Exposing Attributes of C++ Types to QML

calculator.cpp

#include "calculator.h"


calculator::calculator()
{
    this->num = 0;
}

qint32 calculator::get_number()
{
    return this->num;
}

void calculator::set_number(const qint32 &num)
{
    this->num = this->num + num;
    emit number_changed();
}

bool calculator::do_clear()
{
    this->num = 1;
    emit number_changed();
    return true;
}

calculator.h

#ifndef CALCULATOR_H
#define CALCULATOR_H

#include <QObject>
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlEngine>
#include <QQmlContext>
#include <QQmlComponent>


class calculator : public QObject
{
    Q_OBJECT
    Q_PROPERTY(qint32 number READ get_number WRITE set_number NOTIFY number_changed)
    Q_PROPERTY(bool clear READ do_clear NOTIFY number_changed)


private:
    qint32 num;


public:
    calculator();
    qint32 get_number();
    void set_number(const qint32 &num);
    bool do_clear();


signals:
    void number_changed();



public slots:

};

#endif // CALCULATOR_H

main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlEngine>
#include <QQmlContext>
#include <QQmlComponent>
#include "calculator.h"


int main(int argc, char *argv[])
{

    qmlRegisterType<calculator>("my.calculator", 1, 0, "Cal");

    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    return app.exec();
}

main.qml

import QtQuick 2.3
import QtQuick.Window 2.2

import my.calculator 1.0



Window {
    id: main
    visible: true
    width: 400
    height: 300

    Cal
    {
        id : cal

        Component.onCompleted:
        {
            number = 1;

        }
    }


    Rectangle {
        id: rec_show
        x:0
        y:0;
        width: main.width
        height: main.height/3;
        color:"#fa5f5f"
        border.color: "gray"
        border.width: 2

        Text
        {
            anchors.centerIn: parent
            text: cal.number
            font.pixelSize: 80
        }
    }

    Rectangle {
        id: rec_plus
        x:0
        y:rec_show.y + rec_show.height;
        width: main.width
        height: main.height/3;
        color:"#76fa5f"

        border.color: "gray"
        border.width: 2

        Text {
            font.pixelSize: 100;
            text: qsTr("++")
            anchors.centerIn: parent
        }

        MouseArea {
            anchors.fill: parent
            onClicked: {
                cal.number = 1
            }
        }

    }

    Rectangle {
        id: rec_clear
        x:0
        y:rec_plus.y + rec_plus.height;
        width: main.width
        height: main.height/3;
        color:"#5faffa"

        border.color: "gray"
        border.width: 2

        Text {
            font.pixelSize: 80;
            text: qsTr("clear")
            anchors.centerIn: parent
        }

        MouseArea {
            anchors.fill: parent
            onClicked: {
                cal.clear
            }
        }

    }





}