Qt：向 dead/stopped 线程发送信号

Question

我遇到了这个问题，我可能正在从一个 QThread 向另一个发送信号，但是我无法检查执行 slot 的线程是否是运行。使用 Qt::QueuedConnection 时框架将如何处理这种情况？

...
WorkerImp* pWorker = new WorkerImp();
QThread worker;
pWorker->moveToThread(&worker);

QObject::connect(&worker, QThread::finished, pWorker, &QObject::deleteLater, Qt::QueuedConnection);
bool connected = QObject::connect(this, &SlaveMaster::requireWork, pWorker, &WorkerImp::doWork, Qt::QueuedConnection);
assert(connected);

// at this point we have connected the signal, thread is not starded.
// however the object that we use to connect still exists and will after we exit the thread.


worker.start();
worker.exit();
worker.wait();

// note that when we exit the QThread we do not destroy the object - it can be start over

emit requireWork();
...

Answer 1

信号从未被处理过。跨线程的排队连接作为事件发布到线程，由其事件循环处理。如果线程停止（因此它的事件循环），则没有人拾取事件并传递它：

来自 Qt 文档 Signals and Slots Across Threads:

Queued Connection: The slot is invoked when control returns to the event loop of the receiver's thread. The slot is executed in the receiver's thread.

和Per-Thread Event Loop:

[...] If no event loop is running, events won't be delivered to the object.

请注意，阻塞排队的连接会死锁

Qt：向 dead/stopped 线程发送信号

Qt: Sending signal to dead/stopped thread

c++

qt

multithreading

signals-slots

qt-signals