Class template conversion_dispatch
template <class T, bool Expl = true>
class conversion_dispatch;
Class template conversion_dispatch is a dispatch type for explicit or implicit type conversion expressions. It meets the ProAccessible requirements of applicable types. T is the target type for conversion, and Expl specifies whether the conversion is explicit (defaults to true, as recommended in C++ Core Guidelines C.164: Avoid implicit conversion operators).
Member Functions
| Name |
Description |
| (constructor) [trivial] |
constructs a conversion_dispatch object |
operator() |
invokes the dispatch |
Member Types
| Name |
Description |
accessor |
provides accessibility to proxy |
Example
#include <iomanip>
#include <iostream>
#include "proxy.h"
struct DoubleConvertible : pro::facade_builder
::add_convention<pro::conversion_dispatch<double>, double() const>
::build {};
struct Runnable : pro::facade_builder
::add_convention<pro::operator_dispatch<"()">, void()>
::build {};
struct CopyableRunnable : pro::facade_builder
::support_copy<pro::constraint_level::nontrivial>
::add_facade<Runnable>
::add_direct_convention<pro::conversion_dispatch<pro::proxy<Runnable>, false>,
pro::proxy<Runnable>() const&, pro::proxy<Runnable>() &&>
::build {};
int main() {
// Explicit conversion
pro::proxy<DoubleConvertible> p1 = pro::make_proxy<DoubleConvertible>(123); // p1 holds an integer
std::cout << std::fixed << std::setprecision(10) << std::boolalpha;
std::cout << static_cast<double>(*p1) << "\n"; // Prints: "123.0000000000"
// Implicit conversion
pro::proxy<CopyableRunnable> p2 = pro::make_proxy<CopyableRunnable>(
[] { std::cout << "Lambda expression invoked\n"; });
auto p3 = p2; // Copy construction
pro::proxy<Runnable> p4 = p3; // Implicit conversion via const reference of pro::proxy<CopyableRunnable>
std::cout << p3.has_value() << "\n"; // Prints: "true"
// auto p5 = p4; // Won't compile because pro::proxy<Runnable> is not copy-constructible
pro::proxy<Runnable> p6 = std::move(p3); // Implicit conversion via rvalue reference of pro::proxy<CopyableRunnable>
std::cout << p3.has_value() << "\n"; // Prints: "false"
(*p6)(); // Prints: "Lambda expression invoked"
}
See Also