Re: [Quantlib-dev] QuantLib-SWIG, the observer pattern and destructor call during update

[Bojan N. <bo...@bn...>]

Hi Luigi,

I haven't fully worked this one out, but I think that it is possible to
some progress on this by making the destructor of the Observer class
private and then creating some helper classes (probably inheriting from
shared_pointer) that are friends of Observer and define proper clean
order, i.e., disconnect the Observables before starting the main
destruction.

This approach would enforce code correctness at compile time (because
non-safe destruction of Observer objects would be a compile time error)
but would obviously require changes to existing code. It should play
fairly well with SWIG which is I think already aware of the implications
of a private destructor.

There is no less invasive way I can think of at moment -- the goal of
having easy composition of objects in C++ makes it very hard to re-order
destruction operations! Possibly one can do something very clever with
clone()-able objects and overriding the operator new() for Observer but
that would be getting really complicated....

Best,
Bojan

-- 
Bojan Nikolic          ||          http://www.bnikolic.co.uk