Creating custom plugin

[T4ng10r]

Hi,
I want to create a plugin system. So - first I create Interface

class ShopInterface
 {
 public:
     virtual ~ShopInterface() {}
 
     virtual QStringList shopNames() const = 0;
	 virtual QIcon getShopIcon() const = 0;
	 virtual bool checkPrices(QString strCompName, double & dPrice, QString strURL );
 };

class ShopInterface
 {
 public:
     virtual ~ShopInterface() {}

     virtual QStringList shopNames() const = 0;
	 virtual QIcon getShopIcon() const = 0;
	 virtual bool checkPrices(QString strCompName, double & dPrice, QString strURL );
 };

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Then in separate CMake/VS project plugin is created.

class Shop1Plugin : public QObject, public ShopInterface
{
	Q_OBJECT
	Q_INTERFACES(ShopInterface)
public:
	virtual ~Shop1Plugin ();
	virtual QStringList shopNames() const;
	virtual QIcon getShopIcon() const;
	virtual bool checkPrices(QString strCompName, double & dPrice, QString strURL );
};

class Shop1Plugin : public QObject, public ShopInterface
{
	Q_OBJECT
	Q_INTERFACES(ShopInterface)
public:
	virtual ~Shop1Plugin ();
	virtual QStringList shopNames() const;
	virtual QIcon getShopIcon() const;
	virtual bool checkPrices(QString strCompName, double & dPrice, QString strURL );
};

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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

[Lykurg]

Ehm, where is Q_DECLARE_INTERFACE?

[T4ng10r]

Oh, I forgot to add this. To be sure - this time its entire interface header.

#ifndef _CCS_SHOP_INTERFACE_INCLUDE_
#define _CCS_SHOP_INTERFACE_INCLUDE_
#include <QtCore/QStringList> 
#include <QtGui/QIcon> 
 
class ShopInterface
 {
 public:
     virtual ~ShopInterface() {}
 
     virtual QStringList shopNames() const = 0;
	 virtual QIcon getShopIcon() const = 0;
	 virtual bool checkPrices(QString strCompName, double & dPrice, QString strURL );
 };
Q_DECLARE_INTERFACE(ShopInterface, "ShopInterface/1.0");
 
#endif //_CCS_SHOP_INTERFACE_INCLUDE_

#ifndef _CCS_SHOP_INTERFACE_INCLUDE_
#define _CCS_SHOP_INTERFACE_INCLUDE_
#include <QtCore/QStringList> 
#include <QtGui/QIcon> 

class ShopInterface
 {
 public:
     virtual ~ShopInterface() {}

     virtual QStringList shopNames() const = 0;
	 virtual QIcon getShopIcon() const = 0;
	 virtual bool checkPrices(QString strCompName, double & dPrice, QString strURL );
 };
Q_DECLARE_INTERFACE(ShopInterface, "ShopInterface/1.0");

#endif //_CCS_SHOP_INTERFACE_INCLUDE_

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And - of course - in implemented plugin there is correct #include.

[wysota]

Does the plugin have the Q_EXPORT_PLUGIN2 macro?

[T4ng10r]

Yes, but placed in cpp file. In plugin examples I see that all of them have this macro there.
On the other hand - it looks like MOC compiler tries to expand Q_INTERFACES define and have problem to find appropriate interface definitions.

[wysota]

Did you include the file containing the interface definition in the plugin header file?

[T4ng10r]

#ifndef _CCS_SHOP_1_INCLUDE_
#define _CCS_SHOP_1_INCLUDE_
#include <ShopInterface.h>
#include <QtCore/QtPlugin>
 
class Shop1Plugin : public QObject, public ShopInterface
{
	Q_OBJECT
	Q_INTERFACES(ShopInterface)
public:
	virtual ~Shop1Plugin ();
	virtual QStringList shopNames() const;
	virtual QIcon getShopIcon() const;
	virtual bool checkPrices(QString strCompName, double & dPrice, QString strURL );
};
#endif

#ifndef _CCS_SHOP_1_INCLUDE_
#define _CCS_SHOP_1_INCLUDE_
#include <ShopInterface.h>
#include <QtCore/QtPlugin>

class Shop1Plugin : public QObject, public ShopInterface
{
	Q_OBJECT
	Q_INTERFACES(ShopInterface)
public:
	virtual ~Shop1Plugin ();
	virtual QStringList shopNames() const;
	virtual QIcon getShopIcon() const;
	virtual bool checkPrices(QString strCompName, double & dPrice, QString strURL );
};
#endif

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It seems most likely that #include isn't processed. Like MOC can't finding Q_DECLARE_INTERFACE, but as you see - its there. I'll make test and put entire interface in one file with its realization.
PS. And it worked. If Interface is in the same file as its realization - it worked. Why MOC can't find this include? Maybe I should add this include to MOC processing line.

[wysota]

Make sure the directory containing ShopInterface.h is in INCLUDEPATH.

[T4ng10r]

I use CMake to create configurations and projects. And this is the first time that MOC requires includes. Now I now what need to be fixed.

[hereiam]

Make sure the directory containing ShopInterface.h is in INCLUDEPATH.

thanks really a great tip because in previous projects from me cmake always seached all header files automatically.

I had the same problem but it is fixed now.