Transfer of a QByteArray to main.cpp

[dolin93]

Hallo,
with the attached program I can get a csv file from Yahoo Finance and store it in a QByteArray. But till now I didn`t succeed in transmitting the QByteArray or a QVector from filedownloader.cpp to main.cpp. I have already in vain tried many proceedings. Has anybody an idea how to overcome these difficulties?

[anda_skoa]

You are calling your data transfer function transmit() right after creating the downloader object.
There has been no time to actually get the data yet, the QNetworkAccessManager get() request is processed once the application has started event processing, i.e. when app.exec() is being called.

You already have a signal that is emitted when you've received the data.
Connect to that.

Cheers,
_

[dolin93]

Thanks for Your help!
After insertion of

connect(&m_WebCtrl, SIGNAL(finished(QNetworkReply*)),
SLOT(transmit(QList<QByteArray>)));

I got the massage

Object::connect: No such slot FileDownloader::transmit(QList<QByteArray>)

and unfortunately there was no improvement.

A happy new year!

[anda_skoa]

Why on earth did you even try that?
What could that possibly improve?

Just because some random code compiles doesn't mean it will do anything useful and even less often mean it will do what you need.

Take a step back and think about what you actually need.
And then come back and ask for that.

Cheers,
_

[dolin93]

Thanks for Your help!
With PHP it is not difficult to get csv files from Yahoo Finance, use them for simple calculations and display the results in tables.
But with Qt/C++ I`d be more flexible and could even graphically display results and charts. Therefore I tried to get the csv files also with Qt/C++ and transfer the data to main.cpp or another source file where I could use them.

Cheers

[wysota]

I don't think you understood what anda_skoa means. Please explain what you though this:

connect(&m_WebCtrl, SIGNAL(finished(QNetworkReply*)),
SLOT(transmit(QList<QByteArray>)));

connect(&m_WebCtrl, SIGNAL(finished(QNetworkReply*)),
SLOT(transmit(QList<QByteArray>)));

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would do and how you think it would solve your problem. Then take a piece of paper, a pencil and write down a step-by-step algorithm that achieves what you want. Then we will help you "translate" it to C++. Remember you are dealing with an asynchronous system.

[dolin93]

Thanks for Your answer!
Only after failure with

connect(SIGNAL(finished(QNetworkReply*)),
SLOT(transmit(QList<QByteArray>)));

I tried the above mentioned Qt Code

connect(&m_WebCtrl, SIGNAL(finished(QNetworkReply*)),
SLOT(transmit(QList<QByteArray>)));

.
Now I use a class PrCalClass for calculations and call this class in filedownloader.cpp through

PrCalClass demo(m_DownloadedData);
demo.PrintM();

. For the drawing of charts and results I`ll use another class.
But nevertheless I`d be very pleased if You showed me how one can bring the QByteArray m_DownloadedData into main.cpp.

[anda_skoa]

But nevertheless I`d be very pleased if You showed me how one can bring the QByteArray m_DownloadedData into main.cpp.

You have to understand that, for the rest of us, this goal does not make any sense.

Once the linker has linked all object code into the executable, there is no distinction anymore which source file the code came from.

You could just put the code of your file downloader class into main.cpp, remove the now unnecessary header and source file and still have the same program.
That would not change anything your program is doing, it would just increase the length of the now only cpp file.

Cheers,
_

[dolin93]

Thank You for Your answer!
Unfortunately I didn`t succeed in bringing downloaded data to the class mainWidget for drawing.

[jefftee]

I downloaded your zip file that contains your project. You are trying to fit a square peg into a round hole... You are dead set on getting a QByteArray back into your main routine, but here is the problem with your design.

You instantiate FileDownloader in your main() routine, which creates your QNetworkAccessManager, does the get request for your URL, etc. The signals for the get request won't actually be executed until your main routine runs the following code:

return a.exec();

return a.exec();

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This is because there is no message loop running yet, so no signals will be dispatched. What you should be doing, is doing all of your processing in your FileDownloader class and forget about trying to get the result into your main() routine.

Once your download completes in FileDownloader::fileDownloaded, what do you want to do next? Write new methods for FileDownloader to process the results of the download or use signals/slots to process the result, for example:

void FileDownloader::fileDownloaded(QNetworkReply* reply)
{
    m_DownloadedData = reply->readAll();
    // do all of your processing of the result here or add a new method, emit a signal, or call another method in FileDownloader, etc.
    return;
}

void FileDownloader::fileDownloaded(QNetworkReply* reply)
{
    m_DownloadedData = reply->readAll();
    // do all of your processing of the result here or add a new method, emit a signal, or call another method in FileDownloader, etc.
    return;
}

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Hope that helps.

