Memory leak from Promoted class of QDoubleSpinBox - qt

Question

I am promoting the QDoubleSpinBox class as i want to catch the mouseDoubleClick Event.
This is the Promoted class.
class SumDoubleBox : public QDoubleSpinBox
{
Q_OBJECT
public:
explicit SumDoubleBox(QWidget* parent = nullptr);
void setSingleStep(double val);
double singleStep() const;
void stepBy(int steps) override;
protected:
virtual void focusInEvent(QFocusEvent *e) override;
public slots:
void setZero();
void setOne();
signals:
int signalUndoRedo();
private:
double m_defaultStep = 1.0;
double m_CurrentStep;
bool m_stepUp;
};
SumDoubleBox::SumDoubleBox(QWidget* parent) : QDoubleSpinBox(parent)
{
SumLineEdit* lineEdit = new SumLineEdit(this);
setLineEdit(lineEdit);
setMinimum(0.0);
setMaximum(99999.0);
}
Since i am creating a pointer in the Constructor of the SumDoubleBox Class.
SumLineEdit* lineEdit = new SumLineEdit(this);
Do i need to Explicitly delete this in the Destructor ?
/////////////////////////////////////////////////////////////////
The Defination of the SumLineEdit class.
class SumLineEdit : public QLineEdit
{
Q_OBJECT
public:
explicit SumLineEdit(QWidget* parent = nullptr) { };
protected:
void mouseDoubleClickEvent(QMouseEvent* event) override;
};
void SumLineEdit::mouseDoubleClickEvent(QMouseEvent* event)
{
if (event->button() == Qt::LeftButton)
{
selectAll();
event->accept();
return;
}
QLineEdit::mouseDoubleClickEvent(event);
}

Answer 1

Since you've parented the new lineedit to the SumDoubleBox, it should get deleted with its parent.
There is, however, a more Qt-centric way to handle this case that I would strongly recommend you use or at least look into: Installing an event filter on the built-in line edit and handling the events for it. I've made many spinbox variants, and this approach usually works out best:
SumDoubleBox::SumDoubleBox( QWidget *parent ) :
QDoubleSpinBox( parent )
{
lineEdit()->installEventFilter( this );
}
bool SumDoubleBox::eventFilter( QObject *object, QEvent *event )
{
if( object == lineEdit() && event->type() == QEvent::MouseButtonDblClick )
{
QMouseEvent *mouseEvent = static_cast<QMouseEvent*>( event );
if( mouseEvent->button() == Qt::LeftButton )
{
selectAll();
event->accept();
return true; //swallow the event
}
}
return false; //let the event through to the lineedit
}
This makes the custom class entirely redundant. It's nice because inheritance is a big hammer that easily gets out of control as a codebase scales up, and if there are other simpler ways to achieve your goal, it's often worth considering.