Passing a predicate to QWaitCondition?

Question

I'm writing some threads in Qt and I can't figure out how to pass a predicate to my condition variable to protect against spurious wake up.

Working solution in C++:

std::mutex(mu);
std::condition_variable cond;

std::unique_lock<mutex> alpha_lock(mu);
cond.wait(alpha_lock, [](){ return //some condition;});
alpha_lock.unlock();

//Continue to do stuff...

Qt equivalent:

QMutex mu;
QWaitCondition cond;

QMutexLocker alpha_lock&(mu);
cond.wait(&mu, [](){return //some condition;})

Error:

"no matching member function for call to wait"

Any ideas on how to use a predicate in this Qt code?

Answer 1

As the compiler and @xaxxon have already pointed out, there is no such wait() overload in QWaitCondition.

If you want to check a condition before going on you can do it like this

while (!condition()) {
    cond.wait(mutex);
}

You can of course put that into a helper function that takes a QWaitCondition, QMutex and std::function if you need this in more places. Or derive from QWaitCondition adding the overload doing the loop above.