having trouble reading from textstream

[kook]

Greetings..
I am having some problem reading from the text stream
in the below code first i am reading the whole content of a file to a string and check if the pressed item is present if it is present then i will proceed further

if i remove int pos = str.indexOf(item->text()); and datafile.seek(pos);
these two lines it will not enter the while loop
why so

i dont want to seek to any position i want to read from the beginning only but it is entering to the while loop only if i add above mentioned lines

void MainWindow::on_listWidget_itemPressed(QListWidgetItem *item)
{
    
    QFile datafile("/home/msg.txt");

    if(!datafile.open(QIODevice::ReadOnly))
    {
        qDebug() << "file not opened";
    }

    QString line;
    QTextStream in(&datafile);
    QString str = in.readAll();

    if (str.contains(item->text()))
    {
        int pos = str.indexOf(item->text());
        datafile.seek(pos);
        
        while (in.readLineInto(&line))
        {
            
            //skipping commented line
            if (line[0] =='#')
            {
                continue;
            }
            QStringList list = line.split(QLatin1Char(':'), QString::SkipEmptyParts);
            qDebug()<<list;
            if (list[0] == item->text())
            {
                msgname = list[0];
            }

            if( list[0] == "MSG_ID")
            {
                msgid = list[1].toInt();
                qDebug()<< msgid;
            }
            ui->textEdit->setText(QString("Messagename = %1").arg(msgname));
            ui->textEdit->append(QString("MessageId = %1").arg(msgid));
        }
    }

}

Thanks in advance

[JonB]

@kook said in having trouble reading from textstream:

QString str = in.readAll();
...
while (in.readLineInto(&line))

If you have already done a readAll() from the stream, where do you expect a subsequent readLineInto() to start reading from? Either do your work on the str containing all the read data or don't do that and do the readLineInto(), not both. Or if you do want to use both as you have shown, it is not surprising you have to go datafile.seek(pos); to reposition the reader; but I would either do everything off the str or everything off the in.