C++20 std::variant optimization guide as expected with lambda capture during event handling
I've been researching this but I'm experimenting with After trying multiple solutions online, I still can't figure this out..... I'm sure I'm missing something obvious here, but I'm stuck on something that should probably be simple. I'm working with an scenario when using `std::variant` in combination with lambda captures in a simple event handling mechanism. I have a class that holds a `std::variant` of two possible types: `int` and `std::string`. My intention is to handle these types separately when an event is triggered. However, the lambda I’m using to process the event seems to be capturing the wrong type, leading to incorrect outputs. Here’s a simplified version of my code where I’m working with the scenario: ```cpp #include <iostream> #include <variant> #include <string> #include <functional> class EventHandler { public: using EventType = std::variant<int, std::string>; void triggerEvent(EventType event) { auto handler = [event]() { if (std::holds_alternative<int>(event)) { std::cout << "Integer event: " << std::get<int>(event) << std::endl; } else if (std::holds_alternative<std::string>(event)) { std::cout << "String event: " << std::get<std::string>(event) << std::endl; } }; handler(); } }; int main() { EventHandler eh; eh.triggerEvent(42); // Expected: "Integer event: 42" eh.triggerEvent(std::string("Hello")); // Expected: "String event: Hello" return 0; } ``` When I run this code, the output is not as expected. The first call to `triggerEvent(42)` outputs nothing, and the second call still produces the expected output for the string event. I suspect it has something to do with the way the lambda is capturing `event`, but I can’t seem to find a fix. I’ve tried adjusting the capture from `[event]` to `[&event]` to see if it makes a difference, but that led to a compilation behavior with the variant. Could this be a lambda capture scenario, or am I misusing `std::variant`? Any insights would be appreciated! My development environment is Linux. What's the best practice here? My development environment is Linux. Any help would be greatly appreciated! I'm working on a service that needs to handle this. Any help would be greatly appreciated! I've been using C++ for about a year now.