[anda_skoa]

Unfortunately I didn`t succeed in bringing downloaded data to the class mainWidget for drawing.

You can emit the data as part of a signal and connect it to a matching slot in this "mainWidget" class.

Cheers,
_

[dolin93]

Thanks for Your answers!
In my program there are now the header files (abbreviated)

class FileDownloader  : public QObject
   {
       Q_OBJECT
   public:
        FileDownloader(const QUrl &KUrl);
       virtual ~FileDownloader();
        QByteArray downloadedData() const;
 
   signals:
           void downloaded();
           void DataA(const QByteArray&);
 
   public slots:
       void fileDownloaded(QNetworkReply* pReply);
   private:
       QUrl kUrl;
       QNetworkAccessManager m_WebCtrl;
       QByteArray m_DownloadedData;
   };

class FileDownloader  : public QObject
   {
       Q_OBJECT
   public:
        FileDownloader(const QUrl &KUrl);
       virtual ~FileDownloader();
        QByteArray downloadedData() const;

   signals:
           void downloaded();
           void DataA(const QByteArray&);

   public slots:
       void fileDownloaded(QNetworkReply* pReply);
   private:
       QUrl kUrl;
       QNetworkAccessManager m_WebCtrl;
       QByteArray m_DownloadedData;
   };

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class mainWidget : public QWidget
{
    Q_OBJECT
public:
  mainWidget();  
public slots:
  void Receiver(const QByteArray &QBA);
protected:
   void paintEvent(QPaintEvent *event);
private:
   QByteArray A;
};

class mainWidget : public QWidget
{
    Q_OBJECT
public:
  mainWidget();  
public slots:
  void Receiver(const QByteArray &QBA);
protected:
   void paintEvent(QPaintEvent *event);
private:
   QByteArray A;
};

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and the source files

FileDownloader::FileDownloader( const QUrl &KUrl) : kUrl(KUrl)
   {
       connect(&m_WebCtrl, SIGNAL(finished(QNetworkReply*)),
                   SLOT(fileDownloaded(QNetworkReply*)));
       QNetworkRequest request(kUrl);
       m_WebCtrl.get(request);       
   }
 
   FileDownloader::~FileDownloader()
   {
   }
   void FileDownloader::fileDownloaded(QNetworkReply* pReply)
   {
       m_DownloadedData = pReply->readAll();
       pReply->deleteLater();
       emit downloaded();
       emit DataA(m_DownloadedData);
       mainWidget *mW=new mainWidget();
       connect(SIGNAL(DataA(const QByteArray&)),mW,
               SLOT(Receiver(const QByteArray &QBA)));
   }

FileDownloader::FileDownloader( const QUrl &KUrl) : kUrl(KUrl)
   {
       connect(&m_WebCtrl, SIGNAL(finished(QNetworkReply*)),
                   SLOT(fileDownloaded(QNetworkReply*)));
       QNetworkRequest request(kUrl);
       m_WebCtrl.get(request);       
   }

   FileDownloader::~FileDownloader()
   {
   }
   void FileDownloader::fileDownloaded(QNetworkReply* pReply)
   {
       m_DownloadedData = pReply->readAll();
       pReply->deleteLater();
       emit downloaded();
       emit DataA(m_DownloadedData);
       mainWidget *mW=new mainWidget();
       connect(SIGNAL(DataA(const QByteArray&)),mW,
               SLOT(Receiver(const QByteArray &QBA)));
   }

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mainWidget::mainWidget()   
{
    setWindowTitle ( "paintEvent - Demo");
    resize( 1000, 400 ); 
}
void mainWidget::paintEvent ( QPaintEvent * event ) {
   QPainter painter(this);
   painter.begin( this );
   painter.setPen( QPen(Qt::black, 2) );
   painter.drawEllipse( 40, 40, 100, 100 );  
   painter.setPen( QPen(Qt::green, 2) );
   int u,z,x1,v1,ku,ku1;
   for(int i=1;i<100;i++){
       u=4*i;
       x1=4*i+4;
       ku=CloseAdj[i+2];
       ku1=CloseAdj[i+3];
      painter.drawLine(u,z,x1,v1);
  }  
}
void mainWidget::Receiver(const QByteArray &QBA){
    A=QBA;
    int j=0;
    while(A[j]!='2')
    {j++;
    }
    QVector<QString> days;
    QVector<float> CloseAdj;
    QVector<int> Volume;
    for(int i=j;i<1100;i++)
    {QString day =" ";
    QString volume = " ";
    QString CloseAd =" ";
    qint32 volume_=0;
    float Close=0;
    for (int k=0;k<10;k++)
    {day+=A[i+k];
    }
    i+=9;
    while(A[i]!=',')
    {//qDebug(" Problem   bis Komma ");
     i++;
    }
    while(A[i+1]!=',')
     {i++;}
    while(A[i+2]!=',')
     {i++;}
    while(A[i+3]!=',')
     {i++;}
    while(A[i+4]!=',')
     {i++;}
    while(A[i+5]!=',')
     {volume+=A[i+5];
      i++;
     }
    while(((A[i+6]>='0' && A[i+6]<='9') || A[i+6]== '.')&& !(A[i+6]=='2' && A[i+7]=='0' && A[i+8]<='1' && A[i+9]<='5') )
    {CloseAd+=A[i+6];
    i++;
    }
    i+=6;
    Close=CloseAd.toFloat();
    days.append(day);
    CloseAdj.append(Close);
    volume_=volume.toInt();
    Volume.append(volume_);
    }
    for(int l=0;l<10;l++)
    {QString tag=days[l];
    }
    return;
}

