Understanding signals and the handler event system in QML

Previously, we learned how to connect signals and slots inside C++ source files and use them with the Qt Widgets module. Now, let's look at how we can communicate in QML. QML has a signal and handler mechanism, similar to signals and slots. In a QML document, a signal is an event, and the signal is responded to through a signal handler. Like a slot in C++, a signal handler is invoked when a signal is emitted in QML. In Qt terminology, the method is a slot that is connected to the signal; all the methods defined in QML are created as Qt slots. Hence, there is no separate declaration for slots in QML. A signal is a notification from an object that some event has occurred. You can place logic inside JavaScript or a method to respond to the signal.

Let's look at how to write a signal handler. You can declare a signal handler as follows:

onSignalName : {
//Logic
}

Here, signalName is the name of the signal. The...