NAME

std::any::has_value - std::any::has_value

Synopsis

bool has_value() const noexcept; (since C++17)

Checks whether the object contains a value.

Parameters

(none)

Return value

true if instance contains a value, otherwise false.

Example

// Run this code

#include <any>
#include <iostream>
#include <string>

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

std::any a0;
std::cout << "a0.has_value(): " << a0.has_value() << "\n";

std::any a1 = 42;
std::cout << "a1.has_value(): " << a1.has_value() << '\n';
std::cout << "a1 = " << std::any_cast<int>(a1) << '\n';
a1.reset();
std::cout << "a1.has_value(): " << a1.has_value() << '\n';

auto a2 = std::make_any<std::string>("Milky Way");
std::cout << "a2.has_value(): " << a2.has_value() << '\n';
std::cout << "a2 = \"" << std::any_cast<std::string&>(a2) << "\"\n";
a2.reset();
std::cout << "a2.has_value(): " << a2.has_value() << '\n';
}

Output:

a0.has_value(): false
a1.has_value(): true
a1 = 42
a1.has_value(): false
a2.has_value(): true
a2 = "Milky Way"
a2.has_value(): false

See also

reset destroys contained object
(public member function)