Question

I have this class template:

template<class... T>
class Test {
  std::vector<TestCase*> test_cases;
public:
  Test() {
    // Here, for each T an instance should be added to test_cases.
    test_cases.push_back((new T)...);
  }
};

This works fine for one template argument, but for multiple arguments I get this error:

error: too many arguments to function call, expected 1, have 2

How can I use variadic templates with new this way? What is the correct syntax?

---

EDIT: I think my question wasn’t quite clear. What I want is this:

Test<TestCase1, TestCase2, TestCase3>;
// The constructor will then be:
test_cases.push_back(new TestCase1);
test_cases.push_back(new TestCase2);
test_cases.push_back(new TestCase3);

---

My compiler is clang 163.7.1 with this flag: -std=c++0x.

Answer 1

vector::push_back expects one parameter so you can’t expand the variadic template in the function call.
Also I added a template parameter for the base class (from which all other classes derive).

Here’s something that compiles.

struct base{};
struct d0 : base{};
struct d1 : base{};
struct d2 : base{};

#include <vector>

// termination condition for helper function
template <class T>
void add(std::vector<T*>&) { 
}

// helper function
template <class T, class Head, class... Tail>
void add(std::vector<T*>& v) { 
       v.push_back(new Head()); 
       add<T, Tail...>(v);
}

template <class T, class ... U>
class test
{
    std::vector<T*> vec;
public:
    test() {
       add<T, U...>(vec);      
    }
};

int main() 
{
    test<base, d0,d1,d2> t;
}