How to run functions in different QThreads - c++

Question

How can I run loop functions in different QThreads? I need to run in different threads because if I don't do it, the loops break.
How to make the on_pushTurnOn_clicked be executed in other thread, and the loop that pushTurnOn must be able to be canceled by on_pushTurnOff_clicked even on a different thread.
MainWindow .h code:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QDebug>
#include <QThread> //I don't know how to use it
#include <QTimer>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
private slots:
void on_pushTurnOn_clicked();
void on_pushTurnOff_clicked();
private:
QTimer *timerLoop;
};
#endif // MAINWINDOW_H
MainWindow cpp code:
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pushTurnOn_clicked()
{
timerLoop = new QTimer(this);
timerLoop->setInterval(3000);
timerLoop->setSingleShot(true);
connect(timerLoop, SIGNAL(timeout()),
SLOT(on_pushTurnOn_clicked()));
qDebug()<<"the loop was started";
timerLoop->start(); //start the loop
}
void MainWindow::on_pushTurnOff_clicked()
{
qDebug()<<"the loop was stoped";
timerLoop->stop(); //stop the loop
}

Answer 1

I will start with a side note. Your memory allocation for timerLoop in on_pushTurnOn_clicked() will cause a memory leak due to absence of deallocation, even though it is a single shot timer. You are creating a new QTimer without destroying the previous allocated one. The better approach is to just allocate memory once in the constructor and just start the timer in on_pushTurnOn_clicked().
Coming back to your question, you will have to split your class into two, one is your mainWindow which has the slots for on_pushTurnOn_clicked() and on_pushTurnOff_clicked(), other possible UI elements and non-intensive tasks.
The second class is a worker which contains the QTimer along with the actual work load. So you would essentially have something like this:
MainWindow.cpp:
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
//constructor
ui->setupUi(this);
this->worker = new Worker(); //object of WorkerClass type
QThread *thread = new QThread();
worker->moveToThread(thread);
connect(this, SIGNAL(startOrStopTimerSignal(bool), worker, SLOT(startStopTimer(bool));
}
void MainWindow::on_pushTurnOn_clicked()
{
if(Busy==1){
qDebug()<<"Is busy!";
}
if(Busy==0){
FuncaoLoop(RandomParameter1, RandomParameter2);
}
//start the timer through a signal (timers need to be started in their own threads)
emit startOrStopTimerSignal(true);
}
void MainWindow::on_pushTurnOff_clicked()
{
emit startOrStopTimerSignal(false); //stop the timer
}
WorkerClass.h/.cpp:
WorkerClass::WorkerClass(QObject *parent) : QObject(parent)
{
timerLoop= new QTimer(this);
connect(timerLoop, SIGNAL(timeout()), this, SLOT(workLoad())); //timer connect to your actual task
}
void WorkerClass::startStopTimer(bool start)
{
if (start)
timerLoop->start();
else
timerLoop->stop();
}
WorkerClass::workLoad()
{
//whatever task for your PLC
}
Hope this helps you out.