Q_OBJECT in cpp file



  • Hi

    I have a problem with the macro Q_OBJECT. My source code:
    @
    // myclass.h
    #ifndef MYCLASS_H
    #define MYCLASS_H

    #include <QObject>
    #include <QtCore>

    class MyClassPrivate;

    class MyClass : public QObject
    {
    Q_OBJECT
    Q_DECLARE_PRIVATE(MyClass)
    public:
    explicit MyClass(QObject *parent = 0);

    signals:

    public slots:

    private:
    void* const d_ptr;
    };

    #endif // MYCLASS_H
    @
    @
    // myclass.cpp
    #include "myclass.h"

    class MyClassPrivate: public QObject {
    Q_OBJECT
    public:
    MyClassPrivate():QObject(NULL){}
    signals:
    public slots:
    };

    MyClass::MyClass(QObject *parent) :
    QObject(parent),
    d_ptr(new MyClassPrivate())
    {
    }
    @

    when compiling, I got error "undefined reference to `vtable for MyClassPrivate'". But if I comment the Q_OBJECT declaration inside MyClassPrivate then compilation successful. Could anyone tell me why? And what if I don't use Q_OBJECT in MyClassPrivate?
    Thanks for help!



  • You need to moc that .cpp as well. The usual trick is using a #include "myclass.moc" (or "moc_myclass.cpp") at the end of the .cpp, then rerun qmake. May I ask why do you need a private that inherits from QObject?



  • Thanks for quick help peppe! It worked. I would want to use signal/slot mechanism whatever it might be unnecessary :D, but I would want to try if sometime I want to use derivations of QObject inside cpp files.



  • What I usually do, it not moc the cpp file, but just create a myclass_p.h file.



  • yep, I used to do that



  • Sry, I have the same problem and I don't get it how to include the moc file. Could you give me a short example how to do it? Would be nice.

    Edit:
    Okay nevermind...I just have to include "moc_myclass.cpp". First I tried modul1g.moc and failed. I was wondering why the compiler didn't find moc_myclass.cpp, so I didn't try this.


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