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[SOLVED] Qt Visual Studio Add-in, Signal & Slots problems

  • I'm trying to compile the basic Qt signal and slots example given "here": with the Visual Studio 2010 add-in (version 1.1.11), and it's giving me a bunch of link errors:

    bq. 1>main.obj : error LNK2001: unresolved external symbol "public: virtual struct QMetaObject const * __cdecl Counter::metaObject(void)const " (?metaObject@Counter@@UEBAPEBUQMetaObject@@XZ)
    1>main.obj : error LNK2001: unresolved external symbol "public: virtual void * __cdecl Counter::qt_metacast(char const *)" (?qt_metacast@Counter@@UEAAPEAXPEBD@Z)
    1>main.obj : error LNK2001: unresolved external symbol "public: virtual int __cdecl Counter::qt_metacall(enum QMetaObject::Call,int,void * *)" (?qt_metacall@Counter@@UEAAHW4Call@QMetaObject@@HPEAPEAX@Z)
    1>main.obj : error LNK2019: unresolved external symbol "protected: void __cdecl Counter::valueChanged(int)" (?valueChanged@Counter@@IEAAXH@Z) referenced in function "public: void __cdecl Counter::setValue(int)" (?setValue@Counter@@QEAAXH@Z)

    I looked around and it seems to indicate that the project isn't moc'ing correctly, however I'm not sure how to fix this.

    This is the code:

    #include <QtCore/QCoreApplication>

    class Counter : public QObject

    Counter() { m_value = 0; }

    int value() const { return m_value; }

    public slots:
    void setValue(int value);

    void valueChanged(int newValue);

    int m_value;

    void Counter::setValue(int value)
    if (value != m_value) {
    m_value = value;
    emit valueChanged(value);

    int main(int argc, char *argv[])
    QCoreApplication a(argc, argv);
    Counter a1, a2;
    QObject::connect(&a1, SIGNAL(valueChanged(int)), &a2, SLOT(setValue(int)));

    return a.exec();

  • You should add your class declaration in header(.h) file. In VS moc'ing is done only on .h files.
    P.S.: you can also add custom Build Step to .cpp files and include .moc in .cpp...

  • thanks, that solved my problem.

  • Please add "[SOLVED]" left to the topic subject.

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