gistfile1.cpp

#include <cassert>
#include <memory>
#include <stdexcept>
#include <tuple>
#include <utility>
#include <vector>

class base {
public:
	virtual ~base() = default;
	int id() const {return m_id;}
	
	template<typename...T>
	const std::tuple<T...>& virt_data() const;
protected:
	base(int id): m_id(id) {}
private:
	int m_id;
};

template<typename...T>
class derived: public base {
public:
	derived(T...data, int id): base{id}, m_data{std::move(data)...} {}
	const std::tuple<T...>& data() const {return m_data;}
private:
	std::tuple<T...> m_data;
};

template<typename...T>
const std::tuple<T...>& base::virt_data() const {
	auto& casted = dynamic_cast<const derived<T...>&>(*this);
	return casted.data();
}

template<typename T, typename... Args>
std::unique_ptr<T> make_unique(Args&&... args) {
	return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
}

int main() {
	std::vector<std::unique_ptr<base>> misc_data;
	misc_data.push_back(make_unique<derived<int, float>>(2, 3.4f, 0));
	misc_data.push_back(make_unique<derived<double>>(43.23, 1));
	auto data = misc_data.at(0)->virt_data<int, float>();
	assert(data == std::make_tuple(2, 3.4f));
}