so_5/modify_resend_as_immutable/main.cpp

/*
 * Example of usage of mutable_msg with resending it as an immutable_msg.
 */

#include <iostream>

#include <so_5/all.hpp>

// A message which will be modified.
struct envelope final : public so_5::message_t
{
  // Payload to be modified.
  // Please note: it is not a const object.
  std::string m_payload;

  envelope(std::string payload) : m_payload(std::move(payload)) {}
};

// An agent which will mutate message.
class modificator_agent final : public so_5::agent_t
{
public :
  modificator_agent(context_t ctx,
    std::string prefix, std::string suffix,
    so_5::mbox_t receiver)
    : so_5::agent_t(std::move(ctx))
    , m_prefix(std::move(prefix))
    , m_suffix(std::move(suffix))
    , m_receiver(std::move(receiver))
  {
    so_subscribe_self().event( &modificator_agent::on_envelope );
  }

private :
  const std::string m_prefix;
  const std::string m_suffix;
  const so_5::mbox_t m_receiver;

  void on_envelope(mutable_mhood_t<envelope> cmd)
  {
    // Show message address and its old content.
    std::cout << "modificator, msg_addr=" << cmd.get()
        << ", old_content=" << cmd->m_payload;

    // Modify message's payload.
    cmd->m_payload.insert(begin(cmd->m_payload), begin(m_prefix), end(m_prefix));
    cmd->m_payload.insert(end(cmd->m_payload), begin(m_suffix), end(m_suffix));
    std::cout << ", new_content=" << cmd->m_payload << std::endl;

    // Resend the message to receiver as an immutable message.
    so_5::send(m_receiver, to_immutable(std::move(cmd)));
  }
};

// Type of agent which will receive modified message.
class receiver_agent final : public so_5::agent_t
{
public :
  receiver_agent(context_t ctx) : so_5::agent_t(std::move(ctx))
  {
    so_subscribe_self().event( &receiver_agent::on_envelope );
  }

private :
  void on_envelope(mhood_t<envelope> cmd)
  {
    // Show message address and its resulting content.
    std::cout << "receiver, msg_addr=" << cmd.get()
        << ", content=" << cmd->m_payload;

    so_deregister_agent_coop_normally();
  }
};

int main()
{
  try
  {
    so_5::launch( [](so_5::environment_t & env) {
      so_5::mbox_t modificator_mbox;
      // Create a coop with agents
      env.introduce_coop( [&](so_5::coop_t & coop) {
        auto receiver = coop.make_agent<receiver_agent>();
        auto modificator = coop.make_agent<modificator_agent>(
            "<{(", ")}>", receiver->so_direct_mbox() );
        modificator_mbox = modificator->so_direct_mbox();
      } );

      // Send mutable message with initial content.
      so_5::send<so_5::mutable_msg<envelope>>(modificator_mbox, "hello");
    } );
  }
  catch(const std::exception & x)
  {
    std::cerr << "Oops! Exception: " << x.what() << std::endl;
  }

  return 0;
}