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