Properties with getter/setter function calls

properties.cxx

//      Properties with getter/setter function calls
//      
//      Copyright 2011 Michał Papierski <michal@papierski.net>
//      
//      This program is free software; you can redistribute it and/or modify
//      it under the terms of the GNU General Public License as published by
//      the Free Software Foundation; either version 2 of the License, or
//      (at your option) any later version.
//      
//      This program is distributed in the hope that it will be useful,
//      but WITHOUT ANY WARRANTY; without even the implied warranty of
//      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//      GNU General Public License for more details.
//      
//      You should have received a copy of the GNU General Public License
//      along with this program; if not, write to the Free Software
//      Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
//      MA 02110-1301, USA.

#include <iostream>

#include <cassert>

using namespace std;

struct Observable { };

template <typename var_type, typename T, var_type (T::*Getter)() = 0, void (T::*Setter)(var_type) = 0>
class Property
{
	public:
		typedef var_type variable_t;
		typedef variable_t (Observable::*GetterType)();
		typedef void (Observable::*SetterType)(variable_t);
		
	private:
		GetterType m_Getter; /* Getter function */
		SetterType m_Setter; /* Setter function */
		Observable* m_Owner; /* Owner */
		
	public:
		Property(Observable* obj):
			m_Getter(reinterpret_cast<GetterType>(Getter)),
			m_Setter(reinterpret_cast<SetterType>(Setter)),
			m_Owner(obj)
		{
				
		}
		
		/* Call getter */
		variable_t value()
		{
			return ((*m_Owner).*m_Getter)();
		}
		
		/* Call setter */
		void setValue(variable_t value)
		{
			(m_Owner->*m_Setter)(value);
		}
		
		/* Call setter */
		Property& operator=(variable_t value)
		{
			setValue(value);
			return *this;
		}
		
		bool operator==(variable_t value)
		{
			return this->value() == value;
		}
		
		/* Cast op */
		operator variable_t()
		{
			return value();
		}
};

/* Ugly macros */
#define CLASS(class_name, ...)\
	class class_name: public Observable, ## __VA_ARGS__ \
	{\
		private:\
			typedef class_name object_type_for_property;\
		public:\
			static string getClassName() { return #class_name; }

#define PROPERTY(var_type, getter, setter) Property<var_type, object_type_for_property, &object_type_for_property::getter, &object_type_for_property::setter>
#define DEFAULT_PROPERTY(classname, var_type, var_name) \
		var_type m_##var_name;\
		var_type get##var_name() \
		{\
			return m_##var_name;\
		}\
		void set##var_name(var_type var_name)\
		{\
			this->m_##var_name = var_name;\
		}\
		Property<var_type, classname, &classname::get##var_name, &classname::set##var_name> var_name;

class Object: public Observable
{
	public:
		DEFAULT_PROPERTY(Object, int, X)
		DEFAULT_PROPERTY(Object, int, Y)
		
		Object(): X(this), Y(this)
		{
			
		}
};

int main(int argc, char* argv[])
{
	Object obj;
	obj.X = 69;
	obj.Y = 79;
	assert(obj.X == 69);
	assert(obj.Y == 79);
	return 0;
}