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!