coroutine-examples/future_test.cpp at main · txia23/coroutine-examples · GitHub

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#include <iostream>
#include <folly/futures/Promise.h>
#include <fmt/core.h>


int main() {
    folly::Promise<int> prom;
    folly::Future<int> fut = prom.getFuture();

    std::thread t([p = std::move(prom)]() mutable {
      std::this_thread::sleep_for(std::chrono::milliseconds(2));
      p.setValue(42);
    });

    fmt::print("Waiting for result...(1)\n");
    fmt::print("Waiting for result...(2)\n");
    fmt::print("Waiting for result...(3)\n");

    auto g = std::move(fut).thenValue([](int result) {
      if (result) {
        fmt::print("Branch taken, result was non-zero\n");
      } else {
        fmt::print("Branch not taken, result was zero\n");
      }
      fmt::print("Result: {}\n", result);
      return result; // optional, just to keep g as Future<int>
    });

    fmt::print("Main continues without blocking.\n");

    std::move(g).wait();

    t.join();
  }