c++ any implementation

any.cpp

// http://staryoshi.hatenablog.com/entry/2015/10/27/173925
#include <iostream>
#include <memory>

class Any {
private:
	struct base {
		virtual std::type_info const& type() const { return typeid(nullptr); }
		virtual std::unique_ptr<base> clone() const { return nullptr; }
	};

	template<class T>
	struct derived :public base {
		T data;
		derived(T const& it) : data(it) {
		}
		template<class ...Args>
		derived(Args ...args) : data(args) {}
		std::unique_ptr<base> clone() const override { return std::make_unique < derived<T>>(data); }
		std::type_info const& type() const override { return typeid(data); }
	};

public:
	Any() {};
	template<class T>
	Any(T const& it) : data(new derived<T>(it)) {
	};
	Any(Any const& it) : data(std::make_unique<base>(*it.data)) {}
	Any(Any&& it) : data(std::move(it.data)) {}
	Any& operator=(Any const& it) {
		data = it.data->clone();
		return *this;
	}
	Any& operator=(Any&& it) {
		data = std::move(it.data);
		return *this;
	}
	template <typename T>
	Any& operator = (T const& it) {
		data = std::make_unique<derived<T>>(it);
		return *this;
	}

	template <class T>
	T& get() const {
		auto p = dynamic_cast<derived<T>*>(data.get());
		if (p == nullptr) {
			throw std::bad_cast();
		}
		return p->data;
	}
	std::type_info const& type() const {
		return data->type();
	}
private:
	std::unique_ptr<base> data;
};

int main(void) {
	int input = 4;
	Any any = input; // construct & copy
	printf("%s\n", any.type().name());
	printf("%d\n", any.get<decltype(input)>());
	Any any2;
	any2 = any; // copy
	printf("%s\n", any2.type().name());
	printf("%d\n", any2.get<decltype(input)>());

	return 0;
}