Plugin and shared class between plugin and application

[wishper]

Hi !
Well, I need to create a plugin manager, and some plugins to my application.
The goal of a plugin is to provide new items to the main application, extended from QGraphicsWidget with a few more methods and signals.
Since a plugin must be a pure interface, I realized one with some functions to communicate with the application.
Since the item is used by the application, but also need to be know by the plugin to create them, I include in the header of the plugin the declaration of the Item (it's a QGraphicsWidget with some pure virtual methods)

I manage to get my program and my plugin to compile. However, when I load the plugin, I get this error (came from pluginLoader.errorString() ) :

PluginManager : instance failed "Cannot load library /home/wishper/trunk/release/Plugins/lib_basicitems.so: (/home/wishper/trunk/release/Plugins/lib_basicitems.so: undefined symbol: _ZN4Item16staticMetaObjectE)"

Here is the light version of the header :

class Item : public QGraphicsWidget{
    Q_OBJECT
public:
    Item(QGraphicsItem * parent) : QGraphicsWidget(parent){};
    ~Item(){};
    virtual bool isBackground() = 0;
    virtual QList<PropertyInfo> getProperties() = 0;
 
signals:
    void background(bool background);
    void propertyUpdate();
};
 
class ItemCreator{
public:
    ~ItemCreator(){};
    virtual Item * createItem(QByteArray init);
};
 
class Plugin
{
public:
    virtual ~Plugin() {};
    virtual QString getName() = 0;
    virtual QList<QMenu * > getMenus() = 0;
    virtual ItemCreator getItemCreator() = 0;
    virtual QList<QByteArray *> getInitValues() = 0;
};
 
Q_DECLARE_INTERFACE(Plugin,
                    "fr.neticoa.xsimulbeta.plugin/1.0")

class Item : public QGraphicsWidget{
    Q_OBJECT
public:
    Item(QGraphicsItem * parent) : QGraphicsWidget(parent){};
    ~Item(){};
    virtual bool isBackground() = 0;
    virtual QList<PropertyInfo> getProperties() = 0;

signals:
    void background(bool background);
    void propertyUpdate();
};

class ItemCreator{
public:
    ~ItemCreator(){};
    virtual Item * createItem(QByteArray init);
};

class Plugin
{
public:
    virtual ~Plugin() {};
    virtual QString getName() = 0;
    virtual QList<QMenu * > getMenus() = 0;
    virtual ItemCreator getItemCreator() = 0;
    virtual QList<QByteArray *> getInitValues() = 0;
};

Q_DECLARE_INTERFACE(Plugin,
                    "fr.neticoa.xsimulbeta.plugin/1.0")

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What I see with the error is that the problem came from the Item class. I really don't understand what is the problem. I tried many things, but the result is always the same.

Am I doing things wrong ?

Thanks a lot, regards.
wishper.