C++ abstract class template + type-specific subclass = trouble with linker
- by user333279
Hi there,
The project in question is about different endpoints communicating with each other. An endpoint sends events (beyond the scope of the current problem) and can process incoming events. Each event is represented in a generic object as follows:
#pragma interface
... // some includes
template<typename T>
class Event
{
public:
Event(int senderId, Type type, T payload); // Type is an enum
Event(int senderId, Type type, int priority, T payload);
virtual ~Event();
virtual int getSenderId();
virtual int getPriority();
virtual T getPayload();
void setPriority(const int priority);
protected:
const int senderId;
const Type type;
const T payload;
int priority;
};
It has its implementing class with #pragma implementation tag.
An endpoint is defined as follows:
#pragma interface
#include "Event.h"
template<typename T>
class AbstractEndPoint
{
public:
AbstractEndPoint(int id);
virtual ~AbstractEndPoint();
virtual int getId();
virtual void processEvent(Event<T> event) = 0;
protected:
const int id;
};
It has its implementing class too, but only the constructor, destructor and getId() are defined.
The idea is to create concrete endpoints for each different payload type. Therefore I have different payload objects and specific event classes for each type, e.g.
Event<TelegramFormatA>, Event<TelegramFormatB>
and
ConcreteEndPoint for TelegramFormatA,
ConcreteEndPoint for TelegramFormatB
respectively. The latter classes are defined as
class ConcreteEndPoint : AbstractEndPoint<TelegramFormatA>
{
...
}
I'm using g++ 4.4.3 and ld 2.19. Everything compiles nicely, but the linker complaints about undefined references to type-specific event classes, like
Event<TelegramFormatA>::Event(....) .
I tried explicit instantiation using
template class AbstractEndPoint<TelegramFormatA>;
but couldn't get past the aforementioned linker errors.
Any ideas would be appreciated.
