Doing multiple QNetworkRequest on the same QNetworkAccessManager

Dimbreath

I have a QStringList with some urls to text files (Changelogs) on the internet. (Github RAWs from gist, if interesed). Each version has it's struct (Inside that struct i have QString to place the changelog).
I have no problem requesting the changelogs, but i don't know how to assign them to their specific Version struct.

@ struct VersionInfo {
QString versionID;
QString updateVersionTo;
QString updateDate;
QString operatingSystems;
QString changelog;
QString downloadLink;
};
@

That's the struct of each VersionInfo. And i use this code to request:

@ m_manager = new QNetworkAccessManager(this);

QStringList m_urllist;
m_urllist << "Link 1" << "Link 2";
for(int counter = 0; counter < m_urllist.length(); counter++) {
    QNetworkRequest m_request;
    m_request.setRawHeader("User-Agent", "Autoupdater");
    m_request.setUrl(QUrl(m_urllist[counter]));
    m_manager->get(m_request);
}@

Max13

Hello,
QNetworkAccessManager is an asynchronous API, which means if you want to do multiple calls, you'll have to connect them to multiple slots. Or calling 1 by 1 the requests, and connect them to the same slot where you would manage them.

But I don't know if calling 2 times the same slot will call 2 difference slot and not the same one.

Moreover, I noticed that you're using non-pointer QNetworkRequest, which means it will disappear and be removed from the known variables, so I think the SLOT wouldn't be called if maybe the SLOT corresponding to "counter==0" is called DURING "counter==1" for example...

Sorry if it's not clear, if you need precision, I will ;)

Dimbreath

[quote author="Max13" date="1356829581"]Hello,
QNetworkAccessManager is an asynchronous API, which means if you want to do multiple calls, you'll have to connect them to multiple slots. Or calling 1 by 1 the requests, and connect them to the same slot where you would manage them.

But I don't know if calling 2 times the same slot will call 2 difference slot and not the same one.

Moreover, I noticed that you're using non-pointer QNetworkRequest, which means it will disappear and be removed from the known variables, so I think the SLOT wouldn't be called if maybe the SLOT corresponding to "counter==0" is called DURING "counter==1" for example...

Sorry if it's not clear, if you need precision, I will ;)[/quote]

Now that i think about it, i have the same question. o.O

My problem is that i can't identify each QNetworkReply with each VersionInfo.

JKSH

One solution is to create one QObject to handle each VersionInfo + QNetworkReply pair, e.g.

@
for(int counter = 0; counter < m_urllist.length(); counter++) {
QNetworkRequest m_request;
m_request.setRawHeader("User-Agent", "Autoupdater");
m_request.setUrl(QUrl(m_urllist[counter]));
QNetworkReply *reply = m_manager->get(m_request);

    // Store the reply, and connect the QNetworkReply::finished() signal
    // an internal slot that creates a VersionInfo based on the URL and the reply
    ChangelogProcessor *processor = new ChangelogProcessor(m_urllist[counter], reply);
}

@

(Just be careful of memory leaks: You need to delete the ChangelogProcessor AND the QNetworkReply when you're done!)

Dimbreath

@ void Updater::requestChangelogDownload()
{
QNetworkRequest m_request;
m_request.setRawHeader("User-Agent", "Autoupdater");
for(int counter = 0; counter < m_versionList.size(); counter++) {
m_request.setUrl(QUrl(m_versionList[counter].changelog));
m_changelogRequest.insert(m_versionList[counter].versionID, m_manager->get(m_request));
qDebug() << "A";
connect(m_changelogRequest.value(m_versionList[counter].versionID), SIGNAL(finished()), this, SLOT(changelogDownloaded()));
}
}

void Updater::changelogDownloaded()
{
qDebug() << sender();
QNetworkReply a = (QNetworkReply) sender();
qDebug() << a->isFinished();
qDebug() << a->readAll();
}
@

I can say, not a pretty code. FOr some reason it keeps printing "A" even though m_versionList.size() is 2.
Still it doesn't work, a->readAll() returns nothing. But i think i'm doing it poorly.

JKSH

[quote author="Blastcore" date="1356846308"]
@
QNetworkReply a = (QNetworkReply) sender();
@
[/quote]

Try a qobject_cast<> instead of a C-style cast

Dimbreath

Nope, it didn't work. :/ I wonder what's going on o.O

sender() is a QNetworkReplyImpl. Both are different.

Dimbreath

Using readyRead() signal from QNetworkReply fixed the issue.

lgeyer

Be aware that readyRead() only indicates that data is available, not necessarily that the reply has finished.

If you want to pass information, for example a reference to the <code>VersionInfo</code> which was used to initiate the request you can use an "attribute":http://qt-project.org/doc/qt-5.0/qtnetwork/qnetworkrequest.html#setAttribute.

QNetworkAccessManager provides a "finished":http://qt-project.org/doc/qt-5.0/qtnetwork/qnetworkaccessmanager.html#finished signal which passes the QNetworkReply.
@
struct VersionInfo
{
...
};

Q_DECLARE_METATYPE(VersionInfo*)

static const QNetworkRequest::Attribute VersionInfoAttribute = QNetworkRequest::User;

...

connect(m_manager, &QNetworkAccessManager::finished, [](QNetworkReply reply)
{
VersionInfo versionInfo = reply->request().attribute(VersionInfoAttribute)
.value<VersionInfo*>();
if (versionInfo != nullptr)
{
versionInfo->...
}

reply->deleteLater();

});

...

for (int counter = 0; counter < m_versionList.size(); counter++)
{
QNetworkRequest request;

request.setAttribute(VersionInfoAttribute,
                     QVariant::fromValue<VersionInfo*>(&m_versionList[counter]));
request.setRawHeader("User-Agent", "Autoupdater");
request.setUrl(m_versionList[counter].changelog);

m_manager->get(request);

}
@
If you don't want to connect to the finished(QNetworkReply*) signal (for instance because you are reusing the QNetworkAccessManager object and don't want to receive finished signals from other requests) you can use sender() (QNetworkReplyImpl is-a QNetworkReply).