Delete created Qt elements and subclasses - c++

Question

I have a question about Qt. I am wondering how it is I should delete all the pointers I create. For example:
.h file
#ifndef MAINCALENDAR_H
#define MAINCALENDAR_H
#include<QWidget>
#include <QMap>
#include <QComboBox>
#include <QCalendarWidget>
#include <QRadioButton>
#include <QString>
#include <QtGui>
#include "selector.h"
#include <QInputDialog>
class mainCalendar : public QWidget
{
Q_OBJECT
public:
mainCalendar(QWidget * parent = 0);
~mainCalendar();
void showAppointments();
public slots:
void showLCFunc() {select->getTod()->getIntf()->getListClass().orderListChronologic(); printer * test = new printer; test->setList(TodFace->getList()); test->show();}
void showLPFunc() {select->getTod()->getIntf()->getListClass().orderListByPriority(); printer * test = new printer; test->setList(TodFace->getList()); test->show();}
void loadFile() {QString fileName = QFileDialog::getOpenFileName(this, tr("Open File"),"", tr("M-Calendar Files (*.mca)"));}
void saveFile() {QString fileName = QFileDialog::getSaveFileName(this, tr("Save File"),"", tr("M-Calendar Files (*.mca)"));qDebug() << fileName << endl;}
void intshow();
void updater() {if (!Interface->isHidden()) { app->setList(Interface->getList()); app->Beta_update(1,calendar->selectedDate()); }
else if (!TodFace->isHidden()) {tod->setList(TodFace->getList()); tod->Beta_update(1,calendar->selectedDate());} }
private:
QPushButton *showLC;
QPushButton *showLP;
QPushButton *searchButton;
QPushButton *updateButton;
QPushButton *saveButton;
QPushButton *loadButton;
QLabel *instructions;
QPushButton *backButton;
QPushButton *taskButton;
interface * Interface;
todFace * TodFace;
showTod * tod;
showApp * app;
QCalendarWidget *calendar;
QGridLayout *mainLayout;
Selector * select;
};
#endif // MAINCALENDAR_H
.cpp file:
#include "maincalendar.h"
mainCalendar::mainCalendar(QWidget *parent)
: QWidget(parent)
{
QHBoxLayout * footButtons = new QHBoxLayout;
showLC = new QPushButton(tr("'to-do' (chrono)"));
showLP = new QPushButton(tr("'to-do' (priority)"));
searchButton = new QPushButton(tr("&Search"));
saveButton = new QPushButton(tr("&Save calendar"));
loadButton = new QPushButton(tr("&Load Calendar"));
updateButton = new QPushButton(tr("Update"));
footButtons->addWidget(searchButton);
footButtons->addWidget(saveButton);
footButtons->addWidget(loadButton);
footButtons->addWidget(showLC);
footButtons->addWidget(showLP);
instructions = new QLabel(tr("To view or add data, double-click date in calendar"));
calendar = new QCalendarWidget;
calendar->setGridVisible(true);
calendar->setMinimumDate(QDate(2012, 1, 1));
calendar->setMaximumDate(QDate(2016,12,31));
backButton = new QPushButton(tr("&Back to calendar"));
select = new Selector(0,calendar,instructions,backButton, updateButton);
tod = select->getTod();
TodFace = tod->getIntf();
TodFace->hide();
TodFace->setCalendar(calendar);
tod->hide();
app = select->getApp();
Interface = app->getIntf();
Interface->hide();
Interface->setCalendar(calendar);
app->hide();
backButton->hide();
updateButton->hide();
connect(showLC,SIGNAL(clicked()),this,SLOT(showLCFunc()));
connect(showLP,SIGNAL(clicked()),this,SLOT(showLPFunc()));
connect(updateButton, SIGNAL(clicked()), this, SLOT(updater()));
connect(backButton, SIGNAL(clicked()), this, SLOT(intshow()));
connect(loadButton,SIGNAL(clicked()),this,SLOT(loadFile()));
connect(saveButton,SIGNAL(clicked()),this,SLOT(saveFile()));
connect(calendar, SIGNAL(activated(QDate)), this, SLOT(intshow()));
mainLayout = new QGridLayout;
this->setMinimumHeight(800);
this->setMinimumWidth(1000);
mainLayout->setColumnMinimumWidth(0,500);
mainLayout->addWidget(calendar,0,0);
mainLayout->addWidget(app,1,0);
mainLayout->addWidget(Interface,1,2);
mainLayout->addWidget(tod,1,0);
mainLayout->addWidget(TodFace,1,2);
mainLayout->addWidget(backButton,0,0,Qt::AlignTop);
mainLayout->addLayout(footButtons,2,0,Qt::AlignLeading);
mainLayout->addWidget(instructions,2,0,Qt::AlignTrailing);
mainLayout->addWidget(updateButton,2,2,Qt::AlignRight);
setLayout(mainLayout);
setWindowTitle(tr("M-Calendar"));
}
mainCalendar::~mainCalendar()
{
}
void mainCalendar::intshow()
{
if (Interface->isHidden()&&TodFace->isHidden())
{
select->setDate(calendar->selectedDate());
select->show();
Interface->setdate(calendar->selectedDate());
TodFace->setdate(calendar->selectedDate());
} else
{
backButton->hide();
updateButton->hide();
Interface->hide();
app->close();
TodFace->hide();
tod->close();
calendar->show();
instructions->show();
}
}
I am stuck here. Am I supposed to do to delete all the pointers (QPushbutton, etc) and subclasses so no memory leaks occur?

Answer 1

Short answer: No, you don't have to explicitly delete them.
In Qt, the QObjects are organized in object trees. The parent-child relationships of the various widgets also implies that the parent takes ownership of the child widgets.
As a result you do not have to explicitly delete them when your application finishes. Each parent will take care of the cleanup of its own children. Only when you create a (pointer to) a widget/object which has no parent, you will need to explicitly delete it.

Answer 2

via addWidget you create a parent-child-relationship between these to widgets.
Any parentless widget has to be destroyed manually, which in turn free its children recursivly.
As long as your widget has a parent, and that is either freed manually or child to another Widget, no manual free is required.
Same accounts for QObject derived classes.