Assuming I have the following snippet, is it safe to call deleteLater in qto's destructor for other QT objects it might administer?
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MyQTObject qto;
qto.show();
return a.exec();
}
Because I've analyzed similar code like this with a leak detector and all the objects for which deleteLater was called, weren't deallocated correctly unless I replaced the call with a normal delete. If I've understood this correctly, deleteLater only registers a deletion event in the QT message queue. Can this be the problem that qto's destructor is called at the end of main's scope whereas the QT message loop already ends with the return from a.exec? Thus the deletion event will never be processed, in fact not even pushed into a message queue since there is none?
Answer
This post is rather aged, but I would like to add the answer I would have liked to come across when I was asking this myself.
deleteLater() can be very useful in combination with asynchronous operations. It especially shines, I think, with the more recent possibility to connect signals to lambda functions.
Suppose you have some longComputation() that you want to execute asynchronously (not in the sense of multithreading, in the sense of scheduling execution in the event loop). You can do like this:
void MyClass::deferLongComputation()
{
QTimer* timer = new QTimer();
connect(timer,
&QTimer::timeout,
[this, timer](){this->longComputiation(); timer->deleteLater();});
timer->setSingleShot(true);
timer->start();
}
where deleteLater() takes care of safely disposing of the QTimer once its duty has been carried out and avoid the memory leak that one would have otherwise.
The same pattern can be used in multithreading with QFutureWatcher.