Passing strings to SLOT function

[anda_skoa]

With this run() method You never receive any signal because thread event loop is never started.

Actually it should, unless ServerThread has been moveToThread() into itself.

What are You doing in this "never ending" loop ?

That is, of course, a good question.

Since the suggestion not to use a thread seems to have been ignored, I have to assume it is because of the 0MQ library, i.e. it only works with blocking calls.

All speculation until we see the actual code for ServerThread::run()

Cheers,
_

[ashboi]

Yes, that's correct, I'm using 0MQ for my sockets. There isn't any SERVER running on the app itself, the server script is running on another device.

Here is a simplified version of my socket thread function;

On serverthread.cpp

void SocketThread::send(QString message)
{
this->message = message;
}

void SocketThread::run()
{
string addr1 = "tcp://localhost:8886";
char *addr1_cstr1 = (char *) addr1.c_str();

zmq::context_t context(1);
zmq::socket_t sender(context, ZMQ_PUSH);
sender.connect(addr1_cstr1);

string addr2 = "tcp://localhost:8887";
char *addr_cstr2 = (char *) addr2.c_str();

zmq::socket_t reply(context, ZMQ_SUB);
reply.connect(addr_cstr2);
reply.setsockopt(ZMQ_SUBSCRIBE, "", 0);

string addr3 = "tcp://localhost:8888";
char *addr_cstr3 = (char *) addr3.c_str();

while(1)
{
string string_in = message.toStdString();
string to_send = "";

cout << "Input here: ";
getline(cin, string_in);
if(string_in == "test")
{
to_send = "test";
s_send(sender, (char *) to_send.c_str());
receive_msgs(reply);
to_send = "";
}
}
exec();
}

on socketthread.h

#ifndef SOCKET_H
#define SOCKET_H
#include <QThread>

class SocketThread : public QThread
{
Q_OBJECT
public slots:
void send(QString message);

private:
void run();
QString message;
};
#endif // SOCKET_H

[anda_skoa]

In this case you need to make sure that
1) the connect to send(QString) uses connection type Qt:irectConnection (the receiver thread does not run an event loop).
2) use a QMutex member in SocketThread to protect both accesses to message

void SocketThread::send(QString message)
{
  QMutexLocker locker(&mutex); // assuming the mutex member is called mutex
  this->message = message;
}

void SocketThread::send(QString message)
{
  QMutexLocker locker(&mutex); // assuming the mutex member is called mutex
  this->message = message;
}

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while(1)
{
  mutex.lock();
  string string_in = message.toStdString();
  mutex.unlock();
...

while(1)
{
  mutex.lock();
  string string_in = message.toStdString();
  mutex.unlock();
...

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Cheers,
_

[ashboi]

I've tried the QMutex method, not sure what I might have done wrong, but for some reason I am still unable to receive the string when i click the pushbutton.

[wysota]

Could you elaborate on what you mean by "unable to receive the string"? Which code runs, which does not?

[ashboi]

Seems good now, I tested it with qdebug, and it was able to print out the emitted string. Sorry for the confusion.

I was wondering is it possible to use qdebug or something equivalent and use the message.toStdString with getline to use the emitted string as an input(cin)?
Correct me if I'm wrong about this, am I correct to say that qdebug can only be used for cout and not cin? On the other hand, if I'm using string string_in = message.toStdString(); as suggested, the app doesn't seem to be able to take the emitted string and do what it needs to do. The app just sits there waiting for an input, which it never gets when the pushbutton is clicked.

Also, I've tried using

QTextStream qtin(stdin);
qtin >> message;

doesn't seem to work.

[wysota]

For debug is for debugging output. If you don't want to use cin, you can use QTextStream with stdin. I assure you it works, apparently you're using it wrong.

[anda_skoa]

The app just sits there waiting for an input, which it never gets when the pushbutton is clicked.

You have two types of input: one through the button and the signal, one through reading from cin. The latter will of course block until it can read something from stdin.

Or did you mean it is hanging somewhere else?

Cheers,
_