C++ templates can be used in a nice way for factory stuff

enum_to_constructor_test_with_x_macros.cpp

#include <iostream>

using std::cout;
using std::cin;
using std::cerr;
using std::endl;


// Pass the name of some other macro to list_of_sprite_classes()
#define list_of_sprite_classes(other_macro) \
	other_macro(sprite_base) \
	other_macro(sprite_a) \
	other_macro(sprite_b) \
	other_macro(sprite_c) \
	other_macro(sprite_d)


//enum sprite_type
//{
//	st_sprite_base,
//	st_sprite_a,
//	st_sprite_b,
//	st_sprite_c,
//	st_sprite_d,
//	
//	lim_st,
//};

// These two enums are the same
enum sprite_type
{
	
	#define gen_enum(spr_class) \
	st_##spr_class,
	
	list_of_sprite_classes(gen_enum)
	
	#undef gen_enum
	
	lim_st,
};


class sprite_base
{
public:		// functions
	virtual ~sprite_base()
	{
	}
	virtual void update()
	{
		cout << "sprite_base!\n";
	}
};

class sprite_a : public sprite_base
{
public:		// functions
	virtual void update()
	{
		cout << "sprite_a!\n";
	}
	
};

class sprite_b : public sprite_base
{
public:		// functions
	virtual void update()
	{
		cout << "sprite_b!\n";
	}
	
};


class sprite_c : public sprite_base
{
public:		// functions
	virtual void update()
	{
		cout << "sprite_c!\n";
	}
	
};

class sprite_d : public sprite_base
{
public:		// functions
	virtual void update()
	{
		cout << "sprite_d!\n";
	}
	
};


template<typename spr_class>
sprite_base* gen_sprite()
{
	return new spr_class();
}



typedef sprite_base* (*spr_generator)();


//const spr_generator test_spr_gen_arr[] 
//	= { &(gen_sprite<sprite_base>), 
//	&(gen_sprite<sprite_a>), 
//	&(gen_sprite<sprite_b>), 
//	&(gen_sprite<sprite_c>),
//	&(gen_sprite<sprite_d>) };

#define gen_func_ptr(spr_class) \
&(gen_sprite<spr_class>),


const spr_generator test_spr_gen_arr[lim_st]
= {
	list_of_sprite_classes(gen_func_ptr)
};

#undef gen_func_ptr





int main( int argc, char** argv )
{
	sprite_base * base, * a, * b, * c, * d;
	base = test_spr_gen_arr[st_sprite_base]();
	a = test_spr_gen_arr[st_sprite_a]();
	b = test_spr_gen_arr[st_sprite_b]();
	c = test_spr_gen_arr[st_sprite_c]();
	d = test_spr_gen_arr[st_sprite_d]();
	
	base->update();
	a->update();
	b->update();
	c->update();
	d->update();
	cout << endl;
	
	base->update();
	a->update();
	b->update();
	c->update();
	d->update();
	
	delete base;
	delete a;
	delete b;
	delete c;
	delete d;
	
	return 0;
}