Nevermind. It's a problem at the macro level. This will only work when the
Tasklet class is created from the main thread. I was creating it from deep
down inside calls originating from a QThread object, which is apparently a no-no.
I'll refactor to notify the main thread to create these instances, and all
should be well.
Sorry to bother.
On 11/23/2016 8:16 PM, Bob Hood wrote:
I did some Googling about this, and found a LOT of hits about QFutureWatcher
not emitting its signals (like finished()) when the QFuture it's watching
completes. However, in all cases I've seen, people were using an auto
version of QFutureWatcher which dropped out of scope on them (i.e.,
allocated on the local stack). Allocating it on the heap seemed to solve all
problems I found.
Well, it isn't solving it for me. I'm using Qt 5.6.2. I have a simple
tasklet class that performs a discrete function in a separate thread
independent of the main process. Its basic structure looks like this:
Definition:
class Tasklet : public QObject
{
Q_OBJECT
public:
Tasklet(...args...);
~Tasklet();
signals:
voidsignal_result(const QString& reference, bool result);
private slots:
voidslot_future_finished();
private:// methods
boolrun();
private:// data members
...args...
QFutureWatcher* watcher;
};
Implementation:
Tasklet::Tasklet(...args...) : ...init...
{
QFuture future = QtConcurrent::run(this, ::run);
watcher = new QFutureWatcher();
connect(watcher, ::finished, this,
::slot_future_finished);
watcher->setFuture(future);
}
bool Tasklet::run()
{
...processing...
return true;
}
void Tasklet::slot_future_finished()
{
emit signal_result(reference, watcher->result());
watcher->deleteLater();
}
Tasklet::slot_future_finished() is NEVER called. I've verified that the
connect() returns true, tried using the old-style syntax for connect, and
I've also tried having a class member for QFutureWatcher instead of
allocating it on the heap. No joy.
Can another pair of eyes see what am I doing wrong here?
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