重载QDebug打印输出

namespace {
    enum Day {
        Monday,
        Tuesday,
        Wednesday,
        Thursday,
        Friday,
        Saturday,
        Sunday
    };
}

QDebug operator<<(QDebug debug, const Day &day)
{
    switch (day) {
        case Monday:
            debug << "Monday";
            break;
        case Tuesday:
            debug << "Tuesday";
            break;
        case Wednesday:
            debug << "Wednesday";
            break;
        case Thursday:
            debug << "Thursday";
            break;
        case Friday:
            debug << "Friday";
            break;
        case Saturday:
            debug << "Saturday";
            break;
        case Sunday:
            debug << "Sunday";
            break;
        default:
            break;
    }
    return debug;
}

Day day = Monday;
qDebug() << day;
打印输出：
Monday