Another issue.

Posted by Johan Bosaeus-3 on Jan 18, 2002; 1:41am
URL: http://quantlib.414.s1.nabble.com/Another-issue-tp1843.html

Hello Luigi,
1) The last lines I wrote in yesterday's mail was:
 "Of course, STRATEGY must have a fixed interface, but our implementation can maintain its "inheritance" hierarchy. I think the Observer would benefit of an analogous template class also."

That isn't true, since if I subclass ObservableStrategy, any interface of STRATEGY is OK, as  long as the subclass can adapt the interface of "ObservableStrategy" to what the STRATEGY needs, everything is OK. Sorry, about that.

2) How do you implement persistence? We makes use of the OO database VERSANT. So our persistent classes, such as our Instruments, inherit from the VERSANT class PObject, in order to make them persistent. Then there are some other stuff to make it work, like schema compilation. I our case the same arguments to create an "ObservableStrategy" template class, applies for persistence too.

For example:

  .hh/.h file:

        template<class INSTR_IMPL, class OBSERVER_IMPL, class OBSERVABLE_IMPL>
        class InstrumentStrategy : public ObserverStrategy<OBSERVER_IMPL>,
                                   public ObservableStrategy<OBSERVABLE_IMPL>
        {
          public:
            InstrumentStrategy(const INSTR_IMPL& instrument_impl,
                               const OBSERVER_IMPL& observer_impl,
                               const OBSERVABLE_IMPL& observable_impl,
                               const std:string &isinCode="",
                               const std::string &descriptions="")
            .....
          private:
            INSTR_IMPL& _impl;
        }

This would offer complete freedom with regard to the local implementations. The strategy's merely works as adapaters.
Would appreciate very much your comments about it. It's valuable indeed!

                                     Bye Johan