Hi,
I want to create a plugin system. So - first I create Interface
Qt Code: 
  1. class ShopInterface
  2.  {
  3.  public:
  4.      virtual ~ShopInterface() {}
  5.  
  6.      virtual QStringList shopNames() const = 0;
  7. 	 virtual QIcon getShopIcon() const = 0;
  8. 	 virtual bool checkPrices(QString strCompName, double & dPrice, QString strURL );
  9.  };
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Then in separate CMake/VS project plugin is created.
Qt Code: 
  1. class Shop1Plugin : public QObject, public ShopInterface
  2. {
  3. 	Q_OBJECT
  4. 	Q_INTERFACES(ShopInterface)
  5. public:
  6. 	virtual ~Shop1Plugin ();
  7. 	virtual QStringList shopNames() const;
  8. 	virtual QIcon getShopIcon() const;
  9. 	virtual bool checkPrices(QString strCompName, double & dPrice, QString strURL );
  10. };
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File Shop1Plugin.h file is sent to MOC which reports 'Error: Undefined interface' in line with Q_INTERFACES().
Why? Using Qt version 4.7.3