QNetworkAccessManager finished signal emitted to late

Radu.Amh

I am trying to save a reply in other object which doesn't have anything to do with the downloader class but the finished signal is emitted at the end of the program so I am passing an empty string to the other object. Any ideas how to make response = m_response; work?

#include "downloader.h"

Downloader::Downloader(QObject *parent) : QObject(parent)
{

}

void Downloader::doDownload(QUrl &url, QString &response)
{
    p_manager = new QNetworkAccessManager(this);

    connect(p_manager, SIGNAL(finished(QNetworkReply*)),
           this, SLOT(replyFinished(QNetworkReply*)));

    p_manager->get(QNetworkRequest(url));
    
    response = m_response;
}

void Downloader::replyFinished (QNetworkReply *reply)
{
    if(reply->error())
    {
        m_response = reply->errorString();
    }
    else
    {
        qDebug() << reply->header(QNetworkRequest::ContentTypeHeader).toString();
        qDebug() << reply->header(QNetworkRequest::LastModifiedHeader).toDateTime().toString();;
        qDebug() << reply->header(QNetworkRequest::ContentLengthHeader).toULongLong();
        qDebug() << reply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
        qDebug() << reply->attribute(QNetworkRequest::HttpReasonPhraseAttribute).toString();

        m_response = reply->readAll();
    }

    reply->deleteLater();
}

sierdzio

@Radu.Amh said in QNetworkAccessManager finished signal emitted to late:

response = m_response;

What is response and m_response? You do not set either of them to any value in doDownload().

Radu.Amh

in void Downloader::replyFinished (QNetworkReply *reply) you can find m_response = reply->errorString();
response is what i want to pass to the other object

mrjj

Hi
Why not hook up the other class to finished signal too ?
I assume there cant be any response to copy before finished has been seen.

Also you sentence.

the finished signal is emitted at the end of the program
sounds a bit odd. does it means it takes LONG time to download or
WHY first in the end of the program ?

sierdzio

@Radu.Amh said in QNetworkAccessManager finished signal emitted to late:

response is what i want to pass to the other object

Connect that object to finished() signal, then.

Or set the response in the replyFinished() method. Doing it in doDownload() is way too soon.

J.Hilk

@Radu.Amh said in QNetworkAccessManager finished signal emitted to late:

void Downloader::doDownload(QUrl &url, QString &response)
{
p_manager = new QNetworkAccessManager(this);
connect(p_manager, SIGNAL(finished(QNetworkReply*)),
       this, SLOT(replyFinished(QNetworkReply*)));

p_manager->get(QNetworkRequest(url));

response = m_response;
}

hi p_manager->get is not a synchronus function, therefore m_response in the next line will always be an empty string!

only after the replyFinished signal is fired, is m_response not empty anymore and you can pass it along.

also your p_manager leaks memory!

Radu.Amh

Well, this is what I am trying to do:

class WebPage
{
private:
QUrl m_url;
QString m_name;
QString m_location;
QString m_response;
QFile p_file;

public:
WebPage(const QString &url, const QString &name, const QString &location);
WebPage(const WebPage &)=delete;
void download(Downloader &down);

};

void WebPage::download(Downloader &down)
{
down.doDownload(m_url, m_response);
if(p_file.open(QIODevice::ReadWrite))
{
QTextStream stream( &p_file );
stream << m_response;
p_file.flush();
p_file.close();
}
}

downloading a webpage but also being able to download another webpage later in the same program.

Radu.Amh

@J.Hilk I understood get is not a synchronous function but I need the reply for the other object, webpage, so how do I make it to deliver it in time?
@sierdzio how do I connect the object to the finished() signal?
@mrjj why at the end, I've watched it with the debugger and void Downloader::replyFinished (QNetworkReply *reply) is the last function called, after that deconstructors are called

J.Hilk

@Radu.Amh
we would have to see a good part more of your implementation.

however, this quick and dirty solution should also work. But I recommend rethinking your approach:

void Downloader::doDownload(QUrl url, QString &response)
{
    QNetworkAccessManager *manager = new QNetworkAccessManager();
    QString str;
    QNetworkReply *reply = manager->get(QNetworkRequest(url));
    connect(reply, &QNetworkReply::finished, this, [reply, &str]{
        str = reply->readAll();
        reply->deleteLater();
    });


    QEventLoop loop;
    connect(manager, &QNetworkAccessManager::finished, &loop, &QEventLoop::quit);
    loop.exec();

    manager->deleteLater();

    response = str;
}

Radu.Amh

@J.Hilk Actually it is something I had in mind but I didn't know about QEventLoop. Thank you! Until a better solution comes this is the best.

J.Hilk

@Radu.Amh
It is a Bad solution
It forces synchronus behaviour on an asynchronus method

Better would be a Signal from your download Class that sends the recieved Data to a Slot in your other class
Signals can have arguments, for example a String, to send Data across