Keeping the old question. See below for resolution. It is probably something simple, but still. I have the following C++11 code fragment:
#include <vector>
template <typename... Ts>
struct typelist
{
};
template <typename T>
struct EventContainer
{
typedef T Type;
/// TODO. Ring buffer
std::vector<T> container;
void push(const T& t)
{
EventContainer<T>::container.push_back(t);
}
virtual ~EventContainer()
{
}
};
template <template <typename...> class TL>
class EventStorage:
public EventContainer<Ts>...
{
};
class Event1
{
};
class Event2
{
};
typedef typelist<Event1,Event2> Events12;
int main()
{
EventStorage<Events12> ev;
return 0;
}
How can I make EventStorage inherit EventContainer templeted with each of the types in the typelist. I could do it with Loki:: library, but I want to use C++11 with variadic templates.
Thank you.
Resolution1: Fixing EventStorage template template issue. This will make EventStorage, multiple inherit all EventContainer templated with each type of Ts.
template <typename...>
class EventStorage
{
};
template <typename... Ts>
class EventStorage < typelist<Ts...> >:
public EventContainer<Ts>...
{
};
Now I have compile time error, on the following main():
int main()
{
EventStorage<Events12> ev;
Event1 ev1;
ev.push(ev1);
return 0;
}
In function ‘int main()’:
error: request for member ‘push’ is ambiguous
error: candidates are: void EventContainer<T>::push(const T&) [with T = Event2]
error: void EventContainer<T>::push(const T&) [with T = Event1]
Why the compiler is confused? After all I push with specific type. GCC 4.6.1 here.
Resolution2:
As @Matthieu M. suggested I can present a forwarding method int EventStorage, but at a cost of one extra functin call:
template <typename T>
void push(const T& t)
{
EventContainer<T>::push(t);
}
According to Alexandrescu, the compiler will optimize this forward call as long as parameters are references. Now the question is officially closed :)
