proxy_cast// (1)
template <class T>
T proxy_cast(const proxy_indirect_accessor<F>& operand);
// (2)
template <class T>
T proxy_cast(proxy_indirect_accessor<F>& operand);
// (3)
template <class T>
T proxy_cast(proxy_indirect_accessor<F>&& operand);
// (4)
template <class T>
T proxy_cast(const proxy<F>& operand);
// (5)
template <class T>
T proxy_cast(proxy<F>& operand);
// (6)
template <class T>
T proxy_cast(proxy<F>&& operand);
// (7)
template <class T>
const T* proxy_cast(const proxy_indirect_accessor<F>* operand) noexcept;
// (8)
template <class T>
T* proxy_cast(proxy_indirect_accessor<F>* operand) noexcept;
// (9)
template <class T>
const T* proxy_cast(const proxy<F>* operand) noexcept;
// (10)
template <class T>
T* proxy_cast(proxy<F>* operand) noexcept;
Performs type-safe access to the contained object of proxy<F> where F is a facade type built from basic_facade_builder.
(1-3) Let p be access_proxy<F>(operand), ptr be the contained value of p (if any). If p does not contain a value or std::is_same_v<std::decay_t<decltype(expr)>, std::decay_t<T>> is false, throws bad_proxy_cast. Otherwise, returns static_cast<T>(expr). Specifically, expr is defined as
(1): *std::as_const(ptr).(2): *ptr.(3): *std::move(ptr).(4-6) Let ptr be the contained value of operand (if any). If operand does not contain a value or std::is_same_v<std::decay_t<ptr>, std::decay_t<T>> is false, throws bad_proxy_cast. Otherwise, returns static_cast<T>(expr). Specifically, expr is defined as
(6): std::as_const(ptr).(7): ptr.(8): std::move(ptr).(7-10) Returns &proxy_cast<T>(*operand) if the evaluation won’t throw, or otherwise, returns nullptr.These functions are not visible to ordinary unqualified or qualified lookup. It can only be found by argument-dependent lookup when proxy_indirect_accessor<F> (if support_rtti or support_indirect_rtti is specified) or proxy<F> (if support_direct_rtti is specified) is an associated class of the arguments. Usage of these functions is similar to std::any_cast.
#include <iostream>
#include "proxy.h"
struct RttiAware : pro::facade_builder
::support_rtti
::build {};
int main() {
int v = 123;
pro::proxy<RttiAware> p;
try {
proxy_cast<int>(*p); // Throws
} catch (const pro::bad_proxy_cast& e) {
std::cout << e.what() << "\n"; // Prints an explanatory string
}
p = &v;
std::cout << proxy_cast<int>(*p) << "\n"; // Prints "123"
proxy_cast<int&>(*p) = 456;
std::cout << v << "\n"; // Prints "456"
try {
proxy_cast<double>(*p); // Throws
} catch (const pro::bad_proxy_cast& e) {
std::cout << e.what() << "\n"; // Prints an explanatory string
}
int* ptr1 = proxy_cast<int>(&*p);
std::cout << ptr1 << "\n"; // Prints an address
std::cout << &v << "\n"; // Prints the same address as above
double* ptr2 = proxy_cast<double>(&*p);
std::cout << ptr2 << "\n"; // Prints "0"
}