Callback with C++ class

callback.cpp

#include <iostream>
#include <vector>

struct callback_interface
{
	virtual void callback() = 0;
};

typedef std::pair<callback_interface *, int> callback_timeout;

std::vector<callback_interface*> callbacks;
std::vector<callback_timeout> callbacks_timeout;

struct classA
{
	struct callback_private:
		callback_interface
	{
		classA *owner;

		callback_private(classA *owner):
			owner(owner)
		{

		}

		void callback()
		{
			owner->callback();
		}
	};

	callback_private cb;
	int i;

	classA(int i):
		cb(this),
		i(i)
	{
		callbacks_timeout.push_back(std::make_pair(&cb, 1000));
	}

	void callback()
	{
		std::cout << i << std::endl;
	}
};

struct classB
{
	struct callback_private:
		callback_interface
	{
		classB *owner;

		callback_private(classB *owner):
			owner(owner)
		{

		}

		void callback()
		{
			owner->callme();
		}
	};

	callback_private cb;
	float f;

	classB(float f):
		cb(this),
		f(f)
	{
		callbacks_timeout.push_back(callback_timeout(&cb, 100));
	}

	void callme()
	{
		std::cout << f << std::endl;
	}
};

int main(int argc, char *argv[])
{
	classA a(1), b(4);
	classB c(2.5), d(7.3);

	for (const callback_timeout &call_time: callbacks_timeout)
	{
		std::cout << call_time.second << std::endl;
		call_time.first->callback();
	}

	return 0;
}