How to store Qfile in Qhash

Question

I want to write the data to many different files randomly, So I store the QFile * to Qhash, But it seams not work. and there is a report

QObject::connect: No such signal QObject::aboutToClose() in ....\include\QtCore\5.3.2\QtCore/private/../../../../../src/corelib/io/qtextstream_p.h:75

Could you help me to solve this problem?

Here is a test code to realize my idea.

#include <QHash>
#include <QString>
#include <QFile>
#include <QTextStream>
#include <QFile>
#include <QDebug>

int main(int argc, char *argv[])
{
QHash <qint32,QFile *> fileHandHash;
for(qint32 i=0; i<1000; i++){
qint32 id = i % 10;
qDebug() << i << "\t" << id;

if( ! fileHandHash.contains(id) ){
QString filename = id + ".out.txt";
QFile MYFILE(filename);
MYFILE.open(QIODevice::WriteOnly);
fileHandHash.insert(id,&MYFILE);
}

QTextStream OUT(fileHandHash.value(id));
OUT << i << "\n";
}
return 1;
}

You're passing `insert` a pointer to a local variable that then immediately gets destroyed. That's never going to end well. — Alan Stokes, Jan 01 '15 at 09:18

score 0 · Accepted Answer · answered Jan 01 '15 at 17:39

As said in the comment, you can't store pointers to local variables. However this may be more or less what you're looking for:

#include <QHash>
#include <QString>
#include <QFile>
#include <QTextStream>
#include <QFile>
#include <QDebug>

int main(int argc, char* argv[])
{
   QHash <qint32, QFile*> fileHandHash;

   for (qint32 i = 0; i < 1000; i++) {
      qint32 id = i%10;
      qDebug() << i << "\t" << id;

      if(!fileHandHash.contains(id)) {
         QString filename = QString("%1.out.txt").arg(id);
         QFile* myfile = new QFile(filename);
         myfile->open(QIODevice::WriteOnly);
         fileHandHash.insert(id, myfile);
      }

      QTextStream out(fileHandHash.value(id));
      out << i << "\n";
   }

   qDeleteAll(fileHandHash);
   fileHandHash.clear();

   return 1;
}

Pay attention to the number of file descriptors. Doing this each file will have an open descriptor while in the hash.

How to store Qfile in Qhash

1 Answers1