Qt for command-line use

Even though the graphical user interface is a big selling point of the Qt framework, it is also possible to use it to develop command-line-only applications. For this, we just use the QCoreApplication class to create an input and an event loop handler, as in this example:

#include <QCoreApplication> 
#include <core.h> 
 
int main(int argc, char *argv[]) { 
   QCoreApplication app(argc, argv); 
   Core core; 
 
   connect(&core, &Core::done, &app, &app::quit, Qt::QueuedConnection); 
   core.start(); 
 
   return app.exec(); 
} 

Here, our code is implemented in a class called Core. In the main function, we create a QCoreApplication instance, which receives the command-line parameters. We then instantiate an instance of our class.

We connect a signal from our class to the QCoreApplication instance, so that if we signal that...