Link error in Windows

[lni]

Hi,

I have a class in library as:

class MY_EXPORT MyWidget : public QWidget
{
  Q_OBJECT
...
};

class MY_EXPORT MyWidget : public QWidget
{
  Q_OBJECT
...
};

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Where in Windows, MY_EXPORT is defined as "__declspec(dllexport)"

Now I use this class to build executable by linking to its library

class DerivedWidget : public MyWidget {
 Q_OBJECT
...
};.

class DerivedWidget : public MyWidget {
 Q_OBJECT
...
};.

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On linking, it complains errors:

moc_DerivedWidget.obj : error LNK2001: unresolved external symbol "public: static struct QMetaObject const MyWidget::staticMetaObject" (?staticMetaObject@MyWidget@@2UQMetaObject@@B)

Please help. Many thanks!