QNetworkAccessManager.get(QNetworkRequest) not working.. :(

[matthieunc]

Hey there, I'm completely new to this forum! I'm coming here because I'm having an issue in my Qt code, and my beginner skills aren't helping me a lot...

I'm trying to send a request to get the content of a tumblr blog, at "kauritree.tumblr.com/api/read". The file I should get is an XML file, so I created a class that is in charge of downloading the file, and transforming it in whatever I want. I just cant get the QNetworkAccessManager.get(request) to be working... and I dont know why. The GET request is not even sent (I checked using Wireshark)... Thank you for your help!

here is my code:

main.cpp:


QUrl qUrl;
qUrl.setUrl("http://kauritree.tumblr.com/api/read/");
ListeXml listeXml;
listeXml.downloadd(qUrl);


my ListeXml.cpp


ListeXml::ListeXml(QObject *parent) :
QObject(parent)
{
}

QString ListeXml::downloadd(QUrl url)
{
DownloadManager manager;
manager.doDownload(url.toString());
}


DownloadManager.cpp


DownloadManager::DownloadManager() //Constructor
{
QObject::connect(&manager, SIGNAL(finished(QNetworkReply*)),SLOT(downloadFini shed(QNetworkReply*)));
}

void DownloadManager::doDownload(QString Url)
{
QUrl url;
url.setUrl(Url);
const QNetworkRequest request(url);
QNetworkReply *reply = manager.get(request);
}

[Lykurg]

Hi,

it is because the get function of QNetworkAccessManager works asynchron. That means that DownloadManager::doDownload returns right after calling get, then ListeXml::downloadd returns and finally it proceed at listeXml.downloadd(qUrl); without Qt had had the chance to start the network request and all objects you create on the stack will be deleted, thus the request will never be sent.

[matthieunc]

Right after posting, I kept testing and I found a code that succeeded in downloading the file. The download instruction is in main.cpp, and it's working, so am I missing something about your explaination? here is the main.cpp that got it working (without changing anything else):

main.cpp


#include "mainwindow.h"
#include "listexml.h"

#include <QDebug>
#include <QtGui/QApplication>


int main(int argc, char *argv[])
{
QApplication app(argc, argv);

DownloadManager manager;
manager.doDownload(QString("http://symblr.tumblr.com/api/read/"));

return app.exec();
}


However, I just copied the code from "ListeXml.cpp" to "main.cpp". So... why??
Meanwhile, I'm going to try to code a signal/slot system that ends the doDownload function only when the file is downloaded.

[Lykurg]

In main() it succeed because the manager keeps alive. In your further code it gets destroyed right after it was created. Make yourself familiar with the lifetime of objects and with stack/heap allocation.

[matthieunc]

I'll follow your advice! Thank you soooo much for your help! :)