Dear ROOT users community,
I have rounded up the articles about GetUserInfo() and I could not find a problem w/what I attempted, but it just does not work. I want to have some global values and settings for the data set that is in the root file, to be saved there as well, that’s all.
I have defined a simple TObject to hold three floats for example, like so:
[code]================ ParseACM.h ==================
class ACMHeaderInfo: public TObject {
public:
Float_t blah1, blah2, blah3;
ACMHeaderInfo(): TObject();
~ACMHeaderInfo(): TObject();
void clear() {
blah1 = -999.;
blah2 = -999.;
blah3 = -999.;
}
void printInfo() const{
cout << ACMHeaderInfo::blah1 << "\n";
cout << ACMHeaderInfo::blah2 << "\n";
cout << ACMHeaderInfo::blah3 << "\n";
}
void setBlah1(Float_t val){
this->blah1=val;
}
Float_t getBlah1(){
return this->blah1;
}
ClassDef(ACMHeaderInfo, 1) // ver 1: just a test
};
[/code]
then I fill it like so
[code]===================== ParseACM.C =====================
#include “ParseACM.h”
ClassImp(ACMHeaderInfo)
void ParseACM()
{
// create the output ROOT file/tree
//------------------------------
TFile fileroot(“acmfile.root”,“recreate”);
TTree *ACMTree = new TTree(“ACMTree”,“acmtree”);
ACMHeaderInfo* acmHeader = new ACMHeaderInfo("acmHeader");
acmHeader->setBlah1(1234.5);
cerr << acmHeader->getBlah1() << "\n"; // prints 1234.5
//------ define tree branches, loop, filling etc, works in the middle…
// writing my test header class ;)
ACMTree->GetUserInfo()->Add(acmHeader);
acmHeader->printInfo(); // prints 1234.5. -999, -999 as it should
// Finalize and write the ROOT file etc.
fileroot.Write();
}// end ParseACM()
[/code]
… and try to read the float from the tree as intended, but no luck!
[code]============================ DrawACM.C ===========================
// a very crude example
#include “ParseACM.h”
void DrawACM() {
//connect Tree generated by ParseACM.C
TFile *file = new TFile("acmfile.root");
TTree *T = (TTree*) file->Get("ACMTree");
// try to access my test header class
ACMHeaderInfo *header = (ACMHeaderInfo*) T->GetUserInfo()->FindObject("acmHeader");
//quiet up to above lines
header()->printInfo();// and this throws error
}
[/code]
I get the error:
Error: illegal pointer to class object header 0x0 2248 DrawACM.C:15:
*** Interpreter error recovered ***
I have tried all combinations and permutations 
seems like the object is not in the tree…
What am I doing wrong? Thank you so much in advance,
Sincerely,
Eugene.