TObjArray in a file. The TObjArray is
> filled in a loop where every time the object I would like to store is
> created with a new. Since I set the array as the owner of its objects,
> calling the Clear method at the end would delete all the objects I
> have used to fill the array. This is the only way I have found to make
> everything work creating a new object in every iteration in the loop
> (where I CAN NOT delete them, otherwise the array is not writable!).
> If I don't do like this (i.e. don't call "new" at every iteration),
> but I just change the members of the object, all the objects at the
> end would be the same, and precisely, the same as the last object I
> have created.
> Calling "new" every time would be fine, if the number of objects I
> would like to store was not huge, as, on the contrary, it is in my
> case, which becomes memory consuming....
> What would be the best way to proceed, then?
> In the attached file you find an example (very simple), hopefully
> explaining the problem.
>
> Thanks in advance.
> Cheers,
> Chiara
> ------------------------------------------------------------------------
>
> void testWriteArray(){
> TObjArray *array = new TObjArray(10);
> array->SetOwner();
> // TH1F *h = new TH1F();
> for (Int_t i = 0;i<10;i++){
> TH1F *h = new TH1F();
> TString Name=Form("Histo%02i",i);
> h->Reset(); // useful if new is outside
> h->SetName(Name);
> h->SetTitle(Name);
> h->SetBins(10,10*i,10*(i+1));
> for (Int_t j=0;j<10;j++){
> h->Fill(10*i+j); // different histos to see what I get in the output
> }
> array->AddAt(h,i);
> //delete h;
> //h=0x0;
> }
>
> TH1F *h1 = (TH1F*)array->At(0);
> cout << " name h1 = " << h1->GetName() << endl;
> cout << " name h = " << h->GetName() << endl; // still there, sure
>
> TFile *file = new TFile("testWriteArray.root","RECREATE");
> array->Write("array",TObject::kSingleKey);
> file->Close();
> delete file;
> file = 0x0;
> array->Clear();
> //cout << " name h = " << h->GetName() << endl; // of course, does not
> // work if Clear is used
> return;
> }
>
Received on Wed Jun 20 2007 - 10:57:10 CEST