Problem with QStream adding Extra Characters After a flush?

ndt_mike

I have a work around but do not understand why I am experiencing this problem.

I am using QT 5.6 on Ubuntu (not sure what version).

I have the following code:

    #include <QCoreApplication>
    #include <QDebug>
    #include <QFile>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    bool ok = false, second = false;
    double dr = 0.0;
    double dm = 0.0;
    QString tofile;
    QTextStream debug(&tofile);
    QString line = "the cow jumped over the moon 100.0 -1.0 foo bar";
    QString buffer;
    QTextStream bufferstream(& buffer);
    QStringList list = line.split(" ");

    foreach(buffer, list){
        debug<< "buffer before stream: " << buffer << '\n';
        buffer.toDouble( &ok );
        if(ok == true && second == true ){//found second valid double
            bufferstream >> dm;
            debug<< "buffer after stream and flush: "<< buffer << '\n';
            break;
        }
        if(ok == true && second == false){//found the first valid double
            second = true;
            bufferstream >> dr;
            debug<< "buffer first stream: " << buffer << '\n';
            bufferstream.flush();
        }
    }

    debug<< "dm: "<< dm << "dr: "<< dr;

    qDebug()<< tofile;

    QFile file("StreamTestFile.txt");
    if (!file.open(QFile::WriteOnly | QFile::Text)) {
        qDebug()<<"error!";
    }

    QTextStream out(&file);
    out << tofile;
    file.close();

    return a.exec();
}

After the second stream to extract the second double it adds characters, here is the output

buffer before stream: the
buffer before stream: cow
buffer before stream: jumped
buffer before stream: over
buffer before stream: the
buffer before stream: moon
buffer before stream: 100.0
buffer first stream: 100.0
buffer before stream: -1.0
buffer after stream and flush: -1.\00
dm: 0dr: 100

so you do not get the correct double. Any explanation? I fixed it by making new QTextStreams in each if statement...

just tried this in Windows (minGW) and got the same thing.

kshegunov

You're doing it wrong. Just use the stream to read from the string:

QString line = "the cow jumped over the moon 100.0 -1.0 foo bar", word;
QTextStream in(&line);
while (!in.atEnd())  {
    in >> word;

    bool ok;
    double value = word.toDouble(&ok);
    if (!ok)
        continue;
     // ...
}

ndt_mike

@kshegunov

Yeah thanks I am aware of that method.

Frankly have been reading a bit and 'discovered' the stream method to convert from QString to double and thought, 'Oh Cool let's do this!!" .

Then I ran into the problem shown above. I guess I am one of the few people crazy enough to try it.

Still appreciate the feedback thanks.