signals and slots in plugins

[anderl]

Hi,

i'm trying to use signals and slots in plugins that will be loaded at runtime. But the plugins fails to load and i get this message:

"QLibrary::load_sys: Cannot load libvectorplugin.so.1.0.0 (libvectorplugin.so.1.0.0: undefined symbol: _ZN10App4Calcs11ICalculator10metaObjectEv)"

The plugin contains implementations of the following interfaces:

class ICalculator : public QObject
{
Q_OBJECT
public:
IView * createView() = 0;
(...)
signals:
void calculationDone();
};

class ICalculator : public QObject
{
Q_OBJECT
public:
IView * createView() = 0;
(...)
signals:
void calculationDone();
};

To copy to clipboard, switch view to plain text mode 

class IView : public QObject
{
Q_OBJECT
public:
(..)
public slots:
virtual void renderData() =0;
};

class IView : public QObject
{
Q_OBJECT
public:
(..)
public slots:
virtual void renderData() =0;
};

To copy to clipboard, switch view to plain text mode 

and finally the plugin interface (the implementation of this inteface will be exported as a plugin):

class IPlugin 
{
public:
ICalculator* createCalculator() = 0;
};
Q_DECLARE_INTERFACE(App::Calcs::IPlugin ,"IPlugin");

class IPlugin 
{
public:
ICalculator* createCalculator() = 0;
};
Q_DECLARE_INTERFACE(App::Calcs::IPlugin ,"IPlugin");

To copy to clipboard, switch view to plain text mode 

Implementation inside the plugin:

class VectorView : public IView
{
	Q_OBJECT
public slots:
virtual void renderData()
{
(..)
}
};

class VectorView : public IView
{
	Q_OBJECT
public slots:
virtual void renderData()
{
(..)
}
};

To copy to clipboard, switch view to plain text mode 

class VectorCalculator : ICalculator
{
	Q_OBJECT
public:
virtual void calculate()
{
(...)
emit calculationDone();
}
};

class VectorCalculator : ICalculator
{
	Q_OBJECT
public:
virtual void calculate()
{
(...)
emit calculationDone();
}
};

To copy to clipboard, switch view to plain text mode 

the qmake file:

TEMPLATE = lib
CONFIG += warn_on \
	  thread \
          qt
TARGET = ../bin/vectorcalculator
 
QT += gui opengl
HEADERS += vectorcalculator.h 
		vectorview.h \
vectorplugin.h
 
SOURCES += vectorcalculator.cpp vectorview.cpp vectorplugin.cpp

TEMPLATE = lib
CONFIG += warn_on \
	  thread \
          qt
TARGET = ../bin/vectorcalculator

QT += gui opengl
HEADERS += vectorcalculator.h 
		vectorview.h \
vectorplugin.h

SOURCES += vectorcalculator.cpp vectorview.cpp vectorplugin.cpp

To copy to clipboard, switch view to plain text mode 

The compilation works fine. Why do i get this linker error at runtime?

thanks in advance!

[wysota]

Interfaces can't be QObjects. The interface should contain virtual methods that will be implemented by each plugin. Only the plugin itself should inherit QObject and you can define signals and slots there. Then you can ask the plugin for available signals and slots using the meta object.