QDataStream unable to serialize data

问题:

I am trying to follow the tutorial here and serialize Qt objects. Here is my code:

QFile file("/Users/kaustav/Desktop/boo.dat");
if (!file.open(QIODevice::WriteOnly)) {
    qDebug() << "Cannot open file for writing: "
         << qPrintable(file.errorString()) << endl; //no error message gets printed
    return 0;
}
QDataStream out(&file);   // we will serialize the data into the file
out.setVersion(QDataStream::Qt_5_3); //adding this makes no difference
out << QString("the answer is");   // serialize a string
out << (qint32)42;

When I run this program, the file gets created in my desktop all right, but its size is 0 kB, it is blank. Naturally, when I then try this:

 QFile file("/Users/kaustav/Desktop/boo.dat");
 file.open(QIODevice::ReadOnly);
 QDataStream in(&file);    // read the data serialized from the file
 in.setVersion(QDataStream::Qt_5_3);
 QString str;
 qint32 w;
 in >> str >> w;

I get a blank string in str. What am I doing wrong? If of any help, I am using Qt Creator 3.1.1 based on Qt 5.2.1.

回答1:

Check if there are any errors returned when calling open and ensure you close the file with file.close() when you're finished with it.

As you're using Qt 5, you should really use QSaveFile instead, when saving the data.