C++ Timer difficulties

Question

I'm having issues implementing timing. What i want to do is run this:

//relay 1 power cycle
void MainWindow::relay1PCycle()
{
    relay1High();
    while (true){
        QTimer::singleShot(750, this, SLOT(relay1Low()));
        QTimer::singleShot(750, this, SLOT(relay1High()));
    }
}

as while a button is pressed.

//power cycle button
void MainWindow::on_pushButton_3_toggled(bool checked)
{
    if (checked){
        //run relay1PCycle as a thread.
    }
    else{
        //Terminate relay1PCycle thread.
    }
}

however, so far everything i've tried so far has been a failure.

What's the correct way to go about this?

Thanks

Answer 1

The task they want to implement is not blocking, so it is not necessary to use threads, only a timer with an adequate logic. To make it simple we will assign that task to the next class:

relaycontroller.h

#ifndef RELAYCONTROLLER_H
#define RELAYCONTROLLER_H

#include <QObject>
#include <QTimer>

#include <QDebug>

class RelayController : public QObject
{
    Q_OBJECT
public:
    explicit RelayController(QObject *parent = 0):QObject(parent){
        timer = new QTimer(this);
        state = false;
        timer->setInterval(750);
        //old style
        connect(timer, SIGNAL(timeout()), this, SLOT(onTimeout()));
        //new style
        //connect(timer, &QTimer::timeout, this, &RelayController::onTimeout);
    }
    void start(){
        qDebug()<<"timer";
        timer->start();
    }
    void stop(){
        timer->stop();
    }

    void relayLow(){
        //code here: relay off
        qDebug()<<"low";
    }
    void relayHigh(){
        //code here: relay on
        qDebug()<<"high";
    }

private slots:

    void onTimeout(){
        if(state)
            relayHigh();
        else
            relayLow();
        state = !state;
    }
private:
    QTimer *timer;
    bool state;
};

#endif // RELAYCONTROLLER_H

Then an object is created and used in the slot pressed:

mainwindow.h

private:
    RelayController *controller;

mainwindow.cpp

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    controller = new RelayController(this);
    ui->pushButton_3->setCheckable(true);
}

void MainWindow::on_pushButton_toggled(bool checked)
{
    if(checked)
        controller->start();
    else
        controller->stop();
}