Problem saving TList to a TFile

ROOT
1

Hi,

I would be very thankful if someone could give me a hint whats wrong in my program…

TASK
To read TObjects (calibrations) from a TList saved in a TFile, add new calibrations to the list and save the list back to the file again

PROBLEM
When I read the TObjects from the list they are empty

CODE
The interface to the TList and TFile is below, I use the functions:

//To initialise the TFile and TList (only done once)
void ListHandler::Init(TString filename)
{
printf(“Creating TFile %s and TList\n”,filename.Data());
calib_file = new TFile(filename.Data(),“NEW”);
calib_list = new TList();
calib_file->WriteObject(calib_list,“list”,“SingleKey,Overwrite”);
calib_file->Close();

}

//To open the TFile and read in the TList
int ListHandler::ReadList(TString filename)
{
calib_file = new TFile(filename.Data(),“UPDATE”);
calib_list = new TList();
if(calib_file->IsZombie())
return 0;
else{
calib_file->GetObject(“list”,calib_list);
if(calib_list)
return 1;
else
return 0;
}
}

//To write the TList back to the file and close the file
int ListHandler::WriteList()
{
calib_file->WriteObject(calib_list,“list”,“SingleKey,Overwrite”);//,TObject::kOverwrite);
calib_file->Write();
calib_file->Close();

return 0;
}

//To save a TObject (calibevent) in the TList
int ListHandler::SaveEvent(calibEvent *event)
{
if(calib_file->IsOpen() && calib_list){
calib_list->Add(event);
return 1;
}
else
return 0;
}

Petter

2

I have condensed it down to the following program. It

  • creates a myobject
  • set the myobject flag to 1
  • push the object in a TList
  • write the TList to a TFile and closes the TFile
  • opens it and reads the TList
  • print the flag
    but the flag is 0…

class myobject : public TObject {
private:
Int_t flag;

public:
void SetFlag(){flag=1;}
Int_t GetFlag(){
if(flag==1)
return 1;
else
return 0;
}

};

int wtf()
{
TList *mylist = new TList();
TFile *myfile = new TFile(“wtf.root”,“NEW”);

myobject *mo = new myobject();
mo->SetFlag();
printf(“flag0 %d\n”,mo->GetFlag());

mylist->Add(mo);
printf(“flag1 %d\n”,((myobject*)mylist->First())->GetFlag());
myfile->WriteObject(mylist,“list”,“SingleKey,Overwrite”);

myfile->Write();
myfile->Close();

TFile *newfile = new TFile(“wtf.root”,“READ”);
TList *newlist;// = new TList;
newfile->GetObject(“list”,newlist);

myobject *newmo;// = new myobject();

newmo = (myobject*)newlist->First());

printf(“flag2 %d\n”,newmo->GetFlag());

}

Petter

3

Hi Petter,
you must compile your code (rootcint generate the dictionary file and myobject::Streamer() ).In your second exam simple add two lines:
#include <TFile.h>
ClassDef(myobject, 1); // very important

[quote]root [0] .L wtf.C+
Info in TUnixSystem::ACLiC: creating shared library /home/mucha/./wtf_C.so
root [1] wtf()
flag0 1
flag1 1
flag2 1
(int)0
root [2][/quote]For more info see UserGuide chapters Input/Output and Adding a Class.
By the way, try too ClassDef(myobject, 0)

I hope this help, Jan

4

Thanks! The macro now works :slight_smile:

But, the program in the first post (the actual program Im working on) will be compiled with a makefile. When I include the ClassDef in the classes in this case, the compiler complains with

[pamela@localhost testarea]$ make TestList
g++ -c -o TestList.o TestList.cpp -Iroot-config --incdir -I/home/pamela/src/testarea
g++ -c -o ListHandler.o ListHandler.cpp -Iroot-config --incdir -I/home/pamela/src/testarea
g++ -o TestList TestList.o ListHandler.o root-config --libs
ListHandler.o: In function ListHandler::ListHandler()': ListHandler.cpp:(.text+0x4): undefined reference tovtable for ListHandler’
ListHandler.o: In function ListHandler::ListHandler()': ListHandler.cpp:(.text+0x14): undefined reference tovtable for ListHandler’
ListHandler.o: In function ListHandler::~ListHandler()': ListHandler.cpp:(.text+0x24): undefined reference tovtable for ListHandler’
ListHandler.o: In function ListHandler::~ListHandler()': ListHandler.cpp:(.text+0x34): undefined reference tovtable for ListHandler’
ListHandler.o: In function calibEvent::calibEvent(float, float (*) [12], int (*) [12])': ListHandler.cpp:(.text+0x152): undefined reference tovtable for calibEvent’
ListHandler.o: In function calibEvent::calibEvent(float, float (*) [12], int (*) [12])': ListHandler.cpp:(.text+0x23a): undefined reference tovtable for calibEvent’
collect2: ld returned 1 exit status
make: *** [TestList] Error 1
[pamela@localhost testarea]$

Do I have to inlcude any other headerfiles to make this work?!

thanks again
Petter

5

Please send your TestList.cpp with make file (as attachment files.tar.gz)

Jan

6

Here they are. Main program TestList.cpp, classes in ListHandler.cpp/.h

thanks
Petter
testlist.tar (1.33 KB)

7

Hi Petter,
I attach your test files and strongly recommend that you read the Users’ Guide (Adding a Class).

Jan

8

Edited, things cleared up