Why some examples don't delete the pointer member newed in the destructor?

doodle

E.g in "audio" example :
widget.h:

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = 0);
    ~Widget();

private:
    XYSeriesIODevice *m_device;
    QChart *m_chart;
    QLineSeries *m_series;
    QAudioInput *m_audioInput;
};

widget.cpp:

Widget::Widget(QWidget *parent)
    : QWidget(parent),
      m_device(0),
      m_chart(0),
      m_series(0),
      m_audioInput(0)
{
    m_chart = new QChart;
    QChartView *chartView = new QChartView(m_chart);
    chartView->setMinimumSize(800, 600);
    m_series = new QLineSeries;
    m_chart->addSeries(m_series);
    QValueAxis *axisX = new QValueAxis;
    axisX->setRange(0, 2000);
    axisX->setLabelFormat("%g");
    axisX->setTitleText("Samples");
    QValueAxis *axisY = new QValueAxis;
    axisY->setRange(-1, 1);
    axisY->setTitleText("Audio level");
    m_chart->setAxisX(axisX, m_series);
    m_chart->setAxisY(axisY, m_series);
    m_chart->legend()->hide();
    m_chart->setTitle("Data from the microphone");

    QVBoxLayout *mainLayout = new QVBoxLayout;
    mainLayout->addWidget(chartView);
    setLayout(mainLayout);

    QAudioFormat formatAudio;
    formatAudio.setSampleRate(8000);
    formatAudio.setChannelCount(1);
    formatAudio.setSampleSize(8);
    formatAudio.setCodec("audio/pcm");
    formatAudio.setByteOrder(QAudioFormat::LittleEndian);
    formatAudio.setSampleType(QAudioFormat::UnSignedInt);

    QAudioDeviceInfo inputDevices = QAudioDeviceInfo::defaultInputDevice();
    m_audioInput = new QAudioInput(inputDevices,formatAudio, this);

    m_device = new XYSeriesIODevice(m_series, this);
    m_device->open(QIODevice::WriteOnly);

    m_audioInput->start(m_device);
}

Widget::~Widget()
{
    m_audioInput->stop();
    m_device->close();
}

XYSeriesIODevice *m_device;
QChart *m_chart;
QLineSeries *m_series;
QAudioInput *m_audioInput;

All of them don't have parent to be deleted, but the destructor has not deleted them.

raven-worx

@doodle
because a widget gets the parent set as soon as it is added to a layout, or to be more specific when the layout then gets installed on a widget.
Some other objects take owndership of the objects when they are passed as parameter.
Like m_chart to chartView widget, which then gets added to a layout.

So they are all deleted implicitly when the container widget gets deleted.

doodle

Got it! :)