NAME

std::optional::operatorbool,std::optional::has_value - std::optional::operatorbool,std::optional::has_value

Synopsis

constexpr explicit operator bool() const noexcept; (since C++17)
constexpr bool has_value() const noexcept; (since C++17)

Checks whether *this contains a value.

Parameters

(none)

Return value

true if *this contains a value, false if *this does not contain a value.

Example

// Run this code

#include <optional>
#include <iostream>

int main()
{
std::cout << std::boolalpha;

std::optional<int> opt;
std::cout << opt.has_value() << '\n';

opt = 43;
if (opt)
std::cout << "value set to " << opt.value() << '\n';
else
std::cout << "value not set\n";

opt.reset();
if (opt.has_value())
std::cout << "value still set to " << opt.value() << '\n';
else
std::cout << "value no longer set\n";
}

Output:

false
value set to 43
value no longer set