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Thread: How to emit a signal passed to a function

  1. #1
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    Default How to emit a signal passed to a function

    I am passing a signal to a method using the SIGNAL macro, and at some point I need to emit that signal.
    Something like the below:

    Qt Code:
    1. void Network::get(const QNetworkRequest &request, const char *signal)
    2. {
    3. QNetworkReply *reply = m_manager->get(request);
    4. m_requests.insert(reply, signal);
    5. }
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    the Network class encapsulates QNetworkAccessManager, so in the method above m_manager is QNetworkAccessManager.
    The Network class has the following signal/slot connection:
    Qt Code:
    1. connect(m_manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(onResponse(QNetworkReply*)));
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    the onResponse SLOT is:
    Qt Code:
    1. void Network::onResponse(QNetworkReply *reply)
    2. {
    3. const char *signal = m_requests.take(reply);
    4. // emit signal somehow
    5. qDebug() << "and the signal is: " << signal;
    6. }
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    m_request is: QHash<QNetworkReply *, const char *> m_requests;

    The idea is that various other classes of the application can use the Network class to make http requests. Each of those classes calls void Network::get(const QNetworkRequest &request, const char *signal) passing its own signal that should be emitted once the request is finished.
    I prototype a small concept of the application using PySide and this mechanism of passing the signal worked perfectly.
    But in the C++ version the return of the SIGNAL macro is a const char *, is there a way i can turn the const char * back to an emittable signal?

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    Default Re: How to emit a signal passed to a function

    Why are you trying to reinvent this wheel? Each caller of QNetworkAccessManager::get() is given a QNetworkReply object. They can connect that object's QNetworkReply::finished() signal to any slot they want executed, or to any signal they want emitted, independent of any other reply object.

  3. #3
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    Default Re: How to emit a signal passed to a function

    I am not trying to reinvent the wheel, I just did not realized that QNetworkReply is also emitting the finished signal.

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    Default Re: How to emit a signal passed to a function

    In case you ever need this in a different context, don't pass a signal but a slot.

    If you have receiver object and a slot name you can easily use QMetaObject::invokeMethod() to call that slot.
    Even with arguments.

    Cheers,
    _

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    Default Re: How to emit a signal passed to a function

    If I'm not mistaken a signal is just a member function, so you should able to store pointers to the signals instead of their const char* representation.
    See this for information: http://stackoverflow.com/a/15176860/4206247

    You also need the instance of the QObject that is emitting it.

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