std::optional::value(3)

std::optional::value 💅✨

okay so this is std::optional::value from the C++ Standard Libary manual — yes, “Libary” with one R, the typo is canon, don’t come for me 💀. It’s giving “checked access bestie” and honestly? Obsessed.

NAME 🎀

std::optional::value — std::optional::value. Yep, the name is the name, twice, because why not. Iconic. Periodt.

✨ Synopsis ✨

constexpr T& value() &;               (1) (since C++17)
constexpr const T& value() const &;
constexpr T&& value() &&;             (2) (since C++17)
constexpr const T&& value() const &&;

If *this contains a value, it returns a reference to the contained value.

Otherwise, it throws a std::bad_optional_access exception. That’s the whole plot, no cap 😭.

Parameters 🫶

(none) — literally none, bestie. Zero. Nada. 🧚

Return value 💖

A reference to the contained value. Slay.

Exceptions 🚨

std::bad_optional_access if *this does not contain a value. So like, it will absolutely call you out if you try to access nothing, fr fr.

Notes 📝

The dereference operator operator*() does not check if this optional contains a value, which may be more efficient than value(). That’s the note. That’s the vibe. Lowkey important, highkey iconic. 💅

Example 🌸

Here’s the code, bestie — run it and see for yourself:

// Run this code

#include <iostream>
#include <optional>

int main()
{
    std::optional<int> opt = {};

    try
    {
        [[maybe_unused]] int n = opt.value();
    }
    catch(const std::bad_optional_access& e)
    {
        std::cout << e.what() << '\n';
    }

    try
    {
        opt.value() = 42;
    }
    catch(const std::bad_optional_access& e)
    {
        std::cout << e.what() << '\n';
    }

    opt = 43;
    std::cout << *opt << '\n';

    opt.value() = 44;
    std::cout << opt.value() << '\n';
}

Output: 💬

bad optional access
bad optional access
43
44

👀 See also 👀

• value_or — returns the contained value if available, another value otherwise (public member function)
• operator-> — accesses the contained value
• operator* — (public member function)
• bad_optional_access — exception indicating checked access to an optional that doesn’t contain a value (C++17) (class)

okay bye bestie 🫶 the source is http://cppreference.com, the date on this one is 2024.06.10, and yeah — it’s std::optional::value(3). mwah 💋✨