QDataStream not writing

[tinashe]

hi may you please assist the following code does not work it only ceate and empty file.dat file.
am using Qt 5.15.2 on windows 10 home 64 bit.

#include <QCoreApplication>
#include <QFile>
#include <QImage>
#include <QDataStream>
#include <QDebug>

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

QFile file("file.dat");
file.open(QIODevice::WriteOnly);
QDataStream out(&file);   // we will serialize the data into the file
out << QString("the answer is ");   // serialize a string
out << (qint32)42;        // serialize an integer


QFile file2("file.dat");
file2.open(QIODevice::ReadOnly);
QDataStream in(&file2);    // read the data serialized from the file
QString str;
qint32 b;
in >> str >> b;           // extract "the answer is" and 42

qDebug()<< str << b;

return a.exec();

}

[Christian Ehrlicher]

You should close the file before trying to open it again.

[tinashe]

This post is deleted!

[tinashe]

@Christian-Ehrlicher

thank you it worked

[tinashe]

@Christian-Ehrlicher

nothing written on bytearray can you please assist

QFile file("img.png");
file.open(QIODevice::ReadOnly);
QDataStream out(&file); // we will serialize the data into the file
QByteArray data;
out >> data;
file.close();
qDebug()<< data.size();

[SGaist]

Hi,

You are not checking that the file opening is successful. The path being relative, it's likely failing.

[Christian Ehrlicher]

@tinashe Why do you think a png file contains QDateStream encoded data?

[tinashe]

@Christian-Ehrlicher

I think its my misunderstanding the use if this class I was just looking for a class which can make my life easier in sending picture data using Qudp or QTCP . Thanks

[tinashe]

@SGaist
Thanks