Printf to stream

[MartinD]

Hello,
I have this function:

void app_trace_log(const char * format, ... ) {
//qDebug() << ???????????;
}

The format argument uses printf like syntax for printing variable number of arguments (...). What's the easiest way to transform it to qt stream output (like qDebug())?

[SGaist]

Hi,

You could use QString::asprintf (new in 5.5) or QTextStream

Hope it helps

[A Former User]

@SGaist How would you use QTextStream for this? The only solution I know goes like:

void app_trace_log(const char *format, ...) {
    va_list args;
    va_start(args, format);
    char *result;
    const int n = vasprintf(&result, format, args);
    va_end(args);
    if (n>=0) {
        qDebug() << result;
        free(result);
    }
}

[SGaist]

Sorry, I didn't meant it as drop-in replacement.

Thanks for the example.

Note that I'd rather recommend the use of QLoggingCategory for that kind of task.