How do I use std::optional/variant/any in C++17?

Learn how to use std::optional, std::variant, and std::any in C++17. These features provide ways to handle optional values, multiple types, and any type of value, enhancing type safety and flexibility in your code.

C++, C++17, std::optional, std::variant, std::any, type safety, programming, examples


        // Example of std::optional
        #include <optional>
        #include <iostream>

        std::optional getValue(bool returnValue) {
            if (returnValue) {
                return 42;
            } else {
                return std::nullopt; // No value
            }
        }

        int main() {
            auto value = getValue(true);
            if (value) {
                std::cout << "Value: " << *value << std::endl;
            } else {
                std::cout << "No value returned." << std::endl;
            }
            return 0;
        }

        // Example of std::variant
        #include <variant>
        #include <iostream>

        std::variant getVariant(bool returnString) {
            if (returnString) {
                return "Hello, World!";
            } else {
                return 42;
            }
        }

        int main() {
            auto var = getVariant(false);
            std::visit([](auto&& arg){ std::cout << arg << std::endl; }, var);
            return 0;
        }

        // Example of std::any
        #include <any>
        #include <iostream>

        std::any getAnyValue() {
            return 3.14; // can store different types
        }

        int main() {
            auto value = getAnyValue();
            try {
                std::cout << std::any_cast(value) << std::endl; // Cast to double
            } catch (const std::bad_any_cast& e) {
                std::cout << "Bad cast!" << std::endl;
            }
            return 0;
        }

C++ C++17 std::optional std::variant std::any type safety programming examples

How do I use std::optional/variant/any in C++17?

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How do I use std::optional/variant/any in C++17?

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