GoF design pattern - State

state.py

# -*- coding: utf-8 -*-


""" http://ginstrom.com/scribbles/2007/10/08/design-patterns-python-style/"""


class State(object):
	"""Base state. This is to share functionality"""

	def scan(self):
		"""Scan the dial to the next station"""
		self.pos += 1
		if self.pos == len(self.stations):
			self.pos = 0
		print("Scanning... Station is", self.stations[self.pos], self.name)


class AmState(State):
	def __init__(self, radio):
		self.radio = radio
		self.stations = ["1250", "1380", "1510"]
		self.pos = 0
		self.name = "AM"

	def toggle_amfm(self):
		print("Switching to FM")
		self.radio.state = self.radio.fmstate


class FmState(State):
	def __init__(self, radio):
		self.radio = radio
		self.stations = ["81.3", "89.1", "103.9"]
		self.pos = 0
		self.name = "FM"

	def toggle_amfm(self):
		print("Switching to AM")
		self.radio.state = self.radio.amstate

class Radio(object):
	"""A radio. It has a scan button, and an AM/FM toggle switch"""
	def __init__(self):
		"""We have an AM state and an FM state"""
		self.amstate = AmState(self)
		self.fmstate = FmState(self)
		self.state = self.amstate

	def toggle_amfm(self):
		self.state.toggle_amfm()

	def scan(self):
		self.state.scan()


# Test our radio out
if __name__ == '__main__':
	radio = Radio()
	actions = [radio.scan] * 2 + [radio.toggle_amfm] + [radio.scan] * 2
	actions *= 2

	for action in actions:
		action()