waiting for a signal - qt

Question

I am working on an application which uploads the content of the file to server.
To upload the file to server I am using ‘QNetworkAccessManager’ class. Since it works as asynchronous way, I changed it to work as synchronous way by using QEventLoop.
Class FileTransfer
{
Public :
QNetworkAccessManager mNetworkManager;
Void Upload(QNetworkRequest request, QIODevice *data)
{
responce = mNetworkManager.put(request, data);
EventLoop.exec();
ReadResponce(responce);
}
Void Stop()
{
responce ->close();
}
}
In my sample application I have 2 windows. 1st to select the files and 2nd to show the progress.
When user click on upload button in the first window, the 2nd window will be displayed and then I create the FileTransfer object and start uploading.
While uploading the file if user closes the form then in the destructor of the window I call the stop of ‘FileTransfer’ after that I delete the ‘FileTransfer’ object.
But here the Upload() function is not yet completed so it will crash.
Please help me to:
How to wait in 'stop()' function until the Upload() function is completed

Answer 1

From what I can see from your code, you're executing a QEventLoop but you're not actually connecting its "quit" slot to any signal. Take the below as an example, login is a QHttp - and the code is taken from something different - but the principle applies.
/* Create the QEventLoop */
QEventLoop pause;
/* connect the QHttp.requestFinished() Signal to the QEventLoop.quit() Slot */
connect(&login, SIGNAL(requestFinished( int, bool )), &pause, SLOT(quit()));
/* The code that will run during the QEventLoop */
login.request(header,&logmein,&result);
/* Execute the QEventLoop - it will quit when the above finished due to the connect() */
pause.exec();
This could be applied to your code, if I'm not mistaken, like this...
/* connect the signal to the relevant slot */
connect(&mNetworkManager, SIGNAL(finished( QNetworkReply )), &EventLoop, SLOT(quit()));
/* Execute the code that will run during QEventLoop */
responce = mNetworkManager.put(request, data);
/* Execute the QEventLoop */
EventLoop.exec();
Apologies if I've mistaken your query! I'm only getting to grips with qt again after a break, but I believe this is what you mean! Good luck!

Answer 2

I think you need to add something like that in your upload function:
if (upf->openFile())
{
reply = manager->post(request, upf);
connect(reply, SIGNAL(uploadProgress(qint64,qint64)), this, SIGNAL(progress(qint64,qint64)));
connect(reply, SIGNAL(finished()), this, SLOT(replyFinished()));
isInProgress = true;
emit started();
} else
{
emit finished(true, false, tr("Error: can't open file %1").arg(filename));
}
Here is the full text code: datacod-qt-tools
Hope it help.

Answer 3

Personally, I would recommend to not use any of these answers.
It would be sufficient to connect a countdown latch to the signal.
So you could write:
Latch latch( 1 );
QObject::connect( reply, SIGNAL(finished()),
&latch, SLOT(countDown()) );
latch.wait();
For this you would need a wrapper:
class Latch : public QObject {
Q_OBJECT
public:
Latch( uint count );
void wait();
public slots:
void countDown();
private:
gcl::countdown_latch _latch;
};