[C++-sig] Re: discard reference

[David Abrahams]

"Mike Rovner" <mike at nospam.com> writes:

> Hi all,
>
> I'm trying to find an elegant way of discarding python reference.
>
> I have a pure virtual base class A, my class implementation AA and
> a function with wants to take ownership of A*:
>
> class A
> {
>   virtual f1() = 0;
>   virtual ~A() {}
> };
>
> class AA : public A
> {
>   AA(int) {...}
> };
>
> class B
> {
>   void set_new_owner(A* a) { ... }
> };
>
> I shall use it that way:
> b=B()
> - in C++: b.set_new_owner(new AA(1));
> - in Python: b.set_new_owner(AA(1))
>
> Now I wrap it (according to FAQ) with auto_ptr<A*> and a small wrapper:
>
> void set_new_owner_wrap(B& b, auto_ptr<A*> a) { b.set_new_owner(a.get());
> a.release(); }
> ...
> class_<A, auto_ptr<A*>, noncopyable>("A", no_init);
> class_<AA, bases<A>, noncopyable>("AA", init<int>).def("f1", &AA::f1);
> class_<B>("B").def("set_new_owner", &set_new_owner_wrap);
>
> Now the problem: there is no autoconvertion from AA* to auto_ptr<A>.
> What will be the correct way to solve the problem?

Why is that a problem?  I don't see any A* in wrapped function
signatures or returns here,

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com