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Use of TClonesArray Class

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void write
{
TClonesArray *arr = new TClonesArray("TVector3");
TClonesArray &ar = *arr;
TFile *file = new TFile("file.root", "recreate");
TTree *tree = new TTree("tcl", "tcl");
tree->Branch("array", &arr);
TRandom2 *rand = new TRandom2(1);
for (int i = 0; i < 100; i++)
{
arr->Clear();
for (int j = 0; j < 1000; j++)
{
double x = rand->Rndm();
double y = rand->Rndm();
double z = rand->Rndm();
new (ar[j]) TVector3(x, y, z);
}
tree->Fill();
}
file->Write();
file->Close();
}
void read()
{
TFile *file = new TFile("file.root");
TTree *tree = (TTree *)file->Get("tcl");
TClonesArray *arr = new TClonesArray("TVector3");
tree->SetBranchAddress("array", &arr);
int entries = tree->GetEntries();
for (int i = 0; i < entries; i++)
{
tree->GetEntry(i);
int lines = arr->GetEntries();
for (int j = 0; j < lines; j++)
{
TVector3 *vec = (TVector3 *)arr->At(j);
cout << vec->X() << endl;
}
}
}
void tcl()
{
write();
read();
}
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