Alias template as_weak
Header:
proxy.h
Module:proxy
Namespace:pro::skills
Since: 4.0.0
template <class FB>
using as_weak = /* see below */;
The alias template as_weak modifies a specialization of basic_facade_builder to allow implicit conversion from proxy<F> to weak_proxy<F>, where F is a built facade type.
Let p be a value of type proxy<F>, ptr be the contained value of p (if any), Ptr be the type of ptr, the conversion from type const proxy<F>& to type weak_proxy<F> is equivalent to return typename Ptr::weak_type{p} if p contains a value, or otherwise equivalent to return nullptr.
Example
#include <iostream>
#include <proxy/proxy.h>
struct RttiAware : pro::facade_builder
::support<pro::skills::rtti>
::support<pro::skills::as_weak>
::build {};
int main() {
pro::proxy<RttiAware> p1 = pro::make_proxy_shared<RttiAware>(123);
pro::weak_proxy<RttiAware> p2 = p1;
proxy_cast<int&>(*p1) = 456; // Modifies the contained object of p1
pro::proxy<RttiAware> p3 = p2.lock();
p1.reset();
std::cout << proxy_cast<int>(*p3) << "\n"; // Prints "456"
p3.reset();
pro::proxy<RttiAware> p4 = p2.lock();
std::cout << std::boolalpha << p4.has_value() << "\n"; // Prints "false"
}