QTextStream and QFile pointer

Question

I have a class which is absfilehandler which has a QFILE pointer like this..

QString absfilename;
QFile * absfilepointer;

I have a opening method.

bool  AbsFileHandler::OpenAbsFile()
{


    QFile readfile(absfilename);
    absfilepointer = (&readfile);

    if (!(*absfilepointer).exists())
    {
        qDebug() << "The file" << (*absfilepointer).fileName() << "does not exist.";
        return false;
    }

    else if (!(*absfilepointer).open((QIODevice::ReadOnly) | (QIODevice::Text)))
    {
        qDebug() << "Could not open" << (*absfilepointer).fileName() << "for reading.";
        return false;
    }
    else
    {
        qDebug() << "File ready to read";
        return true;
    }
}

I call the method in the another class with a object of the same class like this myAbsFileHandler.OpenAbsFile()

if it returns true then we execute this

QTextStream readabsstream((myAbsFileHandler.absfilepointer));

But this statement gives critical exception and comes out of execution. Any idea why this is happening? Thanks.

xander xander · Accepted Answer · 2018-02-20T12:19:56

I suggest not using raw pointers when there is no need to, why do you need to save a QFile*? I guess you want to create a stream with QTextStream(QIODevice *device), then you can simply pass a pointer to your file if the method needs one.

The problem you have is you create a pointer to a local scoped QFile readfile, since it's created on the stack it will be destroyed at the end of your AbsFileHandler::OpenAbsFile() method. so the pointer becomes invalid after the method returns!

So the solution is just save a QFile (not a pointer) or create the QFile on the heap with new QFile to keep the object alive, but that is not a good idea if you have to manage the memory yourself and delete it later.

QTextStream and QFile pointer

1 Answers