Qt4.4 学习笔记（二） Making Connections（连接器）

 #include <QApplication>
 #include <QPushButton>
 int main(int argc, char *argv[])
  {
     QApplication app(argc, argv);
     QPushButton *button = new QPushButton("Quit");
     QObject::connect(button, SIGNAL(clicked()),
                      &app, SLOT(quit()));
     button->show();
     return app.exec();
 }

Qt's widgets emit signals to indicate that a user action or a change of state has occurred. For instance, QPushButton emits a clicked() signal when the user clicks the button. A signal can be connected to a function (called a slot in that context), so that when the signal is emitted, the slot is automatically executed. In our example, we connect the button's clicked() signal to the QApplication object's quit() slot. The SIGNAL() and SLOT() macros are part of the syntax; they are explained in more detail in the next chapter.