Passing Data to a slot in another thread

[badzie]

Dear all,

I am a beginner in Qt. In my GUI, I'm getting the values of 3 temperatures in spinboxes and I want these values to be transmitted to another thread on button click. So here is my code
for

MainWindow.h
@
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include"ProcessThread.h"
namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
explicit MainWindow(QWidget *parent = 0);

~MainWindow();

signals:
void SendSignal(unsigned int temp_1,unsigned int temp_2,unsigned int temp_3);

private slots:

void Get_From_SpinBox(void);

private:
Ui::MainWindow *ui;
ProcessThread p;
};

#endif // MAINWINDOW_H
@
MainWindow.cpp
@
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include<QDebug>
#include<QDir>
#include<QFile>
#include<QString>
#include "ProcessThread.h"
#include<QLabel>
#include<QThread>
#include<QObject>

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QThread *prthread=new QThread();
connect(ui->pushButton,SIGNAL(clicked()),this,SLOT(Get_From_SpinBox()));
connect(this,SIGNAL(MainWindow::SendSignal(int,int,int)),prthread,SLOT(Store_Temperatures(int ,int ,int )),Qt::QueuedConnection);
prthread->start();
}

MainWindow::~MainWindow()
{

p.exit();
p.wait();

}

void MainWindow::Get_From_SpinBox()
{
temp_1=ui->spinBox->value();
temp_2=ui->spinBox_2->value();
temp_3=ui->spinBox_3->value();
emit SendSignal(temp_1,temp_2,temp_3);

}

@
The following is my ProcessThread.h
@
#ifndef PROCESSTHREAD_H
#define PROCESSTHREAD_H

#include<QtGui>
#include<QThread>
#include<QString>
#include<QObject>
class ProcessThread : public QThread
{
Q_OBJECT
public:
explicit ProcessThread(QObject *parent = 0);
void run();

signals:

public slots:
void WriteFileToUSB();
void GetValues();
void Store_Temperatures( int temp1, int temp2, int temp3);
private:

};

#endif // MYTHREAD_H
@
and finally, my ProcessThread.cpp
@

#include "ProcessThread.h"
#include<QtCore>
#include "ui_mainwindow.h"
#include<QDebug>
#include"mainwindow.h"
#include<QDebug>

void ProcessThread::run()
{
qDebug() << "hello from worker thread " << thread()->currentThreadId();
exec();
}

ProcessThread::ProcessThread(QObject *parent ):QThread(parent){
moveToThread(this);
}

void ProcessThread::Store_Temperatures( int temp1, int temp2, int temp3)
{
qDebug()<<temp1;
qDebug()<<temp2;
qDebug()<<temp3;
}

@

However, my slot in my thead Store_Temperatures is not getting executed. Is this is a proper way of passing value to a thread?

I tried using the suggestions given in

http://qt-project.org/forums/viewthread/23887

Yet to resolve. Kindly help

[t3685]

Hi,

First of all, the way you are using threads is NOT the way recommended by Qt.

Have a look at the notes at the end of this page:
http://qt-project.org/doc/qt-4.8/qthread.html#details

As for your code. I see that you have a ProcessThread p as member of MainWindow. However in the MainWindow constructor you never start this thread. Instead you are creating a QThread *pthread = new QThread. ProcessThread p is never started or connected to.

There should be error warnings as you run this program because QThread does not have a Store_Temperatures slot.
*More importantly pthread is never deleted, so you're leaking memory.

Hope this helps.

[badzie]

Thanks for the reply.

I made the correction in my code making use of ProcessThread p which is a member of mainwindow.
@
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
connect(ui->pushButton,SIGNAL(clicked()),this,SLOT(Get_From_SpinBox()));
connect(this,SIGNAL(MainWindow::SendSignal(int,int,int)),&p,SLOT(Store_Temperatures(int,int,int)),Qt::QueuedConnection);
p.start();

}
@

But Store_Temperatures slot is present in ProcessThread.h and I'm not getting any errors or warnings. Only that my Store_Temperatures slot is not running.

[badzie]

I solved the problem. The problem was with my connect, where I wrote as MainWindow::SendSignal, instead I made as SendSignal(int,int,int) and it worked. Thanks!