class DBComm

{ 

     ...

     template<typename T>

     T* operator[](DBTableType op)

     {

       std::map<DBTableType,DBTableOperator*>::iterator it=mapOfOperator.find(op);

       if(it!=mapOfOperator.end())

       {

         return dynamic_cast<T*>(it->second);

       }

       return NULL;

     }

     ...

};