Getting Started Programming with Qt tutorial part2 giving assertion fail

[Zlatomir]

You will probably learn to allocate widget on the heap anyway.
You get the error because of the order in which the stack allocated objects get destructed when they get out of scope.

So you can do one of the following solutions:
1)

#include <QtGui>
 
int main(int argv, char **args)
{
  QApplication app(argv, args);
 
  QWidget window; //create the window QWidget first, than the rest
  QTextEdit textEdit;
  QPushButton quitButton("Quit");
//... rest of the example, obviously don't let two copy of the: QWidget window; line

#include <QtGui>

int main(int argv, char **args)
{
  QApplication app(argv, args);

  QWidget window; //create the window QWidget first, than the rest
  QTextEdit textEdit;
  QPushButton quitButton("Quit");
//... rest of the example, obviously don't let two copy of the: QWidget window; line

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2) This is the recommended solution: Learn to use widgets on the heap, use pointers, allocate memory with new, and Qt parent-child relationship.

#include <QtGui>
 
int main(int argv, char **args)
{
  QApplication app(argv, args);
 
  QWidget* window = new QWidget; // this is how you allocate on the heap
  //the main window/widget can be allocated on the stack
 
 
  QTextEdit *textEdit = new QTextEdit; //
  QPushButton *quitButton = new QPushButton("Quit");
 
  QObject::connect(quitButton, SIGNAL(clicked()), qApp, SLOT(quit())); //note that you just write the name without & operator
 
  QVBoxLayout *layout = new QVBoxLayout;
  layout->addWidget(textEdit);   // -> this is the operator to access members if use pointers
  layout->addWidget(quitButton);
 
  window->setLayout(layout); //again without &, and all the widgets added to layout are child of window
 
 
  window->show();
 
  int r = app.exec(); //this is the proper way to free resources if you allocate the main window/widget om the heap
 
  delete window;//here you free the memory for QWidget window, this will automatically delete the childs of window
 
  return r;
}

#include <QtGui>

int main(int argv, char **args)
{
  QApplication app(argv, args);

  QWidget* window = new QWidget; // this is how you allocate on the heap
  //the main window/widget can be allocated on the stack


  QTextEdit *textEdit = new QTextEdit; //
  QPushButton *quitButton = new QPushButton("Quit");

  QObject::connect(quitButton, SIGNAL(clicked()), qApp, SLOT(quit())); //note that you just write the name without & operator

  QVBoxLayout *layout = new QVBoxLayout;
  layout->addWidget(textEdit);   // -> this is the operator to access members if use pointers
  layout->addWidget(quitButton);

  window->setLayout(layout); //again without &, and all the widgets added to layout are child of window


  window->show();

  int r = app.exec(); //this is the proper way to free resources if you allocate the main window/widget om the heap

  delete window;//here you free the memory for QWidget window, this will automatically delete the childs of window

  return r;
}

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