模板函数内的函数指针

Question

Hello Im begginer with c++ and Im stuck with this problem. I have template class as you can see bellow and there is another template method PrintSpecificObject. In real project I have a collection of differents objects and I need for example print just object which could be cast do "K". Anyway, my problem is with "PrintThatObject" method or with that how i call it in main. Thanks for help.

     template<typename T>
        class Foo {
        public:
            std::vector<T*> v;

            template<typename K>
            void PrintSpecificObject(void(*uFunc)(K*)) {
                for (std::vector<T*>::iterator i = begin(); i != end(); ++i) {
                    if (dynamic_cast<K*>(i) != nullptr) {
                       PrintThatObject(i);    //<------- There i call it
                    }
                }
            }

          //<------- How this method shoud look? ------>
            void PrintThatObject(int i) {
                std::cout << i;
            }
        };

    int main() {
        Foo<int*> f;
        f.PrintSpecificObject<int>(f.PrintThatObject); // Error C3867
        f.PrintSpecificObject<int>(&Foo<int*>::PrintThatObject); // Error C2664
      //  <------- Or How should i call that method?  -------> 
  }

Answer 1

You can't pass any representation of PrintThatObject to PrintSpecificObject. The problem is that PrintSpecificObject takes a function pointer. PrintThatObject is a member function. Huge difference !

You could fix PrintSpecificObject, or just add an overload and it won't be ambiguous, like so:

template < typename Object, typename K >
void PrintSpecificObject(Object * o, void (Object::*fun)(K*))
{
    //...whatever...
    // call function
    o->*fun(some_k);
}

You'd call with f.PrintSpecificObject<int>(&Foo<?>::PrintThatObject)

The ? is whatever type you passed to Foo to instantiate the class for f.