Unsolved QMutexLocker - SignalWaiter - how does the example work?
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Hi all,
in the docs for the class QMutexLocker there is an outline of an example for a SignalWaiter given.
It is only an outline. Can somebody give me the details how it will work?I have to solve the following problem:
I have a method like this:
int SomeClass::myMethod()
{
// here I have access to a socket. I must start some network-communication
// over the socket to get the result for the method. E.g.mySocket->sendCommand( "someCommandId" ); // The method should now wait till the result is there (or some error occurs). // So I want to wait for the readyRead-Signal now. // Can the SignalWaiter-class be used for it? How?
}
I know that the Qt socket class already has some waitFor...-methods. But using these methods on Windows is not encouraged (...using this method will randomly fail on Windows...). What can I say? I'm on Windows.... So I'm looking for an alternative.
Here is the example from the Qt-docs of QMutexLocker:
class SignalWaiter
{
private:
QMutexLocker locker;public:
SignalWaiter(QMutex *mutex)
: locker(mutex)
{
}void waitForSignal() { ... while (!signalled) waitCondition.wait(locker.mutex()); ... }
};
Thanks in advance,
Best regardsKai
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Hi,
Not a direct answer but I would have rather used a QEventLoop for that or the old QxtSignalWaiter class which does the job well.
Out of curiosity, why do you need such a blocking behavior ?
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Hi Samuel,
thanks for the suggestions. I will take a look at the QxtSignalWaiter. I think it will do exactly what I want. Of course it is a "little overhead" using a whole new library for solving my little problem.
What do you mean by "using the QEventLoop"? So far I have solved my problem with code like this:
while ( ! _isReadyRead ) { // the boolean-variable _isReadyRead will be set inside of the slot which is called by the readyRead()-Signal QCoreApplication::processEvents(); }
But very often code like this is described as an "ugly hack".
So I'm just looking for a better and elegant solution....
** Why do you need such a blocking behavior ?
Little bit complicated to explain, a try: I have a main-program which I can't modify. The code which I can implement and modify is some plugin-code for the main-program. The main-program expects immediate results. When it calls the plugin-method myMethod which is implemented inside of the plugin a result has to be returned. I can't switch the main-program to asynchronous signal-slot-communication.int SomeClass::myMethod()
{
// do some calculation here
// and return the result of the calculation
return myResult;
}Ok?
Best regards
Kai -
IIRC, it's self-contained so You can extract it from the library.
What I have seen in use:
QEventLoop loop; connect(mySocket, &QTcpSocket::readyRead, &loop, &QEventLoop::exit); loop.exec();
Which work a bit like a modal dialog.
Ok, I see your use case, a classic.