Unlike a DaVinci-Algorithm (DVAlgorithm), Gaudi classes (most of the time) inherit from GaudiAlgorithm, where the possiblity to create an nTuple (in an easy way) is not implemented.

Let your GaudiAlgorithm inherit from 'GaudiTupleAlg' instead of 'GaudiAlgorithm'. Most of the time, you have to replace the following instances: In the .h-File:

#include "GaudiAlg/GaudiTupleAlg.h"
class myClass : public GaudiTupleAlg

In the .cpp-File:

myClass::myClass( const std::string& name,ISvcLocator* pSvcLocator): GaudiTupleAlg ( name , pSvcLocator )
StatusCode sc = GaudiTupleAlg::initialize()
return GaudiTupleAlg::finalize()