Problem using QFile inside QThread

[qlands]

Hi,

I have this code inside the run() of a QThread:

outfile.setFileName(outputFile);
if (!outfile.open(QIODevice::WriteOnly | QIODevice::Text))
  return;
 
outStream.setDevice(&outfile);
outStream << "Some data here!" << "\n";
 
outfile.close();

outfile.setFileName(outputFile);
if (!outfile.open(QIODevice::WriteOnly | QIODevice::Text))
  return;

outStream.setDevice(&outfile);
outStream << "Some data here!" << "\n";

outfile.close();

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Both outfile and outStream are private members of the thread class:

QFile outfile;
QTextStream outStream;

QFile outfile;
QTextStream outStream;

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When I ran it. The out file is created but it has 0 bytes.

Funny thing is that when I use QFile.Write() it works.

Any idea why?

Thanks,
Carlos.

[high_flyer]

what happens if you add flush() before you close the file?

[qlands]

The same thing happens: The file is created but QTextStream fail to move the data into the file.

If I copy the same code outside the thread class into a the main() for example, it works just fine.

[Lykurg]

Warning: Threads are not my strong field!
But maybe it has to do, that outfile and outStream are not in the same thread as the run() method because they are private members of the class? So try to declare and define them in the run method.

[high_flyer]

If I copy the same code outside the thread class into a the main() for example, it works just fine.

Its hard to say without seeing more code.

[qlands]

The full code is:

sqlimport.h

class sqlimport : public QThread
{
Q_OBJECT
public:
    void run(); //The main thread process
    QString outputFile;
 
private:
    QFile outfile;
    QTextStream outStream;
};

class sqlimport : public QThread
{
Q_OBJECT
public:
    void run(); //The main thread process
    QString outputFile;

private:
    QFile outfile;
    QTextStream outStream;
};

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sqlimport.cpp

void sqlimport::run()
{
outfile.setFileName(outputFile);
if (!outfile.open(QIODevice::WriteOnly | QIODevice::Text))
  return;
 
outStream.setDevice(&outfile);
outStream << "Some data here!" << "\n";
 
outfile.close();
}

void sqlimport::run()
{
outfile.setFileName(outputFile);
if (!outfile.open(QIODevice::WriteOnly | QIODevice::Text))
  return;

outStream.setDevice(&outfile);
outStream << "Some data here!" << "\n";

outfile.close();
}

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That's it. If you do:

sqlimport mysubproc;
  mysubproc.outputFile = "/data/myfile.sql";
  mysubproc.start();  //Run the thread

sqlimport mysubproc;
  mysubproc.outputFile = "/data/myfile.sql";
  mysubproc.start();  //Run the thread

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The output file is created but QTextStream fails to write the data.

Carlos.