how to use defer?

[RedTrait]

#include <uWebSockets/App.h>
#include <uWebSockets/Loop.h>
#include <iostream>
void timerTask(uWS::Loop* loop) {
  auto i = 0;
  while (i<10) {
    std::this_thread::sleep_for(std::chrono::seconds(1));  // wait for 1 second
    std::cout << "Timer task is running..." << std::endl;
    std::cout << "Thread ID: " << std::this_thread::get_id() << std::endl;
    loop->defer([]() { std::cout << "Hello, world!" << std::endl; });
    i+=1;
  }
}
int main() {
  auto loop = uWS::Loop::get();
  std::cout << "Thread ID: " << std::this_thread::get_id() << std::endl;
  std::thread timerThread([loop] { timerTask(loop); });
  std::cout << "Thread ID: " << std::this_thread::get_id() << std::endl;
  loop->run();
  return 0;
}

This doesn't look like it has any effect. loop does not execute the method

[uNetworkingAB]

Loop.run will return immediately since you have nothing on it

[RedTrait]

#include <uWebSockets/App.h>

int main() {
  auto t = std::thread([]() {
    uWS::Loop* loop = uWS::Loop::get();
    uWS::App()
        .get("/*",
             [loop](auto* res, auto* req) {
               // This is a dummy handler
               loop->defer([]() {
                 // This code will be executed in the next iteration of the
                 // event loop
                 std::cout << "Task added to the loop!\n";
               });
               res->end("Hello!");
             })
        .listen(9001,
                [](auto* token) {
                  if (token) {
                    std::cout << "Listening on port 9001" << std::endl;
                  } else {
                    std::cout << "Failed to listen on port 9001" << std::endl;
                  }
                })
        .run();

    std::this_thread::sleep_for(std::chrono::seconds(1));
  });

  t.join();

  return 0;
}

Sorry, I still can't trigger defer. Is there any problem with this example?

[markmaker]

I'm answering for what the initial issue asked, i.e. how to use defer() when there is no uWS::App.

Might be considered a duplicate of this:
#1705

I solved it by using libuv and then add an active libuv native handle (that I need anyways) to it:

Build uWS with WITH_LIBUV=1 and uSockets with LIBUS_USE_LIBUV=1.

    // FIRST THING
    // inject our own uv_loop into uWS.
    uv_loop_t uv_task_loop;
    uv_loop_init(&uv_task_loop);
    auto taskLoop = uWS::Loop::get(&uv_task_loop);

    // add an interrupt signal
    uv_signal_t signal;
    uv_signal_init(&uv_task_loop, &signal);
    uv_signal_start(&signal, mySigIntHandler, SIGINT);
    uv_signal_t * task_signal = &signal;

This way the task loop remains alive, even when used without uWS::App. It could be any libuv handle, e.g. a uv_timer_t etc.

_Mark