"""Implementation for Observer and Observables used for out events.
Generated by itemis CREATE code generator.
"""


class Observer():
	"""Observer implementation.
	"""

	def next(self, value=None):
		"""Abstract next method, which must be implemented."""
		raise NotImplementedError('user must define next() to use this base class')


class Observable():
	"""Observable implementation.
	"""

	def __init__(self):
		self.observers = []

	def next(self, value=None):
		"""Calls next function from every observer.
		"""
		for observer in self.observers:
			if observer is not None:
				if value is None:
					observer.next()
				else:
					observer.next(value)

	def subscribe(self, observer):
		"""Subscribe on specified observer.
		"""
		if observer is not None:
			self.observers.append(observer)
			return True
		return False

	def unsubscribe(self, observer):
		"""Unsubscribe from specified observer.
		"""
		if observer is None:
			return False
		if observer in self.observers:
			self.observers.remove(observer)
			return True
		return False