Qt-QTextStream-如何将光标位置设置为一行的开头？

Question

After readLine() , how to set cursor position to the beggining of a line?

Using seek() and pos() doesnt work for me.

Here is how my file.txt look like:

Object1 Some-name 2 3.40 1.50

Object2 Some-name 2 3.40 1.50 3.25

Object3 Some-name 2 3.40 1.50

Here's my code:

QFile file("file.txt");
    if(file.open(QIODevice::ReadOnly | QIODevice::Text)) {
        QTextStream stream(&file);

        while(!stream.atEnd()) {
            qint64 posBefore = file.pos();
            QString line = stream.readLine(); 
            QStringList splitline = line.split(" ");

            if(splitline.at(0) == "Object1") {
                stream.seek(posBefore);
                object1 tmp;
                stream >> tmp;
                tab.push_back(tmp);
            }

           if(splitline.at(0) == "Object2") {
                stream.seek(posBefore);
                object2 tmp;
                stream >> tmp;
                tab.push_back(tmp);
            }

            if(splitline.at(0) == "Object3") {
                stream.seek(posBefore);
                object3 tmp;
                stream >> tmp;
                tab.push_back(tmp);
            }

        }
        file.close();
    }

Answer 1

So, you need (de)serialization .

Try to do it right. Here is official documentation: http://qt-project.org/doc/qt-4.8/datastreamformat.html Here is example: Serialization with Qt

Answer 2

I've made a simple console app for you. All you need to do is a good old QString::split() by spaces and take the first element in the row however you like, i did it via QString::section() method.

Well here is the code for main.cpp :

#include <QtCore/QCoreApplication>
#include <QFile>
#include <QStringList>
#include <QDebug>

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

    QFile f("file.txt");
    f.open(QIODevice::ReadOnly);
    // next line reads all file, splits it by newline character and iterates through it
    foreach (QString i,QString(f.readAll()).split(QRegExp("[\r\n]"),QString::SkipEmptyParts)){
    QString name=i.section(" ",0,0);
    // we take first section of string from the file, all strings are stored in "i" variable
    qDebug()<<"read new object - "<<name;
    }
    f.close();
    return a.exec();
}

File file.txt is in the same directory as the executable file and is copy of your file:

Object1 Some-name 2 3.40 1.50

Object2 Some-name 2 3.40 1.50 3.25

Object3 Some-name 2 3.40 1.50