Qt QNetworkAccessManager and Slot not working

Question

i am a beginner in c++ and i am trying to retrieve data from a website using http request and to download the data in a file .

I am using the classes :

QMainWindow QtNetwork/QNetworkAccessManager QtNetwork/QNetworkRequest QtNetwork/QNetworkReply QUrl

The thing is that the file is created but there is no data in the file and i am getting an error that i don't understand . I searched through the forum found some similar kind of problems but did not understand as i am a beginner . Please help me its a school project and i am really stuck here.

Here is the httpWindow.h code

#ifndef HTTPWINDOW_H
#define HTTPWINDOW_H

#include <QMainWindow>
#include <QtNetwork/QNetworkAccessManager>
#include <QtNetwork/QNetworkRequest>
#include <QtNetwork/QNetworkReply>
#include <QUrl>
#include <QString>

class QFile;

namespace Ui {
class httpWindow;
}

class httpWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit httpWindow(QWidget *parent = 0);
    ~httpWindow();
    void request(QUrl url);

private slots:
    void downloadFile();
    void httpFinished();
    void httpReadyRead();
private:
    Ui::httpWindow *ui;
    QUrl url;
    QNetworkAccessManager *manager;
    QNetworkRequest requete;
    QNetworkReply *reply;
    QFile *file;
    int httpGetId;
    bool httpRequestAborted;

};

#endif // HTTPWINDOW_H

Here is the httpwindow.cpp

#include <QtWidgets>
#include <qnetwork.h>
#include <QString>

#include "httpwindow.h"
#include "ui_httpwindow.h"

httpWindow::httpWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::httpWindow)
{
    ui->setupUi(this);
    downloadFile();
}

httpWindow::~httpWindow()
{
    delete ui;
}

void httpWindow::request(QUrl url)
{
    manager =  new QNetworkAccessManager(this);
    connect(manager, SIGNAL(finished()),
            this, SLOT(httpFinished()));

    //requete.setUrl(QUrl("http://fxrates.fr.forexprostools.com/index.php?force_lang=5&pairs_ids=1;3;2;4;7;5;8;6;&header-text-color=%23FFFFFF&curr-name-color=%230059b0&inner-text-color=%23000000&green-text-color=%232A8215&green-background=%23B7F4C2&red-text-color=%23DC0001&red-background=%23FFE2E2&inner-border-color=%23CBCBCB&border-color=%23cbcbcb&bg1=%23F6F6F6&bg2=%23ffffff&bid=show&ask=show&last=show&change=hide&last_update=hide"));
    requete.setUrl(url);

    reply = manager->get(requete);
   connect(reply, SIGNAL(&reply::readyRead()), this, SLOT(httpReadyRead()));
}

void httpWindow::downloadFile()
{
    QMessageBox msg ;
   QUrl url("http://fxrates.fr.forexprostools.com/index.php?force_lang=5&pairs_ids=1;3;2;4;7;5;8;6;&header-text-color=%23FFFFFF&curr-name-color=%230059b0&inner-text-color=%23000000&green-text-color=%232A8215&green-background=%23B7F4C2&red-text-color=%23DC0001&red-background=%23FFE2E2&inner-border-color=%23CBCBCB&border-color=%23cbcbcb&bg1=%23F6F6F6&bg2=%23ffffff&bid=show&ask=show&last=show&change=hide&last_update=hide") ;
   qDebug() << url.toString();
   QFileInfo fileInfo(url.path());
    //msg.setText("fileInfo = " + fileInfo);
    QString fileName = "C:\\testQt\\" + fileInfo.fileName();
     msg.setText("fileName = " + fileName);

     if (fileName.isEmpty()){

        fileName = "C:\testQt\fichier.html";
        msg.setText(" création d'un nouveau fichier fichier.html ");

    }
    if (QFile::exists(fileName)) {
        QFile::remove(fileName);
        return;


    }
    file = new QFile(fileName);
    msg.setText(" QFile::exists(fileName) == true , file : ");
    if (!file->open(QIODevice::WriteOnly)) {

        delete file;
        file = 0;
        return;
    }


    // schedule the request
    httpRequestAborted = false;
    request(url);

}

void httpWindow::httpFinished()
{
    if (httpRequestAborted) {
        if (file) {
            file->close();
            file->remove();
            delete file;
            file = 0;
        }
        reply->deleteLater();
        return;
    }

    file->flush();
    file->close();

    QVariant redirectionTarget = reply->attribute(QNetworkRequest::RedirectionTargetAttribute);
    if (reply->error()) {
        file->remove();
//        QMessageBox::information(this, tr("HTTP"),
//                                 tr("Download failed: %1.")
//                                 .arg(reply->errorString()));
//        downloadButton->setEnabled(true);
    } else if (!redirectionTarget.isNull()) {
        QUrl newUrl = url.resolved(redirectionTarget.toUrl());
//        if (QMessageBox::question(this, tr("HTTP"),
//                                  tr("Redirect to %1 ?").arg(newUrl.toString()),
//                                  QMessageBox::Yes | QMessageBox::No) == QMessageBox::Yes) {
            url = newUrl;
            reply->deleteLater();
            file->open(QIODevice::WriteOnly);
            file->resize(0);
            request(url);
            return;

    }

    reply->deleteLater();
    reply = 0;
    delete file;
    file = 0;

}


void httpWindow::httpReadyRead()
{
    // this slot gets called every time the QNetworkReply has new data.
    // We read all of its new data and write it into the file.
    // That way we use less RAM than when reading it at the finished()
    // signal of the QNetworkReply
    if (file)
        file->write(reply->readAll());

}

Here is the main.cpp code

#include "httpwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    httpWindow w;
    w.show();

    return a.exec();
}

The errors :

can't find linker symbol for virtual table for `QMessageBox' value
  found `RGB_MASK' instead
can't find linker symbol for virtual table for `QMessageBox' value
  found `RGB_MASK' instead
"http://fxrates.fr.forexprostools.com/index.php?force_lang=5&pairs_ids=1;3;2;4;7;5;8;6;&header-text-color=%23FFFFFF&curr-name-color=%230059b0&inner-text-color=%23000000&green-text-color=%232A8215&green-background=%23B7F4C2&red-text-color=%23DC0001&red-background=%23FFE2E2&inner-border-color=%23CBCBCB&border-color=%23cbcbcb&bg1=%23F6F6F6&bg2=%23ffffff&bid=show&ask=show&last=show&change=hide&last_update=hide"
QObject::connect: No such signal QNetworkAccessManager::finished() in ..\ppe3_trading_test\httpwindow.cpp:24
QObject::connect:  (receiver name: 'httpWindow')
QObject::connect: No such signal QNetworkReplyHttpImpl::&reply::readyRead() in ..\ppe3_trading_test\httpwindow.cpp:31
QObject::connect:  (receiver name: 'httpWindow')

Please do help me its really important for my schooling .

Answer 1

connect(reply, SIGNAL(&reply::readyRead()), this, SLOT(httpReadyRead()));

You're mixing up old syntax and new syntax, it should be

connect(reply, SIGNAL(readyRead()), this, SLOT(httpReadyRead()));

or better yet using new syntax(Qt5 only):

connect(reply, &QNetworkReply::readyRead, this, &httpWindow::httpReadyRead);

QNetworkAccessManager doesn't have a finished() signal it has a finished(QNetworkReply*) signal, read the docs.