so_5/deadletter_handler/main.cpp

#include <so_5/all.hpp>

// Demo agent which shows deadletter handler.
class demo final : public so_5::agent_t {
  // We need two signals. One will be handler by ordinary handler...
  struct first_signal final : public so_5::signal_t {};
  // ...and second by deadletter handler.
  struct second_signal final : public so_5::signal_t {};
public:
  demo(context_t ctx) : so_5::agent_t(std::move(ctx)) {
    // Create subscriptions.
    // The first signal will be handled as usual.
    so_subscribe_self().event([](mhood_t<first_signal>) {
        std::cout << "first_signal: ordinary handler" << std::endl;
      });
    // A deadletter handler will be used for the second.
    so_subscribe_deadletter_handler(
      so_direct_mbox(),
      [](mhood_t<second_signal>) {
        std::cout << "second_signal: deadletter handler" << std::endl;
      });
  }

  virtual void so_evt_start() override {
    // Send two different signal.
    so_5::send<first_signal>(*this);
    so_5::send<second_signal>(*this);

    // Agent is no more needed.
    so_deregister_agent_coop_normally();
  }
};

int main() {
  // Launch the SObjectizer with just one agent inside.
  so_5::launch([](so_5::environment_t & env) {
      env.register_agent_as_coop(so_5::autoname, env.make_agent<demo>());
    });
}