How to get information from QNetworkReply

undac

Hi,

I am using QNetworkManager, and i want to make a get request to an url and print the reply information to a file, but i seem to have a problem with my reply as the information is not available and the ReadyRead or Finished signals are not being triggered.

std::string url = ui.searchLine->text().toStdString();
			QUrl myurl = QUrl(url.c_str());
			QNetworkReply* reply = man->get(QNetworkRequest(myurl));
			connect(reply, &QNetworkReply::readyRead, [&]()
				{
					QByteArray read = reply->readAll();
					QFile out("page.html");
					out.open(QIODevice::WriteOnly|QIODevice::Text);
					out.write(read);
					out.close();
					reply->close();
					reply->deleteLater();
				});

mrjj

Hi
Maybe try using QUrl
manager->get(QNetworkRequest(QUrl(myurl)));

https://www.bogotobogo.com/Qt/Qt5_Downloading_Files_QNetworkAccessManager_QNetworkRequest.php

undac

It seems to have no effect, and i can't seem to be able to see the value of reply!(https://ibb.co/BtYTBy0)

mrjj

@undac
well now it enters the ReadReady it seems ?
So check the errors as seen in link.
maybe be some error if read variable is empty.

 if(reply->error())
    {
        qDebug() << "ERROR!";
        qDebug() << reply->errorString();
    }

undac

When running it now though, it throws me an acces violation reading location exception at the reply->readAll()

mrjj

Hi
Then there must be something with the capture of reply variable if its
invalid inside the lambda.

try
[=]
and not [&]
as maybe it captures the local reply and its out of scope when lambda runs.

Christian Ehrlicher

@mrjj said in How to get information from QNetworkReply:

as maybe it captures the local reply and its out of scope when lambda runs.

[&] captures by reference and the local pointer is no longer valid due to this.
[=] is also not really useful - simply copying all is like using a hammer to open an egg... better is to only copy what you really need -> [this, reply]

undac

It does work both with the [=] syntax and the [this, reply] one, but i opted for the latter. I noticed that it didn't download the data properly and so i changed to &QNetworkReply::finished and it works as desired.

Thank you very much!

Christian Ehrlicher

@undac Then please mark this topic as solved, thx.