passing object to plugin

[folibis]

I have troubles with plugins in my application. In general this is only plugin loader.
I do it like this:

//main module
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QMySettings * conf = new QMySettings("","");
    QDir pluginsDir = QDir(qApp->applicationDirPath());
    pluginsDir.cdUp();
    pluginsDir.cd("plugins");
    foreach (QString fileName, pluginsDir.entryList(QDir::Files))
    {
        QPluginLoader loader(pluginsDir.absoluteFilePath(fileName));
        QObject *plugin = loader.instance();
        if(plugin)
        {
            MyPlugin * iface = qobject_cast<MyPlugin *>(plugin);
            if(iface)
            {
                iface->init(conf);
            }
        }
    }
    return a.exec();
}

//main module
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QMySettings * conf = new QMySettings("","");
    QDir pluginsDir = QDir(qApp->applicationDirPath());
    pluginsDir.cdUp();
    pluginsDir.cd("plugins");
    foreach (QString fileName, pluginsDir.entryList(QDir::Files))
    {
        QPluginLoader loader(pluginsDir.absoluteFilePath(fileName));
        QObject *plugin = loader.instance();
        if(plugin)
        {
            MyPlugin * iface = qobject_cast<MyPlugin *>(plugin);
            if(iface)
            {
                iface->init(conf);
            }
        }
    }
    return a.exec();
}

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In main module I initialize class for storing app configuration. This class I want to share with all of my plugins.

Conf::Conf(QObject *parent) :
    QObject(parent)
{
}
//header
class Conf : public QObject
{
    Q_OBJECT
public:
    explicit Conf(QObject *parent = 0);
    QString getValue(int i);
};
 
//cpp
QString Conf::getValue(int i)
{
    return QString::number(i,16);
}

Conf::Conf(QObject *parent) :
    QObject(parent)
{
}
//header
class Conf : public QObject
{
    Q_OBJECT
public:
    explicit Conf(QObject *parent = 0);
    QString getValue(int i);
};

//cpp
QString Conf::getValue(int i)
{
    return QString::number(i,16);
}

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plugin interface

class MyPlugin
{
    public:
        ~MyPlugin(){}
        virtual void init(QObject * ptr) = 0;
 
};
 
Q_DECLARE_INTERFACE(MyPlugin,"com.trolltech.MyPlugin/1.0")

class MyPlugin
{
    public:
        ~MyPlugin(){}
        virtual void init(QObject * ptr) = 0;

};

Q_DECLARE_INTERFACE(MyPlugin,"com.trolltech.MyPlugin/1.0")

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and finally my plugin implementation

//header
class LIB1SHARED_EXPORT Lib1 : public QObject,public MyPlugin {
        Q_OBJECT
        Q_INTERFACES(MyPlugin)
public:
    Lib1();
    void init(QObject * ptr);
};
//cpp
Lib1::Lib1()
{
}
 
void Lib1::init(QObject * ptr)
{
    Conf * conf = reinterpret_cast<Conf *>(ptr);
    qWarning(conf->getValue(1).toAscii()); // <<<<<<< here error
}
 
Q_EXPORT_PLUGIN2(lib1, Lib1)

//header
class LIB1SHARED_EXPORT Lib1 : public QObject,public MyPlugin {
        Q_OBJECT
        Q_INTERFACES(MyPlugin)
public:
    Lib1();
    void init(QObject * ptr);
};
//cpp
Lib1::Lib1()
{
}

void Lib1::init(QObject * ptr)
{
    Conf * conf = reinterpret_cast<Conf *>(ptr);
    qWarning(conf->getValue(1).toAscii()); // <<<<<<< here error
}

Q_EXPORT_PLUGIN2(lib1, Lib1)

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While compiling I get strange error:

C:\source\PluginTest\lib1\lib1.cpp:11: error: undefined reference to `Conf::getValue(int)'

and what's interesting, using QSetting in place of My class works fine.

P.S. Sorry for my pure English