QT正则表达式显示全文，而不是要求的内容

Question

i'm having an issue with my regex here where i'm trying to get the longitude of a gps data and instead it's giving me the entire coordinate

my code

QRegularExpression GPSLong("((?<=,\\s)([0-9](.*?)+(W|E)))");


 while (!file.atEnd()) 
{
    QString line = file.readLine();
    i++;

    QRegularExpressionMatch matchGPSLong = GPSLong.match(line);

    if ( matchGPSLong.hasMatch()) 
    {
        QString GPSLongCoordinates = matchGPSLong.captured(0);
        qDebug()<< "Longitude : " <<GPSLongCoordinates;
    }
  //....
}

An example line is

43° 31' 8.3" N, 5° 3' 13.2" E, 0m

And the result I'm getting is

Longitude : 43° 31' 8.3" N, 5° 3' 13.2" E

But I was expecting

Longitude : 5° 3' 13.2" E

i'm using Qt 5.9.2 on Windows10 and can't update to a newer version because of the software i'm working on

EDIT : i managed to find a solution, instead of getting DMS(Degrees, Minute, Second) coordinates i switched to DD (Decimal Degrees) and then used global match to obtain a QRegularExpressionMatchIterator

here's the fixed and working code :

QRegularExpression GPSRegex("-|[0-9]+\\.+[0-9]+");


while (!file.atEnd()) {
    QString line = file.readLine();
    i++;

    QRegularExpressionMatch matchGPSLat = GPSRegex.match(line);
    auto matchIterator = CoordinateRegex.globalMatch(line);

    if (matchGPSLat.hasMatch()) {

        QString GPSLatCoordinates = matchGPSLat.captured(0);
        while(matchIterator.hasNext())
        {
            auto result = matchIterator.next();
            if (!matchIterator.hasNext())
            {

                GPSLongCoordinates = result.captured(0);
            }
        }

        double GPSlat = GPSLatCoordinates.toDouble();
        double GPSLong = GPSLongCoordinates.toDouble();
    }
}

Answer 1

You want:

QString GPSLongCoordinates = matchGPSLong.captured(1);

instead of:

QString GPSLongCoordinates = matchGPSLong.captured(0);

The 0-index of a capture is the entire match. If any groups match, those groups starting at index 1 are the respective matches.