make_proxy_viewThe definition of make_proxy_view makes use of an exposition-only class template observer-ptr. observer-ptr<T> contains a raw pointer to an object of type T, and provides operator* for access with the same qualifiers.
template <facade F, class T>
proxy_view<F> make_proxy_view(T& value) noexcept;
Creates a proxy_view<F> object containing a value p of type observer-ptr<T>, where *p is direct-non-list-initialized with &value. If proxiable_target<T, F> is false, the program is ill-formed and diagnostic messages are generated.
The constructed proxy_view object.
#include <iostream>
#include <map>
#include <string>
#include "proxy.h"
PRO_DEF_MEM_DISPATCH(MemAt, at);
struct ResourceDictionary : pro::facade_builder
::add_convention<MemAt, std::string&(int index), const std::string&(int index) const>
::build {};
int main() {
std::map<int, std::string> dict;
dict[1] = "init";
pro::proxy_view<ResourceDictionary> pv = pro::make_proxy_view<ResourceDictionary>(dict);
static_assert(std::is_same_v<decltype(pv->at(1)), std::string&>, "Non-const overload");
static_assert(std::is_same_v<decltype(std::as_const(pv)->at(1)), const std::string&>, "Const overload");
std::cout << std::as_const(pv)->at(1) << "\n"; // Invokes the const overload and prints "init"
pv->at(1) = "modified"; // Invokes the non-const overload
std::cout << std::as_const(pv)->at(1) << "\n"; // Invokes the const overload and prints "modified"
}