I have interesting example. We are have qml form, and button. After click need close window and delete window. Simple. But application stable crash. Example:

main.cpp
Qt Code: 
  1. #include <QApplication>
  2.  
  3. #include "windowmanager.h"
  4.  
  5. int main(int argc, char *argv[])
  6. {
  7.  * *QApplication a(argc, argv);
  8.  
  9.  * *WindowManager manager;
  10.  * *manager.showWindow();
  11.  
  12.  * *return a.exec();
  13. }
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windowmanager.h
Qt Code: 
  1. #ifndef WINDOWMANAGER_H
  2. #define WINDOWMANAGER_H
  3.  
  4. #include <QObject>
  5. #include <QDeclarativeView>
  6.  
  7. class WindowManager : public QObject
  8. {
  9.  * *Q_OBJECT
  10.  * *public:
  11.  * * * *explicit WindowManager(QObject *parent = 0);
  12.  
  13.  * * * *void showWindow();
  14.  * * * *Q_INVOKABLE void closeWindow();
  15.  
  16.  * * * *QDeclarativeView *window();
  17.  
  18.  * *private:
  19.  * * * *QDeclarativeView *m_window;
  20.  
  21. };
  22.  
  23. #endif // WINDOWMANAGER_H
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windowmanager.cpp
Qt Code: 
  1. #include "windowmanager.h"
  2.  
  3. #include <QDeclarativeContext>
  4.  
  5. WindowManager::WindowManager(QObject *parent) : QObject(parent), m_window(0)
  6. {
  7. }
  8.  
  9. void WindowManager::showWindow()
  10. {
  11.  * *window()->show();
  12. }
  13.  
  14. void WindowManager::closeWindow()
  15. {
  16.  * *m_window->close();
  17.  
  18.  * *if (m_window != 0) {
  19.  * * * *delete m_window;
  20.  * * * *m_window = 0;
  21.  * *}
  22. }
  23.  
  24. QDeclarativeView *WindowManager::window()
  25. {
  26.  * *if (m_window == 0) {
  27.  * * * *m_window = new QDeclarativeView(0);
  28.  
  29.  * * * *m_window->rootContext()->setContextProperty("manager",this);
  30.  * * * *m_window->setSource(QUrl("qrc:/main.qml"));
  31.  * *}
  32.  
  33.  * *return m_window;
  34. }
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main.qml
Qt Code: 
  1. import QtQuick 1.1
  2.  
  3. Item {
  4.  * *width: 500
  5.  * *height: 500
  6.  
  7.  * *Rectangle {
  8.  * * * *width: 200
  9.  * * * *height: 200
  10.  
  11.  * * * *anchors.centerIn: parent
  12.  
  13.  * * * *color: "red"
  14.  
  15.  * * * *Text {
  16.  * * * * * *anchors.centerIn: parent
  17.  * * * * * *color: "white"
  18.  
  19.  * * * * * *text: "Click for crash"
  20.  * * * *}
  21.  
  22.  * * * *MouseArea {
  23.  * * * * * *anchors.fill: parent
  24.  
  25.  * * * * * *onClicked: {
  26.  * * * * * * * *manager.closeWindow();
  27.  * * * * * *}
  28.  * * * *}
  29.  * *}
  30. }
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If i use, deleteLater() then applicaition crash in 20% users. If i user hotkey for delete window, all work is good, but why app crash in click button?