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C++ Backend Charts Demo App

 #include "cppdatamodel.h"
 #include <QTime>
 #include <QRandomGenerator>

 CppDataModel::CppDataModel(QObject *parent) : QObject(parent)
 {

   // set timer to send new data every 3 seconds
   timer = new QTimer(this);
   connect(timer, SIGNAL(timeout()), this, SLOT(update()));
   timer->start(500);
 }

 void CppDataModel::loadData() {
   // load data asynchronously or do C++ calculations here
   // for simplicity this example uses dummy data
   QString dummyData = createRandomData();

   // signal that new data is available
   emit dataLoaded(dummyData);
 }

 QString CppDataModel::createRandomData() {
   QString dummyData = "[";
   dummyData.append(createRandomEntry(2017,"Braunau")).append(",");
   dummyData.append(createRandomEntry(2017,"Munich")).append(",");
   dummyData.append(createRandomEntry(2017,"Vienna")).append(",");
   dummyData.append(createRandomEntry(2017,"Tokyo")).append(",");
   dummyData.append(createRandomEntry(2018,"Braunau")).append(",");
   dummyData.append(createRandomEntry(2018,"Munich")).append(",");
   dummyData.append(createRandomEntry(2018,"Vienna")).append(",");
   dummyData.append(createRandomEntry(2018,"Tokyo"));
   dummyData.append("]");

   return dummyData;
 }

 QString CppDataModel::createRandomEntry(int year, const QString& city) {
   auto &rand { *QRandomGenerator::global() };
   return "{ \"year\": \"" + QString::number(year) + "\", \"city\": \"" + city + "\", \"expenses\": " + QString::number(rand.bounded(5000)) +" }";
 }