You must use the SIGNAL() and SLOT() macros when specifying the signal and the method, for example:
QLabel *label = new QLabel;
QScrollBar *scrollBar = new QScrollBar;
QObject::connect(scrollBar, SIGNAL(valueChanged(int)), label, SLOT(setNum(int)));
This example ensures that the label always displays the current scroll bar value. Note that the signal and slots parameters must not contain any variable names, only the type. E.g. the following would not work and return false: