QNetworkReply wait for finished

Question

I am using Qt 4.6.3 and the following not-working code

QStringList userInfo;
QNetworkRequest netRequest(QUrl("http://api.stackoverflow.com/1.1/users/587532"));
QNetworkReply *netReply = netman->get(netRequest);

// from here onwards not working
netReply->waitForReadyRead(-1);
if (netReply->isFinished()==true)
{userInfo << do sth to reply;}
return userInfo;

as this function returns an empty QStringList, the app crashes. How to wait until the request has finished and then process the reply within one function

Mogador

Old question, but still very relevant. Qt honestly should have a waitForFinished()' function for QNetworkReply. – Metacarpal

Answer 1

You can use event loop:

QEventLoop loop;
connect(netReply, SIGNAL(finished()), &loop, SLOT(quit()));
loop.exec();
// here you have done.

Also you should consider adding some shorter then network timeout (20s?). I'm not sure if finished is called even if an error occured. So it is possible, that you have connect to error signal also.

Langelo

Also the other answer also includes mention of QEventLoop, this answer was correct at once. – Confidant

havent come across any situation where the finished slot wasent called. i know that the doc states that it usally gets called but for me it always gets called – Attalie

It only means that you should consider connecting to some additional signals. It doesn't matter if it "always get called for me". There may be situation (as the docs say) when you won't get finished() signal, so your event loop will be stuck – Langelo

Answer 2

These replies here are all using old syntax and do not apply to the latest QT.

To wait for the network request to finish:

QEventLoop loop;
connect(reply, &QNetworkReply::finished, &loop, &QEventLoop::quit);
loop.exec();

Eliathan

Answer 3

First I recommend you to read the relevant documentation from the Qt Documentation Reference that you can find here: http://doc.qt.nokia.com/latest/classes.html.

Looking at your code sample it seems that you already have, along side with QNetworkRequest and QNetworkReply, a QNetworkAccessManager. What you need is to connect a slot to the finished(QNetworkReply *) signal. This signal is emitted whenever a pending network reply is finished.

QNetworkAccessManager *manager = new QNetworkAccessManager(this);
connect(manager, SIGNAL(finished(QNetworkReply*)),
        this, SLOT(replyFinished(QNetworkReply*)));

manager->get(QNetworkRequest(QUrl("http://api.stackoverflow.com")));

Now, in your slot, you can read the data which was sent in response to your request. Something like:

void MyClass::MySlot(QNetworkReply *data) {
    QFile file("dataFromRequest");
    if (!file.open(QIODevice::WriteOnly))
        return;
    file.write(data->readAll());
    file.close();
}

EDIT:

To wait synchronously for a signal use QEventLoop. You have an example here

http://wiki.forum.nokia.com/index.php/How_to_wait_synchronously_for_a_Signal_in_Qt

Perigon

I also know this but how would I be able to return that received data within same function (I dont\cant want\have an extra slot function) – Mogador