#!/python22/bin/python
import types

class Var(object):
	DEFAULT_VALUE = None
	
	def __init__(self, value=None):
		#	create all private variables
		self._value = self.DEFAULT_VALUE
		self._change_callbacks = []

		#	init variables
		self.value = value
		
	def _call_change_callbacks(self, old, new):
		for callback in self._change_callbacks:
			callback(self, old, new)
			
	def bind(self, callback):
		self._change_callbacks.append(callback)
			
	def unbind(self, callback, secure=False):
		try:
			self._change_callbacks.remove(callback)
			return True
		except ValueError:
			if secure:
				return False
			else:
				raise
			
				
				
	def _set_value(self, value):
		_old = self._value
		self._value = value
		self._call_change_callbacks(_old, value)
		
	def _get_value(self):
		return self._value
		
	def _del_value(self):
		self._value = self.DEFAULT_VALUE
		
	def __repr__(self):
		return "<object of %s>  value=%s" % (
			repr(self.__class__)[1:-1], 
			repr(self._value)
		)
	
	def __call__(self, *arg):
		if arg:
			self.value = arg[0]
		else:
			return self.value
			
		
	def __str__(self):
		return str(self._value)
		
	def __int__(self):
		return int(self._value)
		
	def __float__(self):
		return float(self._value)
		
	value = property(_get_value, _set_value, _del_value)
	
class StringVar(Var):
	DEFAULT_VALUE = ""
	
	def __init__(self, value=None):
		Var.__init__(self, value or self.DEFAULT_VALUE)
			
	def _set_value(self, value):
		if type(value) in (types.StringType, types.UnicodeType):
			Var._set_value(self, value)
		else:
			raise TypeError, \
				"Type must be string or unicode, found %s instead." % str(type(value))
			return
			
	value = property(Var._get_value, _set_value, Var._del_value)
	

class IntVar(Var):
	DEFAULT_VALUE = 0
	
	def __init__(self, value=None):
		Var.__init__(self, value or self.DEFAULT_VALUE)
		
	def _set_value(self, value):
		if type(value) in (types.IntType, types.LongType):
			Var._set_value(self, value)
		else:
			raise TypeError, \
				"Type must be int or long, found %s instead." % str(type(value))
				
	value = property(Var._get_value, _set_value, Var._del_value)
	

class FloatVar(Var):	
	DEFAULT_VALUE = 0.0
	
	def __init__(self, value=None):
		Var.__init__(self, value or self.DEFAULT_VALUE)
		
	def _set_value(self, value):
		if type(value) is types.FloatType:
			self._value = value
		elif type(value) in (types.IntType, types.LongType):
			self._value = float(value)
		else:
			raise TypeError, \
				"Type must be float, int or long, found %s instead." % str(type(value))
				
	value = property(Var._get_value, _set_value, Var._del_value)


def out(var, old, new):
	print "Wert von", var.__class__, "aenderte sich von", old, "zu", new