Sent extra data by signal and slot of Qt

stereomatching

@
void MainWindow::update_data(QStringList const &data)
{
int const size = data.size();
for(int i = 0; i != size; ++i)
{
QNetworkReply *reply = theme_get_->request_html(data[i]);
connect(reply, SIGNAL(finished()), this, SLOT(update_message_number()));
}
}

void MainWindow::update_message_number()
{
auto result = theme_get_->read_html(qobject_cast<QNetworkReply *>(sender()) );
if(!result.first) qDebug() << result.second;

int const number = parser_.get_anime_live_message_number(result.second);
anime_live_model_->set_current_message_number(/*index of the row*/, number);

}
@

As the source codes show, I need to send the index(i) to the update_message_number()
but don't know how to achieve by the signal and slot mechanism

I have one solution, declare a map, then
@void MainWindow::update_data(QStringList const &data)
{
int const size = data.size();
for(int i = 0; i != size; ++i)
{
QNetworkReply *reply = theme_get_->request_html(data[i]);
connect(reply, SIGNAL(finished()), this, SLOT(update_message_number()));
mapper.insert(std::make_pair(reply, i) );
}
}

void MainWindow::update_message_number()
{
auto result = theme_get_->read_html(qobject_cast<QNetworkReply *>(sender()) );
if(!result.first) qDebug() << result.second;

int const number = parser_.get_anime_live_message_number(result.second);
if(mapper.find(sender()) != mapper.end() )
  anime_live_model_->set_current_message_number(mapper[sender()], number);
else
  QTimer::single_shot(500, this, SLOT(update_message_number(number ) ) );

}
@

This solution is pretty complicated, how could I solve it by a better way?

stereomatching

Quite expect the new signal and slot mechanism of Qt5
Looks like it is not text-base again and able to co-work
with bind, function and lambda

lgeyer

Your possibilites:

use QSignalMapper to map a QNetworkReply to an index (and which is also the object-oriented-correct version of sender())
@
connect(signalMapper,
static_cast<void (QSignalMapper::*)(int)>(&QSignalMapper::mapped),
this,
&MainWindow::update_message_number);

for (int i = 0; i != size; ++i)
{
...
signalMapper->setMapping(reply, i);
connect(reply,
&QNetworkReply::finished,
signalMapper,
static_cast<void (QSignalMapper::*)()>(&QSignalMapper::map));
}
@

use a lambda to pass the local i
@
for (int i = 0; i != size; i++)
{
...
connect(reply, &QNetworkReply::finished, this, i { update_message_number(i); });
}
@

stereomatching

Do Qt4.8.2 support this kind of signal and slot mechanism?
if I could connect the signal and slot by any callable things like std::function
then I could bind the data directly

stereomatching

I tried it, looks like Qt4.8.2 do not support it yet?
Are you using Qt5.0?I think it is still under developing

lgeyer

No, the new connection syntax is exclusive to Qt 5. But you can still use the QSignalMapper solution and the ordinary connection syntax.

stereomatching

I tried QSignalMapper, but I still need the original sender--reply
QSignalMapper could bind int, but I don't know the original sender