Signals and slots are required for object communication. The signals and slots method is a major component of Qt, and it is likely that it is the most distinct from the features given by other frameworks. The meta-object system concept in Qt enables signals and slots.

We have a substitute for the callback technique: We make use of signals and slots. When a specific event occurs, a signal is emitted. Qt’s widgets provide various predefined signals, but we can always subclass widgets to construct our custom signals to them. A slot is a function that is executed in response to a certain signal. Qt’s widgets provide numerous pre-defined slots, however it is usual practise to subclass widgets and create your own slots to handle the signals of interest.

signals and slots make up a powerful component programming mechanism