[PySide] QThread crash before emitting finished signal

[Sebastian Elsner]

Hi,

1) I'd add an __init__ like this.

def __init__(self,parent=None):
     QObject.__init__(self,parent)

2) I'd move the work method stuff to the init. It looks like you are 
doing the setup there. init is the place to be for this.

3) QMetaObject.invokeMethod(photoWorker, "work", Qt.QueuedConnection) 
looks very strange
use:
photoThread.started.connect(photoWorker.doWork)
instead. place before photoThread.start().

>
> Apart from that, my threads are being destroyed as photoWorker and 
> photoThread objects run out of scope. How can I prevent python from 
> doing this? Making them instance objects is not an option since every 
> time my program reenters the method where they are declared it spawns 
> new threads.

Make a list and add the photoWorker instances to the list. Clean the 
list up now and then.

>
> Thanks,
>
>
> 2012/6/7 William Dias <william.dias at gmail.com 
> <mailto:william.dias at gmail.com>>
>
>     Thank you, Sebastian. I followed the procedures described in the
>     document and it worked. But I have another question.
>     Take a look at the code bellow:
>
>     class PhotoWorker(QObject):
>
>     photoStatus = Signal(str, str)
>
>     @Slot()
>     def work(self):
>     self.db = sqlite_database.SQLiteDatabase("db1")
>     self.timer = QTimer()
>     self.timer.timeout.connect(self.__resendPhoto)
>     logger.info <http://logger.info>("photo worker started")
>     self.timer.start(10000)
>
>     @Slot()
>     def __resendPhoto(self):
>     data = self.db.selectPhoto()
>     if data != None:
>     self.filename = data[0]
>     self.tags = data[1]
>     logger.info <http://logger.info>("trying to resend photo " +
>     self.filename)
>     status = sendPhoto(self.tags, self.filename)
>     self.photoStatus.emit(self.filename, status)
>
>     And in a GUI class, I do the following:
>
>     photoWorker = http_connection.PhotoWorker(self)
>     photoWorker.photoStatus.connect(self.photoStatus)
>     photoThread = QThread()
>     photoWorker.moveToThread(photoThread)
>     photoThread.start()
>     QMetaObject.invokeMethod(photoWorker, "work", Qt.QueuedConnection)
>
>     I realized that when I create the photoWorker object, if I don't
>     set its parent to self, my thread dies. Is this because my
>     photoWorker doesn't have its own event loop? I am bit confused
>     here. How should I proceed?
>
>     Thank you.
>
>     2012/6/7 Sebastian Elner <sebastian at risefx.com
>     <mailto:sebastian at risefx.com>>
>
>         Although it is in the documentation, QThread is not meant to
>         be used this way (subclassing). Have a look at this:
>         http://labs.qt.nokia.com/2010/06/17/youre-doing-it-wrong/ It
>         helped me a lot. Also a complete stripped down example would
>         greatly help in a case of a segfault.
>
>
>
>         On 06/07/2012 09:59 AM, William Dias wrote:
>>         Hi,
>>
>>         I have a subclass of QThread which uploads pictures to a
>>         webserver. For each new picture created in the main thread,
>>         the program spawns a new thread to handle the job. I've
>>         override the __init__ method to be able to pass some
>>         parameters to the thread object, as you can see bellow.
>>
>>             class PhotoConnection(QThread):
>>             photoStatus = Signal(str, str)
>>
>>             def __init__(self, tags, filename, parent=None):
>>             QThread.__init__(self, parent)
>>             self.tags = tags
>>             self.filename = filename
>>
>>             def run(self):
>>             status = sendPhoto(self.tags, self.filename)
>>             self.photoStatus.emit(self.filename, status)
>>
>>
>>         In the GUI thread, the method responsible dor creating the
>>         threads is the following:
>>
>>             def sendPhoto(self):
>>             photoConnection = PhotoConnection(self.tags_to_string,
>>             self.filename, self)
>>             photoConnection.photoStatus.connect(self.photoStatus)
>>             photoConnection.finished.connect(self.threadFinished)
>>             photoConnection.start()
>>
>>
>>         In the PhotoConnection, if I don't set the parent of my
>>         Qthread object to self (for example, if I set to None) or if
>>         I don't override the __init__ method and create another
>>         method to pass the arguments, when the thread finishes the
>>         execution I got a segfault.
>>         Why is this happening? Can you help me?
>>
>>         Thanks,
>>
>>
>>         _______________________________________________
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>>         PySide at qt-project.org  <mailto:PySide at qt-project.org>
>>         http://lists.qt-project.org/mailman/listinfo/pyside
>
>
>         -- 
>         Sebastian Elsner    -    pipeline td   -   r i s e |  fx
>
>         t:+49 30 20180300  <tel:%2B49%2030%2020180300>                  sebastian at risefx.com  <mailto:sebastian at risefx.com>
>                                                    www.risefx.com  <http://www.risefx.com>
>
>         r i s e |  fx  GmbH
>         Schlesische Strasse 28 Aufgang B, 10997 Berlin
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>
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>
>
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>
>
>
>
>     -- 
>     William Marques Dias
>
>
>
>
> -- 
> William Dias


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