2016-02-25 18:24 GMT+01:00 Murphy, Sean <smur...@walbro.com>:
>> > Foo() : QObject(nullptr) {
>> > moveToThread(&m_thread);
>> > m_thread.start();
>> > }
>> >
>> > ~Foo() {
>> > m_thread.quit();
>> > m_thread.wait();
>> > }
>>
>> This destructor is either never run or deadlocks.
>>
>> A QObject can only be destroyed in its thread of affinity. So the above is
>> running in that m_thread thread, which means it hasn't exited. Waiting for it
>> to exit will wait forever.
>
> Just when I think I have QObjects and QThreads figured out, I realize I
> don't... How do I correctly handle my situation?
>
> I've got a QObject-based class that talks to a custom device and needs to
> block while making reads/writes to that device. This thread runs the entire
> duration of my application, because the work it's doing never finishes, it
> just monitors the device for messages and notifies my UI class when data
> comes in.
>
> So currently I'm doing this:
>
> myGUIObject.h:
> private:
> myBlockingObject* blocking;
> QThread* thread;
>
> myGUIObject.cpp:
> myGUIObject()
> {
> thread = new QThread(this);
> blocking = new myBlockingObject();
> blocking->moveToThread(thread);
> }
>
> How/where do I properly delete "blocking"? Right now I'm doing this:
> ~myGUIObject()
> {
> thread->exit();
> blocking->deleteLater();
> }
>
> But Thiago's comment "A QObject can only be destroyed in its thread of
> affinity" sounds like it's not the right way to do it?
> Sean
I was in a similar situation some years ago, talking to a USB/serial
device in a separate thread. I had a look at the code, and what I did
back then was to connect the finished signal of the thread to the
deleteLater() slot of the object I had moved to the thread. I actually
did the same with the thread itself. So the connect() calls I did to
ensure cleanup looked something like this:
// Connect to thread signals to start the sensor and clean up.
connect(m_sensorThread, SIGNAL(started()), sensor, SLOT(start()));
connect(m_sensorThread, SIGNAL(finished()), sensor, SLOT(deleteLater()));
connect(m_sensorThread, SIGNAL(finished()), m_sensorThread,
SLOT(deleteLater()));
Where sensor is the object I had previously moved to m_senseorThread.
Not sure if your approach above with calling deleteLater() explicitly
and immediately after thread->exit() is right or wrong, or if doing it
by signal/slot connections like I did is any better. Just thought I
would chime in :)
Elvis
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