passing by reference... my darkest enemy
actual reason below:
In your case (without reference) the compiler generates a temporary object (int) for the first argument of your MyApplication constructor. You pass this temporary int to QApplication’s constructor (with int reference), which saves the address of this reference. Once your MyApplication constructor is done the temporary int is destroyed but QApplication still has its address.
/*
* Copyright (c) 2009 Nokia Corporation.
*/
#ifndef QASPECTRATIOLAYOUT_H_
#define QASPECTRATIOLAYOUT_H_
#include <QLayout>
#include <QPointer>
#include <QRect>
#include <QWidgetItem>
#include <QLayoutItem>
class QAspectRatioLayout : public QLayout
{
Q_OBJECT
public:
QAspectRatioLayout(QWidget* parent, int spacing =-1);
QAspectRatioLayout(int spacing = -1);
~QAspectRatioLayout();
/* Convenience method */
virtual void add(QLayoutItem* item);
/* http://doc.trolltech.com/qlayout.html#addItem */
virtual void addItem(QLayoutItem* item);
/* http://doc.trolltech.com/qlayout.html#addWidget */
virtual void addWidget(QWidget* widget);
/* http://doc.trolltech.com/qlayout.html#takeAt */
virtual QLayoutItem* takeAt(int index);
/* http://doc.trolltech.com/qlayout.html#itemAt */
virtual QLayoutItem* itemAt(int index) const;
/* http://doc.trolltech.com/qlayout.html#count */
virtual int count() const;
/*
* These are ours since we do have only one item.
*/
virtual QLayoutItem* replaceItem(QLayoutItem* item);
virtual QLayoutItem* take();
virtual bool hasItem() const;
/* http://doc.trolltech.com/qlayout.html#expandingDirections */
virtual Qt::Orientations expandingDirections() const;
/*
* This method contains most of the juice of this article.
* http://doc.trolltech.com/qlayoutitem.html#setGeometry
*/
virtual void setGeometry(const QRect& rect);
/* http://doc.trolltech.com/qlayoutitem.html#geometry */
virtual QRect geometry();
/* http://doc.trolltech.com/qlayoutitem.html#sizeHint */
virtual QSize sizeHint() const;
/* http://doc.trolltech.com/qlayout.html#minimumSize */
virtual QSize minimumSize() const;
/* http://doc.trolltech.com/qlayoutitem.html#hasHeightForWidth */
virtual bool hasHeightForWidth() const;
private:
/* Saves the last received rect. */
void setLastReceivedRect(const QRect& rect);
/* Used to initialize the object. */
void init(int spacing);
/* Calculates the maximum size for the item from the assigned size. */
QSize calculateProperSize(QSize from) const;
/* Calculates the center location from the assigned size and
* the items size. */
QPoint calculateCenterLocation(QSize from, QSize itemSize) const;
/* Check if two QRects are equal */
bool areRectsEqual(const QRect& a, const QRect& b) const;
/* Contains item reference */
QLayoutItem* item;
/*
* Used for caching so we won't do calculations every time
* setGeometry is called.
*/
QRect* lastReceivedRect;
/* Contains geometry */
QRect* _geometry;
};
#endif /* QASPECTRATIOLAYOUT_H_ */