>> I've got an object that I want to live in another thread, so in a class in >> my main thread I've got: >> >> // pseudo-code, may not compile >> QThread* thread = new QThread(this); >> myObject* foo = new myObject(); >> foo ->moveToThread(thread); >> thread->start(); >> >> But when I go to connect the signals/slots between objects in the main >> thread and the "foo" object, should I do that before I move that object to a >> different thread, or after, or does it not matter? >> >> So should it be either: >> QThread* thread = new QThread(this); >> myObject* foo = new myObject(); >> // make calls to connect() before calling moveToThread() >> connect(this, SIGNAL(.),foo, SLOT(.)); // repeat as necessary for all my >> signal/slot connections >> foo->moveToThread(thread); >> thread->start(); >> >> Or: >> QThread* thread = new QThread(this); >> myObject* foo = new myObject(); >> foo->moveToThread(thread); >> thread->start(); >> // make calls to connect() after calling moveToThread() >> connect(this, SIGNAL(.),foo, SLOT(.));// repeat as necessary for all my >> signal/slot connections >> >> Or even delaying the thread->start() call until after everything else: >> QThread* thread = new QThread(this); >> myObject* foo = new myObject(); >> foo->moveToThread(thread); >> // make calls to connect() after calling moveToThread() then call >> thread->start() >> connect(this, SIGNAL(.),foo, SLOT(.));// repeat as necessary for all my >> signal/slot connections >> thread->start(); >> >> I can't find any authoritative documentation that says to do it one way or >> the other, so either it doesn't exist or more likely, I'm not googling well. >> I can find lots of docs on the merits of inheriting from QThread vs. using >> the moveToThread(), but the ones I've found don't address this question in >> detail. >> > It doesn't matter. Qt::autConnection connections (the default connection > type) will evaluate the thread affinity of the current thread* and the > receiver at the moment of the signal emission. So, it doesn't matter if you > connect first and then move, or move first and then connect, only at signal > emission it is evaluated what mechanism to use (direct call, or go through > the event system of the receiving thread).
That's what I assumed, but wasn't sure. > Note that your second example will work in this case, but may end up as a > race condition if you make a connection the other way around from a signal on > your worker to a slot in your current thread. If you start the thread before > making the connection, you run the risk that you'll miss signals as they may > be emitted before you make the connection. > > *) note that the current thread _may_ not match the thread affinity of the > signal's object. I do have signals going both ways so I'll make sure to not use option #2! Thanks, Sean _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
