std::option...::has_value(3)

✨ NAME ✨

std::optional::operatorbool,std::optional::has_value — okay so these two are literally the same vibe check but in different outfits 💅

(this whole page lives in the C++ Standard Libary manual, section 3, bestie 🎀)

🌸 SYNOPSIS 🌸

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

Both of these are asking the exact same question: does *this actually contain a value or not? 👀

🦋 PARAMETERS 🦋

• (none) — nope, nothing, zero, not a single parameter. she takes no args 🫶

💖 RETURN VALUE 💖

1. true if *this contains a value ⭐
2. false if *this does not contain a value 💀

That's it. That's the whole function. iconically simple, no cap.

🌈 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

so yeah, has_value() and operator bool are besties fr fr — one's a method, one's the explicit bool conversion, and both of them are just telling you whether the optional is holding something or is empty 🧚 noexcept and constexpr since C++17, periodt. 💜

mwah, kisses — this page came from http://cppreference.com, dated 2024.06.10 🎀 bye bestie, go check your optionals 💅