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Thread: Signal inside an abstract class

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    Default Signal inside an abstract class

    Hi there guys. I have this abstract class below.
    Qt Code:
    1. class Page : public QObject
    2. {
    3. Q_OBJECT
    4. public:
    5. explicit Page(QObject *parent = 0);
    6. virtual void start_downloading() = 0;
    7. signals:
    8. void done();
    9. public slots:
    10.  
    11. };
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    As you can see that there is a signal Page::done() in the class. I have a bunch of concrete classes that inherit this class and the concrete classes will emit the signal Page::done() above. I have a separate class that works with the concrete classes and problem is connecting the above signal to any slot and I suppose its because the signal exists in an abstract class. Is there a way of connecting this signal.

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    Default Re: Signal inside an abstract class

    The concrete classes inheriting abstract Page class will also inherit the signals (and slots), so connecting to signal should be just as usual, should not be any different for Abstract class signal (or slot) / Concrete class signal (or slot).
    When you know how to do it then you may do it wrong.
    When you don't know how to do it then it is not that you may do it wrong but you may not do it right.

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    Default Re: Signal inside an abstract class

    The "signals" keyword is basically defining a "protected" section in the class definition, so your derived classes will inherit the methods you have defined as signals with protected access.

    You may have to qualify the names with Page:: when you connect (and use the "PointerToMemberFunction" version of QObject::connect()).
    Please use CODE tags when posting source code so it is more readable. Click "Go Advanced" and then the "#" icon to insert the tags. Paste your code between them.

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    Default Re: Signal inside an abstract class

    Quote Originally Posted by d_stranz View Post
    The "signals" keyword is basically defining a "protected" section in the class definition
    Actually Qt5 had to switch this to "public" in order to make the function pointer based connect work.

    Cheers,
    _

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    Default Re: Signal inside an abstract class

    Actually Qt5 had to switch this to "public" in order to make the function pointer based connect work.
    Hmm, I must have been looking at older documentation. Making it public makes sense, though. Thanks for the correction.
    Please use CODE tags when posting source code so it is more readable. Click "Go Advanced" and then the "#" icon to insert the tags. Paste your code between them.

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