Qt - pobieranie plików używając nowej klasy

#ifndef QDOWNLOADER_H
#define QDOWNLOADER_H

#include <QNetworkAccessManager>
#include <QNetworkRequest>
#include <QNetworkReply>
#include <QUrl>
#include <QProgressDialog>
#include <QFile>
#include <QFileInfo>
#include <QDir>
#include <QMessageBox>
#include <QTime>
#include <QDebug>
#include <QString>


class qDownloader : public QObject
{

    Q_OBJECT

public:
    qDownloader();

public:
    void download_clicked(QUrl url);

    void startRequest(QUrl url);

private slots:
    void httpReadyRead();

    void httpDownloadFinished();

    void updateDownloadProgress(qint64, qint64);

    void cancelDownload();

public:
    QNetworkAccessManager *manager;

private:
    QUrl url;
    //QNetworkAccessManager *manager;
    QNetworkReply *reply;
    QProgressDialog *progressDialog;
    QFile *file;
    qint64 fileSize;
    qint64 fileSpeed;
    QTime t;

    bool httpRequestAborted;
};

#endif // QDOWNLOADER_H

#include "qdownloader.h"

qDownloader::qDownloader()
{

}

void qDownloader::download_clicked(QUrl url)
{   
    manager = new QNetworkAccessManager(NULL);

    QFileInfo fileInfo(url.path());
    QString fileName = fileInfo.fileName();

    if(fileName.isEmpty())
        fileName = "index.html";

    if(QFile::exists(fileName)){
        if(QMessageBox::question(0, "HTTP", "Plik %1 już istnieje. Czy chcesz go nadpisać ?", QMessageBox::Yes | QMessageBox::No, QMessageBox::No) == QMessageBox::No)
            return;

        QFile::remove(fileName);
    }

    file = new QFile(fileName);
    if(!file->open(QIODevice::WriteOnly)){
        QMessageBox::information(0, "HTTP", "Nie można zamiać pliku %1: %2.");

        delete file;

        file = 0;

        return;
    }

    httpRequestAborted = false;

    qDebug() << "Pobieranie " << fileName;

    startRequest(url);
}

void qDownloader::httpReadyRead()
{
    if(file)
        file->write(reply->readAll());
}

void qDownloader::updateDownloadProgress(qint64 bytesRead, qint64 totalBytes)
{
    qint64 predkosc = ((bytesRead - fileSpeed) * (t.elapsed() / 10)) / 1024;

    t.start();

    fileSpeed = bytesRead;

    if(httpRequestAborted)
        return;

    bytesRead = (bytesRead / 1024) / 1024;
    totalBytes = (totalBytes / 1024) / 1024;

    qDebug() << "Prędkość pobierania wynosi : " << predkosc;
    qDebug() << "Pobrano " << bytesRead << " z " << totalBytes << endl;
}

void qDownloader::cancelDownload()
{
    httpRequestAborted = true;
    reply->abort();
}

void qDownloader::httpDownloadFinished()
{
    // when canceled

    if(httpRequestAborted){
        if(file){
            file->close();
            file->remove();

            delete file;

            file = 0;
        }

        reply->deleteLater();
        progressDialog->hide();

        return;
    }

    // download finished normally

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

    // get redirection url

    QVariant redirectionTarget = reply->attribute(QNetworkRequest::RedirectionTargetAttribute);
    if(reply->error()){
        file->remove();

        QMessageBox::information(0, "HTTP", "Download failed: %1.");
    }else if(!redirectionTarget.isNull()){
        QUrl newUrl = url.resolved(redirectionTarget.toUrl());
        if(QMessageBox::question(0, "HTTP", "Redirect to %1 ?", QMessageBox::Yes | QMessageBox::No) == QMessageBox::Yes){
            url = newUrl;
            reply->deleteLater();
            file->open(QIODevice::WriteOnly);
            file->resize(0);
            startRequest(url);

            return;
        }
    }else{
        QString fileName = QFileInfo(url.path()).fileName();
    }

    reply->deleteLater();
    reply = 0;

    delete file;

    file = 0;
    manager = 0;
}

void qDownloader::startRequest(QUrl url)
{
    reply = manager->get(QNetworkRequest(url));

    connect(reply, SIGNAL(readyRead()), this, SLOT(httpReadyRead()));
    connect(reply, SIGNAL(downloadProgress(qint64,qint64)), this, SLOT(updateDownloadProgress(qint64,qint64)));
    connect(reply, SIGNAL(finished()), this, SLOT(httpDownloadFinished()));
}

private:
    qDownloader *m;

m->download_clicked(QUrl("http://link-do-pliku-ktory-chce-pobrac.exe"));

QScopedPointer<QNetworkAccessManager> manager;

QScopedPointer<QNetworkAccessManager> manager;

	QScopedPointer<QObject> foo(new QTcpSocket);
	
//	foo->connect(...)
	
	delete foo.data(); // zle!

QScopedPointer<QFile> file;
    file(fileName);

qDownloader *m;

m->download_clicked(QUrl("http://link-do-pobrania.exe"));

if(NULL != m)
        m->someMethod();
    else
        qDebug() << "m = NULL";

void qDownloader::someMethod()
{
    if(NULL != this)
        qDebug() << "Normal behavior";
    else
        qDebug() << "Default behavior in case of null";
}