2012/1/11 Vladimír Třebický <vladimir.trebicky@gmail.com>
On Wed, Jan 11, 2012 at 9:19 AM, Roman Perepelitsa <roman.perepelitsa@gmail.com> wrote:
It can be done. In fact, it has already been done. See http://lists.boost.org/boost-users/2011/09/70647.php.
Nice. I like this. However, once you declare the get_pointer (plus ptr_adater and invoker) there's no way to specify what should happen if lock() returns empty shared_ptr. In the example "invoker" returns default value:
R operator()() const { return ci_.first ? (ci_.first->*ci_.second)() : R(); }
which may (a) not be possible (if R is not default-constructible) or (b) not desired (eg. if user wants an exception to be thrown).
Do you think there would be a way to control the behavior?
In this case one will have to use something like boost::weak_fn or write the trampoline function manually. void do_something(const weak_ptr<foo>& p) { // Complete freedom here. if (shared_ptr<foo> sp = p.lock()) sp->do_something(); else throw "expired weak_ptr"; } bind(do_something, my_weak_ptr)(); In practice, however, I only ever used void-returning functors with weak_ptr. Roman Perepelitsa.