Python-Design-Patterns state
state Model
Python-Design-Patterns state
# file: 'state.py'
#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
Implementation of the state pattern
http://ginstrom.com/scribbles/2007/10/08/design-patterns-python-style/
*TL;DR80
Implements state as a derived class of the state pattern interface.
Implements state transitions by invoking methods from the pattern's superclass.
"""
from __future__ import print_function
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(u"Scanning... Station is %s %s" % (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(u"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(u"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()
### OUTPUT ###
# Scanning... Station is 1380 AM
# Scanning... Station is 1510 AM
# Switching to FM
# Scanning... Station is 89.1 FM
# Scanning... Station is 103.9 FM
# Scanning... Station is 81.3 FM
# Scanning... Station is 89.1 FM
# Switching to AM
# Scanning... Station is 1250 AM
# Scanning... Station is 1380 AM
state.py
Test state
# file: 'test_state.py'
#!/usr/bin/env python
# -*- coding: utf-8 -*-
import unittest
from behavioral.state import Radio
class RadioTest(unittest.TestCase):
"""
Attention: Test case results depend on test case execution. The test cases
in this integration test class should be executed in an explicit order:
http://stackoverflow.com/questions/5387299/python-unittest-testcase-execution-order
"""
@classmethod
def setUpClass(self):
self.radio = Radio()
def test_initial_state(self):
state = self.radio.state.name
expected_state_name = 'AM'
self.assertEqual(state, expected_state_name)
def test_initial_am_station(self):
station = self.radio.state.stations[self.radio.state.pos]
expected_station = '1250'
self.assertEqual(station, expected_station)
def test_2nd_am_station_after_scan(self):
self.radio.scan()
station = self.radio.state.stations[self.radio.state.pos]
expected_station = '1380'
self.assertEqual(station, expected_station)
def test_3rd_am_station_after_scan(self):
self.radio.scan()
station = self.radio.state.stations[self.radio.state.pos]
expected_station = '1510'
self.assertEqual(station, expected_station)
def test_am_station_overflow_after_scan(self):
self.radio.scan()
station = self.radio.state.stations[self.radio.state.pos]
expected_station = '1250'
self.assertEqual(station, expected_station)
def test_shall_toggle_from_am_to_fm(self):
self.radio.toggle_amfm()
state = self.radio.state.name
expected_state_name = 'FM'
self.assertEqual(state, expected_state_name)
def test_shall_toggle_from_fm_to_am(self):
self.radio.toggle_amfm()
state = self.radio.state.name
expected_state_name = 'AM'
self.assertEqual(state, expected_state_name)
test_state.py
