QtC++ - Lesson 024 Signals and Slot in Qt5

signalslot system ensures the type-correctness of callback arguments Similarly, the signalslot system can be used for other non-GUI usages, for

Usually, a connection can only be made if the slot has the same number of arguments as the signal , and if all the argument types are compatible

signal slot The slot does not exist for the given receiver ; The signalslot argument lists is not compatible The elements marked with a do not

signal and slot And when there is a free standing function there is a signature, but there is no instance, so the third and the fourth arguments of the first