Question

This is a classic Boost message_queue example:

#include <boost/interprocess/ipc/message_queue.hpp>
using namespace boost::interprocess;
struct Data { ... };

int main() {
    Data data1;

    message_queue::remove("message_queue");

    message_queue mq(create_only, "message_queue", 100, sizeof(Data));

    mq.send(&data1, sizeof(Data), 0);
}

Now I would like to put the mq message_queue object inside a class as a member variable, with the lifetime of this class’ object:

#include <boost/interprocess/ipc/message_queue.hpp>
using namespace boost::interprocess;

struct Data { ... };

class DataManager 
{
    message_queue mq;

public:
    DataManager() 
       : mq(create_only, "message_queue", 100, sizeof(Data))      // ok
    {
        mq.Open(create_only, "message_queue", 100, sizeof(Data));   // Open does not exist
    }
};

It seems I can only initialise the mq object in the member initialisation list, since message_queue does not provide the member functions to set its parameters at a later time.

Am I wrong? Is there another way to do it?

I would like to be able, e.g., to let an object use a message queue whose name is passed as a parameter to one of its member functions.

Thank you.

Answer 1

How about this :

class QueueManager
{
  boost::scoped_ptr<message_queue> mq;

  // ctor
  QueueManager(string msgqname) 
  {
      mq.reset(new message_queue(create_only, msgqname, 100, sizeof(Data));
  }
};

Just to give you an idea that at least some parameters can be passed to class constructor.
Since message queue uses shared memory underneath, I think most parameters can not be changed after construction.