call to non-static member function without an object argument

[InferusAnima]

I want to make file downloader function that can be called in any place in the programm

But I'm getting that error: call to non-static member function without an object argument

What's wrong

download.h:

#include <QtCore>
#include <QtNetwork>

#include <cstdio>

#ifndef DOWNLOAD_H
#define DOWNLOAD_H


QT_BEGIN_NAMESPACE
class QSslError;
QT_END_NAMESPACE

using namespace std;

class download: public QObject
{
    Q_OBJECT
    QNetworkAccessManager manager;
    QVector<QNetworkReply *> currentDownloads;

    public:
        QString dir;
        download();
        void doDownload(QUrl url, QString directoryName);
        static QString saveFileName(const QUrl &url);
        bool saveToDisk(const QString &filename, QIODevice *data);
        static bool isHttpRedirect(QNetworkReply *reply);

    public slots:
        void execute();
        void downloadFinished(QNetworkReply *reply);
        void sslErrors(const QList<QSslError> &errors);
};

#endif // DOWNLOAD_H

download.cpp:

#include "download.h"


download manager();
download::download()
{

    connect(&manager, SIGNAL(finished(QNetworkReply*)),
            SLOT(downloadFinished(QNetworkReply*)));

    QTimer::singleShot(0, &manager, SLOT(execute()));
}

void download::doDownload(QUrl url, QString directoryName)
{
    dir = directoryName;
    QNetworkRequest request(url);
    QNetworkReply *reply = manager.get(request);

#if QT_CONFIG(ssl)
    connect(reply, SIGNAL(sslErrors(QList<QSslError>)),
            SLOT(sslErrors(QList<QSslError>)));
#endif

    currentDownloads.append(reply);
}

QString download::saveFileName(const QUrl &url)
{
    QString path = url.path();
    QString basename = QFileInfo(path).fileName();

    if (basename.isEmpty())
        basename = "download";

    if (QFile::exists(basename)) {
        // already exists, don't overwrite
        int i = 0;
        basename += '.';
        while (QFile::exists(basename + QString::number(i)))
            ++i;

        basename += QString::number(i);
    }

    return basename;
}

bool download::saveToDisk(const QString &filename, QIODevice *data)
{


    QString filePath = dir + '/' + filename;
    QFile file(filePath);
    if (!file.open(QIODevice::WriteOnly)) {
        fprintf(stderr, "Could not open %s for writing: %s\n",
                qPrintable(filename),
                qPrintable(file.errorString()));
        return false;
    }

    file.write(data->readAll());
    file.close();

    return true;
}

bool download::isHttpRedirect(QNetworkReply *reply)
{
    int statusCode = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
    return statusCode == 301 || statusCode == 302 || statusCode == 303
           || statusCode == 305 || statusCode == 307 || statusCode == 308;
}

void download::execute()
{

    QUrl url = QUrl::fromEncoded(QString("http://downloads.softwarerat.de/Expsoska.rar").toLocal8Bit());

}

void download::sslErrors(const QList<QSslError> &sslErrors)
{
#if QT_CONFIG(ssl)
    for (const QSslError &error : sslErrors)
        fprintf(stderr, "SSL error: %s\n", qPrintable(error.errorString()));
#else
    Q_UNUSED(sslErrors);
#endif
}

void download::downloadFinished(QNetworkReply *reply)
{
    QUrl url = reply->url();
    if (reply->error()) {
        fprintf(stderr, "Download of %s failed: %s\n",
                url.toEncoded().constData(),
                qPrintable(reply->errorString()));
    } else {
        if (isHttpRedirect(reply)) {
            fputs("Request was redirected.\n", stderr);
        } else {
            QString filename = saveFileName(url);
            if (saveToDisk(filename, reply)) {
                printf("Download of %s succeeded (saved to %s)\n",
                       url.toEncoded().constData(), qPrintable(filename));
            }
        }
    }

    currentDownloads.removeAll(reply);
    reply->deleteLater();

    if (currentDownloads.isEmpty()) {
        // all downloads finished
        QCoreApplication::instance()->quit();
    }
}

#include "main.moc"

main.cpp:

#include <QtCore>
#include <QtNetwork>

#include <cstdio>
#include <download.h>

int main(int argc, char **argv)
{
    QUrl bruh = QUrl::fromEncoded(QString("http://downloads.softwarerat.de/Expsoska.rar").toLocal8Bit());
    download::doDownload(bruh, QString("http://test.com/file.zip"));
}

#include "main.moc"

problem with that line of code in main.cpp: download::doDownload(bruh, QString("TEST"));

Help please.

[Bonnie]

Man, you should start with the C++ basics.

[JonB]

@InferusAnima
Either you need to create an instance of download, or you need to rewrite a static version.

[InferusAnima]

@Bonnie Yes I know, i'm bad at C++, but I rly need it, mb you have solution how to fix?

[Bonnie]

@InferusAnima
Even this error is fixed, this application still cannot work.
It has no event loop, the asynchronous network operations won't survive.
Since you are using Qt classes, when starting a new project, you should choose Qt Widgets/Console Application templates.
They'll give you a QCoreApplication/QApplication to start the event loop.

[InferusAnima]

@Bonnie yeah, ik, that just test thing... i just need to fix that error. I just need ability to call download function everywhere in actual programm.

[Bonnie]

@InferusAnima
Well, that should be easy.
First, add an extern declaration on the bottom of download.h:

extern download manager;

Second on the top of download.cpp

//change to this if get error on this line: download manager()
download manager;

Last in the main.cpp

manager.doDownload(bruh, QString("http://test.com/file.zip"));

You may also need to delete this bottom line in the .cpps

#include "main.moc"

[InferusAnima]

@Bonnie It worked, thank you very much!

[vatsk]

This post is deleted!

[jsulm]

@vatsk Please read and follow https://forum.qt.io/topic/113070/qt-code-of-conduct else you will be baned!
I will delete your post as inappropriate and offensive.