#include <QtWidgets>

int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    QStringListModel model({"1", "2", "3", "4"});
    QComboBox cbx;
    cbx.setEditable(true);
    cbx.setModel(&model);
    cbx.show();
    
    return app.exec();
}