Why Qt chart example does not delete dynamically allocated variables

Question

I have been checking the Qt BarChart example, I noticed that the dynamically allocated variables were not deleted at all, why? I try to copy the idea of this example, then use in a layout, and display the chart in a plainTextEditor. However, I want to delete these dynamically allocated variables once I display the chart, but I don't know when and where to delete them. I tried to delete them at the end of the function, but it won't show anything on the plainTextEditor. I don't want to define these dynamically allocated variables as a member variables and delete them in the Destructor.

Here are the example I get from the Qt Documentation

> #include <QtWidgets/QApplication>
> #include <QtWidgets/QMainWindow>
> #include <QtCharts/QChartView>
> #include <QtCharts/QBarSeries>
> #include <QtCharts/QBarSet>
> #include <QtCharts/QLegend>
> #include <QtCharts/QBarCategoryAxis>
> 
> QT_CHARTS_USE_NAMESPACE
> 
> int main(int argc, char *argv[]) {
>     QApplication a(argc, argv);
> 
>     QBarSet *set0 = new QBarSet("Jane");
>     QBarSet *set1 = new QBarSet("John");
>     QBarSet *set2 = new QBarSet("Axel");
>     QBarSet *set3 = new QBarSet("Mary");
>     QBarSet *set4 = new QBarSet("Samantha");
> 
>     *set0 << 1 << 2 << 3 << 4 << 5 << 6;
>     *set1 << 5 << 0 << 0 << 4 << 0 << 7;
>     *set2 << 3 << 5 << 8 << 13 << 8 << 5;
>     *set3 << 5 << 6 << 7 << 3 << 4 << 5;
>     *set4 << 9 << 7 << 5 << 3 << 1 << 2;
> 
>     QBarSeries *series = new QBarSeries();
>     series->append(set0);
>     series->append(set1);
>     series->append(set2);
>     series->append(set3);
>     series->append(set4);
> 
> 
>     QChart *chart = new QChart();
>     chart->addSeries(series);
>     chart->setTitle("Simple barchart example");
>     chart->setAnimationOptions(QChart::SeriesAnimations);
> 
>     QStringList categories;
>     categories << "Jan" << "Feb" << "Mar" << "Apr" << "May" << "Jun";
>     QBarCategoryAxis *axis = new QBarCategoryAxis();
>     axis->append(categories);
>     chart->createDefaultAxes();
>     chart->setAxisX(axis, series);
> 
>     chart->legend()->setVisible(true);
>     chart->legend()->setAlignment(Qt::AlignBottom);
> 
>     QChartView *chartView = new QChartView(chart);
>     chartView->setRenderHint(QPainter::Antialiasing);
> 
>     QMainWindow window;
>     window.setCentralWidget(chartView);
>     window.resize(420, 300);
>     window.show();
> 
>     return a.exec(); }

Answer 1

In Qt, certain functions are designated to take ownership, forming a parent/child relationship. And parents delete their children when they are destroyed.

With the example you've shown, series is the parent of set0 through set4 (from the calls to series->append). chart is the parent of axis and series (from chart->setAxisX). chartView is the parent of chart (from its construction: QChartView *chartView = new QChartView(chart)). And finally window is the parent of chartView (from window.setCentralWidget). And since window is not a pointer, but an actual QMainWindow object with automatic storage duration, it will be destroyed at the end of the scope, taking all of its descendants with it.