How do I pattern match (std::visit) std::optional in C++?

In C++, you can pattern match with `std::optional` using `std::visit`. Here's a guide on how to achieve this effectively.

To work with `std::optional`, you can use `std::variant` along with `std::visit` for a clean and powerful approach to handle optional values. Below is an example demonstrating how to use these features together.

#include #include #include // A variant that can hold either an int or an std::nullopt using OptionalInt = std::variant<:monostate int>; void processOptional(const std::optional& opt) { OptionalInt variant = opt ? OptionalInt(*opt) : OptionalInt{}; std::visit([](auto&& arg) { using T = std::decay_t; if constexpr (std::is_same_v) { std::cout << "Value: " << arg << std::endl; } else { std::cout << "No value present" << std::endl; } }, variant); } int main() { std::optional value = 42; processOptional(value); // This will print: Value: 42 std::optional emptyValue; processOptional(emptyValue); // This will print: No value present return 0; }

C++ std::optional std::visit pattern matching std::variant

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