Writing stl vector to tree

ROOT
1

I am trying to write stl vector to tree :

[code]#include “TTree.h”
#include “TFile.h”
#include “vector”
#include <TBranch.h>
#include <TClass.h>
//using namespace std;
int main()
{
std::vector *a=new std::vector;
a->push_back(3.5);
TFile f(“tree.root”,“RECREATE”);
TTree t(“t”,“t”);
t.Branch(“a”,a);
t.Fill();
f.Write();
f.Close();
delete a;
}

[/code]
While executing , I get following error

Error in TTree::Branch: The pointer specified for a is not of a class or type known to ROOT

What should I do ?

2

Replace

t.Branch("a",a); by

Rene

3

[quote=“brun”]Replace

t.Branch("a",a); by

Rene[/quote]
It seems , that it doesn’t change anything …
PS . I am using root v. 5.20 . Also I compiling this code (I’am not using CINT )

4

You must generate a dictionary for your vector class (see guide) or simply use ACLIC, it will be automatic

//file V.C #include "TTree.h" #include "TFile.h" #include "vector" #include <TBranch.h> #include <TClass.h> //using namespace std; int V() { std::vector<float> *a=new std::vector<float>; a->push_back(3.5); TFile f("tree.root","RECREATE"); TTree t("t","t"); t.Branch("a",&a); t.Fill(); f.Write(); f.Close(); delete a; return 0; }

root > .L V.C+ root > V()
Rene

5

Alternatively, you can also make sure to load the pre-generated dictonary for the vector by executing:gROOT->ProcessLine("#include <vector>");

Cheers,
Philippe