如何从模板类型获取指向模板化成员函数的指针？

Question

The following code does not compile ... any idea why? Is this illegal C++?

class Handler {
 public:
  template <typename T>
  void handle(T t) {}    
};

class Initializer {
 public:
  template <typename T, typename H>
  void setup(H *handler) {
    void (H::*handle)(T) = &H::handle<T>; // fails
  }
};

int main() {
  Initializer initializer;
  Handler handler;
  initializer.setup<int, Handler>(&handler);
}

Answer 1

You need template :

void (H::*handle)(T) = &H::template handle<T>; 

Because the template handle is qualified with a dependent type. (Just like you use typename if a type is qualified with a dependent type.)