Qt application and Multithreading error.

lakshmanGiri

Hi, I am working multi-thread. I have a function called initThread(),
where I am initializing the thread and then I have a thread function
where I have the logic I want to perform in that thread. Then,
I pass it to another function. The thing
is the thread is starting twice on the second click and thrice on the third click and it gets increases as such.

I will provide a sample code here, Please go through it.

//someClass.cpp

someClass::someClass(QObject *parent) : QObject(parent)
{
	initThread();
}
void someClass::initThread()
{
	sampleThread = new QThread(this);
    	connect(sampleThread &QThread::finished, this, [](){
        qDebug() << "sampleThread is finished";
    	});
}
void someClass::callSampleThreadFunction()
{
	sampleThreadFunction();
}
void someClass::sampleThreadFunction()
{
	connect(sampleThread &QThread::started, this, [](){
        qDebug() << "sampleThread is started";
    	});

	connect(sampleThread &QThread::started, this, [](){
        	// My logic here
		sampleThread->exit();
    	});
	connect(sampleThread, &QThread::finished, this, &QThread::deleteLater);
	sampleThread->start();
}

// MainWindow.cpp

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
    , class(new someClass)
{

}
void MainWindow::on_pushButton_clicked()
{
	
    class->callSampleThreadFunction();
}

And I get output like this...

// Output

sampleThread is started
sampleThread is finished

sampleThread is started
sampleThread is started
sampleThread is finished

sampleThread is started
sampleThread is started
sampleThread is started
sampleThread is finished

Why I am getting like this, Am I went wrong anywhere?. Thanks in advance.

KroMignon

@lakshmanGiri said in Qt application and Multithreading error.:

Hi, I am working multi-thread. I have a function called initThread(),
where I am initializing the thread and then I have a thread function
where I have the logic I want to perform in that thread.

Then, I have a standard function where I call the thread function. The thing
is the thread is starting twice on the second click and thrice on the third click and it gets increases as such.

What is a "thread" function and a "standard" function???

And why do you not simply use QtConcurrent::run() if you want to start a function in another thread?
Take a look at https://doc.qt.io/qt-5/qtconcurrentrun.html