I currently write on an event handler system in C++0x. The "handlers" for each event (there can be multiple handlers) are registered by passing any kind of function/method that can be stored in a std::function object. This is done in C# style using the overloaded += operator. My Event-Class looks basically like this (stripped for better readability):
template<typename THandlerReturn, typename THandlerArgs...>
class Event {
public:
typedef THandlerReturn(HandlerSignature)(THandlerArgs...);
typedef THandlerReturn(*HandlerFuntionPtr)(THandlerArgs...);
typedef typename std::function<HandlerSignature> HandlerFunction;
void operator += (HandlerFunction handler) {
_handlers.push_back(handler);
}
// Some other methods for calling all handlers, ctors, etc.
private:
std::vector<HandlerFunction> _handlers;
};
Now I have another internal method for retrieving the actual function pointer from the std::function objects stored in the vector. It basically tries to do something like this:
// Preceeding: Get an iterator 'it' from the vector
HandlerFunctionPtr pt2func = it->target<HandlerSignature>();
At this point, when I use the Event class in my application, the compilation failes. Using a GCC 4.7 build I get the following error messages for the line above:
error: expected primary-expression before '>' token
error: expected primary-expression before ')' token
I've tested a little bit with the target<>() Method and the following works perfectly, assuming that the return type is void and there's one argument of type int:
typedef void(Signature)(int);
typedef void(*FunctionPtr)(int);
std::function<Signature> func;
FunctionPtr pt2func = func.target<Signature>();
But as soon as there is one template argument involved, I get the above posted errors:
typedef THandlerReturn(Signature)(int);
typedef THandlerReturn(*FunctionPtr)(void);
std::function<Signature> func;
FunctionPtr pt2func = func.target<Signature>();
Can anyone tell me why that actually is, and if yes, if there's any way to make it work? Any help and insights are very appreciated! Thanks in advance!
