std::optional::operator bool, std::optional::has_value - cppreference.com (original) (raw)

Checks whether *this contains a value.

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

Run this code

#include #include   int main() { std::cout << std::boolalpha;   std::optional 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