Alias template as_view
Header:
proxy.h
Module:proxy
Namespace:pro::skills
Since: 4.0.0
template <class FB>
using as_view = /* see below */;
The alias template as_view modifies a specialization of basic_facade_builder to allow implicit conversion from proxy<F> to proxy_view<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), the conversion from type proxy<F>& to type proxy_view<F> is equivalent to return observer-ptr{std::addressof(*ptr)} if p contains a value, or otherwise equivalent to return nullptr. observer-ptr is an exposition-only type that *observer-ptr, *std::as_const(observer-ptr), *std::move(observer-ptr) and *std::move(std::as_const(observer-ptr)) are equivalent to *ptr, *std::as_const(ptr), *std::move(ptr) and *std::move(std::as_const(ptr)), respectively.
Notes
as_view is useful when a certain context does not take ownership of a proxy object. Similar to std::unique_ptr::get, std::shared_ptr::get and the borrowing mechanism in Rust.
Example
#include <iostream>
#include <proxy/proxy.h>
struct RttiAware : pro::facade_builder
::support<pro::skills::rtti>
::support<pro::skills::as_view>
::build {};
int main() {
pro::proxy<RttiAware> p = pro::make_proxy<RttiAware>(123);
pro::proxy_view<RttiAware> pv = p;
proxy_cast<int&>(*pv) = 456; // Modifies the contained object of p
std::cout << proxy_cast<int>(*pv) << "\n"; // Prints "456"
std::cout << proxy_cast<int>(*p) << "\n"; // Prints "456"
}