QCustomPlot Discussion and Comments

Hello
I am a new programmer on qt, and I try to do the Realtime Data Demo tutorial but I block for 2 hours, the problem is that I can't display the curves in real time as on the tutorial,
Can you help me please
I put my resources to you:

Maca.pro

QT       += core gui
QT       += core

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets printsupport

CONFIG += c++11

# You can make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \
    main.cpp \
    mainwindow.cpp \
    qcustomplot.cpp

HEADERS += \
    mainwindow.h \
    qcustomplot.h

FORMS += \
    mainwindow.ui

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QTime>
#include <time.h>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

    void setupPlot();


private slots:

    void realtimeDataSlot();


private:
    Ui::MainWindow *ui;


};
#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"


MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    setupPlot();
    realtimeDataSlot();


}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::realtimeDataSlot()
{
    static QTime time(QTime::currentTime());
    // calculate two new data points:
    double key = time.elapsed()/1000.0; // time elapsed since start of demo, in seconds
    static double lastPointKey = 0;
    if (key-lastPointKey > 0.002) // at most add point every 2 ms
    {
      // add data to lines:
      ui->customPlot->graph(0)->addData(key, qSin(key)+qrand()/(double)RAND_MAX*1*qSin(key/0.3843));
      ui->customPlot->graph(1)->addData(key, qCos(key)+qrand()/(double)RAND_MAX*0.5*qSin(key/0.4364));
      // rescale value (vertical) axis to fit the current data:
      //ui->customPlot->graph(0)->rescaleValueAxis();
      //ui->customPlot->graph(1)->rescaleValueAxis(true);
      lastPointKey = key;
    }
    // make key axis range scroll with the data (at a constant range size of 8):
    ui->customPlot->xAxis->setRange(key, 8, Qt::AlignRight);
    ui->customPlot->replot();

    // calculate frames per second:
    static double lastFpsKey;
    static int frameCount;
    ++frameCount;
    if (key-lastFpsKey > 2) // average fps over 2 seconds
    {
      ui->statusbar->showMessage(
            QString("%1 FPS, Total Data points: %2")
            .arg(frameCount/(key-lastFpsKey), 0, 'f', 0)
            .arg(ui->customPlot->graph(0)->data()->size()+ui->customPlot->graph(1)->data()->size())
            , 0);
      lastFpsKey = key;
      frameCount = 0;
    }
    }
void MainWindow::setupPlot()
{
    QTimer dataTimer;
    ui->customPlot->addGraph(); // blue line
    ui->customPlot->graph(0)->setPen(QPen(QColor(40, 110, 255)));
    ui->customPlot->addGraph(); // red line
    ui->customPlot->graph(1)->setPen(QPen(QColor(255, 110, 40)));

    QSharedPointer<QCPAxisTickerTime> timeTicker(new QCPAxisTickerTime);
    timeTicker->setTimeFormat("%h:%m:%s");
    ui->customPlot->xAxis->setTicker(timeTicker);
    ui->customPlot->axisRect()->setupFullAxesBox();
    ui->customPlot->yAxis->setRange(-1.2, 1.2);

    // make left and bottom axes transfer their ranges to right and top axes:
    connect(ui->customPlot->xAxis, SIGNAL(rangeChanged(QCPRange)), ui->customPlot->xAxis2, SLOT(setRange(QCPRange)));
    connect(ui->customPlot->yAxis, SIGNAL(rangeChanged(QCPRange)), ui->customPlot->yAxis2, SLOT(setRange(QCPRange)));

    // setup a timer that repeatedly calls MainWindow::realtimeDataSlot:
    connect(&dataTimer, SIGNAL(timeout()), this, SLOT(realtimeDataSlot()));
    dataTimer.start(0); // Interval 0 means to refresh as fast as possible
}

thx

Solution
.cpp

 dataTimer = new QTimer(this);
 connect(dataTimer, SIGNAL(timeout()), this, SLOT(realtimeDataSlot()));
 dataTimer->start(10); // Interval 0 means to refresh as fast as possible
}

.h

private:
    Ui::MainWindow *ui;
    QTimer *dataTimer;