mainWidget::mainWidget()   
{
    setWindowTitle ( "paintEvent - Demo");
    resize( 1000, 400 ); 
}
void mainWidget::paintEvent ( QPaintEvent * event ) {
   QPainter painter(this);
   painter.begin( this );
   painter.setPen( QPen(Qt::black, 2) );
   painter.drawEllipse( 40, 40, 100, 100 );  
   painter.setPen( QPen(Qt::green, 2) );
   int u,z,x1,v1,ku,ku1;
   for(int i=1;i<100;i++){
       u=4*i;
       x1=4*i+4;
       ku=CloseAdj[i+2];
       ku1=CloseAdj[i+3];
      painter.drawLine(u,z,x1,v1);
  }  
}
void mainWidget::Receiver(const QByteArray &QBA){
    A=QBA;
    int j=0;
    while(A[j]!='2')
    {j++;
    }
    QVector<QString> days;
    QVector<float> CloseAdj;
    QVector<int> Volume;
    for(int i=j;i<1100;i++)
    {QString day =" ";
    QString volume = " ";
    QString CloseAd =" ";
    qint32 volume_=0;
    float Close=0;
    for (int k=0;k<10;k++)
    {day+=A[i+k];
    }
    i+=9;
    while(A[i]!=',')
    {//qDebug(" Problem   bis Komma ");
     i++;
    }
    while(A[i+1]!=',')
     {i++;}
    while(A[i+2]!=',')
     {i++;}
    while(A[i+3]!=',')
     {i++;}
    while(A[i+4]!=',')
     {i++;}
    while(A[i+5]!=',')
     {volume+=A[i+5];
      i++;
     }
    while(((A[i+6]>='0' && A[i+6]<='9') || A[i+6]== '.')&& !(A[i+6]=='2' && A[i+7]=='0' && A[i+8]<='1' && A[i+9]<='5') )
    {CloseAd+=A[i+6];
    i++;
    }
    i+=6;
    Close=CloseAd.toFloat();
    days.append(day);
    CloseAdj.append(Close);
    volume_=volume.toInt();
    Volume.append(volume_);
    }
    for(int l=0;l<10;l++)
    {QString tag=days[l];
    }
    return;
}

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int main(int argc, char *argv[])
    {
        QApplication a( argc, argv );       
        char separator, step='d',tags;
        QString symbol="AAPL";
       int startDay=20,startMonth=7,startYear=2014,endDay=17, endMonth=10,endYear=2014,sM,eM;
       sM=startMonth-1;
       eM=endMonth-1;
       QUrl histUrl(QString("http://ichart.finance.yahoo.com/table.csv?s=%1&a=%2&b=%3&c=%4&d=%5&e=%6&f=%7&g=step&y=0&ignore=.cvs").arg(symbol).arg(sM).arg(startDay).arg(startYear).arg(eM).arg(endDay).arg(endYear),QUrl::TolerantMode);
       mainWidget w;
       w.show();      
       return a.exec();
       }

int main(int argc, char *argv[])
    {
        QApplication a( argc, argv );       
        char separator, step='d',tags;
        QString symbol="AAPL";
       int startDay=20,startMonth=7,startYear=2014,endDay=17, endMonth=10,endYear=2014,sM,eM;
       sM=startMonth-1;
       eM=endMonth-1;
       QUrl histUrl(QString("http://ichart.finance.yahoo.com/table.csv?s=%1&a=%2&b=%3&c=%4&d=%5&e=%6&f=%7&g=step&y=0&ignore=.cvs").arg(symbol).arg(sM).arg(startDay).arg(startYear).arg(eM).arg(endDay).arg(endYear),QUrl::TolerantMode);
       mainWidget w;
       w.show();      
       return a.exec();
       }

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and I received the error message

Fehler:no matching function for call to 'FileDownloader::connect(const char [26], mainWidget*&, const char [33])'

Can somebody the necessary changes post?