how to set tem for qt widgets

how_to_use_qss.cpp

#include <QtWidgets>
#include "addressbook.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    AddressBook addressBook;
    addressBook.show();
		
	// Load an application style
	QFile styleFile( ":/style.qss" );
	styleFile.open( QFile::ReadOnly );
	
	// Apply the loaded stylesheet
	QString style( styleFile.readAll() );
	app.setStyleSheet( style );

    return app.exec();
}