Assigning a Value From .cpp file to .qml file

[Vinay Kumar pusuluri]

import QtQuick 2.2

Item {
id: valueSource
property real kph: 0
property real rpm: 1
property real fuel: 0.85
property int someNumber: 40
// property var aNumber: 100
property string gear: {
var g;
var t=20;
if (kph == 0) {
return "P";
}
if (kph < 30) {
return "1";
}
if (kph < 50) {
return "2";
}
if (kph < 80) {
return "3";
}
if (kph < 120) {
return "4";
}
if (kph < 160) {
return "5";
}
}
property int turnSignal: gear == "P" && !start ? randomDirection() : -1
property real temperature: 0.6
property bool start: true

function myQmlFunction(msg) {
       console.log("Got message:", msg)
       return "some return value"
   }
function myQmlFunction1(msg) {
       console.log("Got message2:", msg)
        valueSource.someNumber =msg
    console.log("valueSource.someNumber Value is:",valueSource.someNumber)
    return valueSource.someNumber
   }
function randomDirection() {
    return Math.random() > 0.5 ? Qt.LeftArrow : Qt.RightArrow;
}

SequentialAnimation {
    running: true
    loops: 1

    
    PauseAnimation {
        duration:1000
    }

    PropertyAction {
        target: valueSource
        property: "start"
        value: false
    }

    SequentialAnimation {
        loops: Animation.Infinite
        ParallelAnimation {
            NumberAnimation {
                
                target: valueSource
                property: "kph"
                easing.type: Easing.InOutSine
                from:valueSource.someNumber
               
                to: 60
                duration:2000
            }
            NumberAnimation {
                target: valueSource
                property: "rpm"
                easing.type: Easing.InOutSine
                from: 1
                to: 6.1
                duration: 3000
            }
        }
    }

}

}
this is my MainWindow.cpp file
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include"QDebug"
#include <QQmlEngine>
#include"QtQuickWidgets/QQuickWidget"
#include"QQuickView"
#include"QString"
#include"form.h"
#include<frnm.cpp>
QQuickWidget *quick;
QObject *item;
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);

          ui->quickWidget->setSource(QUrl("qrc:/qml/dashboard.qml"));

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

void MainWindow::on_pushButton_2_clicked()
{
QString str=ui->lineEdit->text();
int s1=str.toInt();

QQmlEngine engine;
QQmlComponent component(&engine,QUrl("qrc:/qml/ValueSource.qml"));
QObject *object = component.create();

qDebug() << "Property value:" << QQmlProperty::read(object, "someNumber").toInt();
QQmlProperty::write(object, "someNumber", s1);
qDebug() << "Property value:" << object->property("someNumber").toInt();
object->setProperty("someNumber", s1);
QQmlEngine engine1;
QQmlComponent component1(&engine1, QUrl("qrc:/qml/ValueSource.qml"));
QObject *object1 = component1.create();

QVariant returnedValue;
QVariant msg = "Hello from C++";
QVariant v(s1);
QMetaObject::invokeMethod(object1, "myQmlFunction",
        Q_RETURN_ARG(QVariant, returnedValue),
        Q_ARG(QVariant, msg));
qDebug() << "QML function returned:" << returnedValue.toString();
QMetaObject::invokeMethod(object1, "myQmlFunction1",
        Q_RETURN_ARG(QVariant, returnedValue),
        Q_ARG(QVariant, v.toInt()));


qDebug() << "QML function returned2:" << returnedValue.toInt();
delete object;

}

here What ever I am Taking the Value From LineEdit I am Sending to the .qml file ,
In .Qml File also getting but this value should not be assigning...
in .QML file my UserDefined function i have written(i.e. function myQmlFunction1(msg)) In This I am Changing this (property int someNumber:) value. but it is not effecting the SequentialAnimation{

}.I am using this (property int someNumber: ) in SequentialAnimation{

} .can u guide to me how we can use that variable in SequentialAnimation.
thanks

[Pablo J. Rogina]

@Vinay-Kumar-pusuluri a couple of things:

1. you may want to take a look at this article regarding how to integrate C++ and QML; this is QML will be notified when a C++ value changes without writing lots of code, look at the example there.
2. little off-topic, but you're using the QML in a procedural way while it's expected to be used in a declarative way:

QML is a declarative language that allows user interfaces to be described in terms of their visual components and how they interact and relate with